Dorman replacement PI intake manifold comments ?

TripleBlk · Apr 12, 2012

I thought I was the last remaining owner w/o an intake manifold cracking. Well, I just installed a Dorman replacement PI manifold, and have a huge vacuum leak.

The Dorman manifold had "cone" shaped holes for the fuel injectors. The stock manifold has a circular , "machined" surface for the injectors.

The question is : Do I have to tap in the injectors on this Dorman intake ? I had the injectors flow-tested, cleaned and fitted with new o-rings. Checked all the vacuum hoses, EGR, etc. Any help is appreciated.

Frankenstang838 · Apr 12, 2012

Sounds like the plenum gasket isnt sealing to me. I had this happen after a plenum swap and took me a couple days to figure it out. Pull your plenum off and check that first.

TripleBlk · Apr 12, 2012

Frankenstang838 said:
Sounds like the plenum gasket isnt sealing to me. I had this happen after a plenum swap and took me a couple days to figure it out. Pull your plenum off and check that first.

OK - I'll pull the plenum and re-install. Did you have a Dorman intake with the "molded-in" plenum gasket, or the stock setup ? just curious.

TOOLOW91 · Apr 12, 2012

I used the dorman on my 00gt and
had
no issues with it

VOORHEES · Apr 12, 2012

I'm still running the stock intake......hate to think the day it blows. I'm only at 74,000 miles on my 99 GT.

wmburns · Apr 12, 2012

Did you "lube" the injector O-rings before insertion? Is it possible that you have a defective unit? Consider comparing your unit to another.

I used a Dorman intake on a 97 NPI Cougar and had no issues with it.

FWIIW, many all plastic intakes crack when the coolant level is allowed to get too low. Apparently the plastic cross over can not handle the hotter than normal steam. There are tons of ppl out there still using the all plastic stock intake with no leaks. But let the coolant level get low or the motor get hot and crack goes the plastic.

TripleBlk · Apr 12, 2012

wmburns said:
Did you "lube" the injector O-rings before insertion? Is it possible that you have a defective unit? Consider comparing your unit to another.

I used a Dorman intake on a 97 NPI Cougar and had no issues with it.

FWIIW, many all plastic intakes crack when the coolant level is allowed to get too low. Apparently the plastic cross over can not handle the hotter than normal steam. There are tons of ppl out there still using the all plastic stock intake with no leaks. But let the coolant level get low or the motor get hot and crack goes the plastic.

Aha, Mr Burns.. I used the injector service you recommended (InjectorRX in Houston, TX - a very good service BTW)

Yes, I lubed the "o-rings". The difference between the Dorman injector cavities and the stock injector cavities is vast.I wonder how the injectors can possibly seal. It also makes me wonder what other shortcuts were taken by Dorman (they didn't machine and provide inserts for the COP hold down screws, for instance).

Perhaps I should have paid the hundreds of dollars difference for a Ford part ? That is why I asked this question. And thanks for the responses.

TripleBlk · Apr 12, 2012

toolow91 said:
I used the dorman on my 00gt and
had
no issues with it

Thanks for the reply. I used 24 Nm torque on the fuel fasteners. Did you have to really "reef" on them ?

TripleBlk · Apr 12, 2012

TripleBlk said:
Thanks for the reply. I used 24 Nm torque on the fuel fasteners. Did you have to really "reef" on them ?

Oops- Should read fuel rail fasteners.

98COBRA281 · Apr 12, 2012

NO! oem ford, dorman blows

TripleBlk · Apr 12, 2012

98COBRA281 said:
NO! oem ford, dorman blows

C'mon - I'm out a few hundred bucks (plus my labor) so , it looks like I'm down due to crappola parts ? Doomed ? Somebody else may have some constructive comments ? Thanks for the reply, though.

RedDaemon · Apr 12, 2012

can i ask how the car is behaving? as in what is it doing that makes you think its a vacuum leak?

98COBRA281 · Apr 12, 2012

TripleBlk said:
C'mon - I'm out a few hundred bucks (plus my labor) so , it looks like I'm down due to crappola parts ? Doomed ? Somebody else may have some constructive comments ? Thanks for the reply, though.

honestly man, its a crappy intake. the ports are WAY smaller the the oem pi. my friends 99 had one on it when he bought it and it was the first thing we changed, and it completely changed the power, sound and running characteristics of the car.

just order the oem PI from summit i had 2 sitting at my house a year ago, id give you one if i still had one!

Frankenstang838 · Apr 12, 2012

TripleBlk said:
OK - I'll pull the plenum and re-install. Did you have a Dorman intake with the "molded-in" plenum gasket, or the stock setup ? just curious.

it slides down in a grove. I think that's the stock setup.

TripleBlk · Apr 12, 2012

RedDaemon said:
can i ask how the car is behaving? as in what is it doing that makes you think its a vacuum leak?

The car will barely idle - acts like an old-skool muscle car with a huge cam. Doesn't want to idle more than 500 RPM even when cold. Will die w/o throttle input. All vacuum tubes rebuilt/thoroughly checked. IAC checked/cleaned. New plugs (NGK TR55s) Spools up nicely, though, when I romp on the accelerator pedal

TripleBlk · Apr 12, 2012

98COBRA281 said:
honestly man, its a crappy intake. the ports are WAY smaller the the oem pi. my friends 99 had one on it when he bought it and it was the first thing we changed, and it completely changed the power, sound and running characteristics of the car.

just order the oem PI from summit i had 2 sitting at my house a year ago, id give you one if i still had one!

Well, you know, I like Summit's website - pretty good aite. But the two only intakes they had listed for the 4.6L were for the 96-98, and the 99-04 (PI) Maybe disco'd by Ford ?

Bob Hughes · Apr 13, 2012

I have complete pi manifold for sale in classifieds with 60k off my car $150 with everything (tb, plenum, iac, egr, maf, all kinds of stuff) if youre not feeling confident in the dorman.

mr. b_98GT · Apr 13, 2012

I installed a Dorman NPI intake on my 98 a few months ago because of a cracked intake, and it went on without a hitch. I also had a slight idle problem before the intake swap, but not so bad that it would die on me. Also, when the engine was cold, it would make a humming sound every now and then, but the hum would go away once I pressed on the gas. I read that a worn out IAC valve will cause this, so I swapped a new Ford OEM piece in it, and the idle went back to normal and no more humming sounds.

FWIW, I would have gone with a Ford OEM PI Intake because it's cheaper than the Dorman NPI, but I didn't have the scratch to do the head swap just yet.

N8Dogg98 · Apr 13, 2012

mr. b_98GT said:
I installed a Dorman NPI intake on my 98 a few months ago because of a cracked intake, and it went on without a hitch. I also had a slight idle problem before the intake swap, but not so bad that it would die on me. Also, when the engine was cold, it would make a humming sound every now and then The hum would go away once I pressed on the gas. I read that a worn out IAC valve will cause this, so I swapped a new Ford OEM piece in it, and the idle went back to normal and no more humming sounds.

FWIW, I would have gone with a PI Intake because it's cheaper to get than the Dorman NPI, but I didn't have the scratch to do the head swap just yet.

Don't need PI heads to install the PI intake...

mr. b_98GT · Apr 13, 2012

N8Dogg98 said:
Don't need PI heads to install the PI intake...

I have a 98, and from what I've read, I would need to swap the heads to 99 and later PI Heads to do the PI Intake. I think I heard of a kit to install a PI Intake on NPI heads, but I found that after I did the intall.

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