swisscheese

Seen in their catalog that they have the usual Corvette alu heads and some with bowl job.
Whats a bowl job and is it worth the extra $.

Do they fit a 305? (don't know if there's something different to a stock L98 alu head)

Thanks
Pat

five7kid

iTrader: (14)

I looked on their site real quick and didn't see such heads, but, to answer your questions:

A "bowl job" is porting/clean-up of the port area just under the head of the valves - the "valve bowls", if you will. Also known as "bowl work" and "pocket porting" (porting of the valve pockets, same as valve bowls). It smooths and blends the opening to the valve with the port to provide improved flow. This is generally where the most benefit from porting will come from.

Those heads will fit a 305, but they will lower the effective compression because of the aluminum material. They should make the engine run better, but if you have absolutely no plans beyond having these heads on a 305 (such as putting them on a 350 some day), they should be shaved to reduce the chambers by 4 to 6 cc. They also do not have the exhaust cross-over passages.

They are the same heads that the '86-1/2 - up Vette L98 used.

Daz

iTrader: (1)

vette heads are 58cc same as a 305 heads. These heads are perfect for a 305

Daz

five7kid

iTrader: (14)

58cc 305 heads are made from cast iron.

Cast iron L98 heads are 64cc. Aluminum L98 heads are 58cc. They do this because of the heat loss through the aluminum, which lowers power output. To regain the power, they raise the static compression ratio via smaller chambers.

If you use aluminum heads on a 305, you should raise the static compression by about half a point (9.5:1 to 10:1).

58cc aluminum heads are not perfect for a 305.

KiLLJ0Y

iTrader: (1)

so what compression ratio do they raise to on a 355(.030 over bore) with flat top pistons(with 4 valve reliefs)?

Daz

iTrader: (1)

You dont need to raise up the compression going to AL.THe flow characteristics, and bigger valves will overcome the THEORETICAL heat loss. If its a bolt on job it willl be good. Slap the heads and get a matching cam and you will see good gains. You would need to elongate the two middle bol t holes if you have an 86 or older intake.

five7kid

iTrader: (14)

As I said, they should make the engine run better because of increased flow capacity. That still doesn't make them "perfect".

L98's were 9.3-9.5:1 with iron, 10:1 w/Al heads. What they would be on a rebuilt 350 would depend upon the piston pin height, relief volume, deck height, and gasket thickness/volume.

Daz

iTrader: (1)

youre right about "perfect" I shouldve said"theyre a perfect bolt on"..Its a basic replacement job

swisscheese

Ahh, sorry. they are in the printed catalog.

Thanks for the explanation!

Breazlan

iTrader: (1)

Not sure they are a perfect fit. If the D-port are the same as the earlier non-D than they may not be. I fit a set of the early non-D on a 305+.030. When set on the engine and looking at the chamber from the bottom of the cylinder, I saw that the chamber overhung the side of the cylinder opening (exhaust side of head). Would seem to me that the major rush of incoming will slam the top of the block before entering down into the cylinder. I don't know if this is normal but I can't think it is this way with normal 305 heads (guess I could check sometime). Bought these heads to go on a 305 because I earlier found on TGO the same stuff mentioned here. I don't think the benefit will be noticed with the current situation and don't plan on putting them on the 305(310). Or could this actually be a benefit?!@?

FastZ28*84

When I had my original L69 305 I put the aluminum L98 heads on it and noticed it made the exhaust crackley, but I did pick up a little over 3 tenths of a second in the quarter mile. These were stock with no porting so you could see even more performance gains.

mw66nova

iTrader: (13)

actually, i'm quite positive that all the aluminum heads got the same bolt pattern as the pre-86 iron heads and will not need modifications to such said intakes.

paul_huryk

100% correct