whats up guys
I have a gm crate motor in my 68. the motor dynoed 167 whp thru a TH400. I'll be changing to a TKO 600 very soon and i would like to make about 300-350 whp.
the engine has low miles and I would like to know if its worth modding? I want to put aluminum heads and cam on it. Or should i change the rotating assembly and heads/cam. I'm a bit worried about the low compression of this motor (8.5:1).
What do you guys recomend?

here is the engine specs:

Crate Long Block: Goodwrench 10067353 350 long block

Displacement 350 cubic inches
Bore 4.00"
Stroke 3.47"
Compression Ratio 8.5:1
Estimated HP 250 HP
Estimated Torque 350 ft. lbs at 3600 rpm
Block Part #10066034
Casting #10066036
Main Bearings 4-Bolt mains, 2-piece rear main seal
Crankshaft Part #3932444
Flywheel Bolt Pattern Nodular Iron 1985 and older
Connecting Rods Powdered metal (Part #10108688)
Pistons Cast Aluminum (Part #12514101)
Oil Pump G.M. High Volume Pump (Part #12555284)
Camshaft Low End Torque Oriented Hydralic Flat Tappet w/fuel lobe (Part #14088839)
Intake Lift .383"
Exhaust Lift .401"
Intake Duration 194 at .050"
Exhaust Duration 202 at .050"
Lobe Seperation 112
Cylinder Heads* Part #14034808, Casting #33417369
1.94" Intake valve, 1.50" Exhaust Valve
76cc Combustion Chamber
Exhaust Flange 7 Bolt Standard
Intake Manifold Type Pre-1986 Bolt Pattern
Valve Covers Perimeter bolt style

gilbert chevrolet ....

are the 76cc heads the main cause for the 8.5 compression?
could I could get a set of Dart aluminum heads with 58 cc chambers and mill them a bit more to 55cc to get to 9.5 or 10 :1 ratio ?
I realy want to make this motor work because shipping motors to my country costs about $1500-1800. the heads will ship for about $200-300.

Order a complete Dart top end kit. That will solve all your problems.

Right, smaller cc chambered heads and either .015" or .020" shim headgaskets will do fine.

Use this to calculate your CR.

http://www.rbracing-rsr.com/compstaticcalc.html

And then this to calculate your dynamic compression ratio and shoot for right at 8 to 1 so pump gas can be ran w/ iron heads.

http://www.rbracing-rsr.com/comprAdvHD.htm

pdq67

anyone know what is the pistons cc are in the engine above?

I'm guessing that the deck height is between .02-.03 is that right?

no way to tell unless you are really good at math...

Just put good heads and a cam in it and you will be fine

-12 cc's for dish volume is what I'd input.

Can't be far off.

And one way to back calculate this is to start w/ 8.5 to 1 and work backwards until you get to piston top cc.

I do this every so often.

pdq67

-12 cc's for dish volume is what I'd input.

Can't be far off.

And one way to back calculate this is to start w/ 8.5 to 1 and work backwards until you get to piston top cc.

I do this every so often.

pdq67

Thank you. i used the -12 cc input and with a 64 cc head i got about 9.3:1 . and 10 :1 using 58 cc heads.
are these rods and pistons strong enough to take the abuse of road racing ( 20 minutes above 4000 rpm)? i already ordered the Hotchkis TVS kit along with the Speedtech UCA, TKO 600 and wilwood 12 inch brakes.

YES.

He, He!! GM parts are like anvils!

Heck, even the little-bitty 283/302, 11/32" bolt rods will hold up fine!!

pdq67

IU just googled the part number, here they be:
http://www.kb-silvolite.com/spistons.php?action=details&S_id=259

.07" full dish with 4 eyebrow reliefs.
Another reference I found said ~ 13 cc's, so your guess was pretty darned close, Paul!

While swapping those for a set of flat tops would be nice, some decnt small chamber heads and a good cam and kit will get her running happy.

Input 76 cc heads and .038"/.039" or so thick composition headgasket's and I bet you will be close to 8.+ to 8.5.

W/ a DITH piston of .025".....

pdq67

PS., hey Jim, whens our next shared cost road trip?? Let me know so I can save up my nickels and my dimes!!

Had a great trip to the "Dust Bowl" the last time!!

Steaks are on me! You get the tip if our waitress is a doll!! He, He!!

I agree with the guys that say "get 58cc heads". You want the best flowing 180-200cc runner head that you can afford with 58cc chambers. Just bolt them on the stock bottom end and enjoy the roughly 80HP increase (assuming you get a good head like an AFR).

I would also change the cam and use something that is in the 224* @ .050 duration range with a 110* LSA.

For an intake use a Performer RPM. A 650 Holley double pumper would be my choice for carb and a set of long tube 1-5/8" headers.

That should easily bump your power from the stockers 240 'ish at the flywheel to 350-375 (maybe 400 if you really play your cards right)

Ditto Eric here!

pdq67