djtricia

iTrader: (4)

I have a high mileage 305 out of a 91 Formula. It was originally a tpi motor so it has the good cam and heads but runs a performer intake and 600 vac edelbrock carb. Problem is it blows smoke at high rpms and uses about a quart of oil per 1000 miles. As long as I don't get on it, it's not too bad. I have a buddy who has a rebuilt 350 shortblock 70's vintage with a 100 miles on it (he built a 383 instead). No cam, just the block. I can get it cheap. What I want to know is how would it work if I use the heads off the 305 on top of the 350 which has flat top pistons. Another friend has a used 268 cam and lifters he tried but didn't like. Should I mention I don't have much money either. Thanks for the advice...

Apeiron

You might end up with a compression ratio that was uncomfortably high with small chamber heads on a 350 with flat tops. You could be ok with a thick head gasket if the pistons are sufficiently far down the hole.

duckmanquacker

also your 305 heads could be part of your smokin problem like worn valve guides. look around at some local scrapyards you might pick up a set of 350 heads pretty cheap trucks were fairly plenty, just get some from the years close to your car.

SpitotRs305

the year of the 350 truck heads are irrelivant they will pretty much be crap... unless you have alot of vortec trucks in the yard but still you arent going to find those heads on a P-A-P truck

djtricia

iTrader: (4)

I can get a used set of heads from an 89 350tpi that will allow me to use my intake and carb. Will those be good enough heads if I have them redone?

duckmanquacker

yes those heads will work if redone, I offered the truck heads because he said he was on a budget. truck heads offer better torque with upper hp sacrifice thats all.

Pat Hall

iTrader: (31)

I wouldn't suggest using the 350 heads on your 305 if that's what you're thinking. You'll run into the opposite problem of what Apeiron said by having too low of compression. If you had them milled down and used a thin head gasket, they'd work okay. I'd suggest having your existing 305 heads gone through at a machine shop (valve job, guides, seals, etc.), and putting them back on. There's a chance the piston rings are worn out, but most times it's the valve seals/guides in the heads that cause high oil consumption, especially if it smokes when you jump on it. The sudden vacuum drop causes oil to be sucked past the worn guides/seals. A simple compression test will also help determine whether the rings are suspect or not. The heads will only cause low compression if the valve seats are really worn, or a head gasket is leaking.

djtricia

iTrader: (4)

I was thinking of using the 350 heads on the 70's 350 shortblock my friend has.

SpitotRs305

well those will keep your CR in the low 9s with flattops but they are probably the worst you could run...

when you say flat top... what do you mean? +7cc, +6cc, +12cc? or a true flattop?

Sonix

iTrader: (1)

What? Why?
He said heads off an '89 Camaro TPI, those are 083 heads, those are good stuff there.

Flat tops are almost always a 5-6cc dish.

That's a good setup. A used cam is dicey, make sure the lobes look
PRISTINE, then buy new lifters for it. Summit has their basic ones for $60 or so. Since you'll be downgrading to a flat tappet block, you'll need a flat tappet cam (like that 268 one I believe), and the new flat tappet lifters - but also pushrods.

djtricia

iTrader: (4)

The 268 had just a few hours on it before he pulled it for a different cam.

SpitotRs305

yes but with a flat tappet cam it only takes a few minutes to screw it then a few days to pawn it off on someone unfimilar with them...

Sonix

iTrader: (1)

Unfortunately that's enough for it to be married to the lifters. If you put it into your car you need to be EXTRA SURE that each lifter is on the exact same lobe it was on when it was broken in. Or else buy new lifters for $50 and re-break it in.

djtricia

iTrader: (4)

Thanks for the advice. The cam belongs to my best friend from high school. We see each other often and have built many small block chevys together. I don't believe he would try to pawn off a cam on me that isn't any good. Now all I have to do is come up with enough money to make all this happen. I need to have the 89 Formula sell that's posted on TGO.

Pat Hall

iTrader: (31)

[QUOTE=Sonix;3460777]What? Why?
He said heads off an '89 Camaro TPI, those are 083 heads, those are good stuff there.

The 083 heads are definitely one of the nicer factory heads. Good chamber size (64 cc), centerbolt, and a direct fit with TPI. They work nicely "as-is", and with some porting, they're even better. GM used the same castings on a lot of their 300HP/350 crate motors, not to be confused with the ZZ4 crate motors though. Budgetwise, I'd say using those 083's on the mid-70's 350 is probably going to be your best option. Like Sonix said though, unless you're absolutely sure the lifters were kept in the right order when they were removed with the cam, don't take the chance. Buy new ones. In fact, most old-school SBC guys look at me like I'm crazy when I tell them I can re-use the old lifters on a hydrualic roller setup. That's an absolute no-no with flat tappet cams. It'd also be a good idea to call a cam-help tech line, give the the specs on that 268, and make sure it's a good match for a TPI. The duration is probably fine, but you'll want to make sure the lobe separation angle is 112 degrees or higher. TPI's don't agree with lower LSA's without chip work.

djtricia

iTrader: (4)

I'm going with a carb set up.

Pat Hall

iTrader: (31)

Lol. In that case, just disregard the last couple of sentences from my previous post. If you're going with a carb, the 268 is too mild then. The only flat tappet, carbureted motor that cam belongs in is sitting in the engine bay of a Winnebago.