[Gmecm] Chevy 350 Carburated to TBI / TPI?

Tue Jan 9 01:46:17 UTC 2007

I've got an old quadrajet out in the garage somewhere. I can dig it out and 
measure up the hole pattern if no one knows it off the top of their head.

Garrett

>From: Jared Ryan <jryan at caminofx.org>
>Reply-To: gmecm at diy-efi.org
>To: gmecm at diy-efi.org
>Subject: Re: [Gmecm] Chevy 350 Carburated to TBI / TPI?
>Date: Mon, 8 Jan 2007 19:40:17 -0600
>
>Hopefully someone will have a better answer, but the QuadraJet is a 
>spreadbore carburetor, while the Holley is squarebore.  I *think* the holes 
>were closer together at the front than at the back on my QuadraJet, but 
>I've had TBI so long (and sold the carburetor) so I can't verify it.
>
>On Jan 8, 2007, at 7:30 PM, Aphelion79 wrote:
>
>>It shows the
>>"HOLLY MANIFOLD BOLT PATTERN ONLY
>>Q-JET MANIFOLD HOLES ARE NARROWER"
>>
>>Is there a schematic for that or what is the "narrower", and which holes?
>>I do believe the Chevy does in fact have a QuadraJet...
>>
>>
>>Jay Vessels wrote:
>>>Hi there!
>>>
>>>Here is the adapter on the FTP site:
>>>
>>>ftp://ftp.diy-efi.org/uploads/tbiadapter.jpg
>>>
>>>Or, if you can handle the file as a drawing:
>>>
>>>ftp://ftp.diy-efi.org/uploads/tbiadapter.dwg
>>>
>>>Jay Vessels
>>>1982 Chevrolet S-10 Sport, 2.8V6 TBI
>>>1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)
>>>
>>>Aphelion79 wrote:
>>>>Ok, well I guess it is best to look at adapters then, I'll check the 
>>>>website and see if I can find that schematic you spoke of earlier 
>>>>guys....
>>>>
>>>>Chris Reynolds wrote:
>>>>>TBI was not introduced until 1987 on Fullsize trucks with V8s.  That 
>>>>>means that all of them had the later style "High Swirl" heads on them.  
>>>>>      You can however often find the 454 TBI adapter used on the early 
>>>>>454s for a song.
>>>>>
>>>>>Aphelion79 <aphelion79 at cox.net> wrote:
>>>>>   Whoops, to finish that... so at the Junkyard look for a TBI'ed 
>>>>>truck, latest model being a '86, for the whole setup... anyone have 
>>>>>pictures of the differences or is there some big obvious thing I could 
>>>>>notice?
>>>>>
>>>>>Aphelion79 wrote:
>>>>>
>>>>>>Yeah, depending on prices of the adapters (compared to prices, if I 
>>>>>>can find any, of some junkyard intakes for the correct years) I'll 
>>>>>>probably go that route... The engine is brand new with less than 300 
>>>>>>miles on it... so everything about it is currently in near pristine 
>>>>>>condition last time I checked...
>>>>>>Jay Vessels wrote:
>>>>>>
>>>>>>>Hi there!
>>>>>>>
>>>>>>>No need to swap heads. There are several options for the TBI-specific 
>>>>>>>intake:
>>>>>>>
>>>>>>>1) Grab an adapter to bolt the TBI to an existing 4bbl. intake. 
>>>>>>>Holley, etc. make them, or make your own -- there is a drawing on the 
>>>>>>>GMECM website's incoming directory somewhere.
>>>>>>>
>>>>>>>2) Grab a stock TBI intake from a mid-80s fullsize truck. These are 
>>>>>>>likely to be hard to find, since by '87 GM went to centerbolt valve 
>>>>>>>cover heads which have a different angle on the four center intake 
>>>>>>>bolts.
>>>>>>>
>>>>>>>3) Grab an intake from a newer ('87-, but not Vortec) car/truck (i.e. 
>>>>>>>F or B body, or fullsize truck) and redrill the center boltholes. 
>>>>>>>I've done this but do not like it at all. Getting the bolts drilled 
>>>>>>>right isn't fun, and I made special washers to sit under the bolt 
>>>>>>>heads to make sure there was enough surface for clamping. Personally, 
>>>>>>>I would not do this again.
>>>>>>>
>>>>>>>4) Buy an aftermarket intake for a TBI and older heads. Holley 300-49 
>>>>>>>is a choice.
>>>>>>>
>>>>>>>If I was on a tight budget or if I had a really nice intake, I'd do 
>>>>>>>#1. I might do #2 if I got really lucky in the salvage yards. 
>>>>>>>Otherwise, I'd do #4.
>>>>>>>
>>>>>>>For TPI, it's a similar issue. 1985-1986 baseplates will bolt to the 
>>>>>>>heads you have, but after that they're designed for centerbolt heads. 
>>>>>>>These may be easier to modify, or mix-and-match 
>>>>>>>runners/plenum/baseplates based on what you dig up.
>>>>>>>
>>>>>>>Jay Vessels
>>>>>>>1982 Chevrolet S-10 Sport, 2.8V6 TBI
>>>>>>>1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)
>>>>>>>
>>>>>>>Aphelion79 wrote:
>>>>>>>
>>>>>>>>Is this possible? I have a 79' Chevy C20 sitting in my back yard 
>>>>>>>>with a carburetor that sucks. About 300 bucks for a new one... so I 
>>>>>>>>was wondering can I take the head off of a newer model truck with a 
>>>>>>>>350 and TBI (or off a car with TPI) from the Junkyard and if it will 
>>>>>>>>bolt on directly without any problems?
>>>>>>>>
>>>>>>>>
>>>>>>>>*I realize I also need the wiring harness and computer (I've done a 
>>>>>>>>few FI swaps on vehicles already, but this one seems to be the 
>>>>>>>>easiest looking like everything will bolt right on...)
>>>>>>>>
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