Hi guys,

Thanks for all the help in the last month.

I am busying putting reliability upgrades on my Tahoe and Sub, including remoting the PMD, bigger exhaust, gauges, etc.

The Tahoe will take more work, as it is an "S" engine, with all the funny solenoids and the EXTREMELY sooty EGR-laden intake.

I have located an "F" intake manifold (at the local wrecking yard), and will be picking it up this week.

Any 'should know' items as I look at picking up new gaskets and removing/reinstalling an F manifold?

BTW, I was *shocked* :eek: to see the amount of soot in the S-intake. Has anyone done any analysis to see the difference in performance when switching the intake over from F to S? It would seem that the S intake would get very sooty and restrictive over time, decreasing the intake air flow, and affecting power, mileage, etc.

Any comments would be welcome!

Thanks again,

Rob :)

It doesn't do any good for the heads, valves, valve guides etc. either.

Are you getting the intake manifold and the 'F' plenum with it?

NAPA sells a really complete kit for ~$25, intake manifold, plenum, water jackets, pump mount gasket, its a great deal and looks like good quality gaskets, much better than some of the other ones available.

As far as the solenoids/EGR are concerned, until you swap to an 'F' PROM, you have to keep the ECM happy and thinking the EGR is working normally. All you need for that is to run the hose that used to tee from the third solenoid to the EGR valve and the BARO sensor, to just the BARO sensor and eliminate or cap the tee to the EGR valve.

Texas Diesel Guy, Thanks for the info. Yes, I asked the wrecking yard if it was a complete assembly, and he specifically called me back after checking on it. "You need TWO pieces? Whaddayamean?" :)

I called the local dealership, and a set of gaskets to do the upper and lower intake manifold is a total of $45, so the NAPA kit sounds a lot better at $25.

By the way, since the EGR system is designed to decrease the amount of NOx by mixing in 'used' air, defeating the system theoretically causes problems if the engine cannot control the amount of available oxygen in the chamber. This would presumably cause preignition, or ping, in a gasser. Is there an equivalent danger in a diesel?

Sincerely,

Rob :)

http://www.asashop.org/autoinc/nov97/gas.htm

Refers to gassers, does it have applications for us dieselheads?

Sincerely,

Rob :)

Totally does not apply.

Diesel engines run very lean most of their lives. instead of a constant mix of fuel and air entering the chamber, diesel engines take a full charge of air into the cylinder every stroke and only as much diesel as the pump is putting out at that specific time.

When you hit the gas pedal hard, and get that puff of black smoke, thats the signal that the engine is running rich temporarily, too much fuel until the turbo can catch up and give you enough boost to completely burn it all.

Your not treading on any new ground here, this trick has been done on thousands of 6.2s and 6.5s.

Thank you for enlightening me. I appreciate the lesson!

Sincerely,

Rob :)

If possible, I try to use the OEM or FelPro gaskets and find the online dealers will sell at very competitive prices. One I use regularly is www.teamchev.com. Excellent service.

I think that if you call the dealer and tell him you want to buy a prom chip and you give him the desired F prom code they can reference a part number that will simplify buying it but don't give them a VIN or it will confuse them when they notice the two don't corelate. I've heard a prom from the dealer should be ~$40 but they quoted me $70.

I've got an S truck and running a BD Race series chip in it. Boost hits 12 psi anytime I want, and from what I've learned over the years I certainly have more than F truck performance. Many will say you need a larger exhaust but I installed the EGT gauge and have never pulled hard enough to reach the limit. I've probably hit 1000F or so with the stock exhaust including the cat.

I also learned that there are programmers out there who will reprogram the prom for much less than the $300 and $400 that some of them are selling for nowadays, but learned that after I already paid the price.

I can't find the name or link right now, but the folks I talked to are located near Seattle. I believe a chip I was going to get was $65.

95Yukon, that's awesome. Did you change your intake? Are you using the stock downpipe? Is your EGT sensor pre or post-turbo?

