My neighbor has a pontiac 400 with a dyers 6-71 blower. 2- 750 demon blower carbs, timing set at 12 initial, 33 total, msd distributor, msd ig. edelbrock heads. unsure about how much boost, lower 8.0 compression or so.

He is having problems with it backfiring at idle. It was previously running and idleing very rich. would smog you out of the garage in a min. It would backfire out of the exhaust, and basicly idle like crap. Weve finally got it narrowed down for acceleration and cruse, but still idles terrible. Idle speed slots are set at .20 open on the primary and closed on the secondaries.

Any ideas..?? he was going to check if the plugs were fouled, and check his routing of wires for crossfiring..

Many carb problems are actually the ignition. I;d look there first to make sure plugs, cap, rotor, wires, etc are all in good shape. Timing being way off can cause backfilres too.

One thing I would change on the carb is the idle speed screws. I would set both front and back so .020" of transfer slot is showing -- that will add more fuel at idle and hopefully fatten it up a little.

If you have a vacuum gauge you can set the idle mixture by setting for highest vacuum and going leaner a little at a time until the vac just barely starts to drop off. That is usually right about 14:1.

After you set the idle mixture like I suggest let me know how many turns the mixture screws are off their seat. That may indicate how close the IFR is . . . your friends blower motor could want more or less than a typical NA engine.

If this is a Demon blower carb the carb should come with a boost referenced power valve. Otherwise, I believe the Demon blower carb is the same as the "non-blower" carbs.

PS. I hate to suggest this, but you may look at valve lash (or preload). If a rocker or two is very loose you should look into the possibility of a wiped cam lobe.

The first problem I see right away is the timing. Blowers love initial advance, 12* is not enough. I would start at 18* it may even want more. The engine will run a lot cooler as well. I have my timing set at 18-20* initial and 32-34 total. You don't want too much total timing with a blower either.

See if that takes care of your idle and backfiring problems. If not then I would adjust the carb as Eric states, once you set the tranfer slots (VERY important), then adjust the air mixture screws with the car running at idle and warmed up, adjust for the highest idle speed, then you can lower the idle with the idle screw, you just don;t want to open the idle screw if you can help it once the transfer slot is set.

One last thing make sure noth carb are in sync. Meaning that they are both opening the same amount from ide to WOT.

PS. I hate to suggest this, but you may look at valve lash (or preload). If a rocker or two is very loose you should look into the possibility of a wiped cam lobe.

I hope not.. he had just rebuilt this motor and it has less than 100 miles on it.

He was changing the plugs tonight and changing out a fuel regulator. 2 of the plugs were very fouled.. possibly not firing at all.

He had set the timing (or the distributor sliped ) at 20 initial.. however it would have made the total advance at 41 or so.. He was having alot of backfiring and detonation problems while accelerating. Weve backed it off and seems to run best now at the 12.. (hes got the 21 deg msd stop bushing in it now. ) Except for the excesivly rich condition it seems..

I know as well that he Does have a progressive linkage on it.. the rear or front opens later than the other. This is what the blower shop told him to do.

The timing curve is wrong in the distributor for a blown engine. You need to adjust the distributor so you can run 20* initial and still only have 32-34 total (maybe less total if you do not have a timing retard). I can't stress to you enough how important initial advance is with a blower. You just have to limit the total timing. I bet his headers glow red at idle with only 12* initial, check the headers and see.

I would make sure you do not have to much carbs for that motor. I have a 502 w/8-71 blower. I had 2 850 cfm carbs and fought the same problem. I messed with those 850`s changing everything and still had a rich problem. I changed to 2 750 cfm carbs and rejetted them and now I dont have a rich problem at idle. I forget which blower site it was but they have a formula to figure out cfm for a blower motor.

2-750's shouldn't be too much but, that depends on the build as well. Holley 850's are not great cards to begin with so that might be why you has issues with them. I run 2 Holley 750's on my 8-71 on a 388ci small block. I am also running 12lbs of boost and a healthy cam, heads, etc... I was told by a carb company when I ordered my carbs that they do not recommend anything smaller than 2-750's on a 6-71 or larger blower. I followed their recommendation and they were right on the money. Seems like a lot of carb but, the blower needs to breathe.

