Cracked Intake Manifold?

[Nghtshd88]

Long story short, have a ported 18 manifold (IMRC locked) installed with a JLT 120 tube to help hood clearance (still touches), and tuning says Im running 30% lean, suspects a vacuum leak.

I checked over everything twice all connections are tight no leaks even sprayed them. Cant hear nor see any.

Have codes p0300 and p0316 and of course it is noticeable.

The manifold itself looked fine when installing did not see any cracks.

After searching around I see a lot of these crack and the shafts break. Which is surprising to me being I have a 20yr old Ford also and the intake is fine..

However no one seems to post any pics of the cracks..

So im wondering if there a paritcular place they crack? Im assuming underneath?

Unfortunately feel I will be having to remove mine and search over it..

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[illadvised]

Use propane or anything near the manifold yet? See if the idle changes when the intake sucks flammable gas through cracks

Same with most other vacuum leaks, see if any hoses have a hole by using gas like this. Also check and make sure it is bolted to the block correctly, so use gas around there also

 

[WildHorse]

have a ported 18 manifold (IMRC locked) installed with a JLT 120 tube to help hood clearance (still touches), and tuning says Im running 30% lean, suspects a vacuum leak.

Sounds like a tune issue. nominal 18+ manifold volume is 12.5, porting adds another .3-.5 volume. IF that isn't accounted for in the tune, there's your 30%. IF it isn't tune related it would have to be a fairly big crack, or the porter burned through somewhere. Take it off and visually inspect everything, especially along the injectors.

 

[Nghtshd88]

Yes, forgot to say, that is with a tune from Lund for the 120 tube & ported 18 manfiold.

I am logging now cuz of the issue and they suspect a leak.

I would just think a leak or crack like that I would seen. With the regular JLT tube honestly it felt fine.

I did however have a bouncing idle when cold sometimes with both intakes on tue 18 manifold. From other posts ive read here people say that is MAF turbulance.

Running an 18 AFS Brett Barber Manifold.

 

[WildHorse]

I am logging now cuz of the issue and they suspect a leak.

What's your vacuum at idle (warm) ?

 

[Red5.0]

Spray carb cleaner with the car on all over the Manifold and runners. If there is a crack it should change in idle.

 

[Nghtshd88]

What's your vacuum at idle (warm) ?

18-18.3

Just put the old JLT back on logged and no issues. The new 120 JLT has no leaks at all. Lund says there is an issue tuning with the 120 JLT thought despite no leaks and wants to stick with the old JLT. I guess ill have to live with slaming the hood on it. Dont understand really why its 30% lean with the 120 with a 120 tune?

 

[WildHorse]

It is a tune issue with Lund..

Ironic.. cause I just watched the last Alex Flores video and he said you (pretty sure he was referring to you -> described your parts / situation to the tee etc) said you sprayed carb cleaner all over the intake and said it was cracked because of the porting & no way it was tune related.

 

[Nghtshd88]

Not sure, someone elses manifold was cracked but will try to find the video.

They mentioned the MAF surface might be warped on the new 120 JLT but its actually perfect and I sprayed it to test vs the old that isnt perfectly flat. Baffled.. its an intake it cant get any more basic to install with no issues.. AFS mentioned that if the manifold is cracked it would only be lean under one runner.

Whatever the reason guess Ill just stick with the 110 since the 120 cant be tuned. He said they could work around it possibly but not going to risk it.

For my TR3160 & JLT they did a great fast job though tuning it where two others had no idea how to.

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