305 heads on a 383 stroker?

[brothers69c-10]

Hi guys,
I've built small block chevy's beofre, but never a stroker. Nor have i put 305 heads on a 350 block. I have heard that you have to notch the block or something to make them work. I don't know. The heads are 305 HO heads with 1.86 intakes and 1.72 exhaust i belive, could be wrong on the exhoust valve size. They have 58cc chambers. Will this create to much compression to run on pump gas? I'm using the 400 crank and rods for the stroker. Flattop pistons and a somewhat radical cam, 4 barrel holley, alluminum high rise intake, the works. All of this for my 15 year old brothers 69 c-10
I guess my real questions are....
What do i have to do to put these heads on a 350 block?
and...
Will it create too much compression for pump gas?

Tell me what you think
Thanks in advance.

[c10crazy]

In my opinion, I would never use a 305 head on a 383 stroker. They won't flow enough for those cubes. You should go with a 200cc runner. The cubes would eat up the compression increase so that won't matter but it's really a bad choice for a 383. They will hold back the potential of the motor.

[Bob 68327]

Dart makes a nice 200cc intake runner head in alum.and iron that would work great for your application . Just my 2cents. Bob

[Dieselwrencher]

I can't help ya out on the 305 head question, but I would advise just buying a set of vortech heads and run these. I know you don't have the budget to be buying $1000 or more heads and those vortechs will work fine for a good street motor for now. If you are trying to go for gold then yeah I would agree with the other responses so far.

[smoky02]

But be careful with the vortec's if your cam is higher 485/485 then the heads will have to be worked first. And the springs changed.

[Longhorn Man]

dond't do the 305 heads, you'll regret it BIG TIME.

[JMac11]

UMMMM not to correct conventional wisdom.... but those heads work fine on 350 dirt track engines I have built. They will usually cruise through any tech inspection without question because the casting number matches earlier smog heads. I have snuck 1.94 intakes in them and even those fooled the folks in Pensacola one night. The difference in CC's in probably not noticable until over 4800 RPMs, you should have plenty of flow to smoke the tires. If you have a good set and they are what you have, run them. If you have the scratch get something else.

[streetstar]

They should run fine up till about 4500 rpm or so.

there are better choices out there, sure, but if you are just trying to get the thing moving, they'll do

[MudBug]

We use 305 heads on the 350 c.i.d. stock car motors. We put 1.94 intake valves in and they use to pass tech. until somebody through a fit about opening up the cumbustion chamber to fit the seats. They said it was an unfair advantage.That was from the same people that got caught with acid-ported and diguisted dart heads.Good heads to get compression up if your down on money. I would stick with Vortec heads for the street,305 are thin castings.

[Rreemo]

I've played in this space a lot in the past....trust me on this, you do not want to run those 305 heads on a stroker motor!

As mentioned elsewhere, they are a cheap HP alternative on a 350, but that is only b/c of the 58cc chambers....a 350 has a 3.5" stroke (3.48" to be exact), which combined with those smaller combusion chambers will net you in the ~11:1 compression range (give or take depending on piston, head gasket thickness, deck clearance, etc).

The issue you run into with a 383 is that you are stepping up to a 3.75" stroke with that 400 crank. When you combine that with those smaller chambers, you are now cranking your compression up beyond streetable levels....~12:1+ (give or take on the same varibles as above)

Beyond this, the tiny valves and runners in those 305 heads aren't going to be at all sufficient to support 383 cubes. Again, they will do okay on a 350 up to around 4500 rpm, but a 383 is a whole different animal.

To give you an example, I used to have a budget built 406 that I ran a set of good ole 461 heads on (double-humps) which are 64cc...with flat top pistons that engine still made just a little more than 11.5:1 and I was running a thick head gasket too. With a decent flat tappet solid cam it ran pretty hard....made awesome torque, but I still had to run race gas in it....on the street I could get by turning the timing back and cutting 108 octane half-and-half with 93...but that was bare minimum.

The Vortech heads are a good recommendation if you are on a budget....just be sure about which ones you get...some of those castings still had 64cc, and if milled a little, you are still going to be pushing well over 11:1. In your situation you're going to want to run something more in the 72cc range (as long as you are staying with flat tops)....which should put you around 10.5:1 - perfect for a streeter.

Depending on how tight your budget is, you could also get by running a set of the 882 castings, commonly referred to as "truck heads"....I believe they were stock around 75cc, and they are cheap and plentiful. You can find those all day long for $300 or less fresh and ready to go.

Here's some more resources for you:

http://www.mortec.com - a great place to reference casting numbers.

http://www.csgnetwork.com/compcalc.html - a qwk and easy compression calculator.

Feel free to PM me as well....I've been around the block on this stuff and happy to answer questions for you.

Good luck!