Chevy 6.5 IDI randomly dies..

[R.O.R-2.0]

TBI is cake.. you cant really hook it up wrong..

i liked TBI for the smaller engines, but they should have made a bigger version for the big small blocks, and big blocks..

[maxfax]

IMHO GM TBI was one of the best fuel systems on the planet..  Simple, reliable, and performed decently for power and economy.. That's probably why they stopped using it..     And it was available on small and big blocks..  The 305 and 350 used it from '87 to '95..  The 454 used it from '87 till I think '96..  The very early TBI 454's didn't even have a special intake..  They had an adapter that fit the throttle body to the quadrajet intake..

[R.O.R-2.0]

it was very economical, but nothing for power..

look at what happened when they came out with Whoretec in 96, there engines made 100 more HP..

[maxfax]

Great power it wasn't, but acceptable..  Better than the electronic q-jets before it..    The TBI 305 in my '93 Caprice runs circles around the '83 Caprice with a 350 with it's stock carb.. 

The fuel system on the whoretech can take some of the credit for power gains, but the majority of the improvement was in the cam, intake and heads.. IIRC that all brought the compression back up to respectable levels again..

I suspect that the improved fuel system was was allowed them to get away with the other improvements..  Otherwise I'm sure they'd have been too "dirty"..

[R.O.R-2.0]

Great power it wasn't, but acceptable..  Better than the electronic q-jets before it..    The TBI 305 in my '93 Caprice runs circles around the '83 Caprice with a 350 with it's stock carb.. 

The fuel system on the whoretech can take some of the credit for power gains, but the majority of the improvement was in the cam, intake and heads.. IIRC that all brought the compression back up to respectable levels again..

I suspect that the improved fuel system was was allowed them to get away with the other improvements..  Otherwise I'm sure they'd have been too "dirty"..

Roller cam..

VASTLY improved heads (they have a spiral ramp above the intake valve, very cool design)

intake had short intake runners, and a large plenum.. but the single fuel injector was a downfall, they make about 40 more HP with the multi-point conversion kit.

the TBI engines had ~9:1 comp didnt they? and i think the vortec engines were 10, or even 10.25:1?

[maxfax]

The roller cam didn't even do that much..  They debuted in '86 or '87  and still with a CCC they were a DAWG!

The single point injectors was indeed the downfall of TBI..  Not enough fuel and poor fuel distribution..

IIRC compression on L98's was 8 or 8.5 on the CCC engines, 9 on TBI engines, and 9.5 on Vortec engines..  LT1's had 10.25 on aluminum headed versions, 9.5 on cast head versions...  The LS series are in the 10:1 range..  Pretty much anything over 9.5.1 on a run of the mill cast headed engine is gonna be trouble, especially on 87 octane...

Supposedly the '94 and '95 trucks got a version of the vortec heads with TBI, but still had the 9:1 compression, less agressive cam, and the crappy intake..  It was a poor combination as they seemed to get the worst mileage with little power gain..

[R.O.R-2.0]

The roller cam didn't even do that much..  They debuted in '86 or '87  and still with a CCC they were a DAWG!

The single point injectors was indeed the downfall of TBI..  Not enough fuel and poor fuel distribution..

IIRC compression on L98's was 8 or 8.5 on the CCC engines, 9 on TBI engines, and 9.5 on Vortec engines..  LT1's had 10.25 on aluminum headed versions, 9.5 on cast head versions...  The LS series are in the 10:1 range..  Pretty much anything over 9.5.1 on a run of the mill cast headed engine is gonna be trouble, especially on 87 octane...

Supposedly the '94 and '95 trucks got a version of the vortec heads with TBI, but still had the 9:1 compression, less agressive cam, and the crappy intake..  It was a poor combination as they seemed to get the worst mileage with little power gain..

i have an engine that is a bit of a unique combination.. its a 4.3L V6, from a van, carburated, with VORTEC heads.. all original from what i can tell..

[maxfax]

That is an interesting combo.. Probably a fun story to go with it at some point..  IIRC some of the vans kept the carb longer than everything else...  I actually kinda forgot about the 4.3 having a carb in trucks and vans.. 

[R.O.R-2.0]

That is an interesting combo.. Probably a fun story to go with it at some point..  IIRC some of the vans kept the carb longer than everything else...  I actually kinda forgot about the 4.3 having a carb in trucks and vans.. 

it was supposed to be from an 85 Astro.. it has no balance shaft either.. so i know its an early block.

[maxfax]

I didn't even think the Vortec heads would fit the early block..  Wonder if it was some odd combo made for trucks and vans from back in the day..  A fully loaded Astro would need all the power it could get...

[R.O.R-2.0]

I didn't even think the Vortec heads would fit the early block..  Wonder if it was some odd combo made for trucks and vans from back in the day..  A fully loaded Astro would need all the power it could get...

they are truely weird Vortec heads.. they have the intake bolts perpendicular to the intake ports, not vertical like all the other vortec heads.

the DO have the center bolt valve covers, and DO have the vortec intake port, along with bigger valves than most 4.3 heads ive seen..

[maxfax]

Kevin, you ever get the gremlins outta the 6.5???

[R.O.R-2.0]

Kevin, you ever get the gremlins outta the 6.5???

nope. my grandpa didnt seem real interested in me fixing it for him, so i just left it alone. he can just drive it like it is. if it doesnt bother him having to re-start it every mile or so, then i dont care either.

[maxfax]

Good lord he sounds like my father..  I think the last one was "Yeah you can use the truck, but if you load the trailer real heavy be careful, there's no brakes on the truck"   That rusted brake line got replaced 2 years later.. So much for the annual PA safety inspection....

[Patrick]

Maybe this was covered, didn't check the whole thread. I saw someone selling a wiring kit and heat sink to move the electronic piece off the side of the pump with a 6 foot lead. He was claiming there's a heat problem with the 6.5? Mount it far enough from the motor end of problem (or so he said). Might be worth checking into.