Vortec PCMs

[EagleMark]

I've got a 1998 5.7L Vortec to play with. Looks like 1996 to 1999 is the year frame for this type? Are there differences in the years? Wondering if differant years can be re-flased or other displacements? Sure looks like my LT1 PCM...

On a side note, after I play with this for awhile stock... I got a crazy idea of COP like the LS engine! :yikes: Have to look at wiring diagrams to see if stock harness could be used and how hard it would be to repin for 411 PCM.

[jameslleary]

no changes from 96 to 99. some 96 g3500 vans with the Vortec 350 had TBI and a 7427 Though....along with some export Tahoe and Suburban models.

[pmkls1]

96-99 was the year range for the C/K pickups running the L31, but the G vans kept them until 2002. There aren't any noteable differences in the years, they were pretty much all the same for the most part. The 2500 series and up got 4 bolt main blocks (nothing special in all reality) and the cylinder heads had hardened exhaust valve seats that severely restricted flow and resulted in less HP than the standard version. The only PCM difference is with the G vans as the later models used a 411 PCM. There are a lot of resources on swapping to the 411 PCM into the trucks as it is fairly popular. I believe, though, that in order to use the coil-near-plug ignition system like the LS you must use a special crank reluctor that swaps in place of the original to provide a 24x ignition signal to the PCM. There is a site that specializes in these conversions http://www.eficonnection.com/eficonnection/default.aspx but you better be sitting down when you look at the pricing because it is definitely not for the budget minded individual. But, if you have OBDII tuning and reflash capabilities you can really improve the performance of the stock L31 without any major modifications. The biggest limitation is the stock intake and injector configuration but you have to start getting into bigger HP numbers that would require more than just tuning and bolt on mods anyway.

[CDeeZ]

Mark,

I know basically nothing about OBD2 stuff, but my friend has done exactly what you pondered: CNP distributorless ignition. He calls his engine the "LS31" (cross between L31 and LS1)

here is the article that he wrote detailing this CNP swap: http://www.gmtruckcentral.com/articles/24x.html

[EagleMark]

Cool, I look it over later. I just got wiring diagrams for the 1998 Vortec and 2001 LS engine. Thanks Robert! :thumbsup:

I don't plan any major mods to this truck, it fills a basic need right now for transportation and a learning center. Since I have a Roadrunner swapping over to LS PCM and tuning live would be fun. May just use this truck as a hands on learning center to cover Vortec tunes then get one newer with LS engine.

[EagleMark]

What about transmissions? I know pre- 1994 had a couple changes and 1995 4L60E were PWM TCC differant, then I think they were all the same in 1996 up?

[pmkls1]

There are some part and PCM programming differences after 96 as well. Around '98-'01 they used what was called an EC3 converter lock up strategy and I am unaware of the entire range of differences, but I know that there were pump differences and changes to the PCM code. Replacement pumps from GM will work in multiple applications and come with instructions regarding the installation in each particular application. There are also differences in the transmissions used in LS equipped trucks. Although LS style engines have the same bellhousing bolt pattern as the standard V8 chevy, the bellhousing depth is much shallower in LS applications. You can swap in a transmission from a different application regardless of which way you are swapping, but it requires the use of adapters available through GM. Basically, unless you know of the particular differences between different years and applications it is best to stick with a trans from a like-vehicle in order to avoid problems that arise from compatibility issues.

[pmkls1]

Just some simple but useful advice relating to your recent purchase. Go ahead and replace the lower intake manifold gaskets regardless of how new they look. I highly recommend using an aftermarket gasket that has a metal frame with molded rubber instead of the plastic O.E. style gaskets. The Fel-Pro part number for their permadryplus set is MS 98000 T. GM has redesigned nearly all of their lower intake gaskets that were originally plastic and replaced them with a metal gasket, but the L30 & L31 are a couple of the very few that they still make in plastic. This will give you a good opportunity to get a true indication of the state of the cooling system. Many times even though there aren't any visual signs of the intake gaskets leaking, the cooling system is fairly full of the wonderful sludge that Dex-Cool turns into. The sooner you address such issues the less problems you will have later. I'd also install a fresh fuel filter as they are important in maintaining a highly sensitive fuel system like yours.

[1project2many]

With something like 30 vans in our fleet running L31 engines, and mileages exceeding 250k, I've seen a few issues with the intake gaskets. Long before the cooling system shows problems, you start getting unusually high discoloration on the dipstick. You're also likely to see unusual brown crud on the bottom of the fill cap. Not the milkshake you've seen when a bunch of coolant enters the oil, but a harder buildup that's colored like black coffee. If you're lucky you'll see a drop or two of moisture on the bottom of the oil fill cap that alerts you things are close to failure. Many guys have mistaken that warning sign for condensation they thought was normal. No go. I always replace the coolant with traditional antifreeze. I've had far better luck in the long run with traditional inhibitors and a refresher than relying on the organic acid inhibitor used in those vans.

