351c Turbo headers construction in its infancy

[duplox]

I decided to create some 3d computer models of the headers that I'm planning on building for my turbo motor(see bottom for details) so I can see what bends I need to buy. Each one of these uses 4 45* bends, 2 small radius 90* bends(1.5" radius), 2 large radius 90* bends(2.25" radius). These are standard weld-els, schedule 40. Inside diameter is around 1.6", OD is 1.9. I just used 2" in the model, so the ports look a bit big from the inside. I'm more concerned with the outside for the purpose of this model. These point foward, both turbos will be in front of the motor. There will also be a crossover tube that goes to the external wastegate. If I can't fit the headers by the stock mounts, I'll buy/make some motor plates.

The collector won't look that pretty, it'll probably be made out of plate steel with the corners filled with weld to make it nice and smooth inside.

Here is another one with a mocked up engine in there:



I've already bought the header flanges, I'm going to either buy or make the turbo flanges.

About the motor/car:
Ford 351 Cleveland, custom JE Forged blower pistons, Eagle 351w 5.956" H-Beam 4340 rods/ARP Waveloc bolts, stock crank deburred and balanced. Stock block, bored .030 and filled within 1" of the deck with HardBlok. Its goin in a '69 mustang coupe, subframe connectors, roll cage, Ford 9" spooled axle, hopefully a Satchell-type 4-link suspension on the rear. Car is mostly street driven. Plans are to push 6psi for the majority of driving/pump gas, with 10psi on water injection/pump gas, and 12-15 on race gas and water/alky inj. Turbos are two T3's, .60/.63 A/R.

Any thoughts/suggestions?

[mike@af]

Kickass. What program did you use?

[duplox]

Its called Rhinoceros... www.rhino3d.com

[TheSilentChamber]

ever finish your intake manifold? Headers look good, now make them look that good in real life. Turbo headers should have equil length runners though for it to run the best.

[duplox]

I haven't finished the intake, or worked much on it since late august... I've been at school. Thats why I'm stuck modeling exhaust manifolds instead of building them! I'll do equal length if I can figure out a good way to do it. I don't have much room on the sides of the engine. I'll fiddle around in rhino and see if I can't figure something out.

I just remembered - I also have to fit two 2 1/2" pipes in there somewhere for exhaust... hmm.

[psychorallyfreak]

Pressure is pressure. As long as it gets to the turbo, (I think) it doesn't really matter. Look at the 900 Turbo for my point. Equal-length primaries to the turbo? Nope.
Fun as hell? Yep.
One question about the CAD drawings: What's the F/B orientation on the engine for the headers?

[duplox]

Originally Posted by psychorallyfreak

Pressure is pressure.

Turbos are a heck of a lot more complicated than that... even if it was, that pressure comes from each port only when the corrosponding exhaust valve is open... if they're different lengths, the pulses get there at irregular intervals; result:slower spool, less efficient. Exhaust pressure wave tuning is another big consideration. This can help prevent exhaust reversion.
If 'pressure is pressure' was right, everyone would use log-type manifolds - easiest to make and most compact. Unfortunately you then get issues with certain cylinders getting more or less exhaust wastegated. Then you have a big issue with multiple exhaust pulses meeting in the same pipe, which causes excessive heat and therefore thermal expansion and turbulence.

anyways, what do you mean by f/b orientation? Front to back? The turbo flanges point towards the front of the car if thats what you mean...

[Cbass]

Looks awesome! Sched 40 is pretty thick stuff, good for welding, but those aren't going to be light headers by any means. You're going to want to figure out a way of supporting those headers with an external bracket or something.

Equal length headers are theoretically superior for a turbocharged application, for even pulse tuning, but that pulse tuning will only be in one rpm range. If you have nice long tube headers, this will promote the pulse tuning effect in the lower rpm ranges. Unfortunately, you can't make the primaries that long, since you need to fit the whole setup under the hood. Personally, I wouldn't sweat the pulse tuning, since it's not nearly as important to tuning a turbocharged engine as it is to a NA engine.

[TheSilentChamber]

Originally Posted by Cbass

You're going to want to figure out a way of supporting those headers with an external bracket or something.

Yeah, Hes right, once you bolt up the turbo's those are going to be real heavy, and the way the exhaust flange on the 351 bolts up it leave alot of room for exhaust leaks. Only thing with building brackets is those headers are going to get hot as shit so you have to be carefull what the other end of your bracket bolts to. The easyest place would be to run a bracket down to the oil pan bolts, but imagine how hot that would make your oil run, plus probably burn up the oil pan gasket. But you dont have a choise except to bolt it to the motor because of torque twist you couldnt brace it to the fender or anything.

[duplox]

Thanks for the replies! I'm planning on running a bracket off of the front of the motor, either the heads or water pump mounts. I'm running a remote electric water pump to give me more room up front, so i have all the bolt holes for the w/p to secure a bracket too, plus the only accessory I'm running is a alternator so I have most of the accessory mounting points to work with.

[Cbass]

I'd be really concerned about the weight of the headers themselves, sched 40 is pretty thick stuff, a foot of 1.5" sched 40 pipe weighs about 5.5lbs, so it adds up pretty fast. I would at least want to use lightwall pipe for making headers. It's not quite as easy to weld, but it's still plenty thick and as long as you keep moving the gun along at a steady pace, you're not going to blow through it easily.

[TheSilentChamber]

I didnt realize it was that heavy, theres probably 4-5 feet of pipe in each one of those headers.

[mike@af]

Why not use DOM?

[duplox]

The reason I decided on sch40 pipe is its been recommended specifically for turbo applications from a few people, including in Corky Bell's "Maximum Boost". I'm sure some of you have seen this website:
http://www.sdsefi.com/techheader.htm

A stock cast iron manifold weighs around 8-10lbs, and they're log-style, so yeah each fabricated header will weigh in at around 20lbs.

If you have any other recommendations for materials, I'd like to hear them. I won't use anything in mild steel thats much thinner than sch40, from what I've heard thin mild steel will fatigue and break if not thick enough. Stainless mandrel bent tubing will cost me a large fortune, which I unfortunately do not have. What is DOM?

[mike@af]

DOM is mild steel, and stands for drawn on mandrel. It comes in a variety of thicknesses.

You could also use 4130 (CroMo), however it is a pesky material. There are pre heat and post heat methods needed for welding it. 4130/4140 are very strong, and end up saving weight sometimes because they can be a little bit thinner than DOM.