I have a 1991 rs with a 305 tbi that is locked up. I have a 1976 400 sbc in my garage that I can install. I am just not sure of what mods I will have to do to keep the TBI set up. The intake bolts have changed angles between the two. Any suggestions?

 

slot the intake holes. try 454 tbi injectors to make sure the 400 gets enough fuel.

 

Wolfie, welcome aboard thirdgen.org.

As far as the swap itself, the 400 will bolt in place of the 305 with regard to the engine mounts and transmission bell housing. You didn't mention what transmission you have; can we assume a TH700R-4 automatic? If so, you can use the 400 type flexplate and starter. If you have a T5 manual, though, you can't use a "regular" 168-tooth 400 flywheel. You will have to buy a 153-tooth flywheel for a 2-piece rear main seal externally balanced 400 (which the factory never made - it's an aftermarket-only part). You will also have to use the externally balanced (weighted) 400 damper on the front of the engine.

The 400 will have the dipstick on the driver side, which, if you try to use factory exhaust manifolds, will try to occupy the same space as the exhaust manifold. Some members have carefully bent the dipstick tube to clear the manifold, but that's pretty tight. Others have used a Lokar flexible dipstick. If you put headers on, problem solved. Except, using a 168-tooth flexplate (as mentioned above) requires a corresponding starter, which have been known to interfere with headers.

Check the TBI forum for more information about using the system for larger displacement engines. A carb intake (makes the '86-earlier intake mount bolt pattern problem go away), TBI adapter, and the aforementioned 454 TB might be a better route to go. The LO3 305 TBI computer will be pretty befuddled with the 400 - plan on doing chip tuning.

 

Yes it is the factory transmission. I inherited the 400 from a friend. I know it is 1976 model but has been modded up with an aftermarket cam and bored .40 over. I intended to use it for an older car/truck until this one locked up on me. Unfortunately I live in an emissions county in GA so I have to keep the egr and cat. But the smog/AIR system was removed before I got the car.

 

What does that mean? Factory for the car? Factory for the 400? Factory automatic? Factory manual?

 

it is the factory one for the 1991 camaro rs automatic. New to the chevy thing but would have to say 700r4. Sorry for the confusion.

 

that makes us neighbors then. my car had to sit for a year until it was an antique so i didn't need to pass the sniffer test.

 

Real close since I live in Mcdonough and grew up in Riverdale. Right now trying to find a good machine shop to due the intake manifold.

 

i use dixie performance in mcdonough.

 

ok I hit the exhaust/dipstick problem. The stock 305 manifolds fit not fit the 400 heads. I guess I will have to order headers and then see what I need to do for oil dipstick. Any suggestions on a header setup?
Also I need to relocate my oil sending unit from above the filter to somewhere else on engine. Does anyone know what ports on block I can use?
And last so far I cannot remove a 3/8 drive plug on the passenger to install a sensor from the 305. It is a one wire and I think it is for Water temp gauge but not sure. I think the ecm sensor is in the intake manifold.
Any help would be greatly appreciated. This swap has became more of headdache than I thought.

1991 Camaro RS(with IROC body and air intake kit)
305 TBI to 1976 400 SBC
THM-700 trans
Stock rearend

 

sorry the 3/8 plug is in the passenger side head.

 

Ok so far on this swap I had to have intake redrilled. Also had to buy headers to clear the dipstick.(Summit brand. Unforunately money is tight) And get a starter for 1980 C-10 since they had the 400 in them. (Was easier than having to wait for shipment of a new flywheel and the block has staggered starter bolts.) Also had to relocate oil sending unit off the 1991 305 filter base because some one either A) Loctited the 1/4 square drive fitting or B) put something on threads to prevent removal. And also cannot remove the 3/8 drive plug from head for one of the camaro sensors.(possibly water temp.)
Now is time for the drop in. Not sure on how it will work since I arleady installed headers. And then to TBI and fuel issues. I have a chip from a 90 truck that had a 350 and TBI unit from it and hope that gets me decent power until I can upgrade to the 454 setup everyone recommends.

 

the drivers side header may not clear when installing the engine. passenger side...no problem

 

man I think you have done this before. I had to rmove that header after about an hour of trying to manipulate it. Got to head to work so the rest will have to wait for a week...unforutnately.

 

How is your exhaust to starter clearance on the passenger side with the headers and bigger starter?

 

use a starter off a 99 chevy truck, it's a small gear reduction starter and uses the 400 flywheel. No need anymore to drill new holes in the block.

 

99 only?
Which engine?

 

I will get you the part number later today. I don't have it at the house.

I have a 400 that I put in my 89 T/A w/ a 700R4. That trans requires a smaller starter to fit inside the bellhousing. The 400 has a larger flywheel. In the past you would have to redrill the block for a staggered "i think" starter that would fit.

In 99' GM did us a favor and made a starter that would bolt up to the older blocks with a 168 tooth flywheel and a 700R4.

 

96 or newer. 4.3v6 is the same also

 

any updates on this build?

 

my 400 block has an oil passage on top of the cam right by the distbuter...distrebuter??? sorry i cant spell but you know what i mean.

 

distributor? all gen 1 smallblocks have 3 oil passages.

 

yea thats it ... distributor... thank you

 

Know it's been quite some time, but did this project ever get completed? I'm getting ready to do almost exact same to my 89 res, but going with a carburetor.

 

I'm doing this swap in 2 or 3 weeks, 406 in a 85 lg4 car, built it myself, new 750 and 3 inch universal exhaust kit on the way from summit!

 

don't forget that you need to drill holes in the heads for the steam jackets on the 400