H3 3.5 and 3.7lt header/exhaust manifold

[stangster]

hi,

I need to exchange my exhaust manifold as I can't get it to seal up again towards the engine block anymore. I suspect that due to our hilly country side the ports slowly started to bend in all directions due to heat differences. I heard Land Rover had the same problem.
The last two times I had it off, I couldn't line up the bolts anymore and had to widen the holes to get the bolts in, not all, just two outer ones. Needles to say it was a pita.

I found out that the 3.5 and 3.7 headers differ quite a bit. Mine is an early 3.7 and kinda has a pieces of both models

pictures are not mine, found them in an other forum some time ago, each on the left is the stock one

here the 3.5 header


her the 3.7


now my question is: does the 3.5 header fit the 3.7 engine, except for the 2nd co2 sensor and the heat shield bolts?

the funny thing with mine is; mine looks like the 3.5 header but has 2 co2 sensors. I also think the 3.7 one should hold up better as it looks much sturdier.

I could not find a stock 3.7 header for below 500 bucks, so I was thinking of getting the Pacesetter one and weld another co2 sensor port to it.
I need the cat as we need to have our cars checked about every 3 years to keep them registered.

any info is much appreciated.
thanks in advance.

 

[rascole]

bump

 

[alrock]

rascole, what's your question, i.e. what's the reason for the bump?

 

[rascole]

I seen he had asked a question a while ago about headers and there where no responses. I'm looking too so I wanted to poke the thread to get some replies, for him and myself.

 

[humvee]

I seen he had asked a question a while ago about headers and there where no responses. I'm looking too so I wanted to poke the thread to get some replies, for him and myself.

I know this is old, but here are my 0.02c...

Ever since I installed 35s, my 3.7L has been severely underpowered. My answer was AirDoc, header, PCM & Borla pipes... Other than the horrible fact that my H3 sounds like a Nissan GT-R on the outside, and a jet plane in the cabin, I still get 12 second 0-60 acceleration, and 10mpg fuel consumption.

At 3000rpm, you could barely hear yourself think. I attract too much attention while overtaking cars, or while slowly accelerating at a green light (slowly being my only option). I wouldn't mind it if the truck actually went somewhere... It doesn't though!
My advice to you and everyone is, save your money and get an alpha.

If you have an alpha, don't complain...
If you MUST complain, do so quietly...
Alpha owners can save up some money and re-gear to 4.56... Your trucks will fly
i5 owners Cannot re-gear due to differential limitations and Karma (front axle swap possible, but then again... save it & buy an alpha).

Hope this reflects my level of frustration, and helps those who are conflicted on spending all their money on mods.

 

[humvee]

Few more thoughts... Do not add LEDs on TOP of your lifted i5 while running 35" tires, the air resistance will slow you down even further and add to your misery.

That said, and as far as off-road capabilities are involved; the extra bit of power that you get from the header + mods, in addition to the 35" tires, the i5 H3 becomes an ANIMAL off-road and on sand dunes... Nothing it cannot do!

Of course, many might disagree with me here, as they find the power from the i5 power-plant to be sufficient. So I guess this only applies to people who's driving style is similar to mine.
I do not usually drive my H3 at high speeds, but would like it to be on par with most SUVs of the same class, all with 0-60 times of 10 seconds and below.
A bit too much to expect from an i5 in a 2.5 ton truck.

 

[cbetts]

I think I am one of the few that don't complain about power from the I5. I am running 35" tires, have a roof rack and soon will be lifted. The one major difference I have is I am running the manual transmission. If I recall, it takes about 25HP to run the torque converter on a 4L60. Keep in mind that all those other trucks that can accelerate better will not be able to keep up with your H3 offroad. Now if you are willing, you can sacrifice all the offroad mods you did and recover a lot of your performance.

It is all about priorities.

 

[derian06]

I had a 9 second 0-60 in my 3.7L with no muffler, light bar, 35" KM2's, 14mpg and only a PCM tune and Air Doc Intake.

 

[Best4x4]

Kinda off subject, but does the airdoc for an 07 3.7L make a lot of noise or is it just like any CAI? Really thinking about getting one for my wife's 07.

 

[cbetts]

Kinda off subject, but does the airdoc for an 07 3.7L make a lot of noise or is it just like any CAI? Really thinking about getting one for my wife's 07.

I little more noise but not to the level of a K&N CAI.

 

[rascole]

I have had both and I did not hear any difference between the two. I had to remove the K&N due to CA smog regulations this spring. Short version says new rules this year state that the air box can not be modified. Not worth the hassle to argue with them since they are friends of the family. I showed him pictures of the Air Doc and he said that would pass because it does not modify the factory air box. I love CA.

 

[cbetts]

I have had both and I did not hear any difference between the two. I had to remove the K&N due to CA smog regulations this spring. Short version says new rules this year state that the air box can not be modified. Not worth the hassle to argue with them since they are friends of the family. I showed him pictures of the Air Doc and he said that would pass because it does not modify the factory air box. I love CA.

I failed the visual inspection on my last smog. I had to go back home and reinstall the OEM tube. I quickly put the AirDoc back on after I got it certified though!

