I'm hoping to get some input on the results of my chassis dyno run. My combo is as follows:
383 10.1 compresion(i'm told), Canfield Heads 2.05/1.60 valves, 65cc chambers, 195cc intake ports
AFR dual plan intake
hyd cam is 224/230 lift(1.6 rollers) is 520/522
Holley 750 vac secondary
1 5/8 thorley headers into 2.5 inch flowmaster exhaust
700r4 with 2200 stall
2.73 gears
After some basic tuning, my best pull so far is a disappointing 264HP 371TQ. A/F is spot on. I've played with the timing, plug gaps, switched to an edelbrock 750 etc. Cyl pressure is about 170 psi across the board. Car runs pretty decent despite the lack of power. It only pulls about 6-7 inches of vacuum at idle but I can't find any vacuum leaks. Is there anything that I am missing? Would the gearing impact the result of the dyno run?(i have 3.73's ready to go in) I was expecting about 350-375hp and about 400 ft lbs.

What rpm were these recorded at?
If HP is low at higher RPM and torque is good, your probably running out of fuel flow.

Just a guess but I'm thinking 300-325 at the rear wheels is where you should be. Check your valve adjustment, too much preload dropped my vacuum by 2-3". I set mine to Comp spec's - 1/2 turn past zero lash and got it back.

Advance curve comes to mind and the amount of total you are running, more isn't always better. My experience is strokers like less total, try around 32 all in by 3000 rpm. You can pull it all in sooner but gas being what it is today you might even slow it down to 3200 if you have too.

Another thought along the more the better not always being the best, you have huge intake valves, ;) maybe you are dumping in more than you can pump out... If that is the case exhaust port work or a bit larger tube header may help.

I'l be picking up the graphs tonight and I will attempt to post them. I believe the HP peaked at about 4800 rpm but I'll need to check. If there was a fuel flow problem at high rpm, wouldn't I see a problem with the a/f going lean?

I'm definately not an expert, but I'm gunna guess that the people who really are are going to say that:
"the cam is on the small side, where you aren't taking advantage of the heads you ported. Basically you have a motor that is set up to breathe really well(high-cfm heads and bigger ci), but the cam and (possibly) the headers are holding you back."

It might be helpful to tell a little bit more aobut the HP/Torque curves...especially where max torque and HP occured.

It's just a guess graemlins/clonk.gif

EDIT: in the time it took me to post this, 3 people already replied...

I'm thinking the same way as sik but, I'd expect a few more RWHP even with this setup as is. I think the cam duration is a bit short and the 1-5/8 headers are kinda small for a 383 w/Canfield heads.

Are the secondaries opening all the way on the carb?? What is the ignition timing doing?? did you check this stuff while it was running on the dyno??

Paul D.

thanks for the input guys. DJD, i've gone through the valve adjustment twice thanks to your input from a prior post about my vacuum issue. It hasn't helped at all. I was hoping that the dual pattern cam would help out in the exhaust dept a bit. Timing is currently at 34* all in by 2800 (msd 8360 with blue and silver spring). I tried timing from 32 up to about 38 and it seems to like 34 the best.

6 - 7 inches of vacuum at idle with that short a cam? That doesn't sound right to me... :confused:

I agree that the 1 5/8 header's are a bit small for getting good upper rpm HP. How about the tq #'s. They seem a bit low too.

I agree John. I'm glad you responded. AR racing out of summerduck did this motor too. I can't figure out the vacuum either.

You're only about 25 hp short of an average 383 chassis dyno. The gearing won't make any difference in the horsepower as the dyno takes care of these calculations.
Did you notice if your secondaries opened fully? We've had gains of over 20hp by manually opening the secondaries during the pull.
Your vacuum seems very low for a mild cam like that. It should be in the 13" range or better.

That does sound low, I'm pulling around 12 with a 230@50

What is the LSA on the cam if it is 106 or 108 that may cause low idle vacum.

