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Heads and Stall?


Guest datsun75

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Guest datsun75

I have just purchased a set of 64cc double hump heads for my 1975 dished piston motor. Should I get a certain thickness in head gasket to up my compression the best I can? or should I mill these heads to 54cc and still be able to clear valves and pistons and run premium gas okay?

 

I am going to use the stock factory cam now, and I am now getting ready to buy the Wiend Stealth manifold and Holley 600cfm carb. How should this motor perform?

 

I currently have a stock rebuilt turbo 350 should I get a mild stall converter for this setup if so what stall speed?

 

Lots of questions I appreciate any advice you may have. Thanks yall! icon_biggrin.gif

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You should probably invest in a few books:

 

Two I have that are decent:

"How to Build the Smallblock Chevrolet"

By: Larry Atherton, Larry Schreib

"Small-Block Chevy Performance : Modifications and Dyno-Tested Combinations for High Performance Street and Racing Use" By: Dave Emanuel, Jerry Hensley

 

You really need to check the deck height of the pistons before you go with that steel shim gasket. Even a lump of clay on the rim of the dished piston, put the head on and snug the head bolts (no gasket), then measure the clay thickness will give you an estimate. If it's less that say .020", the 0.018 steel shim gasket is too thin. I've heard there's a 0.024" gasket that GM has that may help.

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Guest datsun75

Ok cool! This is very helpfull, Im soaking all this up. My brother may have that book. I'll try and grab it off him.

When you say on the rim of the piston, this is with the piston at TDC and I put on the outside edge of the piston where it meets with the flat part of the heads chambers?

Thanks a bunch for input... icon_smile.gif

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That's correct. By rim, I mean the highest part that would be closest to the head. And yes, use a piston stop to find TDC accurately and calibrate the harmonic balancer/pointer, or better yet, use a degree wheel. If you just turn the motor over, you'll squish the clay to minimum thickness and not need to do that though.

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Make sue you know the history of those heads; they may have been milled a time or two...or three!

 

Be sure & check w/a local machinest whose knowledgeable on those heads...and not merely a machinest who has an ego but no reputation to match!

 

You want honest answers to serious questions. BTW: if you're putting those heads on a "Bone-Stock" low perf.engine then you might consider buying a cheapy $110 cam/lifters from someone. You dont have to go hog wild but a mild increase in cam spec's should be more than adequate even if you're using low comp. pistons!

 

Not knowing your intent/bank account another consideration in choosing your cam is one that will be on the edge of "Almost Too Big" for those pistons...further down the line you can purchase a alluminum intake to better match the cam & heads; a mild dual-plane would supplement a mild perf.cam nicely w/out placing too much a burden on your stock pistons.

 

One other thing if/when you want to up your cam..dont forget to think about your valve springs. Being Double Hump Heads they may already have pretty decent springs/ya never know till properly checked.

 

Just something to think about.

 

Kevin,

(Yea,Still an Inliner)

 

[ October 29, 2001: Message edited by: Kevin Shasteen ]

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Any idea what the volume of the dish is?

 

I guessed 12cc as the dish volume, a standard 4.000" bore, 0.025" (typical) deck height (below the deck) and 64cc's and got 9.4:1 with 0.018 compressed thickness steel shim gaskets. Just keep at least 0.035", but not more than 0.060" piston to head clearance and you're in good shape for quench.

 

My calcs don't include crevice volume, but it's typically 1cc, I believe. So 12cc could be 11cc in the dish, 1 in the crevice.

 

Decking those heads that much sounds like alot. Is that safe (is there enough deck thickness in those old heads to allow that?)

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Guest datsun75

Oops...... The heads are going on a stock 350 motor. I dont know what the dish depth is I dont like it though. I know that the 1975 camaro was running around 155hp in that year. So the motor can't be any more than that stock.

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Guest datsun75

I wish I could take a one day class to understand these clearance measurements and how to figure them out physically. I appreciate the input. I guess I will keep them at 64cc and install the .018 steal head gasket. Should I install the head and rotate motor by hand to check clearance? Im way out there on these technicalities. icon_rolleyes.gif

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