I just installed a 350/290 HP gm crate engine in my truck, and it has no pop. Heads are 76 cc with dished pistons. I have a set of 461 heads and was going to rebuild them with 1.94 valves and new springs etc. the question is, will my comp ratio be streetable? Right now with the 76 cc heads it runs on 87 gas. Many thanx for input..............

 

You should be able to run them. You will have to run medium or high grade gas tho.

 

Any idea what the comp ratio might be?

 

what axle ratio do you run,
what year truck ?

you need low end lower RPM torque

a good towing or RV cam will be one of the best things you can do,

not increasing CR so much

modify it for better bottom end

you need ot have at least 3.42 or preferably 3.73 or 4.10 axle


trust me

been there done it in trucks, all starting in 96 with a 68 c-10 with a 355 th350 and original 3.73 12 bolt, it was no slow poke truck by any means, it was originally 307 2bbl and three on the tree SM326 til i killed the old 307 engine one night

it was 3850lbs and coil trailing arm rear suspension it was a blast i will make another one again for sure eventually,

im a truck freak so i am very curious..

 

A 1986 GMC K1500 4x4 Suburban axle unknown but prolly 3.23 At this time the cam has to stay due to warranty concerns, but it is the 222/222 450/460 chevy cam. I know it has to go but not right now. the induction is an Offenhauser dual port square port with a 3310-4 Holley, and headers are thorley tri y headers itno 2.25 inch duals with msd 6A box.

 

416 or 461 heads?

416 are 58cc chamber 305 heads, with accessory holes for nice things... like and alternator. Good heads to use on a smogger 350 like yours.

461 however, are a variant of the old double hump heads. They have 64cc chambers, and would have roughly the same performance as the 416 heads. They don't however, have hardened valve seats, since they were made with leaded gas in mind, and probably don't have accessory holes, which will cause alot of headaches.

 

416 heads of of my L69 305 Sorry for the misinfo.

 

A good budget hop up for your lame crate motor.
But don't just bolt them on stock. For best results, fully port them and install larger 1.94x 1.60" valves. Pin the rocker studs.
read my posts about porting these heads.
Your cr will be higher. You'll probabily need to run 92 octane gas.
Use Champion RV8c or Delco R42t spark plugs. The stock R45ts plug is for non performance city driving.

If you bolt them on stock 58cc chambers your cr will be 9.67:1 using a .028" thick gasket.

If you follow my recomendations (porting, larger valves, deshrouding)
You'll have a nice $high performance budget head$ with 62-64cc chambers
Your cr will be 9.6:1 using the .015" steel shim gasket.
You could gain 60 or more horsepower if you do it right.

I'd recomend replaceing the camshaft too. It was designed for 1969 corvettes (350-350hp L-46) with skinny bias ply tires. You can pick up a good bit of power and torque with a newer design from Crane Comp or Lunati.