R.O.B.

I wander if anyone makes these. This way we 305 guys can upgrade our heads during a rebuild and not loose compression. Also, just a thought, what about longer connecting rods? Could using a 6" rod instead of 5.7" allow the use of 64cc or 72cc heads?

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Rob
'86 TA 305 TPI

Grim Reaper

If you run flat-tops with 6cc valve reliefs, .040 compressed gasket thickness and leave the deck at 9.025, you endup with a measly 8.6:1 compression.

Using a thinner gasket (.028) and deck the block to 9.000" you still only get 9.3:1 with only flat-tops.

To get more compression than that, you'll either have to use "pop-up" pistons with a dome or mill the heads.

Using 6" rods will not solve your problem as you need pistons that move the wrist-pin further up the piston. Using 6" rods with standard 5.7" pistons will cause the pistons to slap the head and cause a ton of problems.

Also, none of this considers the possiblilty of the valve slapping the piston which needs to be checked if you plan on running a high-lift cam.

I would just have the heads milled to give you a reasonable compression ratio with flat-top pistons...but make sure you check the clearance for the valves.

BTW, this would be better posted in the Tech Section. I think you would get a lot more responses.

[This message has been edited by Glenn91L98GTA (edited November 27, 2000).]

R.O.B.

For those who are interested, I just found Keith Black's web site. Part# KB229 is made for a 305, and with 64cc heads, will make 9.3:1 compression. Great!

New question: What is the largest set of valves that a 305 can handle?
Intake--1.94, or 2.00, or 2.02 maybe?
Exhause--1.50, or 1.60?

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Rob
'86 TA 305 TPI

Grim Reaper

Depends on the head and the lift of your cam. Most heads with 2.02 intakes will not clear the bores or slap the piston with any amount of lift. I think TFS Twisted Wedge heads will work on a 305 (read an article in CHP on a 305 build up about 5 years ago) and those heads worked upto .450". Also AFRs are suppose to work, though I have never seen a 305 buildup proving it. You are best to talk to a couple of head manufacturers and ask them.

But, as for the best heads for a 305, I think you may find 2.02s don't have enough velocity for a "street" 305. So you may find 1.94s better for maintaining velocity on a street engine. Also, check out the Vortecs. They require a different intake but flow extremely well, especially with a little porting. In a recent article by CHP about a 350 Goodwrench build up, they got 408 HP on a 350 with "pocket ported" Vortec heads.

This is after they "pocket ported" the stock heads and then "pocket ported" Aluminum Vette Heads. They did get an extra 8 HP by swapping the "pocket ported" Vortecs with TFS 23* heads. So it shows the potential of the Vortec heads.