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Hey, I have one throttle body I know for sure came off of a 1993 Corvette LT1. But the other is supposedly off of a 1993 also, but its throttle linkage is a bit different. My 1993 Corvette has ASR, so only one cable going to the throttle body, even though I have a 4L60 non electronic. You adjust the TV cable via the ASR.
Is this throttle body from a Camaro? And if you also notice, it doesnt have a IAC hole drilled in it, and this is a TPIS 52mm throttle body they modified an OEM one with.. Left one is OEM GM that came off of the 1993 Corvette LT1 Automatic Lower throttle Body, TPIS modified has no IAC hole in throttle body. Wierd? OEM THrottle Body off of 93 Corvette Ser # TPIS throttle Body Ser #
Last edited by Steve40th396; 05-14-2024 at 06:31 PM.
The bottom plate, assuming that brass fitting is an air bleed, doesn't look like an F-Body part. That might be due to the difference in the cooling system plumbing. The Corvette has a unique closed coolant system with an self-deaerate box. The F-Body system has no deaerater, and places the air bleed screws (2) on the t’stat housing and on the heater supply line. The bottom plate on my 94 (purchased new) did not have the brass fitting, and while the boss for the fitting was there, it was not open and not threaded.
I believe the B-Body (Caprice, SS, Roadmaster, Fleetwood) had a hybrid coolant system, with some elements of both the F-Body and Corvette systems, so maybe they had the bottom plate bleeder.
93 F-Body had the screw-in IAC motor, 94 and up IAC was flanged with 2 screws.
No ASR/TCS on F-Bodies until 95. The 93 throttle body had a pin on the side for the 4L60 TV cable. None after that year.
One of the other administrators on the Firebird Nation site has a 93 Trans Am and a1996 Corvette. I think he's addressed the air bleed procedures on both cars. I'll see if he can confirm what I suggested above.
Thnx,
Yes the Corvette does have the air bleed from coolant via the brass bleeders.
Cant get these pics to show on two browsers.
I do know the 93 had the screw in IAC. But, I think the bottom housing can be swapped?
What is really intriguing is the no hole in the IAC area for the idle air passages LT1s used. Not sure if TPIS filled these? Never seen one without.
Yes, the TPIS is a 1994 LT1 Throttle Body. I cant change the sheave due to the differences in springs, maybe. I may try once I take off the 93s sheave..I will mount it first and see if I can just adjust the throttle cable a bit.
I think you can go to my “profile” (click on my screen name under the avatar, click “View Public Profile” on dropdown). When profile opens look for “Albums” on right hand column, click on “Show Photos”. Should see “My Post Pictures” on the top left album, click there and page 1 of 5 should open. The throttle body photos (thumbnail) are all scattered on page one. Clicking on the photo and it should open.
Thnx. I looked at this photo, and I notice yours does have the 1/8" hole drilled, which is OEM. TPIS doesnt have this hole on any pictures I found.
I know TPIS is very good, and most will say they bolted it on and it was perfect, so I guess I will see.
Just learned something I hadn’t known for the 29 years I've been dealing with the LT1. Checked with the other Admin on Firebird Nation. His 93 Trans Am has the vent fitting on the throttle body. Never knew that…. even Shoebox doesn’t show that in his table of year-to-year F-Body differences.
And the guy I asked said his 96 Corvette has a single vent on the water neck.
Can't explain the TPIS lack of a through hole for the idle air. Again, something I didn’t know. People who buy aftermarket throttle bodies often have to drill a ~1/8” hole in a blade to get enough air to keep the IAC counts within recommended range at idle. I never had a problem with the Holley 58mm, but then I was using a hybrid system with an aftermarket engine management computer, but retained the factory PCM for speedo, IAC, and (sort of) emissions.
I looked at the TPIS to see if they filled up the hole where the other throttle body has one. Nope. Nothing obvious. The part number reads GM 17095238....'95-'96 Fleetwood, Road Master, Caprice, Impala for the housing of the TPIS throttle body.
Maybe Impalas etc had a different intake and idle air control path.
My 96 Impala, owned since new, does have a 1/8" hole for IAC in stock TB. Only bleed port is on T stat housing. I had the 48mm TB bored to 52 by David Kudos many years ago when I did H/C build. It is now on my 383 and for that motor is when I needed to drill the stock 1/8" hole larger, now 11/64". Ed Wright, tuner I used, walked me through the process.
OP, as I mentioned in your thread on another forum, stock IAC hole is 1/8". often camed motors require the hole to be drilled larger (1-3/64" larger) to bring IAC counts down to 32 (30-35) at idle
You can audition the TPI as is and see what IAC counts are if you have scan ability to read them. "Maybe" TPI sets the blades slightly more open using the stop screw to adjust. This however would also require TPS to be modified (slit holes to rotate it) to bring TPS VDC in spec (IIRC .67vdc at idle). You can use a DVM to read what TPS volts are from blades closed to wide open (4,5 vdc). volts should raise evenly and consistently as you open the TB blades to full.
Thnx Chimera96. I will be scanning the car while it runs, after warming up, with ttS datamaster. I have some files of me scanning before I came up north to work. But, I have no way to look at them on my computer here.
I also have a slotted TPS, but on LT1s, it will reset itself each time it starts. We shall see.
How much vacuum are you running to need the 11/64". What size cam are you running?
05-14-2024, 06:15 PM
