its a 1990 tpi 350. Pulled the heads and i see a couple different casting numbers underneath the valve covers not sure which ones to look at. Measured the width of the combustion chamber and its only 3 3/4" accross, freaked out thinking maybe i got robbed and the motor is a 305 but the cylinders are 4" accross. Did someone just put 305 heads on the motor?

What are the casting numbers you have?


Could very well be 305 heads on there, its not uncommon for someone to drop some small chambered 305 heads on a 350 in place of the 76cc smoggers to get the compression up to a reasonable level!

the stock heads for your motor should have 083 as the last 3 digits in casting #.
If they are 081 then they're the 305 version of the TPI heads.

ya but the 305's have smaller valves, and they shroud the top of the cylinders. how does compression help if you cant get enough air. people are freaking stupid.

EDIT: ya they are 081, this sucks now i need to buy new heads for my motor build.

With a little head work you can get them to flow pretty well, thats when that compression will come in handy. Is it the best idea? No. But I know a guy who does that to his dirt track car every season. Different strokes for different folks, right?

Well i guess its not that bad if youre leaving the stock intake considering thats a bigger restriction anyways. However i plan on running a cam around 225/230 duration .050 with 1.6 roller rockers. Want to make around 300+ rwhp and the valves on those heads just wont cut it. woo just means i have to buy new heads that i cant afford.

i'm using 416 heads, roughly the same as 081 heads, just with perimeter bolts, I opened up the intake to 1.94, and hand backcut them. I ported them up well, and i'm hoping for that kind of power output, with a 227/234 cam, with 1.6 rockers, .521 intake lift, .535 exhaust.
You wouldn't be the first person in the world to get good performance out of 305 heads ya know, try searching on these forums.

but if you're dead set on ditching them, 083 heads aren't terribly rare. Or you can of course go to vortecs, or aftermarkets of some kind.

it just seems like a waste of money, and when it comes right down to it if i fell short of 300 hp i would so so bitter all the time that it has 305 heads.

I think my friend has a set of old smog heads, might just spend the money id need to spend on new heads getting the meat ported out of those. Plus my engine shop is looking to see if he has any 350 heads in the back laying around i could buy for cheap.

i think having 305 heads would just eat at me all the time, especially if i was going to dump money into putting the size valves i thought i already had.

I see what you mean, 305 heads just has a stigma of being crappy. My machinist still laughs at me for them.

seriously though, search the boards, people have ported and flow tested 416, 601 and 081 (all 305) heads, and gotten very good results. MUCH better then the 882/993 smogger heads, and you can actually get some compression out of them. The beauty is, you can deshroud the chamber so that you have slightly larger chambers, but the space is in the RIGHT spots, to help flow. also once you port the bowls and ports, they're nothing close to a 305 head anymore. Stock for stock, the 305 heads (i'm not talking crappy '70s ones that had dismal 1.72 intake valves) that we're talking about, out flowed the '70s smoggers, out of the box (well, off of the block, but you know what I mean). Plus, these are heavy castings, meaning you can port them, and make them better. The thinwall 882s etc can't be ported much before you turn them into swiss cheese.

I've done a fair bit to my heads, i've got $340CA into them, which is hot tanking, cutting for bigger intakes, positive stems, threaded rocker studs, milled, bronze guides, etc etc. I'm going to have them flow tested if I can find a shop in town, in the next week or two, if you want more solid proof, stay tuned.

Careful when you point a finger, because 3 are pointing back at you.

As has been enumerated for you, you haven't been "screwed" nor are you up a creek. Those heads are identical to 350 heads except for the chamber and intake valve size. The suggested modifications will make them flow better than stock 350 heads, and doing the modifications suggested will cost you a lot less than buying new heads.

While we're on the topic of heads, pull yours out of where it doesn't belong and go make hay (there's no need to get lemonade receipes, you haven't been handed lemons).

Just because they are 305 heads doesn't mean they are bad. Infact 416 heads have some of the biggest ports of any stock GM heads, even the so called "fuelie" heads. 305 heads are some of the best bang for the buck heads out there. Do alittle porting, valve unshrouding and combustion chamber shaping and you will have some really good heads. Just because you have 350 heads on a 350, means absolutely nothing. You are right alto of people are stupid for thinking 305 heads are worthless. But the people that know, know they are among the best performance budget head.

what if i could get some world products s/r torquers, theyre 76cc milled down to 72cc and i can get em for 500 bucks canadian.

is that a better starting point? im worried about the huge combustion chambers tho.

yea, torquer's are factory replacements, about the same flow as what you've got, but you'd need to pay to get them milled to bring you back to square 1, after shelling out $500.

buy a die grinder, and make up a speed controller. buy a handful of carbide burrs and go to town. cut for larger valves, and put in mr gasket non collared threaded studs. you'll only be out ~$150, and you'll be set.

the torquers have 2.02 intake 1.60 exhaust valves
fair bit bigger then stock
and nicer bowl work

you still sure about using my 305 heads?

EDIT: nevermind my friends an idiot and theyre not actually for sale anymore, well hasnt today been ****ty.

Valve size is not all its cracked up to be. The difference between 1.94 and 2.02 on the street is just about nothing. Your not going to gain a huge amount of power going with a bigger valve unless your spinning the motor really high.

But that being said 305 heads with 2.02 valves would be awesome on a budget 350. Just make sure that you completely unshround the valves and reshape the combustion chamber.

Give me your address and put those 305 heads out by the curb. I'll be by to pick them up. I'm in Markam 3 times a week.
Then you can go and bolt on what ever you think is a better head.
And I'll take them and turn them into a cool set of budget performance heads that rock. Just like these 416's I just finished.
Yu'll feel better and I'll go faster ...

one more for good luck. Princess Auto in Mississauga has elec die grinders for sale (again) for $55.

its not all about valve size. Forget the stigma of 305 heads. They are way better than virtually any 350 head, and will make as much if not more power than those s/r heads.

Whoever says they are junk is a fool. Plain and simple. Do some searching, learn some, enjoy your heads.

SOunds like you found a diamond in a turd.