Greg I thought this sounded familiar but couldn't recall why! Your cam is not all that different than mine an I make about 13" at idle in gear... graemlins/clonk.gif I remember now!

Was your timing assesment based on dyno runs or seat-o-the-pants?

I know guys that have lost large amounts of HP because of torque converter choices. Not stall speeds so much as inexpensive vrs higher quality units. I even have heard guys complain after going to a 700r4 or 2004r about power loss...

Just more places to look into but I think your vacuum is the big issue. Did I suggest putting 1.5:1 rockers on in place of the 1.6's? Might be worth a try to see how it effects you'r vacuum. Oh, what is the cam grind or part number you are running? Mines something like CS-280-H10...

I was told that the cam was a on a 110 lsa. I do not know the part# but was told its a custom comp cams mucle car grind. I'll get another vaccuum guage and retest to make sure its not the guage that is the problem. DJD, why do you feel that the 1.6 rockers are the issue? Just curious. I can swap my old stamped rockers back on if I have to to test your theory out. The tranny and the converter only have about 2K miles on them, but I am starting to think that its the converter too since everything else (besides that vacuum issue) seems to be fine. The timing settings were done on the dyno. The secondaries seem to be opening all the way. I'll check that out tonight.

one other thing that made a big difference was opening up the spark plug gap. Opening up the gap from 35 to 50 netted me about 20HP. Thats the last change that got me up to 264hp. could the fact that the motor is just past break in cost me this much hp?

Since you have a 700r4 you could rig a 3rd gear lockup. If there's excessive slipage you should feel the difference.

Greg - I question your cam spec's... I theory is you have been quoted and are quoting numbers based on 1.5 rockers not 1.6's. If so that means your cam is 224/230 - 520/522 with 1.5's. The lift then would be 555/557 and your duration would effectively change as well due to the higher lift. To compound things, stamped steel rockers are usually 1.4 something not a true 1.5 ratio.

If you put the old rockers on and start making 12-13" of vacuum you can eliminate a lot from this equation...

I read this post and got a question off of the subject, but here goes. I was planning in the future of buying a motor from the place in summerduck also, and kinda got confused after reading this post. When they advertise 450hp, 489hp on certain engines, which HP do they mean? RWHP, engine HP?? I don't want to buy a 450HP advertised engine and be disappointed at the performance.

Kevin

For comparison, a friend has a 406, with afr heads and the Comp 224/230 cam made
440hp@5200 and 500tq@4000 on an engine dyno. The 406 pulled 18"of vac.
so I would think yours has a vacuum prob somewhere. I dont think the 1.6 rockers
are hurtin you because the cam is pretty mellow. I'd throw a 750DP on and try it again,
your missin some power somewhere. But the best way (aside from dynoing the engine)
would be to run it at the strip, look at the mph and the weight of the car, that will
give you a pretty honest indication of how much power the engine is makin, and
if its where it should be. The above 406, is in a all steel 70 Chevelle, and runs 12.0@111,
so a lighter camaro should run about the same or better with a 383.
Good luck. graemlins/thumbsup.gif

DJD,cam lift quoted to me for 1.5 ratio was .488 .490.

I'm planning on getting some track time once I get the posi and 3.73's in it. Oh, and I also need to get seatbelts! I'm thinking about pulling the intake and putting a new gasket on it to rule out the possibility of a vacuum leak there. Man, its frustrating. thanks for everyone's input on this.

Also I have a 383 with a Comp hyd. roller - 224/224 on a 114LS,
it pulls 18-19" of vacuum. The cam is more aggressive then yours, but
its also on a wider LSA, so its similar. This one made 490hp@5900
and 495tq@4500 if youre interested, but I dont know what that may
be at the wheels, but I also dont put too much faith in those rw dynos,
just too many different variables with diff. drivetrains.

