I took the car back to the track today. Tranny is fine, I put a 9.5" BTE super bracket converter in last weekend. My old converter was about ready to fall apart. Put fresh fluid in tranny and everything was good. I also got a new Mallory distributor and fixed the advance issue that I had. Today I took it back to the track and the car ran the same 13.58 @ 98 mph. I checked everything, the lash is still tight but there is copper all through the motor and my oil pressure finally started to drop. The main bearings have been going away in it and today I think they reached their worst point. The motor feels like it doesn't have the power it should and it still doesn't rev like it should. It wouldn't hardly go past 6000 today. I'm pulling the motor out, checking the crank to find out why my main bearings went south on me. I am putting flat-tops in it to bring the compression down to 10.0-10.5:1 max. I'm thinking maybe my dome pistons are killing the flame travel in my cylinder. Pro topline recommends flat tops with all their heads. I'm also changing the cam to a custom grind. With that said, I need a recommendation for a solid flat tappet cam for this motor. I don't really like the 294s, I think I can get a better grind for it. I will also degree this cam in. I remember someone said about my cam being off. Too far advanced or retarded. I installed the cam straight up, but is there a possiblity that it was ground off by Comp? This new cam still needs to be in the same area since I want to keep the new BTE converter I just got and everything else will be the same in the motor. I would appreciate it if someone could help me. I know many of you guys are very knowledgeable when it comes to cam grinds, etc. Basically my combo will be as follows:

355 small block
10-10.5:1 compression
200cc Pro Topline heads
Air Gap intake
750 double pumper carb
1 3/4 headers - 2 1/2 exhaust
4000-4500 9.5" converter recommended by Steve Oldani

This car should run mid to low 12's no problem. All I need is a good solid cam grind. This motor will go on an engine dyno to break in and tune so I will be able to get exact numbers this time. If I left anything out let me know. Thanks for everyone's help.

I would keep the 294s cam, unless it is trashed from the bearing material floating around in there. Get the compression down to about 10.5-1, and I think you'll have a hard running engine. Of course, it should have run hard before too. If you can, post some pics of your pistons after you get the heads off...I'll be curious to see what kind of burn patterns are on the pistons.
One thing to keep in mind too. I don't know if you checked the valvetrain geometry or not, but with my 200cc pro-toplines and a regular base circle 294s cam, I had to use +.300 pushrods to get the geometry right...it was WAY off with stock length pushrods.

Since your going thru the lowend now, it would be a good time to upgrade to a 383 graemlins/thumbsup.gif

if you have dome top pistons and are running pump gas, i'm willing to bet detonation hammered those bearings badly.

Not that domes would do it, but i'm thinking you have alot of compression.....have you tested actual compression.

What gas were you racing with? what is the timing?

I always check the valve-train. I had to also run .300+ long pushrods. 8.100" to be exact. What would cause the bearings to go like that? Crank out of round, bad balance job, etc? The clearances were fine when I put the motor together. I have no idea what went wrong with this motor and why the car is so slow. Anyone have any ideas? Thanks

The compression is 11.37:1. Cranking pressure is 210psi. I run a mix of 110 octane and 93. Works out to 100 octane. Timing was set at 30.

I would venture to say, that would will find out quickly when you pull it apart.


How did you check the clearances? its very critical that you check them with a dial bore gauge, and just becuase the clearances on each housing are good, doesnt mean that they are all aligned.

slightly above and below the parting line is VERY ( i should stress that part) critical.

Did you check the thrust clearance?

Rod side clearance?

connecting rod big end clearances?

did the crank get tight at any particular point when you torqued the main caps down?

Camaro76350,

I agree that the 294s is probably not the best cam for 10-10.5:1 in a 355. With 4000-4500 stall, you could probably get away with a mid-240* @ .050 cam as long as the lobes are fairly agressive (in other words less seat timing).

Something along the lines of the Comp XS 282s would be my pick -- Harold Brookshire at Lunati also has some pretty good grinds that would work nicely for you but they are a little more expensive than Comp.

With the 200cc ProToplines you want as much lift on both the intake and exhaust as you can get --- these heads flow even better at high lifts.

Just my opinion.

I checked all of the clearances and they were all within spec. Eric68, do you think with a cam change and dropping the compression down to 10-10.5:1 will make that motor run like it should? I need to get the bottom end straightened out first, and I will also be putting flat-tops in it. Maybe those domes are hurting me. Eric68, I have the most respect for you, you have one wicked camaro with very impressive times. Do you see anything mismatched with that combo if I were to use that XS282S cam and around 10:1 compression with the rest of my setup? How would that compare to what I have now? I'm not saying I'm definitly going to go with the XS282S cam, just want to get an idea of how the cam will perform. I'd also like to look into some custom grinds for this motor also. Thanks for everyone's help.

Since you already need to go thru the lowend, and will be changing pistons (also requires re-balancing), for not too much more money you could get a Scat or Eagle cast steel 3.75" stroke crank, use your existing rods (or step up to a set of Scats or Eagles...you can get a nice set of capscrew 5.7" Scats for under $260), piston prices for a 5.7" rod 383 are the same as decent pistons for a 350, get an external balanced flexplate and balancer, and you'll forget about ever building another 350. I don't think a 294s is too far off with the rest of your setup...and Eric and myself both run this cam in our 388's. It obviously runs pretty well.

It all makes me wonder now if your lowend was already getting weak, and maybe the rings was leaking enough that it wouldn't go any faster no matter what you added to it. It sounds like you race your car a lot...the lowend may have already been tired and the extra compression may have pushed it over the edge. Just a thought.