Also, as a side note the Vortec distributor cap doesn't seem to vent well. On humid days here, especially in the vans, we have issues with no start due to moisture from condensation. We also have had frequent cap and rotor failures, sometimes as frequently as 30k miles. The fix has been to epoxy a small 90 degree fitting into one of the distributor vents and tee it into a ported vacuum line to provide positive ventilation in the distributor when the throttle is open. For a while I was concerned about fuel vapor entering the distributor from the intake while the engine was shut off, but I've been doing this for several years with nothing but good results.

[EagleMark]

Luckily this one has green anti freeze! Hopefully it was done years ago. What is a good way to flush the death cool if there is an issue?

I've got some left over LT1 Opti vent parts I may put to good use with a new Vortec cap and rotor.

[pmkls1]

The sludge that I was referring to would be what you would find around and under the radiator cap and the crossover passages where the heads and intake meet. Since leaking intake gaskets were so common, us dealer techs would look for them and upsell them and as a result I haven't seen too many engines that went long enough to make a milkshake in the crankcase. The biggest cap and rotor problems that I have seen would be mainly on aftermarket pieces. I have seen brand new pieces that would arc between the cavities in the cap and cause the engine to run worse than before. the O.E. parts still have issues, but I've had much better luck with them. As for a good way to flush the cooling system if needed, the best stuff that I have seen by far would be the 2-part prestone heavy duty radiator flush that GM recommended using in the bulletin pertaining to heater core issues in the S/T trucks equipped with the 4.3. It is a little harder to find than regular radiator flushes and the process is way more involved, but the results are worth the extra trouble. I'll look for that old bulletin as it has a GM assigned part number for the flush along with listing the Prestone number and post them.

[pmkls1]

Well, after doing some searching it appears that the Prestone product has been discontinued. The GM part # is 12346500 and the Prestone # was AS100. I know that there is still stock sitting on parts shelves at numerous GM dealers. But, since it is a discontinued part you have to contact dealers individually as the inventory search program they use does not show discontinued parts. It would be a good idea to grab some if you ever come across any as it is some good stuff. The cleaner is potent enough that it required the use of a neutralizer (included in the container) in order to prevent damage due to any residue left behind. I also know of a similar type of cleaner that Ford used in a bulletin for a very similar problem that they had with the Vulcan 3.0 liter V6 in the mid-'90's. I would have to dig a little deeper to find that info though. I came close, but never used the Ford cleaner so I don't have any personal experience. But, I would imagine that it was also a lot stronger than the stuff that the average consumer could buy off of the shelf. The sludge issues that Ford had were just as bad as GM's issues and also just as difficult to completely flush out of the system. Anyhow, a good cleaner such as the two products that I am aware of can come in handy on any vehicle that has severe cooling system deposits. I figure it's at least worth the effort to find out where to obtain such a product and post it for anyone that wants to know.

[pmkls1]

Ok, so I did a little searching and found the Ford bulletin I was referring to and got the part numbers for the cleaner and cooling system conditioner which I think is just a stop-leak additive. The part number for the cleaner is Motorcraft # F8AZ-19A503-AA and the conditioner is FW-16. I did some looking online and it is difficult to obtain the motorcraft cleaner, but it is available. From what I found during looking around on the web it further reinforces my speculation that the cleaner used in the bulletin is also much stronger than what you can find on the parts shelf anywhere else.

[belaw]

some 96 g3500 vans with the Vortec 350 had TBI and a 7427 Though....along with some export Tahoe and Suburban models.

Any idea what bcc's they used?

[EagleMark]

We've got one here and use it for a baseline spark advance Vortec head swap.

[belaw]

We've got one here and use it for a baseline spark advance Vortec head swap.

That's exactly why I'm interested! So what is the BCC?

[EagleMark]

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?408-fuel-curves-for-7747-running-stock-vortec-shortblock&p=2902&viewfull=1#post2902

[JeepsAndGuns]

Any idea what bcc's they used?

Possiably BNKM? BCC find lists it as being used in 95 and 96.
http://www.gearhead-efi.com/BCCFind/result.shtml?BCC=bnkm

[belaw]

We've got one here and use it for a baseline spark advance Vortec head swap.

I loaded BRDW into TunerPro and (using $0D definitions) ran a comparison with BJYL, focusing on the spark tables. Even to my uneducated eyes the results were surprising; main spark tables were identical but the CTS spark advance table was very different.

[belaw]

Mark:

I don't even know if there's a hack for the OBDII PCMs, but could you possible extract the MAF flow/frequency table data?

I've found tables for just about every other MAF except for the one GM used with the L31! (And yes, I'm off on another tangent...)

Brian

[EagleMark]

I'll let you know when my EFI Live get's here...:jfj: