first questions of a newbie.....

[dougg01]

So....

I have much experience with the GM LT1 and the TBI truck motors (4.3 to 5.7), but not so much this CPFI in this 2000 Jimmy.

I see in some folks build a 'CFM throttle blade'. What is that...? I don't care for the throttle blade on this TB as it has that bell on the leading edge which ultimately restricts air flow and inhibits tip-in.

I also see quite a few trucks with a TB spacer. This helped the TBI trucks I've had. How's it do on these...? Worth it...? Anything is better than nothing.

What about under-drive pulleys...? I added them to my 94 S-10 and saw a little gain and it's the couple here and the few there that eventually add up. Worth it on these or more trouble than its worth...?

I see something about a 'headlight support mod'. Can someone detail to me if that could/should/would transfer to the GMC composite...? this truck was in a frontal collision some time before my ownership and it seems nothing lines up and it too me forever to get the headlights adjusted properly. They shake too. Yes, I have them seated in the pockets, they just aren't tight.

Thank you.... I'm learning here....

[HenryJ]

I see in some folks build a 'CFM throttle blade'. What is that...? I don't care for the throttle blade on this TB as it has that bell on the leading edge which ultimately restricts air flow and inhibits tip-in.

The CFM throttle blade is a blade without the diffuser. That diffuser ("bell") helps to smooth the throttle as it opens. Making it lees dramatic on opening. Sort of numbs it. Some have trimmed it down with good results. I have the CFM blade. I like it but it takes some getting used to. It can be very touchy in low range. Just a heads up.

I also see quite a few trucks with a TB spacer. This helped the TBI trucks I've had. How's it do on these...? Worth it...? Anything is better than nothing.

Meh. Not really worth the money if you are looking for performance. It does make thermostat changes easier and line things up after a body lift though. I like mine for that.

What about under-drive pulleys...? I added them to my 94 S-10 and saw a little gain and it's the couple here and the few there that eventually add up. Worth it on these or more trouble than its worth...?

most are aluminum and do not last as long as steel, in a dirty environment of a 4x4. The issues of needing more rpm for the alternator worry me. I am not running them and do not plan to. Someone else who is might have a different opinion.

I see something about a 'headlight support mod'. Can someone detail to me if that could/should/would transfer to the GMC composite...

Probably not a GMC thing.

[dougg01]

Touchy throttle...? This coming from someone sporting a hefty HenryJ...? My old S-10 is so tightly-wound with its mods it jerks the tires idling into 2nd gear. My Dremel is ready....That stupid thing inhibits airflow for my 4.3 air pump.

I might do the TB spacer for giggles and then it will be of benefit when the body lift comes along.

I ran steel pulleys on my old S-10. Didn't do much, but it all adds up. Most pulleys available now seem to be aluminum. I might pass. Might not. It's of questionable value for what I am doing with this thing so I defer for now.

Yeah, it seems to be more of a Chevy thing (headlights) and I haven't found any mention of it for GMC, but that doesn't rule it out completely.

Thanks for answering....go specs on the HenryJ..? We're trying to go to the HRR at Beech Bend next month. Been trying for a few years and something always gets in the way. Did the goodguys event last fall though. Mmmm.

[HenryJ]

I ran steel pulleys on my old S-10. Didn't do much, but it all adds up. Most pulleys available now seem to be aluminum. I might pass. Might not. It's of questionable value for what I am doing with this thing so I defer for now.

Our alternators benefit from a slightly faster idle rpm. I have not been able to find a pulley small enough to do that with the under drive pulleys. Add to that our power steering pump needing all it can do to turn the larger tires and I see the under drive pulleys doing more harm than good. Actually an over drive pulley might be of more benefit?

Look hard at the LS1/LT1 e-fans install. I think that has more pros than cons. That alone will do more than the under drive pulleys. IMO.

[F9K9]

..............Look hard at the LS1/LT1 e-fans install. I think that has more pros than cons. That alone will do more than the under drive pulleys. IMO.

[dougg01]

..............Look hard at the LS1/LT1 e-fans install. I think that has more pros than cons. That alone will do more than the under drive pulleys. IMO.

No matter how much you try to pursuade me to scavenge parts off the race car or my old daily-driver (that is collecting dust in the garage), I'm not taking the fans off our F-bodies for the Jimmy....

I might take one off someone elses though.

I've read they fit and I do not like the clutch fan. I put a 180 stat in the former 99 Blazer and I put on in my Jimmy and the clutch fan doesn't lock up until 195 or so.

I think my next major purchase is programming software. I have TunerCat for my 'Bird and can do most of what I need on that. The Jimmy needs correction for tires, turn down the after-cat O2 sensor, maybe fidldle with shift points, etc. I'd also like to have a ZR2 rear diff and a 3.73 front pumpkin. That'd wake this thing up and I have decided is also a prerequisite before I do the 2" BL and try 32s/33s. The 3.42s won't cut it.

IS there an aftermarket option for 4.10s in the front diff...? That'd be nice.

[HenryJ]

I think my next major purchase is programming software.

Keep us informed on what you do there. I'd love to find affordable software to program our trucks.

IS there an aftermarket option for 4.10s in the front diff...?

Yes. Hobie (a2b) did those gears in his truck.

[WileyHunter]

Touchy throttle...? This coming from someone sporting a hefty HenryJ...? My old S-10 is so tightly-wound with its mods it jerks the tires idling into 2nd gear. My Dremel is ready....That stupid thing inhibits airflow for my 4.3 air pump.

Uh... Yeah, touchy would be one word for it.

I tend to 'forget' about the response that mine now gives me, and get flipped off frequently as people think I'm spinning my back wheels because of 'road rage' or something. With stock size wheels and tires it don't take much to light up coming off a stop.