james_fearn

I need to reduce the combustion chamber of my aluminum heads from 66 cc to 60 cc. I know that people get their AFR angle milled lower than the factory 68 cc.

Which one is better and when is it better? At what point do you go from getting a standard mill job to an angle mill job? and what about valvetrain geometry and intake face angles?

Background: I have the TFS 23* CNC heads. I thought they had 64 cc chambers, but I recently learned that they are 66 cc. Removing 4 cc is not that bad but 6 cc is a little more than I wanted to. Maybe I'll return them for 60 cc edelbrocks (6085).


James

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1985 Z-28 305 TPI 223,000+ mi., Original Eng.,T-Tops,Blue/Grey
STB,SFC,GW "wonderbar",145 Speedo

jcb999

It usually runs about 250 bucks. You need to have the bolt holes for the intake redrilled at the new angle. Angle milling works better and can allow you to take off as much as 10 cc. It does "roll" the head a little (a good thing). Are you dealing with a 350 with zero deck height? If this is a computer motor I think your be better off with the larger chambers. The ecm will take care of the advance for you and the small compression drop will not make much difference in the 10 to 1 range.


[This message has been edited by jcb999 (edited May 26, 2001).]

james_fearn

I haven't measured the current specs of the engine. But with 64 cc chamber it was advertised to be 9.6:1 CR. I want to be around 10:1 with my aluminum heads (TFS 23* CNC). I calulated that I would need 60 cc chambers to achieve that goal. I know the displacement of the gasket I will use but I do not know the dispacement of the gasket the engine was advertised with, so I assumed the displacement was equal.

I got a quote from a respectable engine shop and they said removing 4 cc didn't require an angle mill. But now I find I need to remove 6 cc to reach a 60 cc combustion chamber.

This is a TPI with an accel bae/runner setup.

Thanks,
James



[This message has been edited by james_fearn (edited May 26, 2001).]

jcb999

Well, according to summit, the TFS23 is 64cc. But, most 350s have the piston down the hole about .015. Thats about 3cc there. Most felpros gaskets for 350s (.041 thick) are about 9cc. Once you add in abour 4cc for valve relief your about 10 to 1. If you want more than that, a better way to go is zero deck the block. It reduces the chance for detonation. You can get 3cc there.

[This message has been edited by jcb999 (edited May 26, 2001).]

james_fearn

TFS-30400006-CNC

Technical

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* 66 cc CNC machined combustion chambers, 2.02 in./1.60 in. stainless steel valves
* Tungsten alloy valve seats, compatible with unleaded fuels
* 1.47 in. diameter valve springs for cams up to .540 in. lift
* Angled plug design that will fit most straight plug headers
* Bronze alloy valve guides
* Use intake gasket FPP-20-1205 and exhaust gasket FPP-20-1404


This page is on summits site that is brought up by java, so no direct linkage

I was surprised when I saw the 66 cc. I still haven't measured it, but it would make sense. I supose they take the regular castings and just CNC them, removing more material and increasing the chamber size.

James

jcb999

Well, if you really have your heart set on 10to1, your going to need to find out what the other clearances are. Valve reliefs can be anywhere from 4 to 7cc and deck height can vary from 0 to .020". You need to have about 80cc above the piston (gasket+deck height+valve relief+chamber) to get 10 to 1.

I would not just mill the heads in an effort to get 2cc. The combination would work better if you have your machinist zero deck and you get a piston that you know is about 4cc valve relief. Your still really not going to know what the chamber volume is after you mill it, it would require CCing them to make sure and it is probably not worth the trouble and cost.

[This message has been edited by jcb999 (edited May 27, 2001).]

BadSS

To expand a little on jcb999's posts. On a 10:1 350 engine producing 350 horses with a mild cam, you're looking at about 1 horsepower for each additional cc. Assuming 60cc will in fact give you 10:1 compression, 66cc would give you 9.37:1. On a 350 horse engine with a mild cam,, that's about 6 horses at the fly wheel and no more than 5 horses difference at the rear wheels. I also agree that "decking" the block to get near zero deck height, and running -4cc or so pistons is better than milling the heads, but neither will let you take full advantage of the compression ratio you could be running with aluminum heads. Plus you may end up re-shrouding those de-shrouded CNC chambers if you mill them down much. IF it were me,,, I'd mock it up and see how much I could deck the block,, or bolt them on and look straight ahead. Either way,,, I'd pocket the milling money and spend it elsewhere on the build or car. Just my $0.02 if it's worth that to you.