The Stovebolt Site Forums The Shop Area Engine Shop 250 c.i.d. horsepower

I have a 66 C-10 with the original, untouched 250 mated to the original 3-spd Saginaw with a 3.73 Posi out back. Is there an easy way to get a bit more horsepower and torque out of the engine without breaking the bank? I'm just checking out my options before I begin restoring my C-10. Thanks for your help.

Swap the 250 for a 292.

I wonder if you can get nitrous for a 1bbl! Maybe a good hi-perf forum post.

Put a Clifford manifold on with a 2 bbl or little 4 bbl carb.

More carburation is where you want to start. Check out some of the adaptors or manifolds that will accept a small 350cfm carburater or a small progressive 2 barrel like the Weber/Holley.

The exhaust manifold is fine for a stock engine. Long, small tube headers will really help the low rpm torque, but they need to be really long, 35" to 40" of 1 1/5" to 1 5/8" tube. After the headers, it won't make much difference in pipe or size, 2" will work fine for dual pipes, or one 2 1/4" single system. The 250 is a small engine and doesn't move much air in or out!

With out a highly modified head, a bigger cam won't do much except move your power band up the rpm scale to a range you normally don't drive in. All though with your 3.73 gear, alittle more cam wouldn't hurt. Stock cams are good for low rpm torque, under 3000 rpm. You are most likely cruizing above that all ready. Check the rpm range of the cam before buying one. You sure don't want a 4000 to 7000 rpm cam for the street! Joe

Nix the 292 idea. Stock the 292 doesn't have that much more power, and the 250 actually has more power per cubic inch. The 292 is only like 10 more horses. A lot of guys like the 292 and they are a good truck motor. The 292 does have more POTENTIAL horsepower by virtue of the bigger displacement, but it will cost you a bundle to move those horses from the land of potentiality to the land of reality. However, there is no real reason to dump your 250. Especially not if it's an original matching numbers engine. It's certainly bigger and has more power than the 235's and 216's you find in a lot of these guy's trucks. The stock 250 has around 155 horses. If yours really is "original and untouched" it probably doesn't produce much over 100 horses because it is old and WORN OUT.

Here's what I'd suggest:

307 V8 Pistons with new rings of course.

Rod and Main bearings

Cam bearings

A good valve grind done buy a reputable shop

Clevite cam sold by NAPA as The MPG Perfomer. specs are .464" Valve Lift, Intake .490" Valve Lift, Exhaust Duration at .050" 194 Degree Intake 204 Degree Exhaust 110 Degree Lobe Spread. (comes with new lifters.)

Holly / Weber 5200 carb from Langdon's Stovebolt Motor Company. Use Langdon's adapter and stock intake.

Split exhast manifold into dual glass packs.

This will cost about $1000 bucks if you do most of the work yourself. Not cheap, but not breaking the bank either. You get to keep your original matching numbers engine and now it runs around 185 horses compared to the 100 or so you're getting now, and even with those 3.73 gears you should still get 16 mpg on the highway as long as you hold your speed down to around 60 mph. If you want better milage at higher speeds you'll have to go to a more hiway freindly rear end.

Boo

PS
If you decide you want a more hiway freindly rear end, I'll gladly dispose of that old worn out posi for you!

Might I suggest checking eBay? I'm completely stocking my 250 with parts of other people's abandoned projects. Cheeeeeap parts.

One thing on those 307 pistons, they will raise the compression if they are true flat tops. I bought a set once that had more valve relief cuts in them then the stock 250's did. Once I figured out the cc's I had lost due to the relief cuts, the compression was the same as stock pistons! Joe

The stock 250 pistons are dished. I doubt ANY 307 piston is going to have more cut out of the top. :p

Find a late model(78 to 80)one piece head it is already set up for progressive 2 bbl and has dual exhaust outlets

The only problem with the one piece head is the bad about cracking between 3 and 4 and 4 and 5. if you ever let it get hot at all.

super250

And yes; follow GMCPanel's advice and keep a CLOSE watch on ebay.

boo

Stay away from the "boat anchor" one-piece head. Get a Clifford intake manifold for adding a 2 or four barrel carb.

I'm not sure you can get anyone to split the exhaust manifold now days. I tried to use one of the recomended companies on this site and they told me they woudn't do the one on my 66 C10.

They don't like to do L22 manifolds because the iron used was utter junk. You might find a local shop that will do it...I think I'm just going to try on my own.

Ba humbug Go for a 350V8 because in the long run this is what your going toooo do.sounds like you want some HP.Pay me now or pay me later.After everyone passes you on the highway :confused: :confused:

I want to keep the 250 since it is the original, numbers matching engine. The saginaw and rear axle also match numbers. The only modification that I have done is replace the Rochester B with a rebuilt one.

in my 1965 C10 it had the 230 I-6 but it threw the #1 rod and mangeled it badly broked the piston skirt on #1 and the cam shaft was broke clear in two right after the 1st lobe. so i junked it but keep the head intake and exhaust manifold off the 230 and i bought a running 250 out of a 84 c10 and it has that 1 piece head that is set up with dual exhaust manifold but it interfers with the clutch linkage on the 65 so when i got the time i want to put the 230 head on the 250 engine if it works
Nate

Yep, just got an email on that subject myself. Kansas Kustoms says the success rate with the newer I-6 manifolds is so low they don't take those jobs anymore. I think if you clean up the manifold to match the gasket and run the header pipe into a glass pack and then just dump the glass pack on the ground it is MUCH better than stock. My stock exhaust had something like five 90 degree bends in it! The problem with dumping a glass pack on the ground right at the header pipe is that it echos really loud in the cab, but hey, like I've often said, If it's to loud, you're to old!!!

Boo

:rolleyes: