Ok guys

Its time i am making my first set of headers for the GV V6 2.5 with merge collectors.

Ill be posting pics up this week with some progress.

BTW who would be interested in a set with downpipes

josh

Do you know the exhaust valves size and exhaust port size?

im gonna messure the exhaust port i think 1.5 primaries will do well as we rev to 6500. Im gonna dyno the truck before i put the headers on and go from there.

Any progress?

oh man, I want to do the same. I would buy except I have the stuff to make them other than a bender and I like the pride of making my own stuff but if I happen to actually meet someone with a GV other than me I'll tell them about it

can't wait to see, how are you making sure the lengths of the tubes are correct? that's the main thing stopping me from doing it.. that and I odn't have the time or something else to drive while making them

To design a header properly you need to know a number of variables that I haven't been able to find out yet. It can be done with some basics but ideally knowing the cam specs will optimise it. Be nice to get a degree wheel and dial guage on one of these to get some measurements like valve opening and closing timing, duration and lift. Also need to know the distance from the back of the exhaust valve to the exhaust manifold. Also does anyone know the valve sizes and con rod lengths?

Wow cj, that's a lot of questions?!? When we build them for our drag race motors/cars the most important thing for us is getting the tubes as close to the same length as possible and making sure the tubes join at the collector in the firing order so the exhaust will create a swirling pattern to help speed up velocity. Never really took all of your concerns into the design, we've had good luck with our headers on some of our small block chevy's pumping close to 950 hp naturally aspirated.
We have always bought pre-bent "j" bends and sliced and diced them.
Have fun JDMCRX!!!

940 HP N/A....sounds like alot of fun 

Yoak,
With a pro-stock pick-up clutch and tranny and a 9000 rpm launch....hell yah it's fun!!
Will pm you a video in the next couple of weeks, car is almost ready to launch!!

Thats awesome, im looking forward to seeing that vido.

Makes my Turbo Z seem boring now lol

Wow cj, that's a lot of questions?!? When we build them for our drag race motors/cars the most important thing for us is getting the tubes as close to the same length as possible and making sure the tubes join at the collector in the firing order so the exhaust will create a swirling pattern to help speed up velocity. Never really took all of your concerns into the design, we've had good luck with our headers on some of our small block chevy's pumping close to 950 hp naturally aspirated.
We have always bought pre-bent "j" bends and sliced and diced them.
Have fun JDMCRX!!!

Not everything I was asking about was for the headers but the cam is really the brain of the engine and designing your header around that does make a real difference. Getting the primaries to be equal lengths is a given and don't forget that the distance from the exhaust valve to the exhaust manifold is part of the primary length. The Collecter is actually a pretty important part of the header design too. Geting that to be the right dia. is worthwhile, the length is not quite as critical. On one of these engines for general use I reckon making the primaries (not incl. the amount in the head) somewhere in the 1 & 1/8" to 1 & 1/4" I.D. and about 34" to 36" long will get you in the ballpark. The collecter I.D. of 1 & 3/4" to 1 & 7/8" and about 12" long would be good for each bank. This would be a reasonable compromise that would work on the 2.0, 2.5 and 2.7 V6 engines and it is my understanding that the right design should fit them all as the pipes of the 2.0 and the 2.5 are supposedly the same part number and I have also been told but have not been able to confirm this yet that the heads and cams are the same across the various engines..

Trust me ive got alot of time and des lookin into it. Im gonna build them with merge collectors. All i have to say is take a stock manifold hold it up lol. 4 tubes welded to a flange would flow more lol.

josh

Trust me ive got alot of time and des lookin into it. Im gonna build them with merge collectors. All i have to say is take a stock manifold hold it up lol. 4 tubes welded to a flange would flow more lol.

josh

I don't disagree that the stock setup sucks big time but then again I have just recently heard of someone who had some made up for the 2.0 V6 and didn't notice much difference which is my point of designing them right and the gains will be there.

I can't get over how wierd it is that these rigs have THREE catalytic converters. I kept a 3rd on with my custom exhuast but at least it's high flow. I really want to make the 1st 2 high flow and ditch the 3rd. are you doing this? I don't think the motor will run properly without the first 2 cats because there is an o2 sensor on both sides of each.. that's right.. FOUR o2 sensors.. goofy stuff.. and I used to think it was wierd that my V6 was only 2.5 litre.. I was just getting started into learning about these truely unique rigs

First attemp Will be to built a set shorties with the EGR port and merge collectors. Move the the primary o2s down stream to behind the one cat. Or we will use o2 simulators to not trip the ecu.