Michael_D

I purchased a set of used heads from forum member Racingswh. He's building a new engine. He had AHP go through these heads and opted for the MS90 guides. He can add engine use details if he wishes. This a brief summery...

16 days total at 6 different events and 3 trips to the dyno in 1.5 years. Approximately 2000 miles total use.
Shifted at 6500 rpm
Camshaft used was a Katech Torquer 110
OEM Ti intake valves, Ferrea hollow stem exh valves.

I bought these heads because I am in the process of changing my personal car's engine configuration. The heads I have on the engine were extensively ported for race use. 400+ cfm and the intake swirl damn was completely removed. The cam in the engine has about 60 deg seat/seat overlap. Pulls like a sonofabitch over 3000 rpm, to fuel cut off, which I have set to 7400 rpm. I've spent the last two years tweaking the calibration and have ran out of tricks to improve off idle, low rpm drivability. I wan't to go back to OEM heads and just have mild port work done to improve velocity and intake port flow over 600 lift. I saw these heads on the C6 parts for sale board and figured I'd just send them back to Kohle for inspection and R&R whatever as needed. I also need the rocker peds cut down for installation of a rail rocker system.

I'll also confess that I have vested interest in the MS90 guide option AHP offers. I'm the guy that gave Kohle the idea a few years ago. We were looking at seat alloy options for using a Ti Exhaust valve, and after I had a conversation with performance alloys about using MS90 for seats, I learned they supply MS90 to many NASCAR teams for guides. Kohle was interested in using it for some of his higher HP builds. The rest is history.

I normally do not endorse vendors, or their products. I like to stay unbiased. I'm simply being up front with this info, and am not endorsing AHP. Just passing on info.

I asked Kohle to disassemble and document everything. He did so himself. If anyone has any interest in additional info, I'm sure Kohle will chime in. I may check in as I have time to do so. I just took a promotion, which comes with twice as many employees, so my spare time will be drastically reduced.

All in all, I'm pretty impressed with the performance of these guides and inspection results. Not much wear and tear or use on these heads, but in my experience, it doesn't take long for guides to go to crap if there is anything wrong to cause it.

I'll just copy/paste the results below:

PSI 1511ML springs:

We tested the valve springs and found the following:
all measured @1.798" install height
For comparison sake a new PSI511 valve spring measures 127 lbs @ 1.798" IH

1 int 124
1 exh 115
3 int 122
3 exh 124
5 int 121
5 exh 125
7 int 121
7 exh 123

2 int 122
2 exh 123
4 int 122
4 exh 124
6 int 125
6 exh 123
8 int 125
8 exh 118

Seat run out:

Run out is great for a used set of heads.
We measured Less than .002" valve seat run out on the exhausts and right at .002" run out on the intake.

We also did a vacuum test without the springs installed and all valves pulled a quick .8 bar on our vacuum tester

Videos:

Intake run out clip:

Exhaust Run out clip:

Vacuum Testing clip:

Guide clearence measurements:

Mike D M90 heads.pdf

The tips of some of the Ti intake valves show an unusual wear pattern. I suspect the lash cap was spinning. Can't say I've seen that before.

Dan_the_C5_Man

Sweet. Will any action be taken on the intake stem tips? :

MTPZ06

Thanks for the report...glad I run the same heads.

vertC6

Great information Michael, you bought these heads five minutes before I could, lol.

GeneSch

I had my heads off the winter of 2014/2015 and sent them to AHP while I was installing my ECS-1500. At that time I had around 9,500 miles on the car. The valve stem tips looked great. I ran the car that summer with stock cam and AHP set up with BTR .660 springs.

Winter of 2015/2016 I pulled the motor to build the short block for safety. 17,500 miles now. I added a small BTR cam. .625 lift. At the time of the rebuild I also noticed the the intake valve stems had the same pattern on them. I keep all he lash caps in order at time of removal and placed them back on their respective valves. I then checked to be sure they didnt bind. They all spun freely and seem to fit well. I then took a feeler gauge to be sure the caps didn't hit the spring keepers. There was about 0.002 to 0.005 clearance. Really looking at each cap it looks like the pattern inside the cap from machining, imprinted its self into the stem.

I ran the car all summer but we only put about 2,000-2,5000 miles on it. I plane to pull the rockers and do an inspection over winter but I could do this sooner if needed. I could check the clearance between the caps and the keepers. My worrie would be the caps pushing on the keepers causing them to allow a valve to come unlocked and then dropping.

