Topic: Q's on big cam mods and on decking cylinders

[JLeather]

Got a few questions pertaining to my winter 836 build.  I think I am going to be running that RC327 cam I picked up.  I was wondering, however, about how the cam holders will take it.  I've got a head all set up for it with Ti keepers and the aftermarket springs, ported, etc.  I remember that back when the guys that ran cams this big had to machine spacers to use the valve cover as an extra hold-down.  Anyone here done that?  I know a few guys (Terry, 754, Sparty, etc) have run cams about this size.  Anything done to the cam towers?

Another Q I've got is about cylinder decking.  How much meat can be removed from the surface of the jugs before the cam chain tensioner won't take up the slack anymore?  Also, would you want to remove the sleeves and take the material off the bottom of the jugs?  Maybe take half off the top and half off the bottom?  I'd like to take .060" off total.

Last question, can aftermarket cylinder studs be removed and reused?  I've got an engine with aftermarket HD studs in it, but the bottom case is trashed.  I'd like to reuse them on this current build.  I know the stock ones aren't removable/reusable (and why would you want to anyway) but I'd think I can get away with it on the aftermarket ones.

Thanks guys.

[Jerry Rxman Griffin aka MuthaF'er]

In my opinion, for the street this is bling. For a 1080 or 1000 RC Cobra it's not a bad idea. Extra insurance to help hold down the cam towers due to extra high lift cams. For the strip in a 1080, 1060, 1000 Cobra with the extra high lift cam, most definitely for extra insurance.

Another mod that has been done is to go 1 size larger on the cam tower bolts by tapping the holes and using helicoils. If you stay with the stock size bolts, going with helicoils isn't a bad idea either.   

The thing about reusing cylinder studs is an unknown. How many times were your studs reused/retorqued? What kind of condition are they or will they be once removed? Twisted maybe? I have had my engine apart 3 times and it still has the original studs. It's had the 810 Yoshi kit with the Yoshi Daytona cam and stiff springs in it for 25,000 miles. Yes it has a head gasket leak. How many do not including stock engines?! Next tear down coming soon will have either my 900 Henry Abe kit or the APE 1000 kit and YES it will have HD cylinder studs and bottom end studs. I'm older, wiser, and I can afford this stuff now but this wasn't the case in 1976 when I blew it up.

http://i233.photobucket.com/albums/ee84/RxmanGriff/P1020035.jpg[/img]]

[JLeather]

Jerry, who did that to your valve cover and how much was it?  I will atleast go with larger bolts/grade 8's when i do the cam towers.  That's a good idea.  The cam is a .370 lift and a 270 duration, which is stout enough for me to atleast question the puny (and old) bolts on the cam towers.

The studs in question are off an old drag engine (hence the destroyed lower end).  I do not know how many times they've been cycled, but they look good.  Assuming I don't twist them getting them off (and I do have an excellent Snapon stud extractor for this job).

[MRieck]

Jerry, who did that to your valve cover and how much was it?  I will atleast go with larger bolts/grade 8's when i do the cam towers.  That's a good idea.  The cam is a .370 lift and a 270 duration, which is stout enough for me to atleast question the puny (and old) bolts on the cam towers.

The studs in question are off an old drag engine (hence the destroyed lower end).  I do not know how many times they've been cycled, but they look good.  Assuming I don't twist them getting them off (and I do have an excellent Snapon stud extractor for this job).

.370 is a medium lift cam. As Jerry said helicoils are nice....you don't need external supports. I have numbers for decking, milling etc. PM me.

[Steve F]

Jerry, who did that to your valve cover and how much was it?  I will atleast go with larger bolts/grade 8's when i do the cam towers.  That's a good idea.  The cam is a .370 lift and a 270 duration, which is stout enough for me to atleast question the puny (and old) bolts on the cam towers.

The studs in question are off an old drag engine (hence the destroyed lower end).  I do not know how many times they've been cycled, but they look good.  Assuming I don't twist them getting them off (and I do have an excellent Snapon stud extractor for this job).

When I had the head off the last time, I stripped out a bolt hole for one of the cam towers.  I found that the holes are not tapped all the way to the bottom, so I took care of that, and installed studs in the holes instead of using bolts, which i think is a much stronger way of securing the cam towers without the fear of stripping out the holes.  The bolts that are used in the stock setup strip out the holes really easy, even when torqued to the factory specs, which is a real weak point with these heads.