Looking for an internal vacuum leak is a good idea... Check the link below, your cam grind (hyd roller right?) sure shows a lot of duration for the amount of lift when compared to the list of grinds shown. Everything in the same lift seem to be around 206-218 range except maybe what they call 4x4 cams...

Scroll down for the roller cams.

http://www.compcams.com/Technical/CurrentCatalog/HTML/128-169.asp

DJD, its not a roller. Specs i was given seem to put it close to the XE268 but with a bit more lift. I'm hoping i can get the cam card from the builder.

I agree that there is likely some kind of vacuum leak. My old 350 with the same cam (XE268) made 12-13 inHg at idle. Yours should make more.

I also question the cylinder pressure. 170psi seems pretty low for 10:1, XE268, and 383 ci.My current 10.3:1 406 with a Comp HR282 makes 200 psi.

On a Dynojet my 406, dual plane, 800dp, Fastburn head motor with a really crappy tune made 350hp/400tq.

Greg, I have a 406<est. 400/400 @ flywheel> DD2K shows very close to same, and a program I DL'd show very close too. CC280H<230@.050/.486I/E & 110LSA>I was only pulling 6-7" of vacuum too with a 750 3310VS very modified<830cfm est.>. I changed to a box stock 4779 750DP and now pull 11-12". I have no idea why...maybe the smaller venturi's? See if you could borrow one from the shop or a friend. Seat of the pants dyno showed big improvment, but haven't been back to track yet.

My best 1/4 to date is a 13.51@101.7 w/ 2.73posi. This shows about 265 RWHP I think it was. So I think the dyno is near right.

[ 06-09-2004, 06:25 PM: Message edited by: DOUG G ]

I agree the cranking compression is somewhat low. I run a 300+ degree cam, and I'm at 220-230PSI. Sure I'm running 12.5:1, but even with 9.5:1 and a Crane 266 cam in my old 355 it had 175-185.

As far as the low vacuum goes, have you tried another gauge? Sames goes for cranking compression.

GReg,
I also have a 383 from AR.. Drop me an email lets talk.. Ed kroppel@swbell.net

could the low cylinder pressure be due to the fact that the engine has just finished break in?maybe the rings have not fully seated?how many miles are on it?
Eric

Ok, my @*%$ vacuum gauge wasn't working.. I'm actually pulling about 17 inches of vacuum. My car went into the dyno with a minor oil leak.. Suspected the rear main seal. Picked it up last night and on the way home the rear main went on me. Oil was practically pouring out. Ugh! I have less than 500 miles on the motor.

[ 06-10-2004, 06:38 AM: Message edited by: GregD ]

Good, so that eliminates the vacuum problem.

Did you recheck your cylinder pressure with another gauge?

Actually, if I were you, I'd forget the dyno numbers to go to the track and see what it does. I think that will tell you more of what you want to know.

The guy at the shop did the checked the cylinder pressure. So the 170 psi is accurate. I do intend to get to the track at some point but need to do a few things to pass the safety check. The rear main leak is going to set me back a bit. Based on everyone's feedback it seems like my compression might be lower than advertised by the engine builder. Also, I'm going to degree the cam so i can be certain as to what i have there too. Lesson learned, have a local shop build the motor and get documentation to prove whats in there. I'd stay away from these ebay specials.

Kevin,
I didn't see your post. As far as purchasing from the place in Summerduck, I know at least 3 people on this board that have had some major problems with their motors. Here is another link to give you an idea of what i'm talking about.
http://www.camaros.net/forum/ultimatebb.php?ubb=get_topic;f=4;t=006974#000001

Good luck getting it straightened out Greg. I really hope my engine doesn't blow up...

i think you need a carb spacer for the first thing.
then a stouter cam.
your vacum is way too low?
check for vacum leaks aswell.

Followed this thread for a while, waiting to see the outcome. Interestingly, last time I checked their ratings, they sure smelled good, but we have TC memebers that have problems with their equipment?? Hmmm. I always figured that you get what you pay for. I could never figure out how they could build for so cheap.

