Jim, Make sure the front balancer has not SLIPPED ! Meaning the outer ring in relation to the inner one.The rubber bonding between them fails.At least it happened to me on a 400 in a van.Vibration drove me crazy,finally sold it.Buyer knew exactly what it was,came back and showed me. glider.
How big did you have to "waller out" the holes with the dremel to get them to fit? Does the starter make a funny sound when cranking? I am thinking the elongation of the holes maynot be perfect and the rotating m*** is off balance???? As far as 400's - I love the torque they have, I had a 406 in my 61 truck that I just sold, if I had a 350 laying around I would have swapped them and kept the 406. The biggest problem I had was burping the air out of the motor and once I bought a 19-21# cap the cooling world was right. I did a thread on here a few years ago about the heating issue and the cap was the answer. VIVA LA HAMB!
i elongated them about 3/8" not too much, they weren't perfect, but i don't think they where out enough to cause a vibration.Its more like a roughness. I'll check it out good tomorrow, i'm having a BBQ today so i won't have time.If i have to i'll make them"perfect" tomorrow, i got laid off from work,AGAIN!!! JimV
recently built a nasty 406 450 hp 525 torque. i have put both centerbolt and regular heads on it with no prob. drill the steam holes!!! at least the lower two is all you need. get good head gaskets. mine runs 185-190 w/ 180 tstat. got some sweet alum heads on it now. and ou cant run stud girdles wit centerbolt heads or not that I know of. 6000 rpm no prob, 5700 shifts. t took me a while to love the 400 buy will run nothing else now. what a torque monster!!I also had a " burping" problem with air trapped in the block and had to change the cap and hi flo water pump also had it internally balanced. heres a video..or two http://www.youtube.com/watch?v=Msj3mvBsLSU http://www.youtube.com/watch?v=EAluv_tomys
Observations- A stock chevy crank should have a dowel between 2 of the bolt holes to force you to clock it, if your crank is missing the dowel, the extra holes to align should be obvious. Everyone thinks you dremeled the crank bolts. You dremeled the torque converter bolts, which is actually fairly common if you don't have a dual pattern flexplate. Your dremeling is likely totally unrelated to the vibration. To check balancer slip on a 400, the crank's keyway should align with the TDC line on the outer ring. If not, it's slipped. I've had several 400 balancer failures, and 2 of em ruined the crank. YOU CANNOT PAY ME TO REUSE AN OLD 400 BALANCER. Just spend for a new one now before you get burned too. Vortech heads are the best-flowing iron casting you're going to find in that low, low price range. I've used em, and also had sealing issues with that piece of **** intake gasket design. Yeah they're a good deal, but so are lightly used aftermarket castings with a traditional intake gasket. The 406 chevy I have today has aluminum performer RPM heads that were bought for $550 with a few thousand miles, and were easy to find at that price. Some aftermarket heads don't recommend all the steam holes, only the lowers. (Don't know why) Also overheating is not "inherent" to the 400. People that wouldn't use a SBC cooling system on a 396, will use one on a 400, and then blame the 400 for running hot. 400 trivia- early blocks had problems with core sand shakeout at the foundry. And thus were built with sand remaining in the cooling p***ages. The sand comes loose, continually tears up water pumps, thus causing overheating on the "new" 400. If a block is still around today, the sand concern is long gone. But still part of the reputation. Good luck!
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