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Author Topic: Considering drop-in cams? Here's some helpful info  (Read 5155 times)

Offline Dwight-PA

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Considering drop-in cams? Here's some helpful info
« on: November 02, 2002, 10:51:00 AM »
First of all, my intentions are not to promote one cam over another. There's no "mine is better that yours" crap intended here at all. This is strictly to inform you of my findings on "valve retainer to oil seal/valve guide" clearance. If you’re considering drop-in cams or are presently using any cam that has greater lift than the Yosh drop-ins and especially if you DON’T intend to have any valve guide work performed, this info should be of great importance to you.

Let me start by saying, I highly recommend using a valve retainer that yields more "valve retainer to oil seal/valve guide" clearance than the stock retainers and here’s why...

Using a brand new Suzuki issued head, intake valves and oil seals, I used my dial indicator (1" travel, calibrated in .001") to measure the "valve retainer to oil seal/valve guide" clearance and there wasn’t enough to use the Web cams without beating the oil seal and possibly the guide and cam to death! This could be part of the reason why some Web cam lobes are reportedly wearing prematurely, quality of carbon nitriding aside.

Now, as time consuming and tedious as it is, I completely broken down the dial indicator setup at least 3 times initially to check repeatability and my results varied from .361" to .365" of clearance. In any case, that’s NOT enough clearance when using the Web .378"/.330" or any equivalent or higher lift cams so at very least, the oil seals are going to get pummeled. It is enough clearance if you’re using the Yosh drop-in cams as their max intake lift is only .354" and I suspect that’s why Yosh limited their cam lift to only .009" higher than stock, which is nowhere near coil bind.

Why hasn’t anyone else found this clearance issue? Maybe they have and just took the appropriate measures to correct the issue. Perhaps Suzuki has undergone some valve guide milling changes however I consider that highly unlikely. Perhaps the fact that most guys seem to be using the Yosh cams over the Web cams. Perhaps also, the fact that many guys that are building the engine appear to be going 1397cc and have the shorter valve guides installed to function properly with their .395"/.378" or higher cams.

More likely however, is the fact that these so called "drop-in cams" are supposed to be free of "clearance issues" as determined by the cam maker, so few builders are actually checking the "retainer/valve guide clearance" because it's assumed it's not an issue. Just look at how many guys are dropping cams in without degreeing them, let alone checking all possible clearances.

Now, please don't take offense as I’m not knocking anyone here. Simply stated, some guys don’t own a cam degreeing kit or the dial indicator required to degree cams and check clearances so they're accepting, based on the face value of the cam maker's claim and reputation, that their drop-in cams are free of clearance issues. It would never hurt to check though, would it? So I did!

Admittedly, I almost traveled that same path myself. I figured, why take the extra time to check for "valve retainer to oil seal/valve guide" clearances, it’s a drop-in cam and it's a given there aren't any clearance issues, right? So, drop er in, check and adjust the valve lash, degree the cams and bolt her up tight and ride like lightning! Hi ho Silver, away...

MURPHY'S LAW...

It's times like these I find it a blessing having Murphy sitting upon my shoulder, (much like the monkey on my back) poking and heckling me every inch of the way so I don't make assumptions or skip taking every precaution. When ole Murphy starts snickering the loudest, I pay heed. The more I figured I'd skip the clearance check, the louder I could hear Murphy laughing his barnacles off so I knew I had to perform this crucial clearance check. By the time Murphy gets to say, "I told you so laddie! Bah, ha, ha, he, he, he...", it's always too late! Welp, Murphy, you little bastard, you were right! There wasn’t enough clearance for my Web .378"/.330" drop-in cams. And you guys thought I was hearing voices, dudes, it’s just Murphy!    
 
Now your results will vary slightly from mine due to the wear factor of your valve tappets, valve seats, oil seals, and the valves themselves. However, I don’t see them as being off by too many thousandths of an inch from new so I think my findings are significant to those interested in dropping cams in.

I had just purchased APE performance springs so I called APE Racing and requested info on their titanium retainers, specifically, "How much clearance over the stock retainers do the Titanium retainers for the APE springs yield?" Jay told me .030" and he recommends using their Titanium retainers with their APE springs. I must agree. (incidentally, the APE titanium P.N. is TVSR1300PRO) As Jay stated, their titanium retainers actually did yield an extra .030" of clearance.

Naturally, the first thing I did after receiving the APE Titanium retainers was set up the dial indicator to measure this "alleged" extra clearance. (Sorry, by nature I’m cynical and would rather error on the side of caution. The Busa is my baby, second only to my daughter, the greatest joy in my life!)      

My findings after installing the APE Titanium retainers…

I broke down the dial indicator setup only twice this time as I could see Jay was correct about the .030" of extra clearance they yield. My findings were .392" and .395" of clearance using the APE Titanium retainers and that’s enough clearance to use .385" Megacycle cams as well as the Webs. I’ll breath easier now that I know I no longer have a clearance issue. Have a happy and successful caming!  

THEMOTORHEAD

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Considering drop-in cams? Here's some helpful info
« Reply #1 on: November 02, 2002, 12:24:00 PM »
I HAVE USED BOTH WEBBS AND MEGACYCLES
NEVER HIT A SEAL EVER.
BUT I WILL TELL YOU THE SPRINGS GOING TO DICTATE SAFE CLEARANCE FOR SEAL TO RETAINER
ONE THAT IS WEEK AND ALLOWS MOMENTUM COMPRESSION WILL NEED SUBSTATIALLY MORE CLEARANCE THAN ONE WITH GOOD CONTROL.
THOUGH I HAVE HAVE SEEN 2 WEBBS BITE THE DIST DUE TO POOR NITRIDING(LABORATORY TESTED)(1 CONV OIL 1 SYTH.)
I HAVE HAD A FEW DOZEN E MAILS AND MAILINGS AND VISITS WITH PEOPLE WITH TI RETAINERS WITH OVALED SHIM HOLES.
I HAVE NOT USED EM MYSELF BUT ALOT OF PEOPLE WERE EARLY ON.
I HAD WEBBS LARGE WEBBS IN MINE FOR 2 YEARS SO FAR
AND NO PROBLEMS
 LAST YEAR WHEN I CHECKED IT
#65 IS WHERE MY SEAT PRESSURE WAS AFTER ABOUT 8,000 MILES

Offline Jay

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Considering drop-in cams? Here's some helpful info
« Reply #2 on: November 02, 2002, 12:49:00 PM »
When I checked this last year, there was room for a 378 Web, but just barely. That is why we made our retainers shorter.

However, if when using the stock springs, you develope a valve float situation, this will allow the valve adjustment shim to jump up and down in the retainer, and over time it will wear the shim bore.

Jay