[79943]

i apologize in advance but i see such good information on here regarding cam recommendations that i have to ask one myself. here is the application: mark IV 454 plus .060"; ARP studded 4 bolt; 3521 forged crank; 291 rect port heads w/2.250 intakes; SRP forged pistons 10.2 CR; I beam rods; GM alum hi rise; 800 cfm holley; 3.73 12 bolt (w/posi); beefed 350TH and i dont have the torque converter yet but i would like to stay around 2400/2500 stall. use will be mostly street, it is going in the '72 elky. question is:
I am looking at the 402A3LUN, solid lifter or the 502A3LUN, roller. which would be better for my application (compare and contrast) or is there a better one i should be considering? thanks for your help in advance.

 

[Tom Mobley]

answer number 10,000 coming up.

A roller is almost always better than a solid. That 502a3 roller looks good. it's 276/284 or @.050 it's 245/253. I like it on 112 LSA and installed at 108. Two things to watch out for: it's got a little lift, advertised at .660. You'll need to check the valvetrain carefully with your own eyeballs or pay somebody who knows what he's doing to look at it. the other thing is with any roller you'll need to go through the PITA process of setting the end play. Be prepared to R&R the timing cover several times during the process. IOW, don't install the oil pan till it's done.

You'll get substantially more power out of the roller and there won't be a question about losing a lobe during break-in at all.

Double check to what distributor gear they say it requires, get that one and no other. They may have an option where you can get it with a cast iron gear or something. If they say to run a bronze gear then avoid the HV/HP oil pump like the plague. It'll kill gears regularly.

Tom

 

[79943]

thanks tom. do you see any cylinder pressure concerns with that roller profile at 10.2 CR? as far as clearance i guess i will just have to mock up a cylinder with clay and measure the gap (hopefully there will be one). my machinist has seen my components and believes they should handle that roller but like you he says check it out first. i am assuming that the closed chambers (109) increase the risk of interference, or is that not the case? also thanks for the heads up on the end play and distributor gear. i was not aware of that.