Greg, are they willing to fix your rear main problem??

Greg D ( too !)

I had similar results. Except I have a 350 ci with the holley systemax package /750 holley proseries,400 turbo tranny. I dyno's 278 wrhp/378 wrtq. They say if your convertor is slipping it will cause that

I haven't even been able to get in touch with the shop in Virginia. I have left several messages and called several times and have gotten no response. I'm going to eat the rear main seal and pray that the leak isn't the result of some bigger issue(unbalanced crank etc.) The guys at the dyno shop did a great job and it drives 100% better than when i first brought it to them. Has some good power but I was expecting more. I have the dyno but I don't know how to post them.

OK, I have some good news. I haven't had much time to even look at the car laterly. This weekend I got into it and it turns out that it isn't the rear main seal (yeehaw!) I had used a 2 inch long brass fitting for my oil pressure sending unit in order to gain some clearance over my intake. Well, I think the guys at the dyno shop must have hit it accidentally because it had cracked at the threads. The oil was leaking down the back of the motor. I assumed rear main because of the amount and location of where the oil was leaking. Thats the good news. Bad news is that my car won't shift into second gear. Winds out in first and eventually goes directly to third. UGH!!

A tranny problem certainly could explain the low rear-wheel numbers. The engine may be just fine and the power is getting eaten up in the drivetrain.

Just a thought.

Eric, I hope you're right. Dropping the car off wednesday to get the transmission looked at. Less than 600 miles on it. I'll keep everyone posted.

You didn't knock the vacuum modulator hose off when you were back there fixing the oil leak did you?

Greg, the 700r4 doesn't have a vacuum modulator. Good thought though.

Originally posted by rojo:
Greg, the 700r4 doesn't have a vacuum modulator. Good thought though. There you go.............he must have knocked it off. :D

I figured I'd give everyone an update. I got the car back from the transmission shop last night. 2nd and 3rd gear clutch packs were toast. They took care of me even though i suspect that the dyno shop screwed up the TV cable adjustment and subsequently burned up my transmission. I took off the holley 750 and put on my edelbrock 600 just for the heck of it since I have not been able to get the car to run right with the holley. The car drives so much better now its amazing. Idles smoothly, has crisp throttle response etc. I know its a bit small for a 383. This car will rarely see the track so will I be missing out on much performance if I stick with the 600?

I've wondered how they run a 3rd gear dyno pass on a 700r4 when it's not going to stay in 3rd when you nail it at a low rpm. So does that mean they messed with the TV trying to keep it in 3rd. Hmmm...., if so that's something for us 700r4 guys to watch out for.

Greg
I'm gettin my 200-4R and the trans guy told me that the Holley and carter/edel.
tv cable brackets are different. I didnt reread the whole post but if you switched
carbs and not brackets that may have cause the trans to burn up. But I've never
had one of these OD trans so I'm not sure.

Originally posted by 67RS502:
Greg
I'm gettin my 200-4R and the trans guy told me that the Holley and carter/edel.
tv cable brackets are different. I didnt reread the whole post but if you switched
carbs and not brackets that may have cause the trans to burn up. But I've never
had one of these OD trans so I'm not sure. They are different but not likely to cause a burn up. As long as the TV cable starts to pull the plunger as soon as the throttle moves and is completely extended at full throttle then there shouldn't be any melt down. The linkage (brackets) determine the arc swing to control the personality of the trans, shift timing, firmness, etc.
Now if someone unhooked the TV cable and did a full throttle run that's a different story. Here's some good info (http://www.tvmadeez.com/article/index.php) .

Thats precisely what happened. The jackass unhooked the TV cable so that the trans wouldn't downshift. I'm working with them on getting some form of reimbursement. Any thoughts on the 600 vs the 750? Boodlefoof, hopefully this takes a load off your mind a bit as my car runs much better now. not sure if I'm making the power that was advertised but it sure feels strong.

