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i never owned a street 400 SBC in my shop we only ever built them to race, and the steam hole angle is very important 1/8" hole and the gasket as well -- we must have over the early years broke 20 / 30 of them before the boe ty - became available -- had to go and look at the one today i saved its been years since i looked at a stock 4 bolt 400 block and its really not what is known today as a Siamese cylinder -- not like the newer stuff anyway - we used 8 EGTs years back than to try and figure out what was up with the engine temp problem and what we found in the 80s was running a water line front to rear of the manifold really helped ( air was traped in the block tops of the deck ) but the temps of the motor at the turnaround at the track end was still 240 / 260 -- alloy radiator helped as well it all seamed to on the drive back to bring the engine temp down quicker -- but the overall high temp never came down to what a 540 BBC would be 210 maybe on gas alky no engine has a heat problem --- the issue with using 350 heads the iron 492 head 64 cc Flat piston 2 valve relief .039 head gasket and a zero deck netted 11 to 1 with a 406 motor as the best out of all of them -- iron heads in drag racing means more consistent times alloy heads car is faster is it the weight of head the difference ??/ never got an answer that made sense to that question its been better than 12 or 15 years since we used a 400 block and would never go back we broke every part in them every time we made it work with a MOD something else failed of course you may have had better luck --- not us -- jz
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