What size {If Any} are you guys running on Dart Big-M blocks ?
Thanks

bird,
I want to hear some answers on this one too. I am in the middle of building a 598 for a drag car and have the same question. Dart says to drill the restrictors to .030-.060" ? Talked to a couple of engine builders I know in other parts of the country and both of them said no restrictors at all ! I compromised and drilled them to .104. It looks like the left side is fed by a passage that is only about .200 anyway.

Now keep in mind I am building an engine that will only run a minute or so at a time so valve spring cooling etc will not be a big issue. In a boat, I would probably want to see more oil goiing to the valve train but ... you have to balance it with your oil pan capacity etc. The lifters are only going to meter a certain amount up top anyway, so maybe the restriction is not even needed ?

Hydraulic roller will probably completely change the equation, I would think no restriction at all.

Hope to hear some more answers.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Birdog,
What type of camshaft and valvetrain will you be using?
Is this a marine application?
Thanks,
Bob

call my cell . I have been trying to reach you Larry. I will tell you what to do.

Thanks,

Dean Gellner

He didnt want to bother you....
I told him you would reply to this......

rmbuilder..Bob....Thanks for replying...This is for a non-computer friend of mine.

We, the boss, designed the restrictors for the aftermarket style blocks. They have a .060" orfice. This cuts oil flow by 70% and diverts it to the main and rod bearings. These are designed for engine with roller rockers and SOLID Roller valve train. These are machined from stainless steel and are an inverted hex design.

Available from the following board sponsors:
Trick
JC Performance
Gellner
Chief
REX
Teague

NOTE: You need to consult a marine HP engine builder on using restrictors in your application.

Thanks Chris....I think he is talking to Dean {Gellner} now....