Hi all, Happy New Year,

I've got a '65 c10 currently with the 250,trying to track down a 292 for it but until I do I'm planning rebuilding the 250. This is my first inline 6 build, well I guess my first "full" build of anything actually.

Initially I was just going to get one of the blueprint kits from Clifford to take the guesswork out of the build because the truck is my daily driver but I'm deploying next year so I'll have time to do more of the planning, which is what I wanted anyway. So I've got a couple questions(for now):

My goal is around 300hp, planning on running a CAR Saginaw 4 speed(3.50 first gear)
I'm going to do a .030 bore, flat top pistons Clifford intake and a 4 barrel carb. my first question comes in at the cam selection...
I have front disk brakes with an 11 inch booster, I'm wondering if anyone has any suggestions for a good low end performing cam that won't affect/be affected by the vacuum of the booster?

On to the head work...I'm planning on porting the heads and a lump bolt kit. What else do I NEED when it comes to head work? I'm real lost in the weeds when it comes to the head to be honest.

Also planning on running dual exhaust from the headers, I know that there's some added cost doing that. Is there really any notable benefits from that or could I save some money here and just bring the exhaust to one pipe from the headers?

These are my only questions as of now. Please let me know if it sounds like I'm overlooking something as this is my first inline 6 build. I welcome correction.

Thanks all

At 300 HP in a 250, you will have no low end to speak of. And installing it in a near 4000 lb. vehicle may be disappointing to drive until you get up to freeway speeds. We did a pretty thorough series of dyno tests a few years back with a 250 and a 292. You may try to search for them read through them. A 292 would be a better candidate at the 300 HP level for your application, or maybe consider a turbo to help regain the low end power that is lost by the N/A build of the same level. I went ahead and found the 250 dyno thread so you wouldn't have to search for it.

Here's the 250 dyno thread below:
https://www.inliners.org/ubbthreads/ubbthreads.php?ubb=showflat&Number=56536&page=1

You can use a vacuum reserve canister to store vacuum for the brake booster - so you have some room to play with carbs and cam.

But to CNC-Dude's point when you try to get more than 1 HP per cu-in displaced (in a NA engine) you end up with a HP curve that is tall and narrow with an equally narrow peak power band at the very top of the RPM range. This is great for the track but terrible for the street.

When you put it in the HP per cu-in ratio it makes a lot of sense. Also thank you for the thread, I don't computer good so it probably would have taken me a while to find it haha...

I've been searching for a 292 in my area and even a state north or south but they are still in the trucks and the owners just want to sell the whole truck. I may just hold off on starting anything until I find one.

Thanks for the info!

Tom,
250-275 HP is easy to hit with a 250 and be driven regularly. Making vacuum for power brakes may be marginal. Idle vacuum will be around 14-15" Stock vac is higher around 18 or higher.

Head work- I'd say to start with a bolt in lump kit and enlarged valves along with port work. Also machine it for screw in rocker studs.
I did the Dyno testing on the 250 and 292 with financial support from fellow inline enthusiasts and physical support from my local inline buddies. Parts came from a # of places. It was a bunch of work.

Why not just start off with a 290HP (stock engine SAE NET) GM inline 6? You have a ton of room for it. They are readily available for under $1500.

https://www.inliners.org/ubbthreads/ubbth...90741#Post90741

oh geeze....


Anywho... 250 build:

Offy intake: $200-ish
Holley 390 CFM carb: $100 + rebuild or $300 or so.
Langdon headers: $300
Exhaust: Figure another $500 or so.
HEI: You can get them cheap on Fleabay for under $100 or go with a nice one for $300.
Cam swap: $500 or so (figure cam, springs, lifters, gaskets)
Radiator and electric fan (frees up 15-20 hp): $200 cheap or up to $1000 for something that won't do much more than the $200 setup will
2004r trans swap: Figure anywhere from $500 to $2,000 depending on how far you go there.
Rear-end gears and posi: $600 if you do it yourself.
Lumps and oversized valves: $800 or so

That'll scoot you down the road pretty well. It'll be like having a stock 350 and with the right gears and trans you'll knock down some decent mileage too (I'm guessing in the 20's). You'll be around 250-275 hp and have the gearing to use it properly.

You'll run into a lot of "while I'm in there's" so add 10% to your budget. Also this is assuming you do the work yourself. You can go a step further and do pistons and rods and have it ready to turbo charge it to hit around 350hp or so or just keep the boost lower and hit 325hp with stock internals. If you do that I recommend EFI and water or meth injection to stop detonation.

Here's what mine looks like right now not 40 feet from where I sit:



(plug wires, distributor and battery are out)

More pics: http://imgur.com/oSDlVcI

I'm in the middle of finishing up my transmission swap. I also did some other things (remember when I said "while I'm in there's?"...). That project is in the "engine pulling 101" thread in this forum.

I haven't done the rear end or head work yet. Doing mine in stages. Also no internals at this time either. I probably have 3 grand in the engine spread out over 4 years so it's not too hard on the wallet.

I concur with others that the big CAM will really hurt low end performance. I put in a CAM that isn't supper aggressive. Low end is sluggish, but the high end screams!! If you're pulling stumps worth that truck, be careful on the CAM you choose.