thumper_65590

Hello everyone. I have been lurking here for quite awhile, but just finally registered. All the other forums I am on/read/search point me here, so here I am lol. I have a 1994 GMC G2500 Conversion van that is the family hauler. It has a 350 TBI that is getting pretty tired. The transmission is a fresh rebuild 4L60E, corvette servo, shift kit, firmed up 1-2 accumulator, and a B&M stock stall converter, so I don't want to get rid of it. The van also has true dual exhaust, 2.5 inch pipes, high flow cats, and 60 series flowmasters. If I remember correctly, it has 2.73 rear as well. I have a very nice, low mileage stock 400 SBC, 77 cast block, 2 bolt mains. I have access to a complete TPI system out of an 87 Iroc, including the ECM. Now for the fun stuff. I'm not wanting a high rpm/high horsepower engine. This engine would probably never see over 4200, and most of the time not over 3400. With the 350 in it now it turns around 2200@ 70 MPH, and jumps up to around 2800-3000 when it downshifts into third. All I am looking to get out of this swap is more low end torque. I am planning on getting a boat next spring for the family to go out on (pontoon),and I live in south Missouri. The 350 falls on its face now going up a long grade without any extra weight, I can just imagine what it would do with a boat and a little head wind. I would like to keep the swap engine's main power band from around 1500 up to around 3400 RPM. I would love to get a little more mileage out of it as well, but just keeping the 15 mpg I'm getting now would be great. I have quite a bit of engine experience, but have almost zero EFI, and absolutely zero EFI tuning experience. So now for my questions........ What cam would be good for this? Would the TPI be a good fit, or should I stick with the tbi? (Like the looks of the tpi setup alot). I know I could build and stroke the 350 and all of that, but I can't have the van down for an extended period of time, as it's the only vehicle I have that fits all the family, and I have the 400 already. Any help would be appreciated.

bigal55

iTrader: (1)

The 400 alone will gain you tons of torque and would be a nice combo for towing. The heads on the 400 are the old manifold bolt angles so the 87 TPI manifold will have to be slightly modified (easy). Keeping the rpms down in the range you are looking at, the TPI will be a great fit. For the ECM, are you going to mod the wiring harness for 8 injectors and keep the ECM you have (e-trans control)? You could just use the TBI and see how it "pulls". This would give you the quickest turnaround time but may not be "ideal" for your needs. The TBI manifold would also need the bolt hole mod (same as TPI manifold), and of course, either will need to be tuned for the different engine. Go for it! HTH!

thumper_65590

I have no problem modifying the intake. I was wondering about piggy backing the computers, one to run the engine, one to run the tranny? (Have seen this done for engine swaps in Pontiac Fieros. Also, What would I need to do for the tuning? What equipment would I need to get? I'm not afraid to research and ask questions, just need a nudge in the right direction. I have been looking at Moates and a few other sites, trying to understand bin files, etc. I really like what I have seen about the TPI helping with the torque band in the RPM range that I'm running in. Is there any mods i need to do to the intake before I install it? Also, what would be a good cam for this application? Thanks again from the newbe

thumper_65590

Ok, quick question, and I had to re-read the post a few times before I caught it, and it kind of answers my question as far as piggybacking the computers. I didn't think I could modify the tbi computer/wiring harness to run the 8 injectors, as it would affect the voltage going to the individual injectors. Am I wrong in this? The TPI setup I am getting is off an 87 Vette, so I assume it is a MAF system instead of a MAP system. I may be wrong on this. Thanks again for the help.

thumper_65590

This is the TPI system I am looking at. http://kansascity.craigslist.org/pts/5747904495.html. Would these heads be good on the block after they are drilled? I talked to the seller and he got all the parts with a project camaro, but is making it a Dragster, so is going big block and doesn't need the parts. I also found this set as well: http://springfield.craigslist.org/pts/5820772223.html. Would one be better than the other? Thanks again

thumper_65590

Ok, I think I am my own worst enemy, lol. I keep reading on here about the many mods that are being done, and I realise that I have a van, not a Gen 3, although my wife wants me to get one as a project ( Hopefully I can in the next year) there is so much knowledge on here that it has become my goto place for information on fuel injection. Anyway, before I ramble farther, I figure of I am going to have the van down for my engine swap, would I be money ahead to go OBD2 (411 PCM) while I am at it and have easy access to everything? Since I don't have anything for tuning of OBD1, and all the other vehicles I have are already OBD2, I was thinking it might be better for me to go ahead and do everything at once. Thoughts? If this is a good plan of action, I am going to my local Pick-N-Pull tomorrow and I thought I would see what I can find. Thanks for all the help so far.

redneckjoe

pretty sure you would also need to step the fuel pressure up to go TPI?

while not your answer, i think i'd consider dropping in the 400, keep it TBI, maybe run 454 injectors, and add some rear gear to it. should be fine for towing IMO. a lot simpler swap too.

thumper_65590

Well, I have my tpi now. I purchased a 92 Firebird T-top this evening. The car runs, but tranny is shot, and the body needs work, but it will be a project car for the wife's birthday next year. The tpi is going to be going on the 400, and the engine is going into a 95 suburban for a friend of mine, and to bored 30 over 350 that is in the "trunk" will end back in the Firebird. Anyway, since I have the complete car, what parts do I need to get off of it besides the tpi to install it on the 400?

bigal55

iTrader: (1)

What's in the Suburban, TBI? Look in the stickies section above on how to convert TBI to Speed Density TPI. You probably don't want to remove the TPI harness from the Firebird as that will be needed when you re-do the 350 for your wife, right? So, you will need some injector pigtails for the conversion harness. Converting the Suburban harness for TPI will also let you keep the E-trans control of the stock ECM. As stated above by redneckjoe, you will have to replace the TBI fuel pump (low pressure) with a TPI (high pressure) pump. This type of conversion has been done many times so there is a ton of info, yours being a 400 makes no difference as far as the wiring conversion goes. You already know about the 400 head steam holes and the different bolt angle of the 4 center holes on the manifold so you basically have all the info at hand. As far as going with a 0411 PCM, I do not have any knowledge on that conversion but I do know that conversion has been done numerous times also. Your statement about going OBDII makes sense but you need to know that conversion onto a GEN 1 small block has many hurdles and costs attached to it. My opinion is the cost far out weighs the advantages, especially for "just" a tow vehicle. You will need to get tuning hardware and learn to tune and burn chips, but that is a small fraction of the cost of a 24X conversion for OBDII. HTH!

TURBOTOMMY

From what I've read its pretty easy to mod your existing harness to operate the TPI,,cheaper also..Ill be doing this myself,,installing tpi into a 95 z71....

BLUETA

Thumper, PM sent