The problem with my 850`s was they were modified to flow 930 cfm each and they were on the motor which had bigger heads and cam than I have in it now. I tamed the motor down to run it on the street. Those carbs were fine for racing it and it ran great on the street but kept fouling plugs and it was killing my buddies when they cruised behind me. They always got out of there car coughing. LOL

But on that site it recommended 1500 cfm for my setup. It also depends on what input you tell their program. You had better go conservative and not bigger for the street.

[(D x R) ÷ 3456] x [(B ÷ 14.7) + 1] = C
D = Cubic inch displacement of the motor
R = Maximum engine RPM
B = Maximum blower boost
C = Maximum CFM required

Ill look into it with him tonight.. he out fishing right now instead of working on his car like he should be ;)..

The carbs that he got were recomended by Dyer's blowers for his specific motor.. wether they are right or not, who knows. It is all street car. no track use in the immediate future. Although I keep naggin him to get it out there. :)

Thanks for your comments all.

he had edelbrock carbs on it before, they are Demons now though.
http://webpages.charter.net/dragon0123/DSCF0549.JPG

The first problem I see right away is the timing. Blowers love initial advance, 12* is not enough. I would start at 18* it may even want more. The engine will run a lot cooler as well. I have my timing set at 18-20* initial and 32-34 total. You don't want too much total timing with a blower either.

See if that takes care of your idle and backfiring problems. If not then I would adjust the carb as Eric states, once you set the tranfer slots (VERY important), then adjust the air mixture screws with the car running at idle and warmed up, adjust for the highest idle speed, then you can lower the idle with the idle screw, you just don;t want to open the idle screw if you can help it once the transfer slot is set.

One last thing make sure noth carb are in sync. Meaning that they are both opening the same amount from ide to WOT.

Why does a blower motor need more initial timing? Maybe that is why I am having problems with mine not wanting to run cool at idle?

Why does a blower motor need more initial timing? Maybe that is why I am having problems with mine not wanting to run cool at idle?

My neighbor initially had iron stock heads before he rebuilt it. He had major problems with overheating.. Since he has put aluminum edelbrocks on I dont think its broke 180 deg.

Thats the first Ive heard of the more inital timing thing too. Can anybody explaine this for us. I didnt think that Boost wasnt a factor until WOT.. so why would it need more at initial when its just ideling anyway..?

The initial timing thing is no secret, yet many guys don't know about it. When I first set up my blower, I was running 12* initial, the headers would glow and it would run hot at idle if the outside temp was even warm (~80*). After doing some research I found out more initial timing would be the way to go. I bumped mine to 20* and the engine/coolant temps. dropped by ~20* Throttle response also picked up a LOT. I can idle in 100*+ temps and not overheat now.

While it's true you only make "maximum" boost at WOT, the blower still moves air whenever the engine is running. There is no way around that, this is why roots blowers make so much low end torque even before you see boost on the gauge. Since the blowers move so much more air and fuel, bumping the intial timing helps burn that fuel, instead of just making heat, it turns the fuel into power. With slow timing you are not seeing maximin performance and you are burning a lot of fuel in the headers instead of in the combustion chambers. The difference is a naturally aspirated car doesn't have 1500+CFM of carb sitting on top of the manifold (like a blower car does).

Musclecar, just go out and bump up your timing to 18-20* initial and let the car idle, then come back and tell me what you found. Since your distributor is probably not curved for 18-20* initial, I wouldn't recommend going out and jumping on it because your total timing will likely be WAY to high. Just fire it up set the timing and back off the idle (cause it will increase with the added initial timing), let the car warm up. You might want to wrap the throttle a couple times (not too much), you will be amazed at the throttle response. It doesn't cost you a dime to try it.

There are many old timers that ran/run magnetos on a switch and they run full timing at idle (not needed these days on a street car with the ignition products out there).

Once again I have nothing to gain, by offer my advice. I am only sharing my experiences. I have tuned a few guys blown cars, they heard how well mine starts and idles and doesn't overheat. I tuned them for free and each one was shocked, there was so much they were missing out on.