I was thinking of taking the caps to work and putting them on the grinder and taking 0.005-0.0075 off the open end to add some clearance.

Ether way I'd like to know what causes this. They were like this after the stock cam was ran with heavier springs. I in know way think or feel this has anything to do with the work AHP did to save my heads from the certain LS7 guide death.

GeneSch

After the new springs and guieds. Before install

After around 6500 miles





I don't want them to push on the keepers

AzDave47

Michael, great report overall and details on the wear on the MD90 guides.

vertC6

Micheal, looking at the numbers how close is that from what it was when they left AHP with new guides? How much wear if any has occurred

Bad_AX

So, it looks like the MoldStar 90 guides held up to the OEM CrN coated intake valves and OEM rocker arms. I don't recall having seen the valve tips worn under the lash caps. Could this be a result of high spring pressure with the duel springs?

Michael, have you decided on cam specs for this "new build"?

Dan_the_C5_Man

The Ti tip wear would have absolutely nothing to do with any vendors work. That is a function of the softness of the valve material and the hardness of the cap, and the internal machined surface of the cap - the cap wins in a battle of wear.

Seems like another data point to monitor, might require periodic valve replacement (if it concerns you).

Next time I have mine apart, I will take some pics.

outhouse

Maybe its time we polished these up with a dremel ?

Michael_D

Yes. Haven't decided what yet. Catch 22.... Should I grind the tips, reduce clearance to the locks? Probably not..... Replace the worn ones (not all are worn) with some new valves, or replace all, and with what? Katech valves at a premium price? Or....just run the f'ers as is.....

I asked what initial clearance is, and was told 0.0013"

If these were sitting on my bench, I'd just bolt them down and not worry for another 25K miles or so..... But......seeing how they are already broke down, on a professional's bench, next to a Serdi......I'm just having they all replaced and the seats touched up.

The 1511 are beehive.... more load than OEM. It may be lack of lubrication when installed? I dunno. I always put a drop of moly on the tip before installing the caps.

I'm working with Geoff / EPS on the cam. Waiting for port flow numbers for him to figure out the valve events. He will be penciling out a different cam than what's on the shelf. His EPS lobe profile, but higher lift. Somewhere in the 232 +/- 3 range for the intake, 8 - 12 deg split, .675'ish total lift. I'm not a cam guru, and can only get close to what I want. The rest I leave to guys like Geoff.

I wanted to try one of Jones' inverse rollers, because I love the concept, but he and I just aren't on the same wave length. Some of his initial recs are over in the parking lot, and I'm on first. Geoff and I tend to have simular views on engine building and tuning.

Bad_AX

I went through the same thing with Mr. Jones, the "Cam King of Overlap". I'm no Engine Master, but once in while I know what's right for me

rio95

I was going to ask the same thing! I thought they would have been a little tighter than .0013, leading me to believe they did wear a bit.
​​​​​​
Let's keep in mind here that 2,000 miles isn't much even if it's on a track. Also, sounds like it wasn't shifted above 6,500 either, which kind of makes sense with that cam. Lastly, this is a baby cam, especially the intake lift. Even the exhaust lift isn't as high as many others. I guess all I'm saying is this is definitely a nice data point, but I don't think there is a ton to pull from it. Itd be nice to see how they are after 10k+ miles. Either way, thanks for sharing Michael.
​​​​

Michael_D

Before anyone starts commenting on the amount of wear, keep in mind that the clearance differences are in the tens. That's ten thousands of an inch..... And unless you've actually measured small holes with a bore gauge that reads to tens, I suggest you give it a try before jumping to conclusions.....

rio95

​​​​I agree it's pretty much a negligible amount and could even be attributed to measurement error or maybe they weren't even exactly .0013" in the first place.

phipp85

Thanks for posting up results and measurements. Always interesting to see that sort of data. If the moldstar 90 guides had been available when I worked my heads I would have went that route most likely.

I most certainly agree about measuring tenths. Most people don't realize how small a measurement that really is and how difficult it can be to get repeatable accurate measurements to that level of accuracy. In the case of a guide the measurement isn't a go/no go type check. If you measured the guide bore diameter at 5 different points along its axis you'd likely get 5 different measurements. I made sure to measure my guides before I sent them out since I knew no one trying to make a profit was going to waste all that time measuring guides that were going to be thrown away.