I have a 383 that sounds similar to yours, and I was convinced my 650DP Holley was too small and that I needed a 750 until I read this article:
http://www.chevyhiperformance.com/techarticles/148_0403_choose/index.html

I decided that it wasn't worth $400-500 to pick up about 3 horsepower.

As to the diff between Edel and Holley I can't speak - but the diff in CFM rating as far as horsepower/torque are concerned from 600CFM on up was minimal. Very interesting read.

coincidently, I took my '68 Camaro to a chassis dyno last Thursday. I have a 700r4 as well. On my tranny, whatever gear you select with the gear shift, is as high as the trans will attain.

When they let me "drive," I put it in 3rd, started giving it gas, and felt it "rock" into each gear. I then reached 55mph and then punched it to 130mph and let off.

Like most, the results weren't as high as I had been led to believe. But a lot of fun, impressive to stand by as the beast wound its way to 6000rpm, and was happy the engine behaved and didn't complain (throw a belt, valve float, chatter, etc.)
graemlins/thumbsup.gif

So, how did you do?

Thanks for the update. That is a bit of a load off my mind. My 355 seems to run well too, but after hearing some other stories, I was kind of curious if it was going to last... we'll see. Thus far I am very pleased with mine.

Greg - if you switched carbs after getting the car back from the trans shop, how did you deal with the TV setup and adjustment? Both carbs require completely different geometry to make the TV work properly. Just asking as I would not want to see your trans get dammaged again...

With your luck, we must be related ;) I am also curious what setup you are using for your TV bracket. I ended up getting a setup from BTO (bow tie overdrives) that works slick and was easy to set up too.

I'm glad to see all you OD trans experts on here, because I just picked up my 200-4R
but wont get the converter and brackets, lock up switch and all... for a while, but once
I do I may need some help gettin all of it to work since I've been a TH350 guy so far.
This thing cost me $1250 (so much for trying to find a cheap 2004r) and handles 550+TQ,
so I dont want my mild 383 to burn it up.

If the "so how did you do?" question was directed my way, I guess I can confess.

I had about 230hp and 272 ft/lbs at the rear wheels. The engine was rebuilt by a semi-local shop about 10 years ago and with that cam and the heads he set me up with, HE was claiming I'd get about a horsepower per displacement inch. (327+) Obviously, it cam in about 100 short.

This was on something called a Mustang dyno (darn Fords have to insert themselves everywhere don't they?) They also admitted that it comes up about 50hp shy of another one (and another brand) about 20 miles away.

Anyway, they seemed impressed with my car and said it performed well. They must see some real doosies.

I ponied up for the tuning session as well - it was already strapped up, might as well. They determined based on the air/fuel readouts that my secondaries were too rich and the idle was a bit off. We dropped the secondary jets from 78s to 75s and left the primaries at 71.

That plus the minor adjustment netted about 30hp on the top end. It was very noticeable when I drove it around the block. It seemed to find another set of cylinders around 3000rpm.

In a little bit, after I gather all the specs, I'm thinking of starting a thread and directing it towards the gurus of this board soliciting opinions about what in my setup is out of synch with the rest. It seems that with all that I have in the engine/tranny/rear end, it should be a little quicker. Or maybe I'm getting exactly what I should be - hopefully I'll find out once and for all.

Ozzie

Originally posted by DjD:
Greg - if you switched carbs after getting the car back from the trans shop, how did you deal with the TV setup and adjustment? Both carbs require completely different geometry to make the TV work properly. Just asking as I would not want to see your trans get dammaged again... While I had the car at the transmission shop I swapped carbs and asked them to set up the TV cable for me. My intent was just to try the carb out expecting to go back to the holley. The car ran so much better with the edelbrock that i decided to leave it on for now. They had a special bracket that connected the TV cable to the throttle linkage for the edelbrock carb.