variable duration lifters (rhoads)

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green67cuda

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I have a question about these.....won't the fast bleed down at idle possibly cause adverse compression effects?

example:
I am building an iron-headed small-block to about 9.8:1. the cam will have 228 @ .050 and .512 lift.
won't the Rhoads lifters help cause low-rpm detonation?
 
67Cuda, how large is your engine? With 228* @ .050, I don't think I would bother with them, (340/360). The biggest problem I see with using them is some builders will install these AND use a hi-volume oil pump. Since they work off oil pressure and time, as RPM increases, oil pressure increases, time decreases, they can't bleed down so you have (in theory) full lift/duration at RPM. Hi-volume pumps reduce their performance. Don't use them together. JMHO. 67Cuda, 228* @ .050 and .512, sounds like a good grind, with fast rate of lift. Terry.
 
i admit, it's for my 302 ford....my daily driver 68 mustang has 1/8" crankshaft endplay, so i ordered a bunch of parts for a better build on another 302 to drop into it, and already had that new cam on the shelf. I thought it was a bit much for the 302, so i got the Rhoads lifters....but now I need to send them back, i suppose.
They'd be good if they fit the 400 in the cuda, because it only has 8.5:1 and a purple shaft .509 cam. they would definitely improve driveability in it, IF i wanted to improve driveability.
 
Green 67, Cubic inches eats up duration. 228* @ .050 is more radical in a 302 than a 340/360. You might have a need for them in a small package like that. They do work. Have used them myself. Vacuum improves and smooths out the idle some. Behaves like a smaller cam, around 10* or so. Good luck, Terry.
 
Agreed with headsbikesmopars. I also have used a set. They work as advertised. Also agree with the oil pump issue. But they still work with the hi-vol oil pump.
 
excellent.
Thanks. I am just hoping my CR idoesn't end up too high for iron heads and pump gas. I'm coming up with about 8.8:1 dynamic, which is high, so i may want to either mill the pistons or go with a thicker gasket to bring the CR down a hair.
Hopefully, the shop doesn't need to take much off the heads and I can get 9.5:1 out of it with what I have.
It may be beneficial to go with a .050 gasket anyway, because the "nominal" values of everything will put my pistons .003 in the hole with an assumed .006 decking off the block. that's give me .044 quench (current gaskets are .041), if all assumptions and estimates are dead on......which they won't be.

gotta get it all together and take a LOT of measurements.
 
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