Sincerely,

Rob :)

I think that if you call the dealer and tell him you want to buy a prom chip and you give him the desired F prom code they can reference a part number that will simplify buying it but don't give them a VIN or it will confuse them when they notice the two don't corelate. I've heard a prom from the dealer should be ~$40 but they quoted me $70.

A good idea. Does anyone have the F prom code from a 94-95 F-engine?

Sincerely,

Rob :)

Called my buddy at the dealer, he said there's alot of F-prom out there depending on what kind of truck it is. 1/2 ton stanard trans, 1/2ton auto trans, 3/4 auto trans, different one depending on IP, etc... didn't show anything for Blazers/Tahoe/Yukon which makes since being there all 1/2 tons that I know of. Anyways this GM part number is a 3/4ton Suburban with a auto trans 4x4 which is as close as I think we can get to are Blazers/Tahoes/Yukons.
P/N 16244897
$ 60.00

Hope this helps.

Hi guys,

Picked up the intake manifold today. Looks clean and usable. Even came with the two pieces connected, and came with the MAP/Baro and the IAT sensor still on it.

My plan is to pick up gaskets, take off the old manifold and plenum, plug the EGR vacuum tube, and install the new F manifold.

Is there anything else I need to know at this time before taking things apart?

Thanks, guys!

Rob :)

Make sure if you get an 'F' PROM its from a '95, if you get one for a '94 you will have to change to a 5068 IP.

I'm using the stock intake but have the EGR hose unhooked. When the EGR was enabled, there was what many (including GM) called a "chuggle" at about 1400 rpm. It happened when the EGR was turned on or off. I don't know how EGR on a diesel supposed to reduce emissions, but my black smoke cleared up when I disconnected it. Haven't thought about it for over 150,000 miles.

My downpipe is from Jardine (now Pinnacle) and is made from heavy pipe. I started with a BD (I believe it was the same as Banks was selling at the time) and it never fit and was poorly made, thin pipe and welds were not impressive. Everything I've got from Pinnacle has been heavy duty. The downpipe upgrade was well worth it, the factory unit was pretty smashed up.

EGT sensor is threaded into a bung welded into the crossover pipe 2" below the point where it connects to the left exhaust manifold - pre-turbo. Some downpipes come with a fitting, but I want to get the hottest reading I can, and this location is an easy one to get at. Also, it is much easier to adjust the tip of the pyrometer probe to be exactly in the middle of the exhaust stream for the best temp reading. I weld, but had a guy who knows heliarc very well do the bung welding installation into the pipe. I drilled the hole, ran a bolt through the bung to hold it in position then he welded it. Some use the clamp on sensors but if I'm going as far as drilling a hole, I'm going to make sure it it in there solid.

Yea, I have a 94 so I didn't think about that when I called. Sorry Tahoe let me know if you want me to call about F prom for a 95.

95yukon,
Why not just drill and tap the passenger manifold pre-turbo?

94blazer6.5,

That's been done too. For me, I found it much easier to do get it into the crossover pipe, and wires reached the sensor much easier. I would never try drilling and tapping the manifold on the vehicle - and that is my own preference. Some have done it. Knowing my luck, a metal filing would be left behind and either drop past a valve into the engine or hit a turbo vane, etc regardless what kind of safeguards are in place to catch them. There's too much of an opportunity of metal pieces being left inside without completely removing and being sure it is clean. There's also a theory that pre-turbo in the right hand manifold may not read quite as hot as the left side location because crossover flow joining it may be slightly cooler due to traveling through the pipe. What's most important is getting a point of reference so you will know when you start to exceed it.

With all the helpful suggestions from this forum (again, you guys are terrific! Thank you all!) I have a plan of attack.

I plan to drop the crossover and downpipes from the Tahoe, and then drill and tap into the driver's side exhaust manifold runner. This will result in a short cable to the gauges, and will avoid having a bung or clamp-in on the crossover. Having the crossover out will eliminate any issues with dropping metal pieces into the turbo. If I can manage it, I'll be sure to document with photos and post 'em here.

