Project_1986_TA

I have a 350 in my 86 TA right now and was wondering if the heads off of the old 305 would fit? I was thinking about porting and polishing them and puting them on the 350. Would i notice a power increase if i did so? Thanks!

SlowStangEater

Youre kidding right?

Project_1986_TA

no im not actually. IM DONT KNOW A WHOLE LOT ABOUT ENGINES OK?! AND YES I WILL LEARN, IM GOING TO AN AUTO SCHOOL THIS SUMMER. AND IM REALLY TIRED! LOL

SlowStangEater

LOL

Its all good man

I just would suggest upgrading. The restriction would kill the potention for performance. I could be wrong though. Some guys have really made 305 heads flow........but thats on a 305.

Project_1986_TA

maybe ill just save up for some vortech heads or somethin after i deal with getting a new tranny. Thanks for the info!

SlowStangEater

Not a problem but like I said, Im no expert either so do a search and see what you find.

F-BIRD'88

If your 350 is low compression with 76cc smog heads,
swapping on a set of ported 305 heads with bigger 1.94"x 1.60" valves plus some valvetrain upgrades is a good budget way to see a nice performace increase for not too many bucks.
305 heads are 58cc's and will be about 60cc's when sweeped
out for the larger valves.

Stock 305 heads flow a little less than stock low perf 350 heads.
But once ported and upgraded with larger valves they flow suprisingly well. Rivaling some out of the box aftermarket performance heads. Better than some others.

A minor pocket port will not cut it. They need a full port job and the bigger valves. Budget street replacement valves will do nicely.
You can do the required porting yourself with a die grinder and some carbide bits, stones and paper rolls. No real rocket science
to it. Get the Book by David Vizard called :How to Build Max Performace chevy small blocks on a Budget. Everything you need to know is in there. All the cylinder head info is relevant to the 305 heads.

After you're all done porting them a competant auto machine shop can provide all the nessessary machining work required.
They usually can provide the hard parts to complete the job too.
Let them know you're on a budget and get and estimate on the job.


The castings to look for are 416 for pre 86 heads and 081 for 87+ centerbolt heads.

Your compression ratio will be about 1 to 1.2 compression ratio numbers higher than with 76cc heads on a 350.
You can adjust the final cr with different thickness head gaskets,
head milling and or chamber relieving.

Air_Adam

Yup, a good set of the 305 heads with some new 1.94/1.50 valves would make alot more power than your 350 smogger heads.

Sitting Bull

F-Bird'88 guided me along on my 305 port and polish job. I took a lot of pictures to help out those who also want good but inexpensive heads, so follow the link at the end of my sig.

Marshall89ws6

No We do not "just" port them and use them on 305s... i have ported 416s on my engine. You just need to port and polish them....install 1.94 intake valves and unshroud the chamber to match up with the 4.00 inch bore that a 350 has. It's amazing how much this subject comes up.

Hype

Marshall,

just curious if you have any ET's or dyno #'s with those 305 heads of yours, just curious seeing as how I have a set of LG4 heads lying around and most of the tools needed to give them a good porting, or try anyway, lol.
I figure this would put my combo at 10:1 compression, which should run on 94 octane I'm assuming...?

Thanks,

86budgetSC

I have been wondering the same thing.My brother in law's brother.Races stock cars.And has a set of 305 heads.That he claims are "race ported"With bigger valves.He didn't say the size of the valves.I know his stock car ran good when he had them on it.He is selling them.He isn't sure on the price yet.He said probably around 250-300.Which I figure is a good deal.He is a good guy and really smart about racing engines.

SlowStangEater

Hey easy now,

I said I could be wrong! LOL and I was

Sitting Bull

F-Bird'88 is "our leader" in the 305 heads wars and he has flowed his at 243 cfm at .500 lift. That supports 500 hp.

F-BIRD'88

Have to qualify that 500hp expectation. That is a theroretical but possible power level based on peak port flow on a perfect motor with all supporting parts and specs optumily tuned in.
You can read that as big $$$'s and lots of dyno tuning.

I am going to be testing a high compression big bracket cammed
350 with these ported 305 heads. I expect 420 to 440 hp.

(335 to 360 net rear wheel)

these actual heads flow 238cfm. The 243 cfm ones were sold to fellow third gen in Buffalo NY.

Scania

Is it possible to use 350 tpi heads on a 305 tpi?

F-BIRD'88

Yes but the compression ratio will be lower unless you have them machined to 58cc's.
Better to install the larger 1.94valve in the 305 head and port it.

The 350 heads only flow slightly better in stock form.

Exhaust side is the same.

f-crazy

iTrader: (-1)

if you dont want to spend a whole lotta money then these heads are great.. a lot of bang for the buck lol


F-BIRD'88

how would lb9 heads run on a 406 or a 383 with a cam youd put in a 350 and a lt1 intake?

thanks

F-BIRD'88

Sounds like a hodge podge of parts.

Compression could be too high with stock 305 heads on a 400.

Depends on the pistons etc. But it will run.

Would need full porting, big valves and dish pistons.
Not to mention 400 block steam holes.

guza

Wouldn't changing to the 305 head require higher octane gas too? Higher compression+hotter engine=detonation, right?

Scania

So for us 305 people it would be enough to change valves, right???

f-crazy

iTrader: (-1)

the 406 short block im gonna get comes with FT pistons and the compression is 11.4 with a 64 cc head and 10.1 with a 76cc head

yea i dont think it would be a good idea lol

(edit) heres the 383 just for comparo

383 has FT pistons the C/R for 64cc heads is 10.3 and with 76 cc heads is 9.2

this site doesnt give the values with different head gasket thickness though

F-BIRD'88

Never enough.... Depends what you want out of it.

Just changing valves is worth about 10cfm. But full porting and larger valves turns the stock head into a budget hi flow hi perf head.

F-BIRD'88

The 383 is going to be on the regged edge with a 64cc aluminum head.
Probabily too high for a cast iron head.
You could do some creative chamber relieving/ reshaping on a 64cc head to enlarge it some. Or shave a 76cc head to get the cr to 9.8:1 +/-...

You can compute your actual compression ratio with a simple
compression ratio program once you know the clearance specs on your motor.

go to www.download.com and get Engine CR V1.0

F-BIRD'88

Yes

But ; More compression doesn't mean a hotter motor, just a hotter compressed mixture in the combustion chamber.

Needs a higher octane fuel to avoid autoigntion (knock)

Marshall89ws6

haha sorry for seeming hostile i just was simply stating facts.

Dolph88sc350TPI

Unless you used domed pistons, but like you said its better to just upgrade the 305 heads.

Also, wouldn't there be some intake/exhaust valve shrouding when using 350 heads on a 305?

Scania

Yeah i can live with budget hi perf.
Spended all my money on a lt5 and gearbox this winter so
the 305 will be a budget one.

SlowStangEater

Its all good cuz now I learned something

f-crazy

iTrader: (-1)

so f-bird...so a 76cc iron OR aluminum head will work...

ive benn thinkin a little and in a year or so i wanna boost this...
what kinda n/a numbers should i be looking for with a 406 mild cam a 76 cc head with 9.5 C/R

F-BIRD'88

What 76cc head? what camshaft? What intake? Not enough information.

"Boost this" ???

Dane_z28

yes 305 heads will give your 350 a nice compression boost.
you should make shure they are H.O heads though (big valves and tighter compression chambers)

Sitting Bull

Nah, they are all the same and have 1.84" intake valves stock.