[Graham052]

I'm working on degreeing in a set of MHS NA stage 2 cams in my headswapped 96 GT. These are supposed to be set at 110* intake centerline. right side came out 2 degrees retarded at 112* so I adjusted to where I get readings at either 110 or 109.75 so I am good to go there. Went to check PTV clearance on the same valve used to get ICL as described by MHS here
ModularHeadShop Articles on PTV check
My readings come back as follows:
At TDC : .020 clearance
3* past : .015
6* past : .003
9* past : .000
12* past : .005
15* past : .012
18* past : .025
21* past : .033

Obviously too close (touching)
suggestions on how far back I should retard the cam to get safe PTV clearance numbers?
Also can anyone tell me how to double check the valve events listed on the cam card?

[Graham052]

Surely someone else has had some experience degreeing these cams. Assuming all of my measurements are correct I am going to play around with it a little tomorrow and see what kind of PTV clearance I can get out of it retarding it to 111/112/113* although it seems counter productive to get an agressive cam and have to retard it 4* to be safe.
I am really glad now that I am taking the time to install these properly and check everything, installed at 110* there is no PTV issues while spinning the motor but they actually do touch at 9* past TDC - could have been disasterous if I installed them per the cam card and didnt double check.

[Bullitt5566]

When I spoke with Nick at MHS, he said that stage II cams would need to be installed retarded about 4 degrees with the stock pistons. Doing so sacrifices some low end power and throttle response. Since I didn't intend on building an engine with notched pistons yet, I choose stage I cams. I'd just install the cams as far advanced as you can, then move them to ideal ICL when you get notched pistons. BTW, welcome to the forums.

[Graham052]

Thanks Bullitt, figured that what it came down to. I would have the valves machined to get everything out of these cams if it didn't mean pulling the heads/headers again, what a pain in the ass.
I went ahead and retarded the right side cam to 112.5 ICL and came out with these PTV clearance numbers

TDC - .033
3* - .022
6* - .018
7.5* - .018
9* - .019
12* - .024
15* - .034
18* - .048
21* - .070

Double checked my intake valve events at .050
Cam Card:
Open Close
2.5 BTDC 42.5 ABDC

I came up with:
Open Close
1 ATDC 45.5 ABDC
So that shows valve events are retarded ~3-3.5*

.018 is pretty tight but I am planning on sticking with it as long as I get the same clearance #'s for the left side. Obviously anyone doing this needs to check and double check their own numbers but this might help someone to know where I needed to set mine. And just because you can spin the engine by hand does not mean you will not have PTV clearance issues.

[Nitmare67]

Way too close in my opinion. I wouldnt run any less than .030 which I consider VERY tight. I would take them back to 114...

Just machining the valve lips off will give you an extra .040-.060 clearance.

[Nitmare67]

MY VT stage 2 blower cams were supposed to be installed on a 116ICL to fit in a stock motor. By just machining the valves I was able to install them at 112 (advanced 4 degrees over normal) and still had .045" on the intake.... I could drop the to 110 and probably get away with it but I will take the valve clearance over a few HP. Thats with Mahle forged pistons, stock heads, stock valves with .060" cut from the faces

[NeverEnuff]

^ NitMare is right. .030 is too tight for me...but I spin my motor to 8k...6500-7k you SHOULD be ok at .045-.050"

[Nitmare67]

Originally Posted by NeverEnuff ^ NitMare is right. .030 is too tight for me...but I spin my motor to 8k...6500-7k you SHOULD be ok at .045-.050"

For that RPM I dont blame you for wanting .100 lol.

I spin my motor no higher than 6500 more like 6000-6200 honestly and .045" was close but enough comfort for me. You can run alot less, plenty have done it but one weak valve spring or hot motor and you could shatter a valve guide.... I would set them at 114. I honestly would have went for a smaller cam with a lower ICL though. Everyone raves about how to go stage 2 cams over stage 1 bla bla bla but I would rather have less duration and a lower ICL than a huge retarded no bottem end motor...

I would machine the valves, a shop will do it for less than 30 bucks. It will lighten up the valve a bit which is good and give you all the clearance you need for that cam.

[NeverEnuff]

^ Finally. Someone else who understands a properly degreed cam, Stage 1 is better than a backed off Stage 2 cam...

[Graham052]

I appreciate your input, and to be honest I may have went with a smaller cam if I would have known before hand that this cam would need to be retarded 4* to run safely. Like I said earlier, I would like to get everything out of these cams that I can, machining the valves would not be a problem but then I would also be looking at a set of head gaskets and head bolts on top of the extra work I was not planning on doing.
MHS's website claims all of their cams have .035" clearance with PI heads and stock pistons and goes as far as saying the stage 2 is the cam for the PI headswapped car, never making mention that you need modified valves or that the cam would need to be retarded 4* to run safely. I'm just frustrated and don't really want to bash MHS at this point, I emailed nick, maybe he will chime in here.

[Nitmare67]

Nick doesnt hang out here that I know of.... Check out corral or modular fords. I dont blame you on the price of head gaskets and bolts.... Just run them backed off unit you do a top end upgrade or new build.

