Out of curiousity, how much interest do you guys think there would be in a "reasonably" priced 2.375" to 2.56" bore throttle body, that uses GM injector pod, IAC, and TPS? It would use the factory TBI bolt pattern but would obviously need to have the intake bores adjusted...
94 Blazer, Turbo'd 350 TBI - DD
1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
2012 Porsche Panamera Turbo - Date night car :)
1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac
I don't foreseen a SBC truly needing a TBI bore of 2.375" to 2.560". I can foresee a 7.4 liter or bigger engine truly needing bores of 2.375" to 2.56" if truly making more than 1 HP per cubic inch.Originally Posted by 1BadAction
I'll make a flow matched adapter plate, 1" thick, to fit the intake. The pics below are for a TBI to Square Bore, "D" port design for dual plane intake.
dave w
Yea, I don't think it would be something an SBC guy needs, I'm speaking strictly of the higher compression modified big blocks. I'm "thinking" about making a 2.375" bore TB for my 3764 intake and was curious if anyone else may need one. Throttle plates are easily available in both diameters.
On a similar note, have you ever tried notching a TBI intake below the throttle bores? Similar to this but maybe not as drastic.
94 Blazer, Turbo'd 350 TBI - DD
1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
2012 Porsche Panamera Turbo - Date night car :)
1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac
No, I have not notched an intake. I tend to work with 4x4 applications (rock crawler) where low RPM is the primary focus. It's my understanding the notch helps high RPM performance.Yea, I don't think it would be something an SBC guy needs, I'm speaking strictly of the higher compression modified big blocks. I'm "thinking" about making a 2.375" bore TB for my 3764 intake and was curious if anyone else may need one. Throttle plates are easily available in both diameters.
On a similar note, have you ever tried notching a TBI intake below the throttle bores? Similar to this but maybe not as drastic.
Is it actually possible to bore a 454 TBI to the 2.56" diameter? Based on my CAD model, I'm thinking the maximum diameter is about 2.10".
dave w
2.244" (57mm) is basically the absolute max throttle bore on a factory 454 TBI unit, this is after boaring the unit to 2.291 (58.2mm) and installing sleeves to get to the 2.244 final diameter , any more than that and you cut the throttle shaft bearing off of the drivers side of the TB.
Throttle blades are custom made and the shaft is thinned on these units, a gentleman on our 454SS site used to make these and I have done a few myself , not for the faint of heart as bleed holes need to be drilled (one of which is square) and lined up perfectly for it to function properly.
I have a few 56mm BBC TBI's that I run on my junk , work well and I have made well over 1 hp/CID with them on top of a good single plane.
Care to share details on how you plan to reach that bore ?? I am curious .
TOM
Last edited by Nasty-Z; 03-07-2014 at 11:20 PM.
1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
1992 S-10 434 SBC/Tremec - '7427
1986 Monte Carlo SS
1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
1980 Z-28 496/700R4
1979 Corvette 496/700R4
1977 Olds 98 Regency 403/700R4
As Tom said, it's not possible to bore a stock TB nearly that big. The one I'm talking about would be a custom machined part with throttle bores on different hole centers compared to stock. I would also be grinding new shafts. The reasoning behind the 2.375 and 2.56 sizes is mostly because I can easily get throttle blades in those sizes, but also because the increased bore makes the jump worthwhile. 2.12" (what is available now) to a custom 2.25" isn't that big of an increase for the cost, but 2.375+ might be worth it to someone who wants to run a stealthy 502+ in their original BBC truck.
I already have some preliminary models done to figure out how many operations this is going to take on the CNC, between the time intensity of the machining, and how big I can safely go with the intake, I may not even be able to do one for myself, let alone for other people. TBI throttle bodies aren't quite as simple as MPFI TBs.
Boring of the intake is a given, hole centers are offset two ways from stock. If the 3764 can't go to size because of it's water jacket, then it isn't worth sticking with the TBI bolt pattern. Currently, my 3764 is getting bored for the 54mm bore factory casting that I'm using on my 454, I'm just getting some measurements off of it for when I drop a 502 in the truck. lol.If you end up actually fabricating a 2.375" bore TBI unit , you will want to swap to a single plane intake , the 3764 is a restriction with a stock 2" TBI unit on top of it .
TOM
Last edited by 1BadAction; 03-08-2014 at 12:18 AM.
94 Blazer, Turbo'd 350 TBI - DD
1991 2500 Suburban Adventure truck - 4wd conversion, 4-link F/R, 582ci CNP Big Block with Terminator X EFI backed by a 6L90 and twin stick'd NP205 t-case
2012 Porsche Panamera Turbo - Date night car :)
1979 16' Action Marine/"Johnny Cash" Merc Bridgeport Champ Motor - Metalflake Maniac
If you end up actually fabricating a 2.375" bore TBI unit , you will want to swap to a single plane intake , the 3764 is a restriction with a stock 2" TBI unit on top of it .
TOM
1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
1992 S-10 434 SBC/Tremec - '7427
1986 Monte Carlo SS
1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
1980 Z-28 496/700R4
1979 Corvette 496/700R4
1977 Olds 98 Regency 403/700R4
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