Build your own crossover headers

[Mark Worthington]

http://icengineworks.com/icewmain.htm

I got this link from another forum. It's a pretty cool idea - almost any exhaust system can be mocked up by using a series of 1-inch sections of either straight pipe or one of three different bend radii. You buy a set, mock up your headers with these modular blocks, then use the appropriate-sized pieces of tubular steel to replicate your mock up.

The modular blocks:



How they are used to mock-up a set of headers:



THen use the jig to cut steel tubing to the proper size:


The system is pretty pricey, though. This would be a great "community purchase" item for the GT40 community - pool resources to buy a system and rent it out to forum members on a monthly basis.

[BruceLambo]

Wow! What an absolutly brilliant idea!
I know the last set of 180 degree headers I made took me 2 weeks

Shame though, about the price. I cant see how they can justify the price for plastic injection mouldings. But I guess, they're out to make money and we to make headers.

Given me a few good ideas though on jigging and such.

[Mark Worthington]

Oops! I meant to post this in the engine forum, not the transaxle section. Ron or Al, please move this thread at your convenience.

[91740Gt]

Mark,

I too have to agree. That is a very clever design idea and makes life so much easier and accurate.

Graham @ GTA.

[Richard O'Clery]

On the topic of building headers, what do people like as the ideal length for the primaries for say a 400 - 450 BHP V8?

I think the idea is great. I was thinking of doing the prototype out of small sections of pre-cut, pre-bent heavy pipe (used by plumbers - called ells I think?), but that would be the expensive option as their wall thickness is about 2.5mm!

[Phil]

Mark, looks like a really neat setup there, I wonder if anyone on the forum has had experience with these yet. I generally use pre-bent sections of exhaust tubing I get from a header manufacturer..they call them a "box of mistakes". Usually enough tubing in there to make a full set of headers and then some, costs about $100. I see that this system in your photos can create some really tight bends with compound radii, and they look like they can be twisted after assembly which is the real problem when tacking tubes together, one degree or so off makes a big difference. One thing I do when cutting the tubes to size is to use a non-reinforced abrasive wheel, this I got from a friend who does a lot of stainless tube work in dairies and food handling operations. The cuts are square, and butt-up so nicely that only seam welding is required making a really nice job.
Cheers
Phil

[Jim S.]

Mark,

to bad we couldn't buy direct from the plastic injection supplier. That's a crazy price for a plastic injection piece.

Those other parts; aluminum plate/Jig, Half Moon pieces to hold pipe, are
insanely over priced. They could be easily built for about a 1/4 of there cost and the company would still make a profit.
If you could find a cheaper supply for the plastic pipe, I would setup and build the jig parts to complete the kit and maybe the forum could rent it out???????

Just thinking out load. Those plastic pipe pieces almost remind you of a kids toy building block set


Jim

[Jim c]

Richard
The length of pipe is is suited to the induction ,camtiming ect ect.
I think you may find the original systems were about 32 -36 inch mark.

I have used lengths of double the intake runner from trumpet to valve seat.
It does make for a short primary 24-28inch more a race engine ( in its peak rpm more frequent).

The longer the primary the the lower the torque will peak.
the shorter the higher.
the smaller the primary dia the more low to mid range & will nose over early.
the larger the primary the higher the torque will peak.

EG this what I use as a rule of thumb an engine that will see 7000rpm
99000 devide 7000 =14.14 inches thats the inlet length.
14.14 x 2 = 28.28 inches is the exhaust primary length.

If its being used for a more street use them you pick a point between peak torque & peak rpm eg 4500tq 7000 rpm 1/2 way =5750rpm
99000 devide 5750 = 17.21 inchs is the inlet length from seat to trumpet.
17.21 x 2 =34.43 inches.
that should give an all round good length.

I dont know what you are building ,if its a street with a bit of track work better going for mid range to a respectable peak.
Scavanging is less effective with a larger pipe.secondary wave is weaker.(thats another story)
Rule of thumb is go the next pipe size up on exh port size(area is the best way for odd shaped ports).
If exh ports are known to be to large cone up to port & reduce pipe dia.
Having the pipe larger stops reversion.

if you want the authentic look you will be in the 30 plus inches.
I wouldnt be frightened it wont hurt the peak that much.
At the end of the day if you worked out the average rpm it would not go over 4500-5000 anyway.

Making it out of 2.5mm dont bother your just doing it twice besides you would have to use the same radius or you are waisting your time.

