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Vortec heads/header question

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b454rat

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I'm gonna be putting a set of Vortecs on my plow truck, 79 dually with a sweet running 400. With a mild cam, this thing is gonna run like a bastard. I can find a cheap set of headers, but they are 1 1/2" primaries. This isn't gonna be a race truck, but want to get the most power that I can out of it. Biggger 1 5/8" are available, but local place has the smaller ones in stock. Would the smaller ones be OK for a big inch motor??

Also, read that the only difference in manifolds/headers for Vortec heads is the EGR valve is plumbed in, not gonna be running one, so that isn't a problem. But just to verify, the exhaust ports have the same shape as regular heads??
 
Exhaust ports are the same in regards to whether headers will bolt up. They are a bit different, but not enough to matter.

I don't know what's recommended for a 400, I wouldn't want to say bigger is better, but one of the header manufacturers should surely recommend something.
 
Quick glance at a set of header ports looked different than the Vortecs. I would think that the smaller primaries would help at low RPMs, better throttle response and more torque down low where a truck would need it.

Looking at various header companies say the 1 1/2", but that is for small blocks, not just the 400.

I'll see what they go for again, I'd think it will be fine.....
 
The Vortecs will flow pretty darn good, but I suppose since the ports and valves were designed around the smaller engines, flow has to be limited somewhat, so smaller headers MIGHT work ok. I guess it really comes down to the ports themselves...if the primaries are bigger than the ports, you aren't helping anything.

I certainly wouldn't want to choke it too much, have you done any searching for magazine articles with 400's and Vortec heads? If you are lucky, you'll find one with a baseline/post header comparison. Even if it's for a 350, you might gather some data based on whether the small primaries "choked" the test engine or not. I know I've seen header tests regarding primary diameters. Probably quite a few articles out there.
 
My way of looking at it is, if 1 5/8 primaries work well on just about every 350 in a truck out there, why put 1 1/2 primaries on a bigger 400? Sure, it may produce a little more low-end torque, but a 400 isn't gonna need it.
 
Is 1 5/8" the "standard" small block size?

I'm not suggesting the OP go any smaller than whatever "standard" SBC header primaries are. 1.5" does sound pretty small now that I think about it.
 
Years ago I built a TBI 406 for my old truck. Talked to a local engine builder about what I could do to the motor, and mentioned the Vortecs. He said he just got done building one for a guy for hauling his racecar around. I can't remember all the specs on it, but was pretty mild, but said it ran great, had gobs of torque. He mainly does heads, so when he says something about what works and what doens't, tend to listen to him. He said as long as it's not a high RPM motor, the Vortecs on a 400 will work fine. If you are building a race motor, then they probly aren't the best bet, inless you do alot of work to them. But by the time you get done, couple bucks more, you could have a set of Darts or something along that line......
 
dyeager535 said:
Is 1 5/8" the "standard" small block size?
Click to expand...

Generally, yes. Large displacement small blocks in street cars work well with a 1 3/4 primary, but 1 5/8 most common. The small 1 1/2 stuff is usually the cheap low-end headers and, IMHO, is only fit for 267's, 283's and such.
 
My sugjestion is to use stock exhaust manifolds off of a 400 if you do not expect to run over 4000 rpm, sounds like a plow truck would use low end tourqe more than high rpm.
 
Long tubes will make a TON of torque more than manifolds, you'd be foolish not to use them. You lose nothing and gain everything. Even moreso on a 400 than a 350.

So yes, stick with the 1 5/8" headers then. Don't go cheap, get something that won't have you wishing you WERE back to manifolds.
 
Just did some reading on CompCams site. A bunch of magizines did dyno tests of various cams and head combos. A quick note, they were all 350s, and all used at least 1 5/8" headers, so I will be going that route. But, with Vortecs, Edelbrock intake, 750 carb, Xtrme Energy cam, headers, made over 400 horse and torque. I used this cam in a bunch of different engines, and is an awesome cam, has a sweeet choppy idle and sounds sooo good!!!! I will be putting all this into my 79, and will be doing the same build on my 92 Blazer with another 400 that I have.

All I have to do now is get a friggin job!!!!!

(I applied at Fedex Freight, should find out something tomorrow, wish me luck!!!!! :) )
 
My bad on the stock manifolds, my motor build may be to radical for headers, very high compresion ratio, flat top pistons, must lower compresion, literlly burned up those headers. Didn't mean to rob this thread, need more sugjestions on how to build a 400 with Vortec heads, better build my own thread.
Who makes that Xtrme Energy cam?

Good luck on job b454rat, Fex Ex sounds like a good place to work.
 
CompCams makes the cam. I used it in a TBI 406 in a 2wd 90 GMC that I had years ago. Had all kinds of power, got good mileage, idled all day long, and if it weren't for a weak tranny would smolder the 255/55/17s on 10 wheels. Only thing exotic about the motor was the 5.7" rods, and of course pistons, but they were the same price as stock style pistons. Everything else was stock, even the TBI heads....
 
Dont get cheap headers. Waste of money. I have heard Things rust in NY. If they are on a plow truck I imagine it sees a lot of road salt or whatever they use back there.
Cheap headers have thin walls and usually crappy welds. The dont take long to rust thru then you have to buy a new set. Plus they have a tendency to leak and blow gaskets all the time.
Spend some money on your headers and do it right the first time. Quality 1/5/8" 16 guage tubes with 3/8" Flanges would work best and last you many years.
I know they are expensive, but all I run are stainless steel headers. They never rust,and your truck will wear out before they will.
 
The truck is a plow truck, but I dont have and don't plan on getting a salt spreader. And though trucks here get rusted, (wait till you see the box) the front half doens't really get anything. I was looking around on Summit for headers, and no brainer but car headers are cheaper. Being in a truck, shouldn't have any issues for clearance. Seen a bunch of stainless ones on Evilbay, check them out later.

On a side note, it's a plow truck now, but during the summer it could be a driver. Depending on the job situation, could be a tow rig, junk hauler, whatever else it can be used for. Truck is kinda fun to drive, being a 4wd dually, thing gets up and goes pretty good......
 
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