What would a 91 5.7 TBI truck with a Crane 274HO6 cam run like?It already has headers and daul exhaust. I realize that this is not the best or right cam for this combo it has a Crane Compu cam in it right now and runs great. The guy that owns it wants a choppy idle.The 274HO6 is 218 @ .050 .450 lift on a 106LSA. I have it in the 327 in my 67.Will the truck run rich or lean? Thanks Chad

I believe the engine won't run very well due to the short LCA of 106*, read: too low of idle vacuum signal. Computer engines like wide lobes, nothing under 112* & nothing more than 220*@.050.

Check out the rest of the specs of the Crane Compu cam and compare. You can put in a higher lift cam, but, that's about it.

Maybe others here will offer their advice.......

Thanks for the reply Everett. Do you think the low vacume will make it run rich or lean?

Probably rich, less vacuum = more load upon engine.

Thanks again.

I have personal experience with TBI truck motors and they do not respond well at all to major modifications especially cam changes. It`s due to the type of computers that were designed to run the TBI system. They run on a lower pulse than a multipoint injection system. It`s been a while since I messed with the TBI motors. I had a 93 Z71 that I was about to do a rebuild on the motor when I found out the characteristics of that type of motor, so I called Street and Performance and ordered an intergrator harness and installed a junk yard TPI unit with a 383 stroker crank. It was a torque monster to say the least

As long as the truck/TBI subject is open, I have a question too. I'm finishing up a 383 for my 92 Full size Blazer and I am using the Vortec heads drilled for my stock TBI intake. Since the Vortecs dont have a heat crossover, the EGR will not function. So what can I do to keep the check engine light from coming on and setting a EGR trouble code.

Anyone know of a good site with lots of TBI info and discutions?

I tow a large sport boat all over Texas with my Blazer and am really looking forward to the extra power of the 383. It should pull with ease compaired to the stock 350 with 197,000 miles on it.

i don't think you are gonna be able to get the stock TBI intake to seal the tops of the vortec intake ports- they ate a lot taller. i fought that with the engine in my Nova when i first built it- since my vortecs were drilled for the old style intake, i tried to get a n RPM Q-jet intake to seal. tried 3 different gaskets, and none of them sealed.
save yourself a lot of aggravation and get the GMPP vortec TBI intake with the stock vortec intake gaskets, and use the vortec truck exhaust manifold and EGR pieces. that way, everything works and there are no problems down the road.

I have a 91 SS454 pickup which runs the TBI setup as well. Turbo City used to offer several items for TBI engines to help make them more driveable with mods like bigger cams, headers, etc. One item would take the MAP sensor reading and alter it so it would idle better with a bigger cam. TPI is really the way to go. I really want to put a TPI setup on my 454, but my truck runs perfect right now so I'm not messing with it.

Go to the thirdgen website. They have a great EFI section and a TBI section.