American Heritage

Overall we are very pleased with how the Moldstar90 guides did in this report. We have been very pleased with them since we started using them.

The 110 although not a giant cam by any means is not very nice to the valve train, especially with stock rockers. So add this to the results and we are more than pleased.
MoldStar90 is an amazing valve guide material.

Regarding the tips of the ti valves. We have seen this before even on bone stock applications with heads that have never been off the car since the factory. Maybe GM has a hardness tolerance variance when they have them manufactured, it could be a number of things. We do not rockwell hardness test stuff in house but have a place we send out to for testing. Might be interesting to see if the hardness of the ti tip changes over time (from new to used) or even from new to new or used to use, ect...).

We have spoken with Xceldyne about making us a Ti valve to our spec which they will gladly do but the price of the valve goes up quite a bit.

1971 Judge

[QUOTE=Michael_D;1593310742]I purchased a set of used heads from forum member Racingswh. He's building a new engine. He had AHP go through these heads and opted for the MS90 guides. He can add engine use details if he wishes. This a brief summery...

16 days total at 6 different events and 3 trips to the dyno in 1.5 years. Approximately 2000 miles total use.
Shifted at 6500 rpm
Camshaft used was a Katech Torquer 110
OEM Ti intake valves, Ferrea hollow stem exh valves.

I bought these heads because I am in the process of changing my personal car's engine configuration. The heads I have on the engine were extensively ported for race use. 400+ cfm and the intake swirl damn was completely removed. The cam in the engine has about 60 deg seat/seat overlap. Pulls like a sonofabitch over 3000 rpm, to fuel cut off, which I have set to 7400 rpm. I've spent the last two years tweaking the calibration and have ran out of tricks to improve off idle, low rpm drivability. I wan't to go back to OEM heads and just have mild port work done to improve velocity and intake port flow over 600 lift. I saw these heads on the C6 parts for sale board and figured I'd just send them back to Kohle for inspection and R&R whatever as needed. I also need the rocker peds cut down for installation of a rail rocker system.

I'll also confess that I have vested interest in the MS90 guide option AHP offers. I'm the guy that gave Kohle the idea a few years ago. We were looking at seat alloy options for using a Ti Exhaust valve, and after I had a conversation with performance alloys about using MS90 for seats, I learned they supply MS90 to many NASCAR teams for guides. Kohle was interested in using it for some of his higher HP builds. The rest is history.

I normally do not endorse vendors, or their products. I like to stay unbiased. I'm simply being up front with this info, and am not endorsing AHP. Just passing on info.

I asked Kohle to disassemble and document everything. He did so himself. If anyone has any interest in additional info, I'm sure Kohle will chime in. I may check in as I have time to do so. I just took a promotion, which comes with twice as many employees, so my spare time will be drastically reduced.

All in all, I'm pretty impressed with the performance of these guides and inspection results. Not much wear and tear or use on these heads, but in my experience, it doesn't take long for guides to go to crap if there is anything wrong to cause it.

I'll just copy/paste the results below:

PSI 1511ML springs:

We tested the valve springs and found the following:
all measured @1.798" install height
For comparison sake a new PSI511 valve spring measures 127 lbs @ 1.798" IH

1 int 124
1 exh 115
3 int 122
3 exh 124
5 int 121
5 exh 125
7 int 121
7 exh 123

2 int 122
2 exh 123
4 int 122
4 exh 124
6 int 125
6 exh 123
8 int 125
8 exh 118

Seat run out:

Run out is great for a used set of heads.
We measured Less than .002" valve seat run out on the exhausts and right at .002" run out on the intake.

We also did a vacuum test without the springs installed and all valves pulled a quick .8 bar on our vacuum tester

Michael_D, thanks for sharing this information and your background with the project and AHP. The timing of your report is spot on as I just read the 26 pg article on the LS7 from CAC (I just purchased an '08 Z myself) where they promote CHE mag-bronze valve guides over the MoldStar90 (unless your racing).

Would you recommend AHP PM guides for street use or just make the investment on the MS90 and sleep well?

Cheers!

Michael_D

If you can afford MS90 guide material (or tolerate), there really is no down side that I can think of.... The labor rate doesn't change, or I don't believe it would....you are paying more for a chunk of bronze with a different blend of special sauce.

I don't even know what the cost adder is....? $500? 500/16=$31.25 ea CHE guides are about $5.00 ea last time I looked.