The Stovebolt Site Forums The Shop Area Engine Shop Low HP 350, what are my options?

I have a 350 engine in my 66 c10. After doing some acrobatics inside my engine bay, I've found that the block number is a 3970010 and it appears to have a year of 1976. Doing some research on it I get the idea this is most likely one of the lower (sub-200) hp factory engines, but the suffix codes on the front of the block are gone.

The previous owner has dropped an edelbrock intake and 4 bbl carb on it, but it still feels a little sluggish. It still has the old delco-remy distributor and some pretty generic-looking plug wires. What are my best options for getting this guy up into a respectable hp range (250-300)? Is it going to take a bottom to top rebuild to get any performance out of this engine?

I am not positive on this, but if I am that would be an engine you would want to keep. I believe the engines with the 010 on the last 3 digets means it is a 4 bolt main and also it has a quite a bit better grade of cast iron. If it is an original truck engine it would have the low performance heads. Probably a set of better heads, either the 1.94" intake or better yet the 2.02" and a mild cam would make a vast improvement without spending a whole lot of money. If I am right about the engine being a 4 bolt main with the better block, I would hold onto it.

If you do the rebuild look at making in to a 383 .Same mild cam and good heads that crabbyappleton suggested .You will have a great combination . Try AFR heads you could use your old intake until you wanted to upgrade.

vortec heads
cam with duration around [email protected]"
HEI with decent plug wires
600 cfm carb
dual plane vortec intake

should get you in the ballpark

Well, it's good to know that it isn't a waste of time and money to try to take care of this thing. I was thinking that a new set of heads would probably be the place to start, but I understand that vortec heads would require a different vortec intake.

new intake isn't that much $$

If you've got the 76CC heads, you'll have 1.94" intake valves and 1.5" exhausts. Get a valve job done, and have the machine shop install stainless 1.6" exhausts and pocket-port the exhaust ports right under the valves. Have them angle-mill the heads .100" at the spark plug side of the head, tapering to zero at the intake side. This will reduce the combustion chamber volume to 60 CC, and give you a little more compression than those pricey 64CC double-hump heads. You'll also have the same casting number as the low-compression heads, in case a nosy tech inspector is lurking around. That's how I built 300+ HP "claimer" engines for the local round track. Swapping to a set of flat-topped Speed-Pro Hypereutectic cast pistons along with the head modifications will get you approximately 11:1 compression. Add a Comp Cams 268H High Energy cam and a good set of rams' horn exhaust manifolds and 2 1/2" exhaust pipes will get you around 350 HP, basically the same setup as the 300 HP 327's had, with the advantage of 25 more cubic inches to add a little power.
Jerry

Your casting number tells you nearly nothing. It was used for 1968-1979 327s and 350s, both 2 and 4 bolt! Factory HP ranges from 145 to 375. That number was also used as a "Hi-Perf" truck engine.

The only way to tell for sure is the stamped number in front of the left (drivers side) head. With HP ratings all over the board, you need to get the specifics on that engine and see how the HP was rated when it was built. Manufacturers played all kinds of number games to fit their production into Government regulations!

3970010 was also used by GM of Canada. Those engines could be found in some Buicks and Pontiacs. The Canadian engines were often rated higher in HP than identical USA engines.

"10" as final digits means nothing concerning the number or angle of bolts in the main caps.

Get that stamped number off the block for the real story!

I wouldn't do anything to the engine until it had a full tune-up and oil change. Adding an HEI and making sure the exhaust system was open wouldn't hurt either. Then you'll know what you have and can make informed decisions about what to change.

best wishes,

Les

Take your valve covers off and look at the casting number on the heads. You might have the 3998991 heads which have the 1.72 intake valves. If so change to ones with the 1.94. I have basically the same engie out of a 1978 truck that was rated at 185hp.

Aaron