TSP's MS4 cam is huge. No doubt about it. However TSP has stated that with stock heads, or heads that haven't been milled, you don't need to flycut the pistons for clearance. Personally, I believe them, but there still seems to be many people concerned out there.

I have searched but found no one having issues. My question is this;

Has anyone ran into clearance issues with the MS4 cam reguarding the pistons were something actually DID go wrong?

 

nuthin with the clearance just get rod bolts spun a bearing 10k later

 

https://ls1tech.com/forums/generation-iii-internal-engine/827870-little-ptv-problem-pulled-motor-pics.html

 

That doesn't really look conclusive to me that it was caused by a clearance issue. For starters, the kid didn't even have the car tuned with the MS4.

 

The car in the thread above was NOT a cam problem. With the cam properly installed, the MS4 will not have any PTV issues. That being said, you can over-rev the cam and hit the valves with the pistons. You can do that with the stock cam. Yes flycutting would be a good idea to give you added clearance, but it is not a necessity. With a factory headed, stock bottom-end car, the cam won't have any PTV issues.

 

I agree that the car issues in the linked thread was not do to PTV issues.

What would "over-revving" be considered in your book? I have seen guys dyno sheets pulling to 7,000 RPM with stock heads and the MS4. Would that RPM without flycutting still be considered "safe"?

 

The thread above is my car. If you read the thread you will see that what caused the piston to hit the valve was a spun rod bearing which made the piston actually go a lil higher. Thats what caused the problem i had. Ya the car wasn't fully tuned, but it did have a semi good tune in it. Just never went and had it dynotuned ..

Me and Jon @ TSP talked about what had happened and i think the cam is perfect. It was just the bearing problem that caused the contact. Its all good though bc Jon is going to hook me up with some rods, pistons, and new bearings for her real soon .

 

I was just answering your above question. Yes, the problem itself was not cause by the cam.....but because of the ptv clearance of the cam he eyebrowed his pistons. Just answering your question.

 

I understand, but as you said yourself, "it wasn't because of the cam", it was because something else caused the piston to contact the valve which was not directly related to clearance issues with stock heads or un milled heads and the MS4 cam.

 

Hi bjamick,

Just to cure definitively this suspicion about the reasons why your valves hit your pistons heads, the most simply possible give us your Piston to Valve Clereance at the end of your camshaft installation please.

Can't imagine you don't know (because you didn't measure) if you have a 0.040 or a 0.090 of clereance on the intake side...that would not be reasonnable, I think!!!

Waiting to read from you your measurements
Christian

 

Nope your right i didn't measure. All i did was installed cam, turned crank by hand, listened/felt for resistance and that was it. I wasn't really worried about it, nor would i have been even if i knew this was going to happen. The only reason the valve even hit is bc of the spun bearing. So actually it was just fine bc the other cylinders dont even have the slightest mark of contact.

 

And for the OP, I'm guessing you're thinking of getting the MS4 since you posted up this thread. I've got about 8,000 miles so far and no problems. ran a best of 12.0@114mph, full weight, stock suspension, street tires, 1.898 60ft, and 3500 stall. I spin her to 6700-6800 rpms, and will probably be spinning a bearing soon also with those rpms.

 

Hi bjamick,

In the country of freedom I will let you responsable of your own actions....

The technical facts are that with all the dispertions in the numerous parts forming the chain of parts from cranck to valves related to the industry building process of those you can't be sure of how much are your pistons out of the hole.
The 0.007 out of the hole from the factory is an average measurement and can be from 0.004 to 0.12!!!!that I have seen.

I had camshafts from Comp cam doctored and again the regular dispersition due to machining can lead your measurements to be a little off the advertised numbers.
A degreeing of the camshaft is highly recommended to be in line with the numbers of the camshaft designer...

As a consequence of your complete processing (or lack of process) you don't know your PtV Clereance...at all.


No measurements at this level and all your comments are just guesses, and as an hypothesis I will say your intakes valves were kissing the piston's heads in cylinder one and six, and repeated hammering damaged the bearing con rod.
Just a guess....with no value, or the same value that your statements.

On the other hand, congrat for this job about modifying your engine, just take care than your passion doesn't darken the reality...
Christian

 

No matter how technical you want to try and explain anything, I can assure you if the cam was installed properly there is NO WAY the piston hit the valve! What you are saying is even if the piston came out of the hole .012" and Comp was off .002" on a lobe design (worse case on both), somehow the piston covered another .046" to come into contact with the valve? (We see an average of .060" PTV clearance on the intake with MS4 cams.) Then instead of bending the valve on start up, it hit the top of the piston hard enough to beat the bearings out of the motor. There is no way that happened. A bearing can sustain much more punishment than a valve can. If it were hitting that hard, it would have bent a valve on start up! And again, it wouldn't have had PTV problems on 2 cylinders. There would have been a mark on every piston.

Guys, this isn't magic. Pistons don't miraculously come out of the hole and hit pistons. Lobes don't magically become larger after 1,000 miles. It is simple math. Everything can be calculated. Sometimes things happen whether it's just bad luck, an install problem, or a piece of trash in the oil. But I can tell you with absolute certainty that the problem with the motor in question was NOT a cam issue!

 

^^^ ya i've tried to explain to everyone that it isn't the cams fault. It is called low oil which i found out during pulling the motor out. The LS1 bearing is .65 thick so with the spun bearing under the other one made the piston go up far enough to hit a tad. Not even enough to bend a valve i believe.

 

And this is exactly why I created this post to help prove. Lots of people seem to be concerned, but I have still yet to find anyone that actually had an issue.

 

What are the actual PVC on the MS4 with stock heads???Anyone ever measure it???

 

What a smart question, practical and radical...
Anyone ever measured it???

 

I'm pretty sure over-revving is more like shifting into second while attempting for fourth. My wife found this out while making a pass in my car last weekend. I have 2 cylinders w/ zero compression and that's w/ 4cc valve reliefs. All the clearance in the world is not gonna protect you from a mechanical over rev.

 

Well Jimmy, that kind of goes without saying. I was more or less seeing if they thought 7,000 RPM would be over-revving.