Okay guys. I blew a headgasket on my 91 Suburban yesterday. The stock engine has 302k miles, so I think it's time to retire as opposed to repair. I have a fresh built 350 shortblock with a mild cam sitting on a stand, so that's my new base. So far the plan is use the freah shortblock, add a used set of vortech heads, and a TBI vortec manifold. Is there anything I can do to the TBI itself cheaply? Any other "while your in there" ideas?
Replace with four barrel and carb?
^ Ignore the ignorant. there are a ton of TBI mods you can do. Step upto a 454SS T/B and injectors. Delete the ridges on the lip under the injectors. Obviously a PROM to help with the airflow increase. AFPR.
Obviously the supporting mods like headers, exhaust, intake.... It's not hard to push one with good heads around the 250-275hp mark with gobs of torque.
Lots of good info here: http://www.tbichips.com/truckmods.htm
tuna55 wrote: Replace with four barrel and carb?
Or upgrade to multi point? Edelbrock has a plug in tbi-mpfi conversion in the pro-flow efi line.
I know of many TBI swaps, but few tbi upgrades. I do recall GMPP offering an "improved" tbi unit.
Wish I could help and good luck.
I have plenty of carbs and intakes laying around, but I really like the fuel injection.
Bobzilla thanks for the heads up on the 454ss stuff. That's a great starting point.
I'd love to go to a multi port injection system, but I'm trying to do this as cheap as possible. Maybe I can find a used system though.
Bobzilla wrote: Lots of good info here: http://www.tbichips.com/truckmods.htm
This site is a great resource. Thanks!
Bobzilla wrote: ^ Ignore the ignorant. there are a ton of TBI mods you can do. Step upto a 454SS T/B and injectors. Delete the ridges on the lip under the injectors. Obviously a PROM to help with the airflow increase. AFPR. Obviously the supporting mods like headers, exhaust, intake.... It's not hard to push one with good heads around the 250-275hp mark with gobs of torque. Lots of good info here: http://www.tbichips.com/truckmods.htm
I WAS KIDDING!
There was a website with an article about hopping up the L03 code 305. One of which was upgrading to a Holley TBI unit that was offered in the early ninties when TBI was still big. It was a two barrell unit that bolted right onto the factory manifold, but flowed like 670 cfm.
If you think about it, though, that's kindof redundant considering how tiny the TBI intake is. They also had an adapter plate that was TBI pattern on the top, four barrel on the bottom so you could use any single four barrell intake manifold.
I've tried searching for it and can NOT find it.
Slightly off topic:
Say you replace the TBI for a TPI setup. Now my understanding is TBI has 2 injector drivers. TPI is batch fire with 2 injectors (drivers one for each bank) Now I know the pulse width and fuel pressure is different between the 2 sets ups. Would it be possible to just install a new pump and install a chip from a TPI car (or custom)? Just a random though. I don’t really think there is a performance advantage to this either. I just happen to have some parts kicking around.
^ You actuallyswap computers IIRC. But even at that it's not that expensive of a swap. The GOOD thing with a TPI engine in a truck is the ungawdly amount of torque from idle to 4500. I was planning a 350tpi swap into my 93 fullsize waaaaay back when. I got stupid and bought a new sonoma instead.
My truck is a 1995. Not sure what computer I could swap into it since it controls the transmission too. I’ll have to double check but I think the current computer might be able to be reflashed. LT1 computer might be an option too.
okay so TPI is a good option if I can score a junkyard/used setup. What all will I need to grab....just the TPI, manifold, harness, and computer? I assume the best one to get would be off a vette, but they could be a lot harder to come by.
Are you still planing on using the Vortec heads?
the intake for the vette/camaro/firebird are all the same.
Pseudosport wrote: Are you still planing on using the Vortec heads?
I haven't bought them yet, so I don't have to, they just seemed to be a good, cheap option if sticking with TBI.
Reason I ask is there are two different versions of the TPI intake pre 85 and 86+. The only difference I know of are the center bolt holes are at a different angle and some years I think had a cold start injector. Other then that I believe they all flow the same. If you are using the Vortecs then it doesn’t matter which one you get since you will need to get a different lower intake anyway.
^ Correct, but they are the same changes across the vette/fbody range.
actually the vette retained the old school center bolt hole angle through 91. but if OP is using vortecs then the point is moot.
I am actually looking at a very similiar build for my Cab Over Isuzu car hauler. It has a factory 350 TBI, I have a 454 throttle body but it looks like I will need to make an adapter to use it. I plan to take the engine from the challenge car and rebuild it to a 383. You can get adjustable fuel pressure regulators and I hear the TBI can take extra fuel pressure. I plan to try this and use a wideband to get the fuel pressure close enough for the computer to handle the difference. My truck has a 4L80E with the parking brake bult onto the back of the trans so I want to keep the trans and not pay for an aftermarket controller. I don't know if I can find a custom chip for my NPR but I hope to swap in the engine in the spring.
adapter not needed. bore out the intake for the 2" throttle bores. and you can make an AFPR if you are so inclined. i made one for mine.
a vortec headed TBI motor is a really good way to go and is a really easy swap.
get the vortec TBI intake from GM and the motor is a bolt in/plug deal that will run just fine without doing anything else as long as the cam truly is "mild" and has around 20" of vacuum at idle.
to get more airflow thru the throttle body, you can get a spacer to put the injectors up farther away from the throttle blade and out of the throttle bores. get rid of the spacer between the throttle body and the air cleaner to free up a few more cfm- you might even be able to keep the stock air cleaner housing with a little bit of relocating of intake manifold mounted sensors and what not. but if you don't feel like relocating anything, you can buy a cone shaped insert that takes the place of the spacer and helps airlflow.
a 1" spacer between the intake and throttle body also seems to help them breathe better.
one thing that GM TBI motors like is more initial timing- just setting the base timing at 10btdc really wakes them up.
Even if you do nothing as far as mods go, prom and injectors (I think) are different, so just going from the 305 to the 350 will give you some lean running issues. Junkyard should fix that pretty easy.
You'll need to log in to post.