[Terry in Australia]

The thing about reusing cylinder studs is an unknown. How many times were your studs reused/retorqued? What kind of condition are they or will they be once removed? Twisted maybe? I have had my engine apart 3 times and it still has the original studs. It's had the 810 Yoshi kit with the Yoshi Daytona cam and stiff springs in it for 25,000 miles. Yes it has a head gasket leak. How many do not including stock engines?! Next tear down coming soon will have either my 900 Henry Abe kit or the APE 1000 kit and YES it will have HD cylinder studs and bottom end studs. I'm older, wiser, and I can afford this stuff now but this wasn't the case in 1976 when I blew it up.

I'm glad you finally got around to saying you were gonna use H/D studs Jerry, for a minute I thought this was gonna devolve into another "Oil Cooler" thread, ha ha!

Personally, I think the OEM studs are pisss-weak and are the reason for the majority of head gasket failures. I'd have very little hesitation in installing used H/D studs as long as you don't "score" them with your stud remover.

Regardless of how many times they've been torqued, they're still stronger, with much less "stretch" than the OEM studs, and the worst you're gonna do is bust one, but unless you accidentally add a "0" to the 25 ft/lb torque value, you'll be fine.

I'm gonna modify some valve covers like Jerry's for my "Hotrod" engines, last time I took my cam towers off to seal a leaky puck I saw that two of the original threads were starting to pull out, and while the drilling out/installing bigger screws/studs is a fine idea when using a bigger cam/heavier springs, the modified cam cover says, "Beware mere mortal, evil lurks within"! Ha ha, Cheers, Terry.

[Jerry Rxman Griffin aka MuthaF'er]

JLeather,

I actually found that cover on EBay during another of my numerous late night episodes and said whatthahell.  I couldn't remember who until I pulled the shipping box back out. R. Fortin in Ottawa shipping date 5/7/2007 in a "Kennametal" box thats just the correct size for it. I went back through my feedback ratings but did not find him. Think I gave a little over $100 but I do not remember. I can provide an address if you're interested. My only concern might be slight oil leakage from around the screws. I figure I can always use teflon tape or another sealer to help with that potential situation. No o-rings, etc. 

[754]

I think the use of those covers would be dictated more by spring pressure and time spent at High RPMs.

This from the RC catalog,

RACING ROCKER STAND SUPPORTS

Special supports installed in your cam cover.Provides positive control of cam and cam tower flex in hi-revving motors. Prevents cam tower bolts from stripping and aids in valve control.

Sure cant hiurt..

JL if you get tired of that cam I may have a 315 to trade..

[Big Jay]

Back in the day, RC had springs from a Pinto, or something like that, and they would lift the rocker stands. When correct valve springs were designed for the Honda, the need for that mod went away.


As for the decking, how do you intend to compensate for the .060"? Sure you don't mean .006"?
Jay

[JLeather]

Jay,
  I do in fact mean .060".  I'm still looking to run a set of DOHC750 rods, which are .060" shorter.  I was wondering if it was possible to mill the jugs down .060" without compromising strength or losing an oil passage or something.  It's also a question of whether I'd need to remove a link from the cam chain.  Ever take that much off an engine before?

I talked to a guy a while back who ran mini sprints with CB750 engines in them (cut the tranny off, ran an external oil pump and a driveshaft back to a 4spd box).  He ran CB900 rods (1.5mm longer) with an .060 spacer under the jugs and a camchain with an extra link.  I'm just wondering if it's possible to go the other direction?  If not I might give 900 rods a try.

[MCRider]

Jay,
  I do in fact mean .060".  I'm still looking to run a set of DOHC750 rods, which are .060" shorter.  I was wondering if it was possible to mill the jugs down .060" without compromising strength or losing an oil passage or something.  It's also a question of whether I'd need to remove a link from the cam chain.  Ever take that much off an engine before?

I talked to a guy a while back who ran mini sprints with CB750 engines in them (cut the tranny off, ran an external oil pump and a driveshaft back to a 4spd box).  He ran CB900 rods (1.5mm longer) with an .060 spacer under the jugs and a camchain with an extra link.  I'm just wondering if it's possible to go the other direction?  If not I might give 900 rods a try.

