Gibson

so im looking at an 86 z28 with a carb'd 305, and since it needs a slight refresh (the top end needs just a little help, the bottom end is fine) i was thinking why not rebuild the heads, have en machined down just a hair, run a thinner head gasket, an lt1 or lt4 cam, ls1 valve springs, 1.6 roller rockers, a good set of hydrolic lifters, and a cheap mid rise intake for around 230 whp. sound like a plan? headers will come later when i have the cash.

Gibson

nothing?

Doom86

Not going to be remotely close to that power with stock exhaust manifolds.

Gibson

what would that put me at with stock manis you think? with headers?

oamhmad

iTrader: (1)

In order to increase HP and TQ one of the first thing you need to do is address whatever is holding your motor back, and on a stock 305, the drinking straw Y-pipe is a huge bottleneck. So start with the exhaust. The entire factory exhaust needs to go. It's pointless doing one piece at a time because all you're doing is pushing the bottle neck further towards the tail pipe.

So get some headers, Y-pipe, high flow cat or no cat if you can get away with it, a better flowing muffler and larger diameter exhaust piping. Do all that and trust me your car will feel much snappier. I think some magazine did a build on a stock 305 and to get a baseline HP rating all they did was install headers, pipes and a muffler and they got like something around 200 flywheel hp.

Save the heads, intake and cam for later, you'll get a much better return on that investment once they have a better exhaust to exhale through

naf

iTrader: (7)

Full exhaust and a mild cam, maybe the Comp XE256. Don't waste your $ on the heads and rockers yet. See:

https://www.thirdgen.org/forums/carb...tions-lg4.html

zraffz

If you are going through the trouble of taking out the motor and rebuilding it, why not start with a 350?

Gibson

i would love to do the exhaust first, but the top end needs a refresh



im not taking the motor out, just the heads off to refresh the top end. the bottom end isnt making any funny noises, so im just gonna leave it alone until it does then pull it and drop a built 320 in it (400 block, 265 crank) along with rebuilding the 305 to put in a first gen s10 for some cheap fun.

oamhmad

iTrader: (1)

What's wrong with your top end, does it need a head gasket? If so, then by all means get better heads. Other wise you could just get away with new valve seals, (cheap) and a valve adjustment to "refresh" your top end.

Like wise, if you have a broken timing chain, broken lifters, or completely worn out cam shaft, then do the top end first as well. Otherwise, start with the exhaust. The roller rockers, although good for reducing friction, and allowing you to rev up better, will not by them selves increase your hp.

Gibson

well with 140k on it, it has sticky lifers, the timing chain is stretched, and worn valve springs, so i thought might as well give it a little punch while i have the heads off and timing chain off. i know a full rebuild or a crate 350 would be best, but im a poor broke high school kid.

oamhmad

iTrader: (1)

Oh ok. In that case I'd do the heads, cam, lifters and rockers first too. Really hard to say exactly how much HP you'll make but definitely not 230. You'll easily reach that figure once you get the exhaust done as well and everything starts working harmoniously together. I think people regularly get 300 flywheel, hp with a good set of heads, intake, camshaft, headers and full exhaust on 305s, but all these things have to work together you know.

Dr. Phil

if you have that much to spend, im sure you dig up enough cash to spend $50 for a good cheap set of shorty headers off craigslist and another few bucks for gaskets and your gold.