BC

"Just say'in"

Seems like it makes a very big difference from 1.5 at the same length when the HP is above 600. Like 100 hp difference.

BC

Okay....

928SS

depends on cams, usage... smaller can give mo torque on bottom end. bigger for big end hp

BC

With boost, it seems like my setup just needs as much diameter and breathing as is physically possible, with very little downside.
Cams are big, with overlap. - It wouldn't really match the ex ports though. It would have a big ledge around the whole diameter at the port exit.

soupcan

1.5" diameter primary header pipes are tiny for 600+ hp. I changed headers from 1-3/4 to 1-7/8 primaries with the same 3'' collector on a 452ci Chrysler, HP went from 512 to 566. Changed to 2-1/16 primaries and 3-1/2" collectors, HP jumped to 580. Obviously I had to up the jets on the carb but no other changes were made.

BC

Well, that is what the software is telling me Brian.

largecar379

Same experience on the Quick 16 car......back when I was running my SS/DA car, we only had either 1-7/8 or 2 inch available--30 years ago, mind you. the 2 inch was needed once the heads were ported/port matched, but lost a little on the low rpm of things.

the Quick 16 car is running a 572 BBC with Dart heads, but we're working on a 630in motor that is going to require stepping up to 2-1/2in primaries.


sounds like your software is on target.......


--Russ

soupcan

This is purely from Drag Race experience. Build a headers primaries for HP and use you collector length to tune for torque. It's amazing how much you can tune a car with collector length, I used to get more runs out of my slicks by shortening the collectors to move the torque curve higher so the tires would still hook-up. Would do the same if the track was not prepped well.

largecar379

well said---

you could also make the collector removeable/changeable to fine tune your application or track. primaries could also be adjustable.


--Russ

90 S-4

Brendan,
The ones I had Mark Anderson' guy specially make for me (2'' O.D. w/1- 7/8"
I.D.) are of a size that I was told would support my 1050 crank hp at 6800 rpm target ) If your target crank hp is higher than that and your rpm to is higher than the 2" I.d. probably is the right size
Joe
P.S.
anymore intake manifold info ??

BC

So that guy will make one offs? I just got his number today and should call him. Can I ask how much he charged you? The engine analyzer is giving me like 75 or more hp and nearly as much torque at all other constants simply by my changing the 20 inch exhaust primary from 1.5 to 2.0.

Intake Manifold - its 1st on my list after work and family right now. I spent the entire weekend learning CAD CAM software called ALIBRE from scratch, and I figured most of it out. The design I have in my head allows a very modular assembly of whatever you want, all with the same port flange, with the flange, seats for the 2 or 2.25 runner, and the injector boss is also on the flange as well.

Like this (only the port entry will be at an axis off of the flange so there is no change in direction):

Dennis K

What's the gain from 1-7/8" to 2"?

90 S-4

I think it was only about $100 to $150 more on top of the regular price.
He was concerned that my 2'' OD pipes might have some clearance issue
that I would have to deal with--No sweat ! But if you go bigger than mine
than you might have some serious problems. You are most welcome to test
fit my 2'' OD set onto your car to see if a larger set is even do-able ???

& Dem are some tasty Flange **** Pics there, no **** !

BC

There may need to be a compromise there with the 1 7/8. I mean whats physically possible... Just is. Past that is not worth it.

Thanks for the offer. I need to do more research on this. I mean, the analyzer could be wrong. I have to get my cams back from Performance Developements so I can get the full cam specs in the software. Then I can verify this.

BUt whats said here by two separate people shows what I found.

928SS

I went from devek L2 1 3/8" to devek L2 1 3/4". didn't seem to cut bottom end at all, but top end gained about 45rwhp. also put in a blackbird, 42# injectors and sharktuned, so it's hard to tell what did what, but the net gain was cool.

not sure if there's a lot more room in there though. was pretty tight...