Just get into it if you make the wrong cut use it somewere else.
You wont waiste that much,if you want to get critical on lengths tack the pipes, tape them & fill with water.
Work out how much an inch of pipe will hold in water & devide.

Hint
make or buy your collectors first.
Set up your collectors on a bracket taking into account longest pipe length.
Use a merge collector they do work.
That shit pressed cone the local exhaust guy sells that you make a 4 into one out of will lose power.
The merge assists in scavanging & that is how they make more power.

its all a compromise
All of the above I have tryed over & it has always worked well.
Some may not agree with the above but thats ok as well.
Sorry if I have over answered the question Richard.
Jim C

[Richard O'Clery]

Hi Jim

Thanks for your answer. That is really helpful information.

[patbarry]

Speaking of headers, here is what was supplied by RF. Having no experience with individual pipes, is this amount of seperation normal? In order to get them into the collector they really need some force to pull them in. I am concerned this may not be best for either the aluminum heads or the exhaust assembly. Thoughts?

[Alex Hirsbrunner]

Hi Pat,

Do you have standard exhaust port location heads? I know that my Canfield heads move the exhaust ports up vertically about .400" which results in about .280" horizontal displacement (outwards) per head. I'm guessing it would result in about what is shown in your photo. Looks like a short tubing spacer of that size welded into the two crossover pipes per side at the rear where they run perpendicular to the car would solve the problem.

Regards,

Al

[Bill Musarra]

Jim C
There was a post some time ago about primary and secondary tube lenght and size, titled "Exhaust Science". I still have the article on this post from Popular Hotroding if you are interested. I could scan it and send along. It goes along with prettymuch what you are saying. It goes into not only those areas, but in muffler choice and its affect on HP. It is a little slanted toward the Dynamax line as the author was one of the researchers that led to the Dynamax muffler.Still a good read.

Reclaiming lost horsepower

[Ian Anderson]

Or this
Primary pipe length formula

Adam Christian did a lot of work and graphing here

Ian

[Jim c]

wbmusarra & Ian
All good info.
any info is good info I will take whatever you have.

The best result I ever had from a muffler was one I made on info I was given.
I used perforated sheet metal(cant remember the perforation ratio it been to long to many fumes)built a tube around it filled with steel wool.

2lt in line 4
secondary pipe was 2.25"dia primary pipe length 26.5" .
double the dia over 2/3rds the primary length
so I ended up with a cone 2.25 to 4.5 over 17.6"
On the open end another cone short & steep coming back to 2.25 over about 1.5 to 2".
A megaphone

The main cone slows the gas speed & gives a wider window of opertunity in the top end for the nevative wave to do its business on the scavange .

But you lose mid to low range.
The reversion cone on the rear brings that back .

It made 20hp.
I will make some for my 40 if I get enthused.

Jim C

[PaulGT40]

Hi,
What is the cost, couldn't find it on their website.
Thanks
Paul

Originally Posted by RamboLambo

Wow! What an absolutly brilliant idea!
I know the last set of 180 degree headers I made took me 2 weeks

Shame though, about the price. I cant see how they can justify the price for plastic injection mouldings. But I guess, they're out to make money and we to make headers.

Given me a few good ideas though on jigging and such.

[Brian Kissel]

Hello Paul !
Look on their website, the index is on the left side of the page. The 7th and 8th lines ( 1625 seies and 1750 series ) if you click on either, it will describe what is in each kit and the price, but the last update was Jan. of 2007. I hope this helps !!!

Regards Brian

[PaulGT40]

Brian,
Helps alot, $5.85 each piece ouch!! I am definitely thinking these guys are primed to be copied, put another $800.00 with that $1050.00 and you can
buy SS crossovers ready to go.
Thanks
Paul

Originally Posted by Brian Kissel

Hello Paul !
Look on their website, the index is on the left side of the page. The 7th and 8th lines ( 1625 seies and 1750 series ) if you click on either, it will describe what is in each kit and the price, but the last update was Jan. of 2007. I hope this helps !!!

Regards Brian

[Gary Kadrmas]

Nobody said these cars are cheap to own/operate/or repair.

Welcome aboard to the fine and wonderful world of GT40s! Hope your piggy bank is full now, because it will definately drain towards empty, on anything that you do are related to a GT40.

Cheers....(the cheaper part about GT40s!), so go and have one now