jhainer

ok i have an issue I have been fighting with for a few weeks. i would adjust the solid lifters in the 468 they would stop rattling for a few then start rattleing again. they are solid lifters. so i pulled the motor apart to try to adjust them again and found that one lobe on the cam was gone and the others showed signs of wear. so a new cam is in order. i didn't build the motor 15 years ago when it was build my father in law did but can't remember. He states the cam is a 600+ lift and over 300 duration cam. and he also states teh motor has keith black 12 to 1 pistons and with the 3919840 closed chamber heads bumps it up to about 13 to 1 compression. the intake that was on the motor was a single plane torker 2.0 intake now has the victor jr 454-r intake the carb is a 930 cfm. thats about all i know about the motor. so last night i pulled the cam. the numbers on the cam ar bm562 8 and also has 109 and hd Lunati. so i am guessing it is a bracket master cam with 562 lift and 109 lobe seperation. I need to get a new cam I have a th350 and 3.42 gears and want a cam that will work and everyone i have talked to summit comp cams and lunati all give me a cam with almost 600 lift I do not want to smack the pistons with valves. does any one know the specs on this cam. or could point me in a direction with a safe cam size .
and is there a way to check the clearances without popping of the heads

Atilla the Fun

The trouble with piston-to-valve clearance is that interference never happens when the assembled, running engine has a piston at TDC, even if the cam has a lot of overlap. That's why we have rules of thumb ablut how much clearance you need at TDC, but to check that, you have to pull the heads and use modeling clay. Head gaskets aren't that costly, and if your heads aren't ported, then this is a good opportunity to get some better flow while getting back toward 12:1, giving you more cam options. Do you really need solid lifters? You're a prime candidate for rollers, but those are far more costly than head gaskets, let alone a head swap. Going to a wider lobe separation angle will improve your piston-to-valve clearance, and will let you run more streetable lobes. But to get this in a shelf cam, you're looking at marine cams, like Comp's 11-252-4, or blower cams. If you want a safe cam choice in a solid-lifter, look at the 11-106-3 instead. That's the original LS6 cam.

jhainer

I ended up going with the comp cams CCA-CL11-213-3. It has .550 lift on both intake and exhaust and the duration is 244 /244 @50 or advertised 292 it's hydraulic so it shouldn't need adjusting like the solid did. in going back and forth with lunati I did finally find out which cam i had it was in there second to oldest book they have it was a 562 intake 568 exhaust lift with 265/271@ 50 duration with a 109 lobe seperation. the new one has 110 lobe seperation. I spent the weekend installing the new cam new lifters and also at teh same time i did the springs too. CCA-924-16 after putting it back together i did the 20 minute breakin. idled it down boy does it sound nice now. and the throttle responce is amazing. raps up quick. now what was funny the reason i couldn't get teh motor to tune right before was after i got the old cam out one lode was wipped out but in trying to find the cam specs using calipers and mesuring the lobes i couldn't get any thing that sounded right i was getting lift numbers of something like 488 so the only thing i can figure is each lobe was wore down that much with one being wiped out. the cam is 20 plus years old. now i understand why i had to adjust the solid so much and why it always seemed to not run correctly well with the new cam it runs nice now. just a few notes tho while i did this i found out some info from the 2 cam companies i talked to both said the same thing the oil manufacturers have changed oil not sure when they did it but most oils no longer have zddp (zink additive) added to oil and that is the most likly reason for the cam going bad. they stated everytime i change the oil i should add the additive to the motor. so when i was at the parts store the other day i wanted to see what oil still had it and only one still had the zink additive in the oil and that was castrol synthetic racing oil. at $9.00 per quart. oh well. $9.00 a gallon of gas and $9.00 per quart of oil this is beginning to be an expensive motor. so far on the motor i have changed intake valvve covers oil pump and screen cam lifters springs had the carb rebuild which needed new base plate. timing chain and cover all gaskets minus heads. distributor and rockers

AlkyIROC

Providing the pistons have deep enough valve pockets, the amount of lift is only a small part of the piston to valve clearance. Valve timing (when they open and close) is what really determines the clearance.

When the intake valve opens, it's chasing the piston as it goes down the cylinder. As the piston moves back up, it chases the exhaust valve as it closes. Advancing and retarding the cam can change how much piston to valve clearance you get. Advancing the cam decreases clearance on the intake and increases clearance on the exhaust. Retarding a cam does the opposite. Rule of thumb, you want a minimum of 0.060" on the intake valve and 0.100" on the exhaust.

I just got my new shortblock back from the machine shop today. Now I need to install the cam and heads and check all the clearances. .833 Int .806 Exh. The worst part is I now have shaft rockers. Lots of assembly and disassembly to do all the measurement checks. Once it's all done and back together, the shaft rockers will be so much better.