Valves smacked the pistons......pissed
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Staging Lane
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From: Haddon Township, NJ
Valves smacked the pistons......pissed I was told by a few reputable individuals that a set of PRC 243's with the MS4 cam, stock bottom end, stock head gasket would have no PTV clearance issues. The first used set of 243's I purchased were milled and I didnt know. When I checked the clearance there was none. So I replaced them with a set of PRC 2.5's with a 64cc chamber. Stock felpro gasket, cam straight up. Well when I pulled them off, I have bent valves and eylids in all my pistons. Bottom end was stock 98 LS1. Rev Limit was 6800. Car wasnt over revved, Its a auto. Im soo pissed. I know I should have checked ptv again but I was assured no issues. Any suggestions? Different cam? I dont want a thicker gasket because im not giving up compression.
Ive been through that also with a thunder racing rapTR cam. I would change the cam for one smaller the cam may be to big already so it may benefit you. Sucks about the valves make sure you didnt break any guides.
You have some options
1. Flycut the pistons for the MS4
2. Go smaller duration cam like a MS3/V2/V3 or a 228R
Thats why everyone here will tell you to check to be sure. Did you degree the cam? That could be partially the issue as well. The MS4 is pretty wild IMHO with a 239/242-.649/.609. Did intake and exhaust hit? Pics?
I think Texas Speed will tell you the MS3 will clear stock unmilled heads.
1. Flycut the pistons for the MS4
2. Go smaller duration cam like a MS3/V2/V3 or a 228R
Thats why everyone here will tell you to check to be sure. Did you degree the cam? That could be partially the issue as well. The MS4 is pretty wild IMHO with a 239/242-.649/.609. Did intake and exhaust hit? Pics?
I think Texas Speed will tell you the MS3 will clear stock unmilled heads.
Never seen an MS4 that didn't kiss the valves with a garage install. Too much cam for a 346ci anyway....
Take any "assurance" anyone ever gives you about a particular part with a grain of salt. Never assume anything, and always check/measure.
If you've kissed the valves, the heads need to go to a machine shop for inspection to insure the valves and/or guides aren't damaged. At that point you can cut them another .015 or so for more compression, and run a more 346ci friendly camshaft.
I know I should have checked ptv again but I was assured no issues. Any suggestions? Different cam? I dont want a thicker gasket because im not giving up compression.
If you've kissed the valves, the heads need to go to a machine shop for inspection to insure the valves and/or guides aren't damaged. At that point you can cut them another .015 or so for more compression, and run a more 346ci friendly camshaft.
Were the new PRC 2.5 you replaced milled at all? If they were that could be a problem.
But if you're having PTV clearance issues, the only way to fix that is either flycut the pistons or go with a smaller cam. Sorry to hear about your problem. That is frustrating.
But if you're having PTV clearance issues, the only way to fix that is either flycut the pistons or go with a smaller cam. Sorry to hear about your problem. That is frustrating.
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Can you advance the cam a few degrees? I know guys that run there engines with .030" intake clearance and .050" exhaust clearance. Nothing hits if you spec a strong spring and quality components ie: stiff pushrods, lightweight retainers/locks, etc. You may not have over-revved the motor based on your rev limiter, but the springs may have lost control somewhere close to there.
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From: BFE
I was told by a few reputable individuals that a set of PRC 243's with the MS4 cam, stock bottom end, stock head gasket would have no PTV clearance issues. The first used set of 243's I purchased were milled and I didnt know. When I checked the clearance there was none. So I replaced them with a set of PRC 2.5's with a 64cc chamber. Stock felpro gasket, cam straight up. Well when I pulled them off, I have bent valves and eylids in all my pistons. Bottom end was stock 98 LS1. Rev Limit was 6800. Car wasnt over revved, Its a auto. Im soo pissed. I know I should have checked ptv again but I was assured no issues. Any suggestions? Different cam? I dont want a thicker gasket because im not giving up compression.
That is why i get tired of all the persons who know better, done this, done that (no issues), shortcut takers etc... you get the picture.
When you put a cam in, ANY CAM, you should degree it and measure PTVC, prod length etc...
As mentioned above by Damian, change the cam to one that fits your cubes not your ego. LSK lobes for street should be forbidden and are ridiculous.
Also, check to see if any of the rings got cocked in the ring groove or bore. A leak down test (after repairing valves & any damaged guides) can show evidence of a cocked ring. Have seen it happen where the contact between the valve & piston top causes a ring to get twisted & stuck in the groove (cocked).
If I had a nickle every time I've read a post on here where someone swears to someone else that there are no PTV clearance issues...
If I had a nickle every time I've read a post on here where someone swears to someone else that there are no PTV clearance issues...
The sun does shine on the dogs *** every now and then so I won't say it's impossible. Properly installed, you can do a lot with only .040-.050 intake PTV clearance but most people don't take the precautions (either laziness or don't know how) to insure that everything is set up correctly.
Valve spring choice and checking valve spring height are among several other factors that can determine what you can and can't get away with. Weight of the valve, RPM shift points, etc etc etc etc
Above all else, I simply get irritated that vendors flood the market to the 346ci guys with these camshafts that have 15-20 degrees of overlap. That is a recipe for a TQ'less turd with mediocre driving manners and the requirement for steep gearing. Oh well.......
That's argumentative!
The sun does shine on the dogs *** every now and then so I won't say it's impossible. Properly installed, you can do a lot with only .040-.050 intake PTV clearance but most people don't take the precautions (either laziness or don't know how) to insure that everything is set up correctly.
Valve spring choice and checking valve spring height are among several other factors that can determine what you can and can't get away with. Weight of the valve, RPM shift points, etc etc etc etc
Above all else, I simply get irritated that vendors flood the market to the 346ci guys with these camshafts that have 15-20 degrees of overlap. That is a recipe for a TQ'less turd with mediocre driving manners and the requirement for steep gearing. Oh well.......
The sun does shine on the dogs *** every now and then so I won't say it's impossible. Properly installed, you can do a lot with only .040-.050 intake PTV clearance but most people don't take the precautions (either laziness or don't know how) to insure that everything is set up correctly.
Valve spring choice and checking valve spring height are among several other factors that can determine what you can and can't get away with. Weight of the valve, RPM shift points, etc etc etc etc
Above all else, I simply get irritated that vendors flood the market to the 346ci guys with these camshafts that have 15-20 degrees of overlap. That is a recipe for a TQ'less turd with mediocre driving manners and the requirement for steep gearing. Oh well.......
You may have had no clearence and just got lucky.
Good talking to you, Brian. Give me a call when you're ready and we'll get you taken care of and back on the road!
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Largest Stocking Distributor of LS-x Engines / CHECK OUT OUR NEW WEBSITE!
COMP - FAST - PACESETTER - DIAMOND RACING - EAGLE SPECIALTY PRODUCTS - CALLIES - COMETIC GASKETS
RAM CLUTCHES - MOSER ENGINEERING - KOOK'S HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK
POWERBOND - ASP - AND MORE!
