TPI on a SBC 400?!?!?!

[ChevyJr]

I have read many of the threads and different forums on this subject so I don't mean to be redundant when asking can anyone offer any guidance and/or opinions when swap from a carb setup to a TPI setup on a sbc 400. I enjoy barkin' my tires everyone once in a while with the 700r4 paired with my sbc 400, but think a TPI setup might offer slightly better mpg to my daily driver.

Currently I have a Holley Street Avenger 770cfm which I only put on there because I live in Colorado. Figured I'd be able to create a better air/fuel ratio by sizing down the jets with a bigger carb. Works well, for me at least. And although my carb hasn't given too much trouble, I know it can be tuned even better than I "tuned" it. TPI's electronic tuning sounds like something I'd be really interested in and the reliability as well considering my '65 is my everyday driver. (Modern cars make me sick ha)

I've read a lot of sbc 350 conversion just not too many for sbc 400's.

(Oh and running a 3.5" air filter now... that disgusting one is no longer on there)

[tincan1966]

Depending on how your SB400 is built, there isn't much difference adding the TPI to it or a 350.
The stock low compression 400 typically was only about a 180-190HP engine with about 8.5:1 compression, so feeding it with a TPI should be very similar to a 350. There are so many aftermarket pieces available, as well, so tuning or dialing in the right combination shouldn't be difficult.

For a simpler conversion, you could look into doing a TBI(throttle body) install. You can buy adapter plates from places like Howell to bolt the TBI unit to your 4bbl intake.

There are a lot of options out there. I personally like the TBI units for the simplicity and they still look like a carb setup at first glance.

[gofastnut]

Also, the Stock TPI only runs up to 4500 RPM, IIRC. Not sure what you run yours to, but just food for thought.
EZ EFI makes a harness/computer for it, nice operation I'd think!

[blazerkid]

i have stock tbi on a 400 with a cam and it will squawk the 33 on my blazer
so it is a good idea

[chevyrestoguy]

A TPI will make a little more horsepower than a TBI, and there's more performance upgrades available. A TBI is a very dependable, simple, system, but you have to be very careful with your cam selection. You cannot go over 218 @ .050 on your cam specs or the MAP sensor will go nuts and surge badly at idle. The low vacuum signal falls out of the min/max range that the MAP looks for, so the computer tries to "hunt" for the highest vacuum signal return. You can have the computer reflashed, but i'm not too sure how many shops still service the 7747 TBI computers anymore. Keep your lobes centers wide, no tighter than a 112, 114 works best.

A 400 would work nice with Vortec heads, 9.5-1 compression, a cam around 216 @ .050 with around .470 lift on a 112 or 114 lobe center, a 454 TBI throttle body with a Jet injector spacer and a Jet baseplate spacer, along with a matched chip and a free flowing 2.5" exhaust.

[Captainfab]

Quite a few years ago we had a TPI on my son's 400. IMO it ran really good, but we had a starting issue that never did get fixed. My son paid $575.00 for a 'custom' chip, but they never could get it figured out. There are better options available these days, so I wouldn't hesitate going with a TPI again. Just do a lot of research on a ECU/ECM for it.

[bama63]

a wealth of info here http://www.thirdgen.org/techboard/ scroll down everything from diy prom burning to mods to simple how to stuff

[66 C10 383]

I'm getting ready to drop in my 383 with a TPI based setup on it. By that I mean the wiring and ecm is the stock 1989 Mass Air Flow system. The base, runners, and plenum are all aftermarket Accel SuperRam.

You have many choices depending what you want. Stock TPI was originally designed for the 305 so you're almost 100 cu/in past that but with a few mods should work decently. Bigger injectors, bigger runners, tuning ...

As was stated, the stock TPI runs out of air flow about 4800 rpm ... on a 305/350 engine. If you was looking for torque below about 4000 it would be a good choice I think but would still need custom tuning. You can pay someone to tune it for you ... either by mail order chips (least best option) or on a dyno (better but more expensive). With a 400 you'd really need to tune in your fuel and timing anyway.

You can buy the stuff to tune and burn chips yourself for about the cost of a mail order chip if you can learn to tune one yourself. Then you can tune all you want and it won't cost you any more than your original purchase.

From there you can move up to bigger runners and even different intake setups.

Read up at the thirdgen.org link posted to see what your plans and goals are.

[gofastnut]

The one thing I didn't like about the TPI set up was that bigger runners=$300, bigger throttle body=$250, better lower intake=$300.
That sealed the deal AGAINST it for me, but a TPI still looks pretty cool!