He is going to bump up the initial timing and set the stop with the 18 deg. stop in the MSD. what number should he shoot for on total advance..?? 34?? that would bump up his initial to 16. does MSD make larger stops.. 16?14? so he can run more initial..?

He was also going to change out to the lighter silver springs. Any thoughts on that.?

There is no vac advance on it.

Thank you all for your input.. it is very much appreciated.

I would want 32-34* total timing (with timing retard), and no less than 18* initial. The car can probably use less total timing at WOT but, if it's a street car 32-34* should be ok.

I don't know what bushings they have for MSD's you might want to research that.

Thanks for the info. I won't be able to try this until Friday. But as soon as I do I will let you know how it works out for me.. thanks

Garry

[QUOTE=camaroman7d]I would want 32-34* total timing (with timing retard), and no less than 18* initial. The car can probably use less total timing at WOT but, if it's a street car 32-34* should be ok.
QUOTE]

Well He changed out the plugs, changed the stop to the 18 deg one and bumped the initial timing up to 18..... The car ran HOT HOT HOT.... jumped up to 210 within a few min. of idleing. So he was in the process of backing it down to try to curb the heat, was also going to richen the mixture.. any other suggestions..?? I dont believe that he can run that much initial.

He is very concerned about the overal smog factor iof the car. On his initial build he believed that he was running waty too rich and washed out the cylinders and wiped out some bearings. Prompting him to rebuild it again.

How much more do blower motors smog over NA motors.?? I would think that they would be less because the fuel should get atomized better because of the blower.

So basicly this is what weve got..

timing at 12 = cool running, slow pickup, 11 in. vacuum
timing at 18 = HOT, quicker pickup, 15 in. vacuum


Thanks

I think you need to double check your timing marks. There is no way it should have run hotter with more initial. The only way I can see that happening is with a stock converter and the idle set too high. My engine temp dropped 20* by going from 12* - 18* initial.
Something was not done right for it to have made the car heat up quicker. Hard to say when I am not there but, every other blown car I have worked on have all run cooler with more initial timing. They also had better idle quality and throttle response.

Is he running vacuum advance? If so that could have been the difference. This actually sounds a lot like a guy was helping on another board (washed cylinders, etc..). As far as smog goes, if you are trying to be "green" a roots blower with 2 4 barrell carbs is not the best choice. Running them a little rich is not bad, it actually helps on a street car and pump gas (helps prevent detonation).

If he wiped the bearings out before I would want to be sure the ignition system is right and he is not detonating. Detonation will wipe bearings out in short order.

I just thought of one major thing. Is he running lean by any chance? That would explain the heating issue (with advanced timing) and the backfiring (that he was having before). That will aslo create more detonation and hurt performance (and the engine).

You need to set the timing correctly and then tune the carbs to take advantage of it.

im out of town for a few days here now but im sure hell be working on it..

No vac advance.. he runs a MSD distributor with a 6al box. MSD wires.

He was going to fatten it up.. I told him to worry about the smog secondary and get the timing and mixture for idle first. I think that it might be lean as well, and hes going to have to put up with the fumes. This car has never been a clean burner.

the only other thing I might add is that we were partially turning out the mixture screws and the Vac. was going down. Which blows the whole theory of "tune the carb to the best vac setting" bit.

Thanks for your advice..

Mark

Sounds like there are some carb issues that need to be worked out. If you could close the idle mixture screw all the way and the engine still ran/runs, there is a problem. The idle/vacuum should increas a bit as you turn them out, at some point you will go to far and the idle will fall off, turn them back in until it's at it's highest point. Also when tuning two carbs on a blower you have to go around several times to get it right. From the info you are providing, there are definetly some tuning issues. Your buddy needs to start from square one, and get it dialed in. It really shouldn't be any more difficult than a single carb on a naturally aspirated engine, you just have to do things twice. One other thing that MUST be right is that both carbs are opening the same amount at the same time (syncronized). If the linkage isn't adjusted right then you won't get both carbs to do the same thing and that will make tuning harder.