 

[Best4x4]

Ok cool beans I'll order it!

 

[rascole]

I failed the visual inspection on my last smog. I had to go back home and reinstall the OEM tube. I quickly put the AirDoc back on after I got it certified though!

Exactly what I did, I'll find out in 2 years if the Air Doc passes.

 

[scoreh3]

We had 2 I5's (at the same time ) a 3.5 Colorado and a 3.7 H3 , the Colorado had a K&N CAI and the H3 had an AirDoc. The K&N was noisier when you got on the gas. My K&N system passed smog without a problem as long as they could read the CARB id # on the K&N system. My AirDoc passed too even w/o a CARB # ( but it does go in to a closed air box) . As far as I know and have read as long as the intake/exhaust parts you put on have a valid CARB # they should pass Ca. visual inspection without a problem.

 

[rascole]

We had 2 I5's (at the same time ) a 3.5 Colorado and a 3.7 H3 , the Colorado had a K&N CAI and the H3 had an AirDoc. The K&N was noisier when you got on the gas. My K&N system passed smog without a problem as long as they could read the CARB id # on the K&N system. My AirDoc passed too even w/o a CARB # ( but it does go in to a closed air box) . As far as I know and have read as long as the intake/exhaust parts you put on have a valid CARB # they should pass Ca. visual inspection without a problem.

This year or last? The mechanic said the policy has not been rolled out to all test stations yet, kind of like the "Star Certified" crap they would send out with the renewal. The new policy is working to a visual and computer test only (better), no more tailpipe testing for vehicles that are properly equipped. But he said they are even more strict with the visual inspection. Not too worried about it, I will be selling mu K&N CAI soon anyways, I think they both work equally well from my experience.

 

[cbetts]

This year or last? The mechanic said the policy has not been rolled out to all test stations yet, kind of like the "Star Certified" crap they would send out with the renewal. The new policy is working to a visual and computer test only (better), no more tailpipe testing for vehicles that are properly equipped. But he said they are even more strict with the visual inspection. Not too worried about it, I will be selling mu K&N CAI soon anyways, I think they both work equally well from my experience.

I passed smog two years ago from the same shop so I am assuming it was recent. I still had a tailpipe test but rev tested in neutral. He did not have a four wheel dyno.

 

[Steve #1]

I think I am one of the few that don't complain about power from the I5. I am running 35" tires, have a roof rack and soon will be lifted. The one major difference I have is I am running the manual transmission. If I recall, it takes about 25HP to run the torque converter on a 4L60. Keep in mind that all those other trucks that can accelerate better will not be able to keep up with your H3 offroad. Now if you are willing, you can sacrifice all the offroad mods you did and recover a lot of your performance.

It is all about priorities.

The lower 1st gear helps too.

 

[humvee]

Keep in mind that all those other trucks that can accelerate better will not be able to keep up with your H3 offroad. Now if you are willing, you can sacrifice all the offroad mods you did and recover a lot of your performance.

It is all about priorities.

Yep I already mentioned that my 3 is an animal offroad. Just replying to Rascole's old post that with all these mods, an alpha might be a better choice if you can't really prioritize, or invest in a separate daily driver.
With the 35's, my 5cyl struggles more than an alpha to give decent mileage figures (maybe its just my H3). It's doing the same mpg than amrg's alpha :s, I spent $5500 on hp mods when the difference between an i5 and an alpha here in Doha is only $5000. Only reason I didn't swap is because I'm taking it to a different country, and v8's come with a hefty annual tax there.

If it was common, I'd drop a manual gearbox in there... I like the idea of giving back 25hp.

 

[cbetts]

The lower 1st gear helps too.

That was the main reason I ordered a manual transmission. Have a 69:1 crawl rate on a factory vehicle is just so sweet.

 

[amrg]

I spent $5500 on hp mods when the difference between an i5 and an alpha here in Doha is only $5000.

I bet you would've still spent that number if you got the Alpha to get it back to stock performance with your mods!

If regearing was a viable option, bolt on, no hassles, that would've been anyones #1 mod!

 

[Mr_Rich]

I had the choice of an Alpha or an I5/ M5 when I was shopping for a new truck. That was the determining factor; I wouldn't have gone with an I5 without the M5. I still think it was a good choice. The I5 doesn't compare to a V8 and yet it still has enough power to get up steep grades at highway speed with a load.

 

[rascole]

It's a never ending climb. My 96 5.7 Silverado makes the same power as my 06 3.5 (with minor mods) and the new 4 bangers coming out are make the same power and 10 years from now we'll have thumpers under the hood. Give or take a few ponies you get the picture. Being older and wiser, I prefer the lighter weight, better MPG, and the less chance of over throttling it and breaking parts. Where did this thread wander off too?

 

[scoreh3]

Last year , I will call my smog guy .

 

[scoreh3]

You are correct Sir , I called my smog guy and he checked and yes the new Ca. law requires a closed system. Now what's going to happen to all of the open CAI systems that say 50 state legal ? He said as long as my AirDoc has the MAS air in the system it should be ok.