Thread: 400 build, seeking opinions

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Hi all,

Been lurking for a while, but now have some questions as I work through a build-up of a 330817 SBC 400.

72 Camino, had 74 400CI with 4bbl 333882 heads (1.94 1.6 75CC) nylon intermediate shaft / oil pump guide broke and I went no oil pressure on a hard launch. :-( I heard the noise immediately and shut down before it did more than just chunk the bottom end bearings, upon teardown, it's obvious this had a head gasket leak at one time judging from the corrosion on the bearings.

I bought a 'machine work done 400 with engine kit' and so far, everything has plastigaged and measured good, also the pistons, rings, end gaps, clearances, end play... ad nauseum.


New motor:

.030 over for a 4.155 bore, now a 406.
re-using 882 heads, (rebuilt)
stock 3.750 stroke
Dished cast pistons
Edelprock performer and 650 CFM Edelbrock carb.
Headers w/2.5" duals to the rear.
Block has been decked!!!

My problem is I don't know how much it's been shaved, I know the front casting numbers are gone.

The decking has me perplexed, is there any easy way to find out how much has been shaved, (I still have a stock block for comparison).
Should I worry terribly about pushrod length?
Excessive compression ratio?
Should I use a 1.5 rocker ratio or the stock 1.7?
What might be a good cam for this setup.

Will get gearing numbers posted tomorrow, didn't want to lay in the rain to get the diff numbers.

Not after a monster here, just a nice breathing reliable driver with a little attitude.

Thanks,
Andy

There is virtually no way to tell how much was decked off the block. The factory specs are out to lunch in the real world. I have seen them more than .050" over max spec and some just about that much under. Sometimes on the same block and sometimes from end to end on either side.

So If the thing is parallel and the pistons are below deck, you are in the ball park.

Also remember that stock replacement (rebuilders) pistons are built .020" short from the manufacturer.

I would not really worry about pushrod length on this stock type motor unless you are going to use a .480" or more lift cam. Even that much cam lift on stock 882's would be a waste.

Stock SBC 400 rockers are 1.5 ratio not 1.7 (366-454 big block). You will not have excessive compression ratio with dished pistons and 75 cc heads.

Thanks much!

I must have a bad manual, mine states the 400SB (all years) has the same 1.7 rockers as the big blocks...(Haynes) Maybe they confused this with the much better 402 BB :-). I'll go check.

I wasn't too worried with the dished pistons, and plan on measuring, as close as possible the deck height, given a wedged recess, triangular edge and head gasket area. But just wanted to look out for trouble before I get past the bottom end.

I will definitely change the cam profile I was intending to use.

Thanks again,
Andy