Use the black bushing supplied with the MSD distributor.. that will give you 18 degrees in the distributor. If you set total timing at 36, your inital is then 18 degrees. If you set total timing at 34 degrees, the initial timing will then be 16 degrees, etc.

How did it run with the old edelbrocks? what size were they?

I'm the neighbor of dragon0123 with the blown 400 Pontiac problems. I have twin mighty demon 750 double pumper blower carbs on a 6-71 dyers supercharger. Perhaps I have been a little reserved when tuning my engine due to the recent rebuild from washing out the bearings. I had twin 600 Edelbrock's and changed afer the rebuild. I've been adjusting the timing as camaroman7d had suggested from 12* to 15/16* and the idle mix screws as well. I am a little aprehensive when adjusting the mixture screws and stop opening after 3/4 of a turn each. I get a blue haze in my garage and the strong smell of fuel. The idle is satisfactory and doesn't hesitate when I crack the throttle. My vacuum is @12 when I set the initial timing at 15/16*, but the temperature rises above 210 at idle sitting in my garage in short time. Tonight I took the car out on a run for 30 min and it didn't run any hotter than 180 and the engine responded well. This is with the timing set at 13/14* and mixture screws set at 3/4 open. I didn't beat it, just tootled around the back roads around 40 mph stepping into it occasionally. As soon as I returned home the temp raised another ten degrees. I have the 18* advance stop bushing in the distributor and the lightest duty springs (silver) for the counter weights. I know this isn't rocket science, but man am I getting frustrated. Maybe I'm being too cautious. My question for camaroman7d is: Should I have a rich condition at idle enough to visually see a blue haze for the blower to be working normally? Do you run 20* cooler at idle and the car not moving? And last, what good are the "idle ease" adjustment screws on the carbs for. Sorry for all the questions, but you seem to have a pretty good grasp on what the heck could be wrong with my pontiac. No offence to you other guys. All of your responces have been a great help as well

Fullblown,
Glad you singed up, this is a great board with a lot of knowledgable people.

No, you should not get smoked out of your garage. You should have any haze or blue smoke at all. Do your headers glow? I am a Holley guy myself and Demons are a little different to tune and they can be quirky. When I first set my blower up I ran 12* initial, I thought the car ran great but, it would get hot if idling in traffic or sitting in the driveway on a warm day. Once I bumped the timing up to 18-20* the engine temp dropped 20* while idling in traffic or in the driveway on 100*+ days.

What are you running for a cam? If you have the specs please post this could be an issue but, I dount it.

Right now I think your problem is 95% the carbs and 5% timing. You should not be affraid to turn he air mixture screws out more than 3/4 turn. I usually start out with mine at 1 1/2 turn out and tune from there. You need to make sure your power valves are not opening at idle (or that they aren't blown). After that you need to make sure you are not pulling from the main circuit at idle (this is set as Eric68 posted on the first page). You might want to talk with him about your Demon, I know he is running a Demon and he is always on top of things. Have you called the BG tech line? You may also want to try calling The Blower Shop ( www.theblowershop.com ), they sell and run Demons/BG carbs and are great guys to deal with.

Hang in there, you will get it figured out. I wouldn't drive it too much until you get the tuning dialed in. Keep an eye on your oil too, if you are that rich at idle you could get gas in your crankcase.

You might want to do your tuning outside, almost any hot rod will run warm in the garage with no air flow.

Tokyo,
Where do you have your timing set?

600 edelbrocks?..too small and a far cry from the carbs you have now, on a wet flow basis, that is like running twin holley 500's. If you are still very rich and are at just 3/4 turn out from closed on the idle mixture screws, it looks look you may need to change some jets. Are you using a vacuum guage to adjust the screws or better yet an A/F guage? I use both.

You should see not blue smoke..too rich and the reason you washed your bearings with gas. I tune the primary circuit/ air screws just like an NA motor and get 17-18mpg. I try to get at least a 14:1 A/F ratio at idle.

Royce: I have 18 in the distributor (black MSD bushing) and 18 initial for a total of 36 degrees.

