455 Performance upgrades with NO headers

Hey guys i have my 69 C10 build and i have a stock 72 455/th400 combo in it
However i am thinking about pickup another local &2 455/th400 combo..
it definitly needs to be gone through ...

and when i do that i definitly would do a more preformance oriented build and try to squeeze some horsies out of her...
HOWEVER i cant fit headers in the C10 frame rails so i am wondering if it is even worth it
when using stock Manifolds

I can get the Heads milled ,ported locally and stagew 1 valves installed
i can pickup a cam get the block decked
and possibly find a better Intake as the S-divider i have on the motor in the truck right now..

Is it worth it, what can i expect without headers through a 2.5 -3 in exhaust

 

I know people port the stock exhaust manifolds and they flow pretty good. Not as good as long tube headers, but good enough to support performance upgrades. I don't know much about this. I just recall reading a couple posts on it. Maybe do a search for ported exhaust manifolds.

Also, will shorty headers fit?

 

Maybe make some custom headers over the frame?

 

What about shorty headers?

 

Not sure what kind of room you have. The 64-7 Skylarks have issues with headers, but apparently, there's more room for headers by using the Stage 2 heads, the headers for them fit better. Maybe that'll help your situation out?

 

That's tough to know how it will fitnon a chevy truck without buying heads and headers. 3500 gamble????? With no heads available

 

What about modding some small block chevy headers for your C10. Cut the flanges off and weld them to Buick big block header flanges. You would want at least 1 3/4" though.
Greg.

 

You haven’t said what you consider a “more performance oriented build“ but if 500 hp and 550 lb ft of torque will satisfy you, you can get there without headers.

My build is a 475 cu in with stroker crank and stock bore. Intake, carb and exhaust are stock with some expert porting on the manifolds. The key to reaching 500 was aluminum heads with additional porting and a medium roller cam and lifters. Compression is 10.5 and it runs fine on 93 octane with plenty of vacuum for power brakes.

 

With pump gas compression and stock manifolds,..you're gonna hit a wall around 425,... options
stage two heads stage custom headers or I think the shorties would fit
You can trim the rail ledges back a good bit b4 affecting strength
Be happy with 425hp

 

Thanks for all the comment
The issue is the shape and size of the block
Sbc headers are cheap and I could try that.
However it's fab work I was not planning with at this point

Porting the oem manifolds, is there a DIY guide?

500hp is absolutely ok.

I am not investing in stage 2 heads etc.

I agree with @hugger I feel like headers are essential to make power , if she can't breathe all the internal work isn't worth it...

Maybe I just add a nitrous plate to the stock motor lol
150 hp right there lol
I just installed EFI and I can add full timing control which could make the stock bbb live.

 

425 do I get there with
Fully ported heads and stock cam?
Or heads +cam?

Maybe up the CI , forged pistons heads cam and make it strong for 200+ shot?

 

See my post above. My motor Dyno’d at 502 hp with stock iron intake, 800 cfm Quadrajet, and stock ported exhaust manifolds. Heads are TA Stage 1 aluminum with Level II porting. Static compression is 10.5 and runs on 93 pump gas with 35 degrees timing. Jim Weiss has proven it’s doable.

 

My 10:1 462 made 400 hp with stock everything and a 218/230 cam. Some bowl work, a little more cam and I think you could find 430-440 pretty easy. But that said, what are you gonna do with the truck? Unless youre a serious drag racer, you dont need more than 400 hp. Anthing you do on the streeet is all related to torque, and a 400 hp 455 has more of that than anythign you' ll line up against. Maybe you wont be able to break the tires loose at 60 mph but if you live through it, thats a trick you dont want to do more than once anyway...

 

Stock manifolds,...ported opens things up,..but with stockish iron heads and stock manifolds,...425ish is where the party ends,...UNLESS you have over 12 to 1 and lots of cam,...my dad's first engine Dyno'd 504hp thru ported manifolds,..12.8 to 1 and a 107 window rattler,...I drove it to 12.40s at 114.7 mph,..4speed

 

The engine I'm putting together is all stock junk,..with no porting ..just cam and maybe 10.25 comp,....I'm not expecting more than 425,...it will run mid 12s at 102~104

 

hte reason is that i always considered to take part of the Powertour or equivalent
i feel like the truck could be a cool vehicle to drive and drag

 

very nice
What Cam specs would be good for such a build
and How to port the stock manifolds?

 

i like that approach...
I can get the heads proffessionally ported locally by my guys Inkl. magnaflux and milling + bigger valves and springs installed ( i have to provide the parts ) for 650 $
which is a bargain i think he might be able to port the stock manifolds as well?

 

Yes, stock iron heads does place limitations. It's the ported aluminum heads that opens things up considerably.

 

The cam is a hydraulic roller with 23o intake and 244 exhaust duration at .050 lift. on a 112 LC. Intake lift is .590, exhaust is .565. Engine idles at 800 RPM in gear with 15 in. vacuum. This is not a radical cam. Runs on 93 octane pump gas in my full weight '70 GS455 with A/C, PS, PB. Car runs low 12s at about 110 MPH.

As for manifold porting, there are several members on this forum as well as others that do it. If you would like the info on who did mine please PM me and I'll share the info with you. It's not cheap and if you decide not to spend the money on manifold porting it's only good for about 10 to 15 HP (arguably) over un-ported manifolds. The major cost in this build is the roller valvetrain and the Aluminum heads, of course.