[hardline_42]

Originally Posted by johnjzjz

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

I guess everyone has different experiences with the 400s. As far as I know, siamesed blocks are siamesed blocks. It just means the area between the cylinders has no water jacket, just solid metal. It's interesting that you mention the steam being trapped at the top of the deck because that's exactly what the steam holes are there for - to vent the steam. Maybe there were problems aligning the holes in the head/gasket/deck? IMO, 64cc heads are a great upgrade to a stock 400, and as long as the quench is about .040, you can stay out of detonation. As far as iron vs. alum. heads, the iron heads keep a little more compression but weigh more. The aluminum heads allow you to run higher compression since they bleed off more heat and they weigh less. Not sure how the two compare under equal circumstances.