Hi Gents,

I have a LO3 3.08 T5 IROC vert I picked up last December. My Buick Rendezvous is faster as it turns out. Coming from another mild 13 sec car before, this is a little frustrating. The handling is stunning, but sheesh.
I have a 400 sbc in the garage I would like to swap in.

I know the T5 is a weak sister, and thanks to Sofa, the block must be drilled for the missing starter hole,

Reportedly endless chip burning, lack of cfm from a 670 tbi and general time and expense to get a non-factory 406 tbi combo tuned to be fairly right, compared to the simplicity of an almost drop on carb, is why I'd go with a carb.

Driveability with the existing perfectly tuned up tbi isn't that impressive anyway.

Did you gurus think your bigger cubic inch tbi to carb swaps were an all around improvement for you?

Thanks

 

670 tbi? they are more like 480 cfm. all out performance yes the carb will win. driveability no. small block 400 would be better with a carb. depends on mods to the engine.

 

I think the OP was referring to the Holley TB upgrade. Which is basically just a 454 TB.
670 cfm will support 400 HP, the problem is those two 85# injectors. That's like having eight 21# injectors. That's why Holley rates them up to 275 HP.
A perfectly calibrated Q-Jet on a mild 400 should give excellent results. But a basic Holley 0-3310 won't have such good manners.

 

i just did an engine swap between my two cars yesterday one i had a 305 tbi and the other i had a 305 with edelbrock intake, carter 650 carb, and msd hei distributor, and while switching engines i took the carb bak off and put the tbi in, when i was finished i thought i would have more hp but with the tbi replacing the carb i took a great loss in hp

 

Well yeah, the Edelbrock intake manifold alone is worth a solid 25 HP, assuming adequate fuel and heads (not swirl ports).

 

I'm glad you picked up on the starter bolt hole.

Depending on how the 400 is set up (cam most importantly) you might be able to just stick a 454 TB on it, and go. 670 CFM is plenty for such a build.

I'd definitely suggest not using the stock 305 intake manifold though; a Performer RPM with an adapter is the way to go.

 

ive got the edelbrock rpm intake for my carb. theres an adaptor plate for my tbi??

 

nevermind i did some research on my own and found it. i would have never thought about adapting it thanks for the education. One question though. I've swapped engines on several different cars and taken the egr valve completely out the equation will taking the egr valve away from the setup cause any problems. the intake i have has no spot for the egr.

 

EGR helps MPG, so if that matters to you, then adapt the TBI to a Performer EGR. Otherwise, the RPM will make more upper-rpm HP.

 

EGR only helps MPG if the car is tuned for EGR. If you tune for non-EGR, it won't make a lick of difference.

One thing about "worth it" - at emissions inspection time, it certainly isn't.

 

It also depends on how wild your cam is, and your axle ratio. But if you're building for MPG, it'll be a mild enough cam and gear that the EGR combo would get better MPG than the RPM combo.

 

lucky me none are required for s.c.

 

i just wish i could use my hei distributor along with the intake

 

Sorry for the delay. Thanks for all the great specific tech input guys.
Too many decades out of high school, now with a family, I could finally afford a halfway decent stick shift convertible Camaro to put a belligerent fun cam in to go to Dairy Queen with the kids or the track twice a year. After work and weekend use.
Emissions in our area is finally not a concern with an '88, but gas in "Crook " county Illinois still over $4.00 a gallon. I know speed costs money, so how fast do you want to go?
Compared to my other past Chevys, this IROC underhood looks like the Space Shuttle.
I was thinking of the following, before the T5 grenades.
A) Keep ECM in for radiator fan, gauges, fuel pump relay operation, etc.
B) An on-hand QFT 780 vac secondary annular booster carb.
C) Mallory 4309 fuel reg, if the return line is big enough.
D) Weiand 7547 open plenum intake with added plenum divider for 25 more ft. lbs. (it worked on a original Torker I had) Not enough hood clearance for a Performer RPM I'm told.
E) Comp XR276HR 224*/ 230*---- .502"/.510" with 106* LSA per David Vizard because
of--"inadequate 2.02" / 1.60" valve size for a 400 cubes".
F) Recurved vac advance non-computer HEI
G) Edelbrock E-Street 64cc heads w/comp hyd roller beehive springs
H) .030" over 10.0-1 Hypereutectic shortblock
I) Hooker 2055's & Aerochamber 3" catback exhaust.
J) Keep the 3.08 posi.


K) OR, Just keep the 305 shortblock, use TFS super 23 175cc 56 cc Alum Heads, a slightly better cam than the broom stick that's in there, Performer intake, 600 vac sec carb, A, C, F, I, & J.
Thanks for your patience in reading all this.

 

XR276 on 106 LSA, with 3.08:1?

 

Well, maybe 112* LSA might have a little less overlap. You're right.

 

I really don't know, but my own guess is that you'll end up hunting for at least a 3.42:1 gear, whichever LSA you choose. But on the other hand, those LSx guys are running 230-at-50 cams with the T56's even-taller sixth, and stock axle gearing.
This will be interesting when you start driving it.

 

Shouldn't compare LS1 & Gen I cam'ing and gearing. Just completely different animals.

I do know that when I went from 2.93's with the ZZ4 clone with CC carb to 3.23's, it was a lot happier cruising both on surface streets and at freeway speeds. I'm sure with the much bigger cam being considered here, 3.08's would be similarly unfriendly.