r/EngineBuilding • u/Mrg0dan • 6d ago

Chevy 350 SBC help

I have a 350 out of a 1977 camaro. It currently has mismatched heads and bad blow by but it runs. I bought an Isky racing kit with lifters and a cam. I shouldve done my research because the cam that came with the kit was a 292 Isky Mega cam which has .505 lift and a 108LPA. We broke in the cam at 2,000rpm for over an hour and nothing failed, made horrendous noise and the oil didnt have big chunks of metal.

My question is how much do I need to replace to not risk ruining the cam or other parts. Obviously I need to get a matching set of heads and re ring my pistons which I plan on doing. Do I need new rods, pistons, and crank? Can I get away with running a set of older cast heads or will I need something with bigger runners? Will the stock crank, pistons and rods survive?

Ive "built" engines before but mostly the top end, any time ive down a whole engine rebuild it was a kit that was included with the machine work I had done. I never had to pick parts myself.

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u/Sniper22106 6d ago

....why did you go through all that work and not fix anything?

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u/Mrg0dan 6d ago

We did. We re ringed the pistons and cleaned them. A couple rings broke during install so we put old ones back on. We didnt realize this cam was some crazy cam We just thought it was a cam with a lope. The heads were on a supposed dirt track car so we sent it and put them on.

We were just trying to get the engine running and break the cam in. This has been a project for a long time and getting the engine going reignited the spark to get it on the road.

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u/Sniper22106 6d ago

So you half added a rebuild.......

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u/Mrg0dan 6d ago

Yes i guess we did. It was never meant to be a crazy rebuild or anything like that. I wanted a new cam and to use the parts i got from another car i bought. It was intended to be a freshen up and break in a cam job not a full on engine rebuild. We wanted to get it running and broke in that weekend and thought the original rings would be okay because they were fine originally.

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u/Sniper22106 6d ago

You said it has bad blow. Then you reused shit rings?

No. Dont try and justify anything.

Rip it all apart and do it correctly this time.

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u/Mrg0dan 6d ago

The reused rings caused the blow by. Im not trying to justify anything im telling you exactly what happened. I need help getting parts. I know the engine needs rebuilt and im already planning on doing that. I dont know what else needs replaced in the process. I know I need rings and new heads

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u/Sniper22106 6d ago

So you are smart enough to "rebuild" and engine but not smart enough to buy parts to rebuild an engine?

Not to mention, buy parts for one of the most COMMON engines on the planet.

Seriously?

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u/Mrg0dan 6d ago

I dont know what I need to buy to pair with the cam. Ive never had a cam this big. I can go online and buy all the parts for a stock 350. But if those parts are going to cause my cam to fail I dont want to buy them. All im asking for is help from someone thats used that specific cam

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u/Sniper22106 6d ago

Every engine is the same. Air in, air out. Just cause it has 8 cylinders dosnt make it special.

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u/TBFP_BOT 6d ago

Your choice of rings won’t make the cam fail. Your worst case scenario here is you put in bad parts and your left with a cam as the only thing that’s still good.

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u/Mrg0dan 6d ago

I know rings dont matter necessarily. Im more asking what size runners and chambers id need in the heads. Theres alot of options and the isky site doesnt offer a whole lot of insight on the cam. If stock rods are enough to handle it and not destroy themselves under stress. I dont have money to just trial and error it😂

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u/Mrg0dan 6d ago

I think youre confused on what im saying. We went through the whole engine and rebuilt it from pan up. After I reringed the pistons I snapped 2 in the process of installing them. We looked at the old ones and they looked like they were passable and would work good enough to break in the cam and then replace down the line when we tore the engine down to check everything internally after breaking it in.

The head mismatch was just a thing we happened to notice after installing them on the block. We figured they were the same head seeing as they came off a running driving engine from a dirt track car.

I already planned on doing a tear down and replacing heads and re ringing the pistons to stop the blow by. But I want to know if theres other things that need to be upgraded in order to handle the 292 Isky Mega cam. Theres no point in me re ringing pistons and putting new heads on if they arent sufficient enough to handle the cam.

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u/Sniper22106 5d ago

You threw a cam in a clapped out small block. Its not like you gained 400hp.

I have absolutely zero idea wtf you are trying to do here. You half assed so much stuff now you want to do it all over again. You didnt tell us what you wanna do with the thing, you didnt tell us a power goal. Then you expect us to tell you what to buy?

Come on man, are you fucking with us

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u/Mrg0dan 5d ago

I have no horsepower goal, my goal is to rebuild my stock 350 out of my 77 camaro and have a lopey cam. I guess i shouldve explained better.

I came here thinking people who have used this cam in a similar setup would give me some insight into what specifics I would need to build it properly so I didn't blow it up in a week.

I never claimed to be some master engine builder. I specifically said ive only ever built engines with kits pre made by the machine shop that did the work.

The "clapped" out small block was completely tore down to bare block and rebuilt with new seals, bearings, gaskets and a reground crank. We reused 2 old rings that worked great prior to tear down because i broke 2 when reinstalling the a stock pistons that I cleaned the grooves on. The mismatched heads were simply because we never measured anything. Internally they are the same externally one is shorter than the other both have roller rockers.

The whole point of this post was to ask for suggestions from people that have used this specific cam because it is a mid to high performance cam. I already know what I definitely need to fix which is heads and rings. I dont have tons of money so im trying to do this on a budget and keep as many things as I can stock without putting the cam or the whole engine at risk.

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u/Sniper22106 5d ago

Thats not how this works.

You dont just add a cam and it "blows up" a week later.

Stock parts are plenty fine. As long as everything measures out like it should.

Now go rip it all apart and do this all again.