Spreadbore vs squarebore 4 bbl for TBI upgrade

[aerocorey]

Is there an advantage to having a squarebore or spreadbore intake when doing a TBI conversion?

[tgreese]

I don't think so - the TBI throttle bodies are 2V, so there's no advantage to a 4V manifold. I doubt that there's a ready-made adapter for the 4350 spread-bore manifold.

2V 360 manifolds are readily available, and you can buy an adapter for the 2V Holley pattern (used on these manifolds). That would probably be the easiest route.

[joe]

2V 360 manifolds are readily available.

Yeah boy Corey. I've got one I'm tired of tripping over that's free for just the shipping costs. Warning: they're heavy mofo's though and will prolly require a $30 or so donation to Uncle Sugars postal service.
If you're interested send me your zip and I'll box it and haul it to the post office and get you an exact quote. Prolly not $30 bucks but I'll bet it's close to that.

[derf]

The bores on the 2V manifolds aren't great for flowing enough air to support TBI.

Best manifold for the TBI swap is a squarebore 4bbl. You can find factory squarebore manifolds from time to time but your best chance is to get an Edelbrock or some other aftermarket manifold.

[aerocorey]

I've got a 2V that just needs a bit of machine work (I broke off a choke air tube bolt head). I'm trading a guy in my area a distributer for his 4V, but I don't know if his 4V is spread or square. There's a squarebore in a yard in the same '77 Cherokee that I'm gonna get a bench seat from, but the guy won't sell it to me. He's very particular about keeping his engines intact so he can sell them whole. Maybe I can trade him my 2V for his 4V or something. If this 4V I'm picking up tomorrow is spreadbore I'll bet I can trade him my 2V and that spreadbore for his squarebore.

"The bores on the 2V manifolds aren't great for flowing enough air to support TBI." - derf

Thanks for that, derf. I wasn't sure if that might be the case or not, but I can be certain that if I go with a 4V manifold for the conversion that my manifold will not be the limiting factor in performance. Now I don't feel silly spending so much time searching for a 4V.

"I doubt that there's a ready-made adapter for the 4350 spread-bore manifold." - tgreese

Thanks for that, too. Now I don't feel so stupid for pretty much giving away the spreadbore I had a year ago before I had any idea I'd have another FSJ.

[derf]

You could always stack a 4350->squarebore adapter under the squarebore->TBI adapter if you really wanted...

And just to clarify, the airflow restriction in the 2V to TBI adapter doesn't really choke you off until you get into the higher RPM ranges where you don't usually spend a lot of time running. So if you had to do it, you could get by with a 2V manifold and it would work alright at low and mid range RPMs (up to around 4K). You just wouldn't get the most out of the setup at all RPMs.

[crispyboy]

I am using the stock intake with my trucks tbi - works fine though as previously said the 4v probably flows better.
Sometime when I get my GW running I'll be able to give some feedback on how the tbi does with the edelbrock intake. Right now I am working on a fueling issue - tank is full of crud. I'll post some pics next week.

[derf]

I am using the stock intake with my trucks tbi - works fine though as previously said the 4v probably flows better.
Sometime when I get my GW running I'll be able to give some feedback on how the tbi does with the edelbrock intake. Right now I am working on a fueling issue - tank is full of crud. I'll post some pics next week.

I have serious vacuum leaks and I'm trying to move. So my project is on hold for at least another month or two once I have a house again.

[ob1jeeper]

I doubt that there's a ready-made adapter for the 4350 spread-bore manifold.

I bought a 2-4V adapter from Checkers, when doing my TBI install on my spreadbore manifold... Don't recall the PN, as I did this swap 7-8 years ago... Maybe they quit carrying it? If so try Summit, or Jeg's, or direct with Holley, or ebay, or swap meets, or ???