mjk1210

Anyone out there wanna give me a guess as to HP and torque with this rebuilt 350?

It was a block from a '80 vette (I think). I had a shop (recommended by the friend that helped me with the rebuild) clean up the block and also do a valve job and clean up the heads.

I bought items from Summit to rebuild it along with other stuff I got from a couple people. I know the heads I used are complete crap (read all about that already) but the shop said they'd be fine for what I was doing until I can afford something better later. Here's what I have now:

Summit 2423NP cast pistons
EDL 2102 - Edelbrock performer cam
ELD 5802 - valve springs
SUM G66600 true roller timing set
Holley 9895 carb - 650 cfm
HOK 2460 HKR - Hooker headers
10185063 - bow tie intake
462624 (original) - heads
comp cam roller rockers
new Accel HEI vaccuum advance dizzy


stock exhaust after the headers and y-pipe, stock air cleaner with cold air from the bulge in the hood at WOT.

I have a 700r4 trans and a 2.93 rear end with an open diff. Trans will get a rebuild soon and rear end will eventually get replace with a little more grunt and posi.

So first, What do I have now?

Next, what would I have if I put on a Dynomax Super Turbo exhaust system with a magna flow (or other) hi-flow cat and perhaps some Edelbrock 609019 heads? Or other head suggestions? I know vortecs are real good, but if I can still use the intake I have it would be a plus to just bolt on the new heads one day (I think). I also want to change the air cleaner to the K&N with the element across the top and just open up the bulge in the hood to allow cold air in all the time.

My goal is to have a hi torque machine for fun daily driving. I don't need high hp at 6000 rpm.

Thanks!

Atilla the Fun

With a 3" cat-back, you're around 270 HP @ 4700 RPM, because you've built a virtual carbon-copy of the Performer 350 they give their dyno results for. Those heads aren't so bad for flow, they're bad for cracking. Start searching for some # '416 heads now, especially with your dished pistons. Those pistons are 0.020" too short, even if your block was decked 0.025", so consider some steel-shim head gaskets to go with your 416s to fix your excessive quench. That DynoMax Super Turbo exhaust system is crap, I know because I tried it with a mildly built L69. Even with a better muffler, it still isn't good enough for what you have now. You need a true 3" system. The cam is crap, you'd be better for now with either a Comp Pure Energy, or a Comp Dual Energy 255. With '416s, I'd do a Comp XE262, and a better axle ratio. Then when you get the Edelbrock heads ( use a 64-cc version ) you'll have a fun driver.

mjk1210

Hey. Thanks very much for the reply and the info. Only because I want to learn more here, can you explain what the different cam will do that this one isn't? And you mentioned the 416 heads, are they better or how are they different from the edelbrock heads? Lastly, is there a particular 3" exhaust I should be looking for? I mean a brand. Or should I put something together myself. I don't want to get loud with it especially at idle or low rpm but some WOT noise is always good.
Thanks again.

mjk1210

So I did some research on quench (and found squish too) and then looked at the pistons I got from Summit. Now I see what you mean. The dish in the piston, right? So I should have used a flat top? Do you think the current setup will be prone to detonation? Should I worry about it more over time or if it didn't happen in the last 2000 miles or so then I probably shouldn't worry about it too much?

Sorry for all the questions but I know the guys on here are pretty knowledgable. I try to read posts to learn from everyone elses' questions too.

So the heads I have a prone to cracking, understood. Is that even with the setup I have on there? I was under the impression at first that it would probably happen if I were to have gone much more aggressive with the rebuild. Hope I don't sound dumb but I just don't know. I do know that I asked the guy at the shop about it. He said not to worry about it with what I'm building. But maybe he just didn't care to bother telling me. I think he would have to know after doing this stuff for over 25 years. hmmmm.

Atilla the Fun

Maybe I wasn't clear enough. The '416s are what you should be using now, short-term. Their only advantages over the Edelbrocks are compression, stealth, and affordability. Plenty of 3" exhaust systems on the market, lots of choices. I'd suggest Flowmaster's 17151, if you can still find any leftovers, or MAC Performance. Either of the smaller Comp cams I referenced will perform better from idle through 5000, in a 350. But in a 305, they may have driveability hiccups with some stock computers, so Edelbrock played it safe, at the loss of noticeable torque below 2000 RPM, and the loss of upper-RPM HP with headers. Swapping to the '416 heads, the Edelbrock cam would be even more wrong, thus the XE262 suggestion.

Atilla the Fun

The dish isn't the problem. It's the whole piston. Correct compression height, from the center of the pin to the top of the piston, is supposed to be 1.560" But those #423 pistons you got, they're only 1.540". They used to be made and listed at 1.560", and while you can still find the 1.56" listing, the product is all 1.54" now. The #'624 heads were mostly used on 160-190 HP 350s, with L82 'vettes being up to 230 HP with larger valves. No surprise, the big-valve versions are all gone now, all of them cracked decades ago. Any exceptions have been in museums since 1980. Getting a thin head to survive 190 HP for the original 36,000?-mile warranty is one thing. Getting them to survive 270 HP??? For how long??? When they do crack, you'll be fighting with those guys. They will crack, the issue is when, and how bad. Trade them to someone restoring an L82 'vette, that's all they're good for.

mjk1210

Thanks again for the help. That cleared it up a little for me, yes.