307 Chevy with Vortec Heads

[68maliblue]

I'm finally getting around to building a 307 that I have had laying around the shop to go into a 46 Chevy pickup rat rod. I have a set of Mexican 062 Vortec heads and manifold that came off a HT383 crate motor and the engine has been bored out .030" and has cast flat top pistons in it. Planning to run a Comp 260AH-8 camshaft in it with 212 int/ 218 exh @ .050" on a 108LSA and 104 ICL. I'd like to get as much compression out of it and am looking at running a set of .016" steel shim gaskets to get to 9:1 compression. Would like to get feeback on this cam selection and also if Vortec heads are friendly with steel shim gaskets.

[econo racer]

Take a look at a good 27-28 thou. gasket .check gm dealer. I don;t use steel shim on nothing. By the way that is a good combo-RPM intake and a good 1850 carb, maybe vac secondary. Maybe run a 2200 stall but not needed . You basically have a 283 with a 327 crank. Check the bore size to make sure the valves dont hit. Cruise on

[mag2555]

To get the 9 to 1 comp your looking for with what I will assume is a .030" over 307 cid you need a total CC volume above the piston at TDC of 79.72 CCs.

This total CC volume is made up of the following.

Head gasket CCs.
Deck clearance CCs, be it plus or minus.
Piston notch volume CCs.
Head chamber CCs.
And lastly about 1.3 extra CCs added in for top ring land volume.

With that motors Bore to stroke ratio, its piston speed and the good burn rate of the Vortec chamber I would run a 9.5 compression which then calls of a total CC volume of 75.35.

[pdq67]

I HOI, the old steel shim heads gaskets down from .015", (Felpro #1094), to .020" or so, (Mr. Gasket), are fine.

Chevy used .020" or so thick steel shims STOCK for years and years if not mistaken.

Might try 9.25 or 9.5 to 1 CR.??

And maybe the old CC, top of the page hy-cam, "Pure Energy", for starters to make it DD powerful. But the cam you said will do fine....

pdq67

[68maliblue]

Just not sure about these vortec heads with a steel shim gasket. These heads were taken off a low mile ht383 and they are anything but flat. No evidence of being overheated and no cracks but I can fit a .003 feeler gauge between the deck surface and a straightedge in more than one location. If they got this way in a few thousand miles it seems they will again even if I get them resurfaced. Just wondering if anyone has used the steel shim gaskets successfully with these heads without leaking. The vehicle will be driven regularly so I don’t want a maintenance issue. If steel shims are a no go I’ll look into the 5746 mahle .026” composition gaskets.

[rebelyell]

? was that HT383 overheated? if so, that could explain some head warp.
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https://www.thirdgen.org/forums/engine- ... 94-hg.html

last post #14 (No, it's not mine/me)
25K miles on sbc 355 w/ GM Vortecs and all good at 180 degrees
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also felpro 7733SH1 it's THE Uncoated old-fashioned shim SO installer should copper coat or similar & it's beaucoup cheaper than 1094

https://www.summitracing.com/parts/fel- ... plications

see applications --- chevy 350 67-2002 includes vortec (they're 96-2002)

[peejay]

Bore should be fine, 305s had smaller bores

[68maliblue]

No signs of overheating on the engine the vortec heads came off.
From what I understand they usually crack if overheated and I did not find any cracks when I cleaned up the chambers.

[rebelyell]

straight mill-resurface heads only as much as levels them
clean all surfaces w/ brake/carb cleaner or lacquer thinner or acetone
coppercoat 7733SH1 shims and don't look back.

[68maliblue]

I may be wrong but it appears to me that the embossed or raised portion of the 7733SH1 shim gaskets should conform to whatever variation in the heads is present when compressed making them quite forgiving. Especially if coated with copper coat or whatever. On a low hp build like this it would seem that there shouldn't be much of an issue, even if the heads are not perfectly flat.

[rebelyell]

I may be wrong but it appears to me that the embossed or raised portion of the 7733SH1 shim gaskets should conform to whatever variation in the heads is present when compressed making them quite forgiving. Especially if coated with copper coat or whatever. On a low hp build like this it would seem that there shouldn't be much of an issue, even if the heads are not perfectly flat.

That's just it, appears & should may not work for you. Shims are FAR less forgiving than composite. Otherwise, ALL those published references that advise no more than 0.003" were authored with no good reason. Have the shop skim the heads off and make certain it's written on the work order that you're using shim gaskets (so they finish with proper smooth minimal Ra).

[econo racer]

3 thou. is too much. I would surface them. Did you check the deck and see if it is flat. I like composition head gaskets better. I had bad luck with the steel shims when I was young. Never trusted one since.

[68maliblue]

Deck is good. Smallest feeler gauge I have is .002” and it checks out fine with a straight edge.

[rebelyell]

Everybody makes mistakes.
GM had very good luck with shims over many decades of OE serial production use.

[turbo camino]

Composition gaskets are very squishable... which is why the heads are no longer flat. If they'd been run from new with shim gaskets they'd likely still be flat now.