Royce: If you have an MSD distributor, what springs are you using on the centrifugal advance? How fast do you bring it in?

Mike,
I run a Mallory magnetic distributor. My timing is all in by 3200 if I remember right. Once I fire it back up I will let you know for sure. My total is 34* and my initial is 18-20*.

The reason I asked about your timing is, this (the engine in this thread) is the first blown engine I have ever heard of that ran hotter when the initial timing was advanced. I talked to a couple other guys and they are all in the 18-20* range as well. Guys with magnetos are running 28-30* (no advance).

As far as jetting on his Demons, he shouldn't even be on the main circuit until the throttle is cracked. He is way rich at idle, that tells me his primaries are more than likey open to far, which will pull fuel from the primaries and cause a rich idle condition. One other thing I just thought about, make sure you don;t have fuel dripping out of your booster at idle, if you do you probably have your float level too high or trash in your needle and seat.

I'm running a crane cam .458/.473 lift with 288/296 duration and 114 lobe seperation. Dyers recommended this style grind and most importantly the widest seperation I could get. This is what I came up with. I was also wondering about the plugs I'm using. Does it matter if I use hotter plugs? I currently am running two stages hotter plugs than stock. Another suggestion from Dyers Superchargers web site. The Barry Grant carbs came with a video which I followed to the "T". They mentioned if my mixture screw adjustments fell outside the initial setting (1-1/2 turns open) and I had clean exhaust and no off idle stumble that I would probably be o.k. With the 21* stop bushing installed and the initial timing set at 12* with the blue advance springs and the carbs adjusted to 1/2 turn open it ran o.k with temp readings in the low 170's. It just had no power and felt like I was dragging an anchor. I have my carb bowls set to the middle of the sight glass and no fuel dripping out of the squirters at idle fuel pressure at 6-7. I'm going to pull the bowls tomorrow and inspect the float seats. Sometimes I fluctuate fuel pressures from 3psi to 7psi when running or at idle. Any Ideas?

I just read a few past threads on demon carb tuning and a light bulb shattered above my head when I read about the initial primary and secondary slot settings. I know for a fact that my slots are set beyond the recommended .020" square gap thus causing the over rich idle condition. I initially had the slots adjusted correctly but didn't like the way the motor was starting so I opened the slots a little more instead of opening the idle mix screws (another reason why I can only adjust the mix screws 1/2 turn max). I can understand why my neighbor comes to these threads with his problems and questions. All you guys and gals are knowledgeable and have lots of great information. I'm gonna try this theory out tomorrow and get back with my findings.

Sounds like your rich idle has been figured out. Your cam specs are fine, I was concerned you didn't have a wide enough LSA which why I asked. When I asked about fuel dripping from your "boosters" I am not talking about your "squirters". At idle you shouldn't have any fuel dripping into the carb (above the throttle blades), if you do then that would point towards a float or needle and seat problem. You shouldn't have to remove your float bowls to inspect and clean your needle and seat, I now doubt that is the problem (as long as no fuel is dripping).

As far as fuel pressure fluctuation, Are you running a mechanical pump or electric? If it's mechanical and your idle is erratic or surging, then your fuel pressure would do the same. Does the fuel pressure even out once you are at a set RPM (cruising)?

I readjusted the throttle plate gaps last night and it didn't change much at all. Actually, it got worse. After reading more of the set up manual Barry Grant sent with the carbs, I learned that my rich idle probably isn't because the throttle plates were open too far, which is what I thought, but the idle feed restrictors might be too large. This might the reason why I can't adjust the mixture screws open more than 1/2 turn without gassing me out. Also, I learned that the .020" air gap is a good "starting point", not carved in stone. If I understood it correctly, I could open the air gap more if required. So I did. The responce was better when cranking over. Vacuum increased to 14/14-1/2 and had a nice idle. I'm going to contact Barry Grant tech support Monday for more details. I'm not giving up without a fight! I'm going to disect this problem until it begs for mercy!

True the .020 is a starting point but, you don't want to open it very much more if you can help it. Once you get those carbs dialed in you will have a great running car. The Demon carbs can be a handful to sort out. I think calling tech support is your best bet.

