big block chevy headers?

[Jim_PA]

Anybody know what mods it would require to make something like these: http://www.jegs.com/i/Hedman/500/69130/10002/-1?CT=999

bolt up to an LSx block?

Just thinking out loud, and trying to find big tube headers.

[68GMCCustom]

does a big block use 4.4" bore spacing?

[Jim_PA]

I don't know, but LS flanges are cheap enough through GMPP. Wonder if 2" primaries are too big?

[Jim_PA]

I'm mainly adding these BBC header options so I don't have to look the numbers up again, should I attempt anything

Hell, these are 1 7/8 for $129.99

http://www.jegs.com/i/Flowtech/387/11530/10002/-1

How hard can it be? Weld on some LS flanges and away we go, right???

[Jim_PA]

Ok, so center to center on my LSx style exhaust manifold gaskets is right about 4.5" -- anyone know what the center to center measurement is on a std. BBC manifold gasket???

[Jim_PA]

Call me crazy, but I ordered a set for $108 w/free shipping from Amazon.com

Amazon.com: Flowtech 11530FLT Black Standard...
BBC exhaust ports should be like 4.8" - I can't see how there can't be a way to make this work.

[Jim_PA]

Ok, so there only 1 3/4". And I noticed today the price went up to $129???

Guess I got a deal (if they work) - but they are still offering the free shipping.

[68GMCCustom]

our pioneer!

[Jim_PA]

Originally Posted by 68GMCCustom

our pioneer!

Well, I have the 1 3/4" flanges from the F-body flowtechs, so I plan on test-fitting the BBC headers to verify they'll fit...

If they look good, I'll chop off the pipes from the LSx flanges and weld them up, it's fool-proof

[68GMCCustom]

Originally Posted by Jim_PA

If they look good, I'll chop off the pipes from the LSx flanges and weld them up, it's fool-proof

...at least in theory.

[Ackattack]

I've heard of people using mustang (5.0) headers and changing the flange. I would guess you can get some of those in a large diameter.

GL!

[Ceeten]

Let us know how the BBC headers turn out. I was thinking the same thing.

[Super73]

I was thinking about doing something similar for the 418. But I was going to looks for a 2" tube that was a fenderwall exit style rather than turning right away. Should help me with the cubes and bottle.

[Ratpowerd67]

2" tubes are going to kill your bottom end on the street. i ran 1 7/8 with true duals and had to go back and do the y pipe with single outlet to gain back the back pressure. i have the dyno sheets somewhere on the before and after. the big tubes are realy for all out raceing, its all about top end at that point. this was on a 6.0 with a 228r cam

[Jim_PA]

Originally Posted by Ratpowerd67

2" tubes are going to kill your bottom end on the street. i ran 1 7/8 with true duals and had to go back and do the y pipe with single outlet to gain back the back pressure. i have the dyno sheets somewhere on the before and after. the big tubes are realy for all out raceing, its all about top end at that point. this was on a 6.0 with a 228r cam

Makes me feel better about the 1 3/4"

Rest of exhaust is 3" w/12" case Magnaflows with X-pipe, plan to exit out the sides in front of the rear tires.

[cableguy0]

The 1 3/4 should work real good with your combo Jim. Just remember anything fits with a torch and a welder. You might also want to call stahl headers. They arent far from you (York) its possible they will have adapter flanges for what you want to do instead of having to hack up the headers.

[Super73]

I'd agree 2" primaries would hurt some TQ bellow the curve and are geared more towards high rpm stuff. I don't think a stock 6.0 even with big cam and heads will really need more than a 1 3/4 stepped to 1 7/8. Something closer to what I'm doing (418ci with big hit of N20), that's a different story.

[68GMCCustom]

....except when its 6.0L running the new rectangular port big valve genIV heads...Based on what the guys running them are saying......that 1 3/4" is a min. and 1 7/8" is optimal (stepped or not) for most except in all out racing.

[Jim_PA]

I am on my way home to see if they fit. I hope you are all as excited as I am to know the result

[Super73]

If you are refering to the L92 heads, I still don't think they need 2" primaries. Yes the heads don't have good I/E flow ratio and that is why it's best to use a decent size split cam, but you should not need 2" primaries.

[Jim_PA]

Ok, so the pipes are routed perfectly, but the angle of the heads makes just hacking the flanges off, and welding on LS flanges not as straightforward as it seems.

They hang below the frame, but that's where I want them, as I don't need the heat at my feet, or right near my fuel lines.

[68GMCCustom]

Originally Posted by Super73

If you are refering to the L92 heads, I still don't think they need 2" primaries. Yes the heads don't have good I/E flow ratio and that is why it's best to use a decent size split cam, but you should not need 2" primaries.

I am...but I didn't say that they need 2" primaries....I said they need 1 3/4" primaries at least...and 1 7/8" would be better.



So Jim...whats next?

[Jim_PA]

Originally Posted by 68GMCCustom

So Jim...whats next?

At the moment, here's what I'm thinking....

Cut 1st pipe from flange, leaving 0" of pipe @ flange

Cut 2nd pipe from flange, leaving 1/2" of pipe @ flange

Cut 3rd pipe from flange, leaving 1" of pipe @ flange

Cut 4th pipefrom flange, leaving 1 1/2" of pipe @ flange

weld all those pipes to the flanges I have cut off flush (+a little room for butt-welding) from the flowtech F-body headers.

Not sure if this is the route I will take, but it's the best I've got at the moment.


What I'm trying to do with this maneuver is to bring the collectors more towards the trans, rather than towards the frame rail...

It will take planning, but I think I can do it!

This must be done carefully with each step, or the headers could be very quickly ruined

[Jim_PA]

AND --- in case it isn't obvious ---

When you look at the picture of me holding the header against the frame... Then look at the picture of where the flange is in relation to the head....

That is the problem that needs to be addressed.

Any ideas are much appreaciated,

I still think this is doable, and a viable alternative to $550-$1200 headers.

[Jim_PA]

Maybe, just say "F-it" and straight-up weld the LS flanges to these headers, and clearance the frame-rail to fit.

Please help