I've got a set of the CB900 rods for sale. PM me if any interest.

Oops I see you're going the other direction. Never mind.

Oops, after rereading I see you may be interested, so offer still stands.

So much for speed-reading. 

[ken736cc]

I have a modified cam cover. Send me a PM if you are interested.

[voxonda]

If not, I am highly interested. Sorry for interferring.

Cheers, Rob

[voxonda]

In my opinion, for the street this is bling. For a 1080 or 1000 RC Cobra it's not a bad idea. Extra insurance to help hold down the cam towers due to extra high lift cams. For the strip in a 1080, 1060, 1000 Cobra with the extra high lift cam, most definitely for extra insurance.

Another mod that has been done is to go 1 size larger on the cam tower bolts by tapping the holes and using helicoils. If you stay with the stock size bolts, going with helicoils isn't a bad idea either.   

The thing about reusing cylinder studs is an unknown. How many times were your studs reused/retorqued? What kind of condition are they or will they be once removed? Twisted maybe? I have had my engine apart 3 times and it still has the original studs. It's had the 810 Yoshi kit with the Yoshi Daytona cam and stiff springs in it for 25,000 miles. Yes it has a head gasket leak. How many do not including stock engines?! Next tear down coming soon will have either my 900 Henry Abe kit or the APE 1000 kit and YES it will have HD cylinder studs and bottom end studs. I'm older, wiser, and I can afford this stuff now but this wasn't the case in 1976 when I blew it up.

http://i233.photobucket.com/albums/ee84/RxmanGriff/P1020035.jpg[/img]]

Hey Rxman,

Is it possible to show the inside of the camcover? Am highly interested in finding one, or make one myself.
Thanks in advance.

Regards, Rob

[MCRider]

To JLeather and Rob Voxonda:
here's my reinforced rocker box:

It was built by Les Barker of Little Engine Service in Vancouver WA, in 2000. I said this project got stalled for quite a while.    I look to use it as insurance, my cam will be mild. I did experience having a cam twist in half which is the symptom of cam tower flex. It was a very big bump cam and I was touring with it, pretty stupid.

He said he obtained some templates from RC Engineering or something similar. he charged me $185 which I thought was a steal at the time and worth $300+ now I think. I don't know if he's still in business. He did a lot more work with smaller motors which is where i met him (Vintage Jap MC Club)
To Rob: Here's the underside of it:

Very simple and clean really, just the underside of the threaded lugs that were welded in. If one were to thread the hold down bolts to their furtherst extension, they stick down inside the cover about 1/4 to 3/8in.  I assume they make contact with the tops of the cam towers before that.

[Sam Green Racing]

John, like Jay and Mike said, external hold downs are not needed with the cam you are going to use and if you use the correct springs.
More important is a heavy duty straight plate cam chain and the use of an M3 cam chain adjuster (makes for a quiet motor as well)

Sam.

[754]

If there is enough interest I could make up the bushings for these.
You will need;

a drill press or mill

someone to tig weld them.

the rest is pretty straightforward (can explain it to you), but it would help if we can get a measurement of the welded in bushing, I am thinking it is stepped where it goes into the valvecover and has either 1/4 or 5/16 nc threads

[Terry in Australia]

You'd be better off turning them in your lathe Frank, I'm making mine out of 20mm round stock, stepped down to 18mm as they pass through the valve cover (only because I've got a nice 18mm slot drill to cut the holes in the valve cover) and I'll be using 8 x 1.25mm stainless bolts. If you can get hold of a TIG welder, you should offer a "changeover" service. Cheers, Terry.

[754]

What I meant was anyone doing the project needs ,a  mill or drill and a tig welder. They can make their own bushings or one of us can make a bunch.

I am thinking it is more like 5/8 stock or 16mm, then stepped to 1/2 inch  (or 7/16) for about 1/8 or a bit more. After you get the hole in the valve cover (more on that later) you drill it to say 1/2 or maybe 7/16., then spotface the valve cover till most of the 5/8 cutter makes contact. When you weld the bushing in you use a smaller bolt and washers to draw it tight & square to the valvecover, then weld. After welding spotface the tops again.