I checked out the Barry Grant website and noticed the Mighty Demon was for radical camshaft and racing combinations. Even though they recommended the mighty demon app. I could have ran with a speed or road Demon. Yes, you are right about the throttle plate being open too far. I adjusted them only 1/8 to 3/16 turn wider to straighten out the idle and starting condition. I initially set them a little on the reserved side of .020". Did you find any information about running hotter plugs?

Thanks for all your help so far-
Ratt

Spark plugs will depend on the application. You typically will run a cooler plug with a blower or nitrous, not a hotter plug. 1-2 ranges cooler than stock. You will have to keep an eye on them and adjust your heat range as needed. How much boost are you running? Sorry I missed the spark plug question before.

Hey there Paul.. Mark here in Florida.. I was reading as well that you should be using 1-2 steps colder plugs.. not hotter... We'll be back tomarrow night late.. Hows the Dogs, and other critters.. Thanks again..

Barry Grant said I needed a vacuum reference on my primary power valves. I was under the impression that blower carbs were designed so that vacuum reference wasn't needed. I took their advice and it made matters worse. I only had the mix screws 1/2 turn open and the exhaust looked like I had them all the way open. I can't win

This is a good example why it is worthwhile to have a carb shop calibrate the carbs for your specific set up.

When I initially ordered the carbs, they asked specifics about what they were being applied to so I was under the imperssion (again) they knew what I had under the hood. Im going to set the .20" air gap tomorrow and try some more ideas. Camaroman7d has me thinking about my plugs and how hot they are running. I have a hunch that when I change to a cooler running plug, I will be able to set my timing to 18* without boiling over. I really don't like the idea of vacuum referencing my carbs. The whole reason why I bought these things was they were designed for blowers and had boost reference not vacuum referenced power valves!

I can recommend a place ( www.allcarbs.com ) to get a set of blower carbs. I know that's not what you want to hear right now but, I know for a fact they will work GREAT and be easy to tune. You might even be able to send them your Demons and have them "set-up" for less. I just checked their site and they do work on Demons as well, might be cheaper to have them go over your carbs. You really don't want to ruin your engine over a bad tune up. There are some issues with your carbs no doubt.

I contacted Barry Grant after trying to vacuum reference the power valves and finding out it wasn't working. They said there is a problem with the valves themselves. I took the carb bowls back off to verify this belief and found the valves to be o.k, but the valve seats had metal fragments from the machining process stuck to them. I studied the how the valves operated and determined the boys at Barry Grant were right. There's no way these valves could possibly work correctly without a vacuum source. The were staying open all the time (hense the richness issue). After playing with them and making sure I didn't over look anything, I put the bowls back together and tried them again. They worked great! I changed my advance stop bushing back to 21* and lowered my initial advance to 12*. No more over temp and no more misquito fogger. Was also able to open my mixture screws as well. Problem solved. The back firing issue was caused by faulty plugs. Specifically #5 and #7. I changed them to one stage cooler than stock and gave it another oil change. Now I can enjoy driving my car. Thanks again for all the help you have given me! I'll keep in touch! I'll post some pictures!

Ratt

Ratt,
That's good news. Thanks for coming back to post the results.

Yeah Demon went through a spell with lots of metal chips. I am told that has been fixed, but if you have a 1-2 year old Demon you might check it. That includes time sitting on the shelf or in a warehouse waiting for you to buy it ;)

glad to hear that you got things all sorted out. Sorry to hear about another demon carb full of metal chips.

I know this is old BUT!

This was a very good Post with many good suggestion we should have a Blowers section.

Good suggestion. Maybe a blower, superharger, nitrous section... however that pretty much is already covered under the performance catagory.. although I would read it daily... :)

On a side note.. we took his his TA for a dyno run in september and it made 418 RWHP.. Still some tuning left to do, and he only wanted it reved to 5600, but we got it out there at least. You can check out the runs on my website in my sig..

