Time for me to address the 800lb Gorilla in the room.(Engine knock thread) REVIVED!

[slabghost]

question- Has anyone measured the depth of the combustion chambers in the 1000, 1100, and 1200 heads? Specifically the distance from the head face to uppermost valve edge? If they are the same I think that would assure adequate valve clearance.

 

[dan filipi]

question- Has anyone measured the depth of the combustion chambers in the 1000, 1100, and 1200 heads? Specifically the distance from the head face to uppermost valve edge? If they are the same I think that would assure adequate valve clearance.

I haven't measured them but I've run mine with 1100 heads and early 1000 cam and run it past 8 grand quite often and never took out any valves.

Keep in mind I have run mine for several thousand miles on a early 1000 cam in the right side I didn't know I had.
That to me proves at least the early cams work in an 1100.

The 1200 head design is different and the piston notch for the valves is smaller so there is