[NeverEnuff]

NIck will prob tell you the same thing we are. I know Nick...

Head gasket change kit is like 112$ on summit racing....comes with everything.

[Graham052]

I linked this thread in my email in case he wanted to look at the numbers I got. At this point I will probably just run it as is for now. Honestly If Nick is going to tell me the same thing you guys are he should say it on his website... its misleading at best

[Nitmare67]

Nick has a ton of info on his website and is very active in the forums (more so than any other parts vendor). Did you email him about cams before you purchased? With all my past experience with him he has always disclosed all the details and helps to recommend a cam for your build.... That being said you should check out corral or modularfords for specific detail. Modded mustangs is a great website but is greatly lacking in the technical department when compared to either of those websites..... it has gotten better but your still sort of in the wrong place if you want a ton of insight into more detailed subjects such as cam degreeing or engine building.

[NeverEnuff]

Ok. Well Ill just say that if I had a shop and knew the clearances...id run more than .020-.030. I would expect Nick to do the same. Thats all.

[NeverEnuff]

Originally Posted by Nitmare67 Nick has a ton of info on his website and is very active in the forums (more so than any other parts vendor). Did you email him about cams before you purchased? With all my past experience with him he has always disclosed all the details and helps to recommend a cam for your build.... That being said you should check out corral or modularfords for specific detail. Modded mustangs is a great website but is greatly lacking in the technical department when compared to either of those websites..... it has gotten better but your still sort of in the wrong place if you want a ton of insight into more detailed subjects such as cam degreeing or engine building.

Correct. Not the place to be for great tech advice.

Wish ModDepot was what it used to be...

[Graham052]

Yeah I used to be be on modulardepot quite a bit too, it was great before it went downhill. I am not looking for any more specific degreeing or engine building info. I got exactly what I was hoping for from you guys (confirmation that my numbers are not out of line of where they should be and suggestions from those with experience) - props to you guys
The amount and quality of information on MHS's website is great and one of the main reasons I went with the cam I did. I did not contact him first, I have a fairly basic build, a bolt on headswapped car. It says clearly "this is the cam for you" on the website, so I assumed if I called I would get that same answer...

[nicksecondaddress]

This is Nick McKinney - my regular screen name here has been locked since the day I signed onto this site (and if someone knows who can fix it please let me know)

This cam has a 225 degree intake duration lobe. On a totally stock engine it clears with 0.030-0.035" of clearance when installed at 110 intake centerline. There have been quite a few others that posted publicly that they found this same measurement when they did theirs as this was a large public debate when this cam was first released. This same intake lobe is also used on the MHS Stage 1 Nitrous Only cam. At this point I have sold probably 60-100 cams with this same intake lobe for stock motors and this is the first PTV problem I have heard of.

The comp 262AH and the VT Stage 1 NA have roughly the same intake duration, and those are known as well to not have PTV issues with a stock motor.

After talking with OP via email we have zeroed out every cause but one that I just thought of. There is roughly 3 degrees of dwell at TDC. That is the piston holds the same position while the crank moves 3 degrees. If using a piston stop with a 2V head since the plug is so angled its hard to get the degree wheel right in the center of this dwell. 1 degree is worth roughly 0.015" on this measurement here. We took a large diameter 18" degree wheel and welded a hub to mount it permanently to the crank snout so we could repeat within this 1 degree range. We could not repeat our own results under controlled conditions with an engine on a stand until doing this.

I will answer some of the other things I see here that I do not agree with.........

[nicksecondaddress]

Originally Posted by Bullitt5566 When I spoke with Nick at MHS, he said that stage II cams would need to be installed retarded about 4 degrees with the stock pistons. Doing so sacrifices some low end power and throttle response. Since I didn't intend on building an engine with notched pistons yet, I choose stage I cams. I'd just install the cams as far advanced as you can, then move them to ideal ICL when you get notched pistons. BTW, welcome to the forums.

MHS Stage 2 Blower cams which have a 228 intake lobe duration would need to be retarded 4 degrees to clear a stock motor, not a MHS Stage 2 NA cam which has the 225 intake duration lobe that we are talking about here.

As far as I am concerned talking cams with "Stages" and not their true specs is a crock of crap but its what we are stuck with now since that is the way everyone wants to describe it. One "Stage" can be totally different than another. My Stage 1 Blower cam is a TON bigger than others Stage 2 Blower cams for example.

[nicksecondaddress]

Originally Posted by Graham052 Honestly If Nick is going to tell me the same thing you guys are he should say it on his website... its misleading at best

I only post the truths on my site, you can always trust me on that. If I wanted to BS people I would have gone into a different line of work that actually makes money...............

IMHO - redo the piston stop and see if you can find the center of the dwell, if you mark the zero point on the wheel when the piston first touches the stop you could be a country mile off. The 3 degrees of dwell is one issue, the piston able to rock in the bore a few thou is another, and the extreme angle of the piston stop in a 2V head is yet another.

Only way I like to do a true TDC measurement that I know is 100% accurate:



You notice the measurement is done at the rear edge of the piston, even here you can rock a cold piston 0.005" Its even worse when you try to measure where the spark plug is pointing at, the piston does move quite a bit in the bore.