Mark,
Gotta love the torque of the roots blowers. Looking at the dyno sheet it's funny to see how the torque shoots up and just stays there. Pontiac 400's aren't typically high reving engines. How much boost is he making? The sounds good and healthy.

Think hes running about 10-12.. he needs to drive it more.. I try my darndest to get him to get it out there. We live in wisconsin so there is a certain window of driveability here.... Like not yesterday when we got 2 inches of snow....

Anybody know off hand what he would need with the blower to pass tech.?. Im going to try to get him to take it to the track.. Aluminum housing bolts he has.. blower straps needed..???

Any guesses on what it would run on 15" street tires..?????

Smoke and burning rubber are not acceptable answers....!! ;)

What it runs will totally depend on traction. A 10 second car with poor traction becomes a 14 second car pretty easily. Traction will be the challenge, what kind of tires and suspension does he have? If they are regular street radials he will be very lucky to run 13's if he has decent tires then that will make a huge difference.

As far as tech for a blown car, there is nothing special needed since it's a street car running pump gas. If the car runs 9.99 or quicker then all oil lines and fuel lines mut be shielded where they pass the supercharger drive belt. Meaning protected in the even of a broken blower belt.

Traction will be the challenge, what kind of tires and suspension does he have? blower belt.

Regular old 15 inch street tires (bf goodrich i think) Maybe 10 inches wide or so.. Dont have the exact tire specs handy..

Stock suspension, stock driveline. t10 stick. centerforce clutch. Made 418 HP RWHP last year.

Ok in that case I say very high 13's to mid 14's. Not trying to be funny but, in all honesty there is no way he will get that car to hook. Making things worse it's a stick car. Just tell him to be careful, he will have his hand full. I personally wouldn't bother to go to the track with regular radials on that car. Bare minimum he needs ET Streets (not radials, because it's a stick car). Only way to know for sure is to go run it I guess.

I know that this is a very old thread. But I had to say, Thank you.
After reading through it. I was able to get my blower car going, and going good.
I have been beating my self up trying to get this thing tuned.

I went all over the net looking for some good info on my blower motor, and nothing good came up.
Until I started reading through this thread. There was more helpful information in this one thread than in any 10 combined that I found.



I just wanted to say thanks to the people that post on the site.

.I made a short video of it running.

Travis

Travis,
The car sounds real good, nice job. Finding good roots blower info is kind of hard. There a lot of them out there but, not many that really run to their potential. I hope I was in a small part able to help. Feel free to PM me if you ever have any questions or issues. I don't know it all but, I will help where I can.

Travis..I like the Detroit roll you have and find my blown big block has better throttle responce with some roll/surge.I can tune the roll out for a steady idle rpm..but it is not as responsive off idle if I do so.

Camaroman.
A lot of the tuning I used came from some of your post.
I thought I knew a little about blowers. HA,, I have a lot to learn.
Thanks again.



Fatblock.
I have tuned about 90% of the surge out. I found it sounds cool, but with the 2500 stall I have, it's not too street friendly.
I found it a little easier driven around town with the surge cut down to a minimal.
That surge does make people look when you pull up to a saturday night cruise.



Travis

Travis..I like the Detroit roll you have and find my blown big block has better throttle responce with some roll/surge.I can tune the roll out for a steady idle rpm..but it is not as responsive off idle if I do so.


George mine is the same way. Doesn't respond nearly as well with the surge tuned out. I can see how a2500 stall and surge could be an issue. I have a 3500 stall and the surge doesn't bother me a bit.

Travis, out of curiosity what is the range of RPM's for that surge? Rough estimate is fine.
Thanks.

The rpm surge in the video is almost 1000. Way too much to drive.
I have got it down to around 200 to 300 range.

The motor is a 30+454,,, 8.25 to 1,,, 8.71, 5psi boost,,, two 750 Holley's w/75jets in the front and 76 in the rear,,, all msd,,, 350th w/2500 stall.
I set the timing per earlier post in this thread.

Motor runs about 180 driving, and goes up a little when I am sitting at a red light, but then goes back down when I start going down the road again.

Does this combo. sound ok to you guys?
Is there any thing that I should change or add?



Travis