Well, it looks like the motor will be going back together as a 383. I just don't see any reason why not to. The parts will only cost a little more, but I think in the end it is well worth it. I'm looking at Speed Pro -12.5cc dish pistons with skirt coating. That would yield a 10.1:1 compression ratio with my 64cc heads and a .045" quench. This will being running off of straight 93 octane. I'm tired of mixing race gas so the compression has to come down. I am also looking at a Eagle cast crank that uses 5.7 or 6.0 rods. I want to reuse my 5.7 forged rods that I have now. It is an internal balance crank but it says you have to use a neutral balance flexplate and balancer. Is that still a 350 flexplate and balancer? This is the first time I will have built a stroker motor. The extra cubic inches will make so I don't have to rev the motor to 7000 to make power and it will last longer. I do want to get a new cam, maybe a custom grind. I do not need as much duration this time, being my compression is only 10.1:1. With the right cam, I think this motor will be very strong. It should put me way into the 12's no problem. The motor I have now should have too, but thats another story. Would that XS282S from Comp be good for this 383? I know Eric68 said it would work in the 355, but what about a 383? In my opinion, I think it would be about perfect. A little less duration which would put my dynamic compression around 7.7-7.8 or so. I'm not sure where the intake valve closes at on that XS282S, but it has to be earlier (or later?) than the 294S I have now. Thanks for everyone's help.

Thanks -- but remember anyone can build a ride like mine if you pay attention to detail. Its nothing really exotic or even expensive.

You know -- when an engine doesn't respond to mods like you expect and you know the change was a good one, there is usually something else wrong. In this case I think that your bottom end was getting worse and holding the combo down. There was never anything grossly mismatched with your setup IMO.

Now if you are going to rebuild it as a 383 there are a couple watchouts esp if you've never done one before.

1st - not sure what pistons you are looking at, but don't just use 350 pistons -- they have to have the right compression height (wrist pin height) for a 3.75" stroke AND the connecting rod length you will be using.

2nd - the extra 1/4" stroke will build about an extra point of compression.

3rd - there are some extra clearance issues with a 383. connecting rods to block at the oil pan rail, counterweight to block at the oil pan rail, counterweight to piston (especially if using a 350 piston and a short 5.565" rod), connecting rod bolt to cam lobe (especially #1, 2, 5, and 6)

Hope that helps. Again, your combo looks good for a 383. 10.5:1 and the XS 282s should go togther pretty well. The ProTopline heads will flow well in the 2000-6000 RPM band (also matches cam and compression)

Originally posted by Camaro76350:
Timing was set at 30. Is that total timing? If that's total timing, do those heads have an efficient enough combustion chamber to run best at that timing setting? Having the timing set several degrees below optimum can make a big difference in performance.

I've tried all different kinds of timing settings. 26 through 36 total timing and it responded to none of them. The car ran the same no matter what. The pistons I am looking at are 383 pistons with a 1.425 compression height. The pistons are made to work with 5.7" 350 rods. The motor will have 10.1:1 compression. I ran everything through Pat Kelley's compression calculator. Will that XS282S work with that compression? Does anyone know what the intake valve closes at so I can calculate the dynamic compression? Thanks for everyone's help. I think this will be a much more realistic combination than what I have now. It will be much better suited to my 3.73 gears and everything else that I have. The peak power point will drop and I don't have to spin the motor so high to make power. Right now, I have a motor that needs to rev high, but I don't have low enough gears in the car to make it run like it should. I want more midrange power that I can use and peak around 6300 or so. I think that would get me down the track much faster than what I have now. I feel like I'm chasing my tail with the 355. Big heads and a big cam in a small cubic inch motor with 3.73's. In my opinion, it doesn't match and I think its hurting me. Any other opinions or cam recommendations or anything that you see wrong about my new setup? I appreciate everyone's help. You guys are great. graemlins/thumbsup.gif graemlins/beers.gif

383 small block
10.1:1 compression -12.5cc dish flat-tops
Eagle 3.75 cast crank
5.7" forged PM rods
Pro Topline 200cc Iron heads-64cc chambers
Scorpion 1.5 roller rockers
Comp Solid XS282S 244/252 @ .050" 282/290 ADV. .520/.520 lift 110 lobe sep.
Air Gap intake
750 Double Pumper
Mallory HEI distributor, MSD 8.5 wires

I believe the pistons you are refering to are the speed-pro H602's. You might want to check availability because someone had mentioned on here recently that they was discontinued.
As far as the cam is concerned...unless you just want a new cam, I think that with your gears and stall convertor that the 294s will work nicely in a 10.1-1 383. The reason I say this is because my 388 is nearly identical to what you are proposing with only .2 more compression. On street tires it will turn sideways at 45mph. I know thats not any real indication of performance, but it seems to hit plenty hard. Eric runs this same cam in his 388 with less gear than me, and he does have 1 more point of compression but he also has aluminum heads. I think his performance numbers prove that this cam isn't too big, and my butt dyno (recently calibrated BTW tongue.gif ) agrees. I don't see much reason to use a dual pattern cam with the pro-topline heads as they have an excellent exhaust port, and a single pattern cam will make more midrange power. A dual pattern MAY have an advantage at the top end of the powerband.

camaro76350, ive got a new-(still in the box) never used, set of custom ordered 8cc dish JE pistons for 5.7 rods. floating pins with keepers. for a 383 i can let go of. they will yeild a CR of 10.5 with a 64cc head and .039 head gasket. my email dosent work most of the time so you may have to respond on this post. Dave