ice95z

iTrader: (10)

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.

sweet99ss

iTrader: (41)

Smaller cam will fix the problem....

01 WS6 6.0

iTrader: (8)

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.

badazz81z28

iTrader: (6)

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.

Damian

iTrader: (89)

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.

Bramlok

iTrader: (7)

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.

joelster

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.

redtail2426

iTrader: (10)

yeah get a smaller cam or flycut,those are your only options.Im sure you will measure next time

stunna p

iTrader: (4)

I highly recommend the polluter cam from tick performance.

01ssreda4

iTrader: (96)

Smaller cam, and always check with something like an MS4.

Austinma62

Smaller cam+ higher compression= Winning!

PREDATOR-Z

Ice, I know you feel like crap; but it is your fault and no one else's. Motors (or anything involving mechanical engineering) will require certain protocol (procedures) to follow when doing a build.
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.

LS1-450

iTrader: (33)

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...

Mr. Hyde

iTrader: (10)

Not to be argumentative, I but I ran a 'garage install' MS4 and had both 241's and 243's over the years and neither had PTV contact.

PREDATOR-Z

lucky.....

Damian

iTrader: (89)

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.......

Mr. Hyde

iTrader: (10)

I'll take that as a compliment; most people don't know how to properly install a roll of toilet paper. I'll concede that the cam was not the best choice, but I was saved by the fact my car is lightweight so the lack of bottom end wasn't as noticeable. Definitely could have used more gear (had 3.73's) NA but on the squeeze it ran out of gear quick so I compromised.

badazz81z28

iTrader: (6)

I wouldnt be so quick to say this cam fits. .040-.050 is not very much (the thickness of a few pieces of paper. Like many will say. Not every engine is the same, some tolerences are not exact from engine to engine. Thats why everyone will not say "a cam will fit or not without issues". Hell, I couldnt even get people to say a 228R would be ok...Theres a guy running the same combo as mine except his heads are mill .030 and mine are .020. I had .125" clearence on the intake and he had .100" One would assume I would only have has an additonal .010". You need to measure....

You may have had no clearence and just got lucky.

Sales2@Texas-speed

iTrader: (5)

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!

tom falco

Just a thought!!!!

ALWAYS CHECK IT!!!! Dont take any ones word for anything. All setups are are different. In my view .100 -.125 is min Just my $.02