K-dawg

I've got a 91 305 rs camaro with tbi. I also have a sbc 400 bored 60 over,from the research I've done over the past few weeks I've heard that I can reuse the 305 heads, the exhaust and the intake and the accesories from the 305.

I plan to port and polish the heads, put new larger exhaust and use larger injectors for the throttle body.

I would like to know some stuff on the following. Will the car run without a knock sensor(regardles of if the check engine light shows), if not where can I find one and what kind of price am I looking at? I also need to know where I can get chip burning equipment to reprogram the ecu chip with because I don't think it's gonna be easy to find chips for a tbi 400 with a race cam. Is there anything else I should knowabout and can someone point me in the direction of a good size injector for this thing?

five7kid

iTrader: (14)

Forget the TBI 305 heads. They choke a 305, imagine what they'd do on a 400. Porting isn't going to help enough to make a difference.

A .060"-over factory 400 block is skating on thin ice - literally. I wouldn't do anything with that block until it was sonic tested for wall thickness. .030"-over is the typical safe max for a factory 400 block.

A 454 TBI unit is what you need. The TBI forum will have more info (a lot of it will be about 350s, but will apply for you as well).

Check the DIY PROM forum for info about the equipment needed for the PROM burning equipment.

lowflyr

I agree with five7kid on the block....0.060 over on a 400 is very dangerous without having it checked for wall thickness. Make sure you have at LEAST 0.200 wall thickness. Less than this is sketchy. Especially if you want to make power, since the cylinder walls will begin to flex and ring sealing will suffer. Worst case, you crack the block. Some 400 blocks will have enough thickness though.

The 305 heads will have plenty of flow up to about 4500rpm, so use a smaller cam if you run this combo. If you use a large cam you are wasting your time, they will not flow past 5000rpm on a 400.

My second last combo ran 13.3's @103MPH.....this was with a comp cams XE268H cam and 84' 305HO heads I pocket ported myself. This combo was a torque monster from 1500-4000rpm. It still had pull to 5000, but it hit a wall after that. It was an extremely fun car to drive, but a big cam would lose the strong torque, and you would gain nothing on the top end because of the flow limitation. BTW it was a 0.040 over 2 bolt 400. This exact same setup except putting on L98 heads netted me a 13.009 @108.3MPH and both of these combo's were on all seasons (p215/65R15).

SR-71

I just completed this swap into my '88 Formula, so it's all fresh in my mind. I'll try to share what you need to know. Check out my sig, and you'll see my build.

I'll add another vote to check the cylinder thickness. 0.060 is a lot for a 400. If it's too thin, though, don't sweat it. Have your machinist re-sleeve it. Cheaper than another block.

My 305 heads are off of an '82 Crossfire Injection 305 Firebird. They're '416 castings, which are the best-flowing 305 heads you can get. Better flow than your '91 heads. I did a full port and polish job on them-- the inlets, runners, valve guides, pockets-- Everything. I used undercut Ferrea 6000 Competition valves with a 5-angle seat grind. The overall result is a 42% increase of flow over stock (as tested on an actual flow bench). But I have to say the heads are "just adequate" for a mild 400. The flow falls short of the engine's needs, starting at about 4500 rpm. They also require a lot of spark advance to get max power and economy out of them. Ironically, that limits the total power potential.

But I'm running a fairly mild cam, and I built the whole package for torque, torque, torque. So I set my redline at 5500, and the optimum shift point is 4900 with my cam choice. This all fits perfectly with the 140 mph / 8000 rpm instrument cluster I found, which marks 5000 as "yellow line" and 5500 as "red line." It's just that those heads let the power drop off a bit too quickly for optimum performance before the shift point.

With the OER-style pistons, the 305 heads required me to use 0.051" thick head gaskets to hold the compression down to 9.3:1, 'cuz the combustion chambers are only 58 cc's. My power output is about 430 ft-lbs and 360 horses.

My future plans call for a set of aluminum heads with kidney chambers and 2.02/1.60 valves and 200cc runners. That should push my power to about 530 ft-lbs and 420 horses, and solve all the breathing problems. They'll also use thinner head gaskets and need less spark advance, to make power and even better gas mileage. I still won't rev past 5500 rpm.

Almost everything will fit, but 305 components will tend to starve a 400. For instance, because of budget I just re-used my headers. They have 1-1/2" tubes. Great for torque, but they limit the 400's top end. Notice I'm using a Holley Pro-Jection TBI manifold, which is needed to fit the 454 TBI.

Here's what will NOT fit-- A 400 is externally balanced, so you MUST use an external-balance harmonic balancer and flywheel/flexplate. You can't use your '91 305's flywheel/flexplate, because the your 305 uses a one-piece rear oil seal, and the 400 uses a two-piece seal. The diameters of the rears of the crankshafts are different, and the flywheel/flexplate bolt pattern is a different size. For balance, you can use a balance plate between the crankshaft and flywheel/flexplate, but you'll have to get a flywheel/flexplate made for a two-piece seal crankshaft.

The 400 uses a staggered bolt pattern for the starter mount. If you have a 400 starter, you must also use a 14-1/2" flywheel/flexplate with 168 teeth. I had my 400 block drilled and tapped to take a straight mount (153-tooth) starter, the 12-3/4" flywheel (153 teeth) from a '69 350 that I had in the corner, and a balance plate, with my 305's pressure plate and clutch disc. I had to buy an aftermarket starter because the 305's starter didn't have enough power to turn the 400 with 9.3 compression.

The starter/flywheel/balance issue is the biggest problem you'll face.

For computer tuning, since I used a fairly mild cam I started with a stock chip and only changed the BPW setting to match the bigger displacment, bigger injectors, and higher fuel pressure. From there, the fine tuning was fairly simple. The bigger the cam, the more tuning you'll have to do.

Mine should make mid- to upper-12's as it is, upper-11's to low-12's with the heads I want. Those guesses are just that-- guesses-- and will require slicks to get the traction.

I also have no doubt that the engine swap is going to destroy my T-5 one day. I'm already laying down plans to build a 700-R4 for it, to take over 500 ft-lbs. If you're running any third gen stock transmission, a 400 WILL destroy it sooner or later. Choices are to build up a T5, 700-R4, or 200-4R, or swap in a T-56.

Like "lowflyer" said about his, mine is a torque monster. Passes slower traffic like a motorcycle, and can spin the tires at will on wet pavement at 50 mph in 4th gear. It'll break-em loose on dry pavement in gears 1, 2, and 3 just punching the gas on a roll, without a clutch drop. It's an absolute blast to drive. And with the cam choice I made, its street manners are seriously sweet. This car definitely will never be sold, unless some millionaire makes a seriously stupid offer.