Hey Greetings from Mississippi! Hey guys I am gathering parts to build my last 400 small block. I just had my crank turned & when I figure out my piston / rod combo I will get the block bored. It's STD now. Prolly gonna go with the 5.7 rods since the old 400 rods had the caps mixed & were locally resized once already during a previous overhaul. This was a County Pickup engine. Anyway I traded a .30 Carbine a while back for a pretty fresh set of Iron Darts, 72 x 180s w/ the big valves. From a compression standpoint these heads should be good & be able to get 9- 9.5 CR with the right piston. Question is those intake ports seem kinda smallish to use on a 400 cube engine. I'm not gonna build a race engine, it will prolly wind up in a pickup down the road I don't want to buy exotic aluminum heads as I am trying to use up all my old stash of parts. I have experience port matching but didn't know if you could port any significant increase in volume into those intake ports or not. Maybe 180s will be fine, just outta my experience zone! Thanks! Andy
And make sure that the steam holes are in the heads between the cylinders. If not they can be drilled.
.030 overbore with .040 thick head gaskets and 72cc combustion chamber volume should get you to 10:1 CR if you can get pistons with a 12cc dish in the top. Runs great on pump premium.
For the engine you described those heads will be spot on. As previously mentioned, too big a port on a mild engine kills throttle response due to poor carb metering from the lower air velocity.
Well I did something I shoulda done to start with- I asked Dart! They said they would rev a 400 to six grand! I'm sure I DON"T Need Six Grand! But Cool! OK any way let's move to steam holes. I've talked to the dirt trackers around here & they all run 400s & they tell me they plug the holes in the block & don't use them. They also showed me they catch the coolant at the rear of the intake manifold & route it to a spacer under the thermostat housing. They plug the by p*** hole in the block & run restrictor plates instead of thermostats. I know all this is race car stuff that I don't need. Thanks!
NASCAR engines rev 8-9 grand with 390cfm carburetors . Its not how high it will rev , its how long it takes it to get revved up
Those steam hole are not necessary unless you plan on using your car for a taxi cab...sitting and idling.
Steam holes - We never drilled steam holes in the heads of my 400-based circle track engines. If someone wants to explain why it's needed in a low rpm(street) application I'm all ears. Four corner cooling - Yes, especially if your intake already has the pipe bungs for it. A pet**** on the thermostat housing to bleed air isn't the worst thing either. Are you talking the byp*** hole in the block where the water pump bolts on? Many aftermarket water pumps aren't going to have that anyway. I used Stewart pumps way back in the day, don't know what's good now. Your water pump manufacturer will tell you what they want you to start with for a thermostat/restrictor and pulleys. The one Stewart pump I had they wanted you to take the restrictor completely out. Don't imagine in Mississippi cold weather warm up is a big issue.
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