TBI choke collar, and TBI spacer design

[mtrhead]

Hi, I just received my EBL setup, I wanted to improve some stuff that will effect tune in the ECM prior to starting that process, choke collar and TBI spacer design.
I'm running a TBI bored to 46mm with the pod spacer, 68# injectors. 383, 9.1:1, Vortec heads and RamJet cam, tri-ys out a single can, cross-h 4bbl intake GMPP.
I've heard the choke collar needs to go, and heard reports it needs to stay, if I try pulling it off what do I do to fill in that space? I have heard about the bowl thing but never tried it. I think my collar is one from a 76 Seville that I modified down to 1" in height, anyhow it's one inch high.

Regarding the current spacer between the TBI unit and the 4bbl adapter, it is 1" thick and has 2 isolated bores, 2" diameter. I have a big block one lying around that is open between the bores, I believe it is 2" thick, what do you guys think about using that one for more flow by sharing between bores? I could remove the adapter and grind off the edges to smooth the transition from the void created by the open spacer to the bores in the adapter. here is a link to an adapter that is almost exactly what I have, mine is 2" this ebay one is smaller stock 5.7, http://www.ebay.com/itm/TBI-TO-SPREA...924f52&vxp=mtr

I'm planning to use a vacuum referenced fuel pressure regulator set to 24# at 1 ATA, (vacuum line off).

Thoughts or references to other posts?

[kevinvinv]

I am not an expert here but take a look at a 454 TBI.... there is no collar, the air cleaner sits right down on the top of the TB and the injectors poke up into the air cleaner. It looks REALLY good to me. I am not really sure why that collar is there... but I'd get rid of it by trying to use the 454 setup if it were me... just a thought.

[Fast355]

I am not an expert here but take a look at a 454 TBI.... there is no collar, the air cleaner sits right down on the top of the TB and the injectors poke up into the air cleaner. It looks REALLY good to me. I am not really sure why that collar is there... but I'd get rid of it by trying to use the 454 setup if it were me... just a thought.

I have done that on a small block before. Used a 1-ton 454 van air cleaner assembly on my healthy 350. The air cleaner housing and intake ducting were both much larger. No spacer ring on it either. A powerbowl is a good addition to the stock air cleaner setup if you choose to leave it.

[kevinvinv]

The 454 air cleaner comes in two different sizes (at least). The good ones from maybe 93 or so have a snout that is 8 inches across the oval and a correspondingly large accordion style boot which goes over to a large style resonator that connects to the hole in the fender. (this is for mid 90's vintage trucks). Later on Chevy used the SB size air snout which is more like 6" across... and a smaller accordion boot and resonator.

I hunted high and low to find the larger stuff for my SB->BB swap. Just a bunch of trivia I suppose these days....

[kevinvinv]

One other thing I thought I'd mention that may be of interest to you ... if you look around you can find a factory GM adjustable fuel pressure regulator. These came off of GM Marine engines. I picked one up for about 15 bucks. Great deal. If you are interested - I think my source had another one maybe...

You mentioned vacuum referenced though so this may no matter to you. :)

[mtrhead]

I already have the vrfpr, thanks though and for the ideas on this. I do have to check the range on it though, it was used.

Has anyone noticed an improvement with an open spacer.

I keep hearing about idle issues with the 7.4 TBI on a small block, plus it supposedly flows the same as a 46mm unit with shaved shafts. I don't plan to stay with TBI permanently so the 46mm unit stays.

[kevinvinv]

Well- to each his own but I wouldn't put the 454 TBI on a small block. I had one for years with the intention of doing it- even had a special adapting spacer and the IAC adapter harness - but I never did it... I didn't have the patience to deal with the possible non-idealities. I just want the rig to run right and not have to tinker with it all the time. I did buy a bored SB TBI and of course noticed basically no difference in power output. You can spend a ton of money trying to incrementally improve things with virtually no gain-- and being sort of crusty and disgruntled lately... I am getting real tired of that :)

If you go that route, I'd love to hear how it goes!

[Fast355]

Well- to each his own but I wouldn't put the 454 TBI on a small block. I had one for years with the intention of doing it- even had a special adapting spacer and the IAC adapter harness - but I never did it... I didn't have the patience to deal with the possible non-idealities. I just want the rig to run right and not have to tinker with it all the time. I did buy a bored SB TBI and of course noticed basically no difference in power output. You can spend a ton of money trying to incrementally improve things with virtually no gain-- and being sort of crusty and disgruntled lately... I am getting real tired of that :)

If you go that route, I'd love to hear how it goes!

I had ZERO issues getting a 454 TBI to idle well on a smallblock and have even run one on a 305. About the only thing I had to do is adjust the TPS AE and bring in the PE at a lower TPS value.

[mtrhead]

I had ZERO issues getting a 454 TBI to idle well on a smallblock and have even run one on a 305. About the only thing I had to do is adjust the TPS AE and bring in the PE at a lower TPS value.

That is good news. If TBI works good I may look into it. It's time to jump in with what I have and start getting it to work good. even with 46mm, (.070" shy of a 7.4 stock unit) I may need to adjust AE and TPS start angle for PE.



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