bondue

Found me a 400 30 over, has a cracked head on it but i have a set of 195/160 305 heads i am going to have drilled and put on it. What i need to know is what all will i need, I will be using my TPI so i need to know what size injectors, fly wheel, torque converter, rods, etc.... please help!

duckmanquacker

for the 406 I wouldn't use anything smaller than a 24# unit though some have been successful with 19#units,(I feel they're a little lean on the top end)
Flywheel should have the external balance weight and match the starter and bellhousing. Torque convertor is Based off your cam selection. Rods depend on how much RPM's and HP level you wish to atain. Any HP level above 350 your head selection is not gonna work.

bondue

i know the 350 uses 22 # so i was figuring 24-27 # units.

could you explain a little better? Its probably a simple thing your saying but right now its just not clicking.

The cam wont be replaced i'll be using the stock cam i wouldn't think the convertor from the 305 already installed would work with the 400

All i need to know is what i need to get so that it will run, adding power will come a little later i just need it to run.

five7kid

iTrader: (14)

Exactly what heads are you talking about? Do you mean 1.94" intake valve and 1.60" exhaust valve heads? What size chambers to they have? Since you said "305 heads", can we assume 58cc heads?

Be advised that 58cc heads will produce a significantly higher compression ratio on a 400 than they do on a 305. 400 engines typically have dished pistons, but if the engine has been rebuilt, you need to know exactly what the pistons are so you can know whether the heads will result in acceptable compression.

"External balance" is something that the factory did to keep things simple with the longer stroke of the 400 with the limited crankcase space of a small block Chevy. A weight was added to both the harmonic damper and flexplate/flywheel to produce acceptable balance without going to expensive high-density metals added to the crank counterweights. The damper and flexplate/flywheel external weights are standardized, and you can get 153-tooth flexplates or flywheels to mount to the 400 and allow 3rd gen type starters and transmissions to be used, including the 305 torque converter.

bondue

Yes that are the heads i am talking about. The motor hasn't been rebuilt yet but i am doing a rebuild on it. So would it be better to use a 350 head rather than a 305? I checked all the junkyards around my area and none of them have 400 heads, i was going with the 305 heads just because i had them. I knew they would raise the compression but i wasn't sure of how much. i hear that a 400 with 400 heads has about 8.5:1 comp. and was told that with the 305 heads i plan to use it would raise the compression on the motor to 9.5:1 to 10.5:1 is this not true? i don't want to destroy the motor due to ignorance.

five7kid

iTrader: (14)

Factory 400 heads are best used as boat anchors or door stops. The typical JY 350 heads aren't far behind.

What casting # are these 305 heads? The factory never put 1.94/1.60" valves in 305 heads, so they would have to have been modified to have them now. Only some 305 heads would be worth doing that to, and still may not be suitable for a 400. Of course, you could say that about stock TPI on a 400 as well (choke city).

If you haven't rebuilt the 400 yet, you can choose pistons with sufficient dish volume to keep compression at a reasonable level, even with 58cc heads. Various available on-line CR calculators will help you choose pistons, deck height, and head gaskets with whatever heads you end up using. For a mild street engine, keep it around 9.3-9.5:1.

bondue

Why is this? I would like to keep the tpi setup rather than going to a carb. What madifications would be needed for the TPI system to work with the 400.
I assume i would need to upgrade the throttle body to at least a 52mm from the stock 48(?)mm.

And about the heads i don't have the casting number at the mometn they are at my father-in-laws garage but the came off of a 86 monte ss 305 H.O. motor that is as much info as i can give right now. Found a new 400 to buy this one is running and in a truck the guy said he would sel me the motor a th400 trans for 750 total said the 400 had a RV(?) cam in it. He also said he had a 350 for sell so would the 400 or the 350 give me the most low end torque?

Another question i have is i also own a 92 RS V6 manual, i was told they have a 3.11 gear set in the rear is this true or not?

duckmanquacker

More displacement always gives more torque. Don't worry about the RV cam it's probably just a stock cam. The 305HO heads will hold decently for your 400 and give some decent torque figures you would just need a thicker head gasket (.060) if your pistons are stock dished. should the pistons be flattop or domed I wouldn't recomend the 305HO heads at all unless you want 15:1-20:1 compression.
and for the rear gearset I would pull the cover to find out exactly what is there (removes all variables)

bondue

well the motor at the start of the post is no longer a problem i found another one that runs fine. I'm going to pick it up tomorrow, the guy said he would leave it in the truck and let me drive it before i decided if i wanted it or not. So i plan to just keep the stock heads on there until tax time an get me a set of 2.02 heads.

five7kid

iTrader: (14)

TPI was designed for 305's. It was put on 350's with no modifications to the air system. It has small diameter, long tube runners designed for low RPM torque. They can't flow enough to support a 400.

The best "fix" is to replace all of the TPI hardware. A Holley/Weiand Stealth Ram is a good place to start.

The heads may have been on what was called an "HO" engine, but they are not "HO" heads. They are the same thing used on the LG4.

As stated, larger displacement almost always means more torque, all other things being equal.

From the model links at the bottom of every page: https://www.thirdgen.org/1992-chevy-camaro

There is no such thing a a "3.11" gear in 3rd gens. 2.73, 3.08, 3.23, 3.42, 3.73 were the only choices in 10-bolt rears. Most likely a '92 V6 manual tranny car would have had 3.42 gears from the factory, and most likely an open vs. posi carrier.