400 sbc build

[Green79Scottsdale]

I think 373 will be the one I do. Ok so here is what I've been tossing around I've recently found a fuel injection kit that can handle boost for a relatively reasonable price how much boost do u guys think my 400 stock bottom end will take I was thinking 7-8 psi but unsure

Just let me throw this out there...

If you have the $$ to go EFI and throw boost at it... Why the #E!! are you thinking of keeping a STOCK bottom end??? That makes absolutely NO sense.

A stock bottom end may survive at 7-8 psi, but you are going to need to be very good with your complete tune and set-up. Spend some extra $$ and upgrade your crank to at the minimum a high quality cast crank, if not a forged crank. Also upgrade those short 5.565" long rods to at least 5.7" long rods, or go up to 6.0" long rods. Doing this will decrease the side pressure the pistons exert on the cylinder walls. Changing rods will also necessitate new pistons, which is good idea to run with boost also.

Again, for all the people who are going to argue with me, yes, your stock bottom end probably will hold up to 7-8 psi of boost. But for piece of mind I would recommend building upon an upgraded bottom end that will be reliable and long lasting. You will be pissed when your bottom end lets go and you have no $$ left over to spend on rebuilding it because you used for a supercharger or turbo.

 

[Green79Scottsdale]

... been looking into some aluminum 202/160 64cc heads and from what ive seen it will put my compression down to 8.5:1...

This is wrong. Your stock heads are 76cc chambers, which produce about a 8:1 CR. Putting on 64cc chamber heads should RAISE your CR almost a full point to 8.8:1. Run a thin .015 head gasket and you could raise it another half a point, depending on your current head gasket thickness.

 

[74propu]

Just let me throw this out there...

If you have the $$ to go EFI and throw boost at it... Why the #E!! are you thinking of keeping a STOCK bottom end??? That makes absolutely NO sense.

A stock bottom end may survive at 7-8 psi, but you are going to need to be very good with your complete tune and set-up. Spend some extra $$ and upgrade your crank to at the minimum a high quality cast crank, if not a forged crank. Also upgrade those short 5.565" long rods to at least 5.7" long rods, or go up to 6.0" long rods. Doing this will decrease the side pressure the pistons exert on the cylinder walls. Changing rods will also necessitate new pistons, which is good idea to run with boost also.

Again, for all the people who are going to argue with me, yes, your stock bottom end probably will hold up to 7-8 psi of boost. But for piece of mind I would recommend building upon an upgraded bottom end that will be reliable and long lasting. You will be pissed when your bottom end lets go and you have no $$ left over to spend on rebuilding it because you used for a supercharger or turbo.

by the time you get a efi put a bottom end together and find a set of heads and cam that will work with boost on a sb400 why not just go with a stock 4.8 or 5.3 put a set of 60lbs injectors in it and it will take boost and love it mine is a 5.3 with twin turbos with 6lbs of boost with 60lbs injectors and it is 560whp on the dino and it is stock out of a 2000 GMC as far as a rear gear I run 342 and am thinking about going to around a 309 boost likes the higher gears I run 31in tires and can roust them shifting to 2nd imo you need to rethink your build as far as $$$$$ befor you throw that cash in a hole

 

[deano1977]

I wanna save money but idk about the turbo yet but I have been looking into fitech efi and will be doing full msd ignition if I do decide to go turbo what u guys recommend I do engine wise?

 

[68post]

I recommend a different block for boost.

 

[68post]

This is wrong. Your stock heads are 76cc chambers, which produce about a 8:1 CR. Putting on 64cc chamber heads should RAISE your CR almost a full point to 8.8:1. Run a thin .015 head gasket and you could raise it another half a point, depending on your current head gasket thickness.

Unfortunately.. there are no thin gaskets for 400's , wish there were.

 

[Green79Scottsdale]

by the time you get a efi put a bottom end together and find a set of heads and cam that will work with boost on a sb400 why not just go with a stock 4.8 or 5.3 put a set of 60lbs injectors in it and it will take boost and love it mine is a 5.3 with twin turbos with 6lbs of boost with 60lbs injectors and it is 560whp on the dino and it is stock out of a 2000 GMC as far as a rear gear I run 342 and am thinking about going to around a 309 boost likes the higher gears I run 31in tires and can roust them shifting to 2nd imo you need to rethink your build as far as $$$$$ befor you throw that cash in a hole

Not everyone is on board the LS train. Honestly, a vehicle with an LS swap now gets LESS attention from me personally. Seems like everybody and their mother is doing it. Albeit, it is a fantastic swap for great power!

Unfortunately.. there are no thin gaskets for 400's , wish there were.

Good call, thanks for making me do better research. Seems that the thinnest you can get is a Cometic MLS at .027" thick.

 

[bucket]

Not everyone is on board the LS train. Honestly, a vehicle with an LS swap now gets LESS attention from me personally. Seems like everybody and their mother is doing it. Albeit, it is a fantastic swap for great power!



Good call, thanks for making me do better research. Seems that the thinnest you can get is a Cometic MLS at .027" thick.

We have the same thoughts about the LS swap, but that's another discussion altogether.

.027 is still fairly thin, considering the average replacement gasket is right around .040 thick. But maybe there are some NOS shim style GM gaskets out there somewhere? I know GM was still using shim style gaskets in '69, did it continue into the 70's on the 400 as well?

 

[deano1977]

thanks for the input guys im gonna do a new bottom end now may go ahead and go to a 406 and do a single turbp using the fitech efi and see how well it does I was gonna do a 5.3 but im selling it to do the small block I love the lsx stuff but thid project is gonna stay sbc turbo sbc are fading and I wanna be different so that's what im gonna do it will cost about the same as a ls