I have been asked to help with a street 400 that is going to be bored to a 430. The owner wants stage1 valves with hard seats and I told the guy doing the machine work that hard seats with the big valves is asking for trouble. My question is will the stage1 valves even work or help on the 430 bore? Tom
Call Mike at AMP, he has the stage 1+ valves which have a slightly smaller 1.71 exhaust valve. This valve out flows the stainless stage1 1.75 exhaust valve plus uses a seat that stays out of the water. Intake is 2.16 and can really wake up iron heads which only have street/strip work. Both valves use 11/32 guides and have 5/16 undercut for higher flow potential. My street iron heads flowed 221 @ .300 lift and 261 @ .400. Low lift flow is kick butt. High lift depends on how much work is done in the port and short side. Mine flow just under 280 peak. I would tell them to take the motor on out to standard 454 bore or 4.25. This is .062 over the standard 430 size. No problem for later 400 blocks. This makes 442 cui. and uses a standard ring package. This is what we did with the nitrous motor.
I have heard of this valve setup. I will have to find out how far and how much the owner wants to put into the motor. From what I understand he wanted to leave it a 400 but could not find pistons. Tom
I know this is an old thread, but I have some questions about the 454 pistons. How do you get a piston with the proper compression height? Wouldn't you have to either deck the block almost 1/2" or run a piston with a huge dome? How much can you deck a 400?
I think he just meant to use the 454 rings, not the actual pistons. You could see if the 454 rings (meant for a 4.25" bore) would work in a +.060 430 (4.2475" bore). If not, you're looking at custom pistons, or at least asking a company to do a set of 430 slugs in a cusotm bore size, which might be tough since 430 piston selection isn't great to beign with.
So, you think he meant to use 454 rings with a .060" over 430 piston? I'll check out EGGE. Thanks for the suggestion. I could always order the custom JE's from TA, and that may be what I end up doing. It just seems like a lot of $$$$$. Hemi 425 pistons look like they would work, but I don't think anyone is making those for a decent amount of money either.
I was talking about custom race pistons. And its actually .062 over plus any extra wall clearance. Having a nice ring selection like standard 454s is great. Piston cores are less expensive but the deck heigth is custom for the buick. I think the JEs with the rings lowered for nitrous cost $830 total with shipping, tax. Flat tops in our motor is right around 11:1 without decking the heck out it. This combo makes a 442 cube with nice and thick walls.
I get it now... A custom JE with a 4.25" bore, so you can use 454 rings! Smart idea! That definitely seems like the way to go. I'm looking to get 10-10.25:1 with a zero deck height. Any idea what kind of dish I would need to get this with 68 heads and a .040" gasket? How many CC's are the valve reliefs, typically? Thanks for the info.
You may want to ask TA to order you a set of thier conicle dish pistons in this size. Or you could order a set of Wesco or JE with a bathtub shape dish of about 20cc. Your block should be a late 68' or 69' model to be safe to bore this far.
Thanks for the help on this. I'm not sure if the 400 I have is a late or early block. I was actually hoping it was the early block, because I wanted the tall port heads. Now I am hoping it is a later block. I'll have to get the numbers off of it this weekend. I have a later model 455 to build. Do you think that I should just build that block and use the '68 heads? I kind of like the idea of using a 400 in my '69. Also, I've seen some 430's that really run good. As far as the dishes go, isn't it better for quench to have as close to a flat top piston as possible?
