Awd Question

[misterp]

...What's involved in port matching the manifolds?

Well, the idea is that the stock exhaust manifolds may not be "tuned" long-tube headers, but they are actually at least generously sized except for the 4 port openings themselves, at the exhaust flange. The exhaust exits the valve and rushes out the port a couple inches and then runs smack-dab into a 1/4" 'step' or 'lip' because the manifold openings are smaller than the ports, and this may not be enough of a choke point so as to cause restriction (it is!) but the bigger issue is that the abrupt change in port sizes causes big-time turbulence at the flange mating surface. So you remove the manifold and exhaust gasket, and (on a bench) you place the gasket onto the flange of the exhaust manifold and loosely 'bolt' it in place with a couple bolts/washers/nuts so it won't move on you, and you trace the gasket openings with Sharpie marker. Then remove the gasket and set aside, and using a die-grinder (or redneck method, grinding stones in a drill) grind material out of the exhaust manifold ports until the openings are big enough; make sure you grind down the throat of the port as far as you can reach with the tool to make a smooth transistion as possible.

 

It's free, the gaskets are reusable. And it's dirt stupid simple. It's better than nothing! Does it work - well, a true story for you; a good friend here in Plano (don't think he was ever on the forum) who is a great guy and has well-to-do folks was driving a 2WD TBSS in his senior year in high school, and had no money to make it fast. So he port-matched the manifolds, added a 125-shot nitrous kit, did the poor-man's CAI job plus removed the passenger headlight and that TBSS went 11.51 on it's first pass at Texas Motorplex, he was almost kicked off the track. Now granted that is a vehicle with 1000-lbs less weight and an LS2, but still pretty damned impressive! ALSO, I've got 1-7/8" header tubes on my truck and it hasn't hurt it at all, so worrying about making the port sizes larger in the manifolds is a bogus IMO. So IMO yeah it's certainly worth doing, especially if you are short on cash and long on time!

 

Mr. P.

[misterp]

yeah i had mentioned droppin the cats and throwin some longtubes on it earlier.. that list may get put to use here soon when i sell my other truck.

i appreciate the input guys.. really do. maybe but next track season i can see some quicker times. id like to do some things over the winter and drop a few tenths.

maybe not to yall but anyway these trucks sit they are stout!! its fun bustin all the ricers around town and runnin down some gt's that leave the high school in the afternoon. fools that cant drive a stick and crappy ford power..and the fact that our trucks weigh twice as much..ive shocked many people haha good ol chevy power

 

but thanks for that list. i plan on goin through the motor in the next year or so.. do some type of budget built. cam , tune and some top end work .. but its my DD so cant put it down for long and do anything too radical

You sound like an honest gearhead - welcome to the forum

 

Mr. P.

[yfz450_0569]

Well, the idea is that the stock exhaust manifolds may not be "tuned" long-tube headers, but they are actually at least generously sized except for the 4 port openings themselves, at the exhaust flange. The exhaust exits the valve and rushes out the port a couple inches and then runs smack-dab into a 1/4" 'step' or 'lip' because the manifold openings are smaller than the ports, and this may not be enough of a choke point so as to cause restriction (it is!) but the bigger issue is that the abrupt change in port sizes causes big-time turbulence at the flange mating surface. So you remove the manifold and exhaust gasket, and (on a bench) you place the gasket onto the flange of the exhaust manifold and loosely 'bolt' it in place with a couple bolts/washers/nuts so it won't move on you, and you trace the gasket openings with Sharpie marker. Then remove the gasket and set aside, and using a die-grinder (or redneck method, grinding stones in a drill) grind material out of the exhaust manifold ports until the openings are big enough; make sure you grind down the throat of the port as far as you can reach with the tool to make a smooth transistion as possible.

 

It's free, the gaskets are reusable. And it's dirt stupid simple. It's better than nothing! Does it work - well, a true story for you; a good friend here in Plano (don't think he was ever on the forum) who is a great guy and has well-to-do folks was driving a 2WD TBSS in his senior year in high school, and had no money to make it fast. So he port-matched the manifolds, added a 125-shot nitrous kit, did the poor-man's CAI job plus removed the passenger headlight and that TBSS went 11.51 on it's first pass at Texas Motorplex, he was almost kicked off the track. Now granted that is a vehicle with 1000-lbs less weight and an LS2, but still pretty damned impressive! ALSO, I've got 1-7/8" header tubes on my truck and it hasn't hurt it at all, so worrying about making the port sizes larger in the manifolds is a bogus IMO. So IMO yeah it's certainly worth doing, especially if you are short on cash and long on time!

 

Mr. P.

 

 

I love that idea!! That's next on my list.. lol I'd like to get my truck fast with the simplest parts, and shock people I do prefer work over money quite often..

[misterp]

I love that idea!! That's next on my list.. lol I'd like to get my truck fast with the simplest parts, and shock people I do prefer work over money quite often..

Well now I'm not advocating WORK Just using your brain before your wallet!

[yfz450_0569]

Well now I'm not advocating WORK Just using your brain before your wallet!

 

Yeah pretty much.. haha don't want to go buy useless upgrades, although maybe in a year a mild cam and heads, but first get max out of pretty much stock set-up!

 

Are duramaxes like this too? I have actually seen it done on a Cummins before so not sure if the process is just as simple or more complicated.. I'm always scared of the manifold being too warped to put back on, but maybe it's not as bad as I think.

[misterp]

...Are duramaxes like this too? I have actually seen it done on a Cummins before so not sure if the process is just as simple or more complicated.. I'm always scared of the manifold being too warped to put back on, but maybe it's not as bad as I think.

Port-matching is always a good idea, if nothing else to eliminate turbulence. And no, exhaust manifolds are purposely made super heavy so as to not warp; if you're worried about it, take the manifold to a machine shop and have the flanges checked for straightness but on the truck LS-motors I've never seen this issue, not like the thin cast manifolds on an old SBF.

 

Mr. P.