Since I already have the Hypertech chip in the '95 Tahoe, I don't think I'll swap out for a '95 F Prom, unless I am misunderstanding which chip is exchanged. The Hypertech seems to be running fine and providing a good power boost in the stock configuration, with sooty intake, crumpled downpipe, full cat and all.

I am also planning to cut the cat out, liposuction it, and then reconnect, likely using one of those nifty pre-formed stainless exhaust band clamps that Kennedy sells.

I'll stay with the remainder of the stock exhaust for now, but with a Hypertech chip, a new Flowmaster downpipe and crossover (I coated the crossover with ceramic high-temp paint - I'll see if it does anything), liposuctioned cat, and a complete F intake, the only thing left in my upgrade path is a set of gauges.

Thanks again for all the advice. You're a helpful and selfless lot, and I am duly impressed.

Thanks!

Rob :)

Bump.

I'm thinking about putting a 95 prom on my 94 "s". Anyone know the part #?

Dan check out Wester's, Kennedy, Heath if you are going to upgrade really upgrade might as well get the performance bump at the same time.

Damn TD, you feeling ok tonight? Thats the first time i've ever seen you post Westers before Heath? :muahaha:

I'll second what "turbon doc" said. You'll want to control more than just extra boost with an "F" chip. It's a nice feature for the ECM to not look for the EGR system anymore. These guy's can add more fuel, allow more boost, firm up the transmission shift points when needed.
Of course now your going to want the bigger injectors and most deffinately the larger exhaust, front to back and a good set of guages.

Now watch how big your smile gets!:ro)

Yeah, you're certainly right. I was just looking at a possible intermediate point to stop (I'm also trying to convert my FXSTDI into a dual disk billet wheel front end as well as completing the oil injection removal from my 225 Pro Max) but I'd probably be better getting the most bang - literally - for my buck when buying parts.

Thanks for keeping me honest.

I use gmpartsdirect.com

I am in the process of changing my IP and was going to block off my EGR.However I located a F intake and plenum and was wondering if I can use the S engine intake gaskets or do I have to buy F gaskets?Is there a difference?

S gaskets have a hole in them for EGR passage, which may be a source of leakage with F intake, I'd go with the correct gasket so in case it does leak you won't be doing the work twice

Texas Diesel Guy states:

"As far as the solenoids/EGR are concerned, until you swap to an 'F' PROM, you have to keep the ECM (http://www.dieselplace.com/forum/autolink.php?id=40&script=showthread&forumid=21) happy and thinking the EGR (http://www.dieselplace.com/forum/autolink.php?id=42&script=showthread&forumid=21) is working normally. All you need for that is to run the hose that used to tee from the third solenoid to the EGR (http://www.dieselplace.com/forum/autolink.php?id=42&script=showthread&forumid=21) valve and the BARO sensor, to just the BARO sensor and eliminate or cap the tee to the EGR (http://www.dieselplace.com/forum/autolink.php?id=42&script=showthread&forumid=21) valve"

Will this work on my 98 with the MAF sensor?

Thanks

Get a boneyard F PCM and rest of it will be blind, this is low buck minor Hp gain for S 6.5s offroad use only of course, best though is to reflash it

is the gear ratio in the ECM of these old trucks (98 in particular)

I don't think so, I've swapped multiple PCMs from various trucks and it has never made any difference. K vs C is in there I think

I don't think so, I've swapped multiple PCMs from various trucks and it has never made any difference. K vs C is in there I think

I must be dumb ...but "K vs C" ? What is that?

4x4 vs 4x2

AHHH i got you now. I'm having a bad weekend, canadian tire Fked up a 300 dollar part (my thermostat housing) trying to change a 25 dollar part ( the crossover to my heater line) after i told them just to change the o-ring and the plastic clip. I guess the moral of the story is DONT USE CANADIAN TIRE!
I guess i knew that but i was away from home and didnt have a choice saturday at 5pm.

Do away with the plastic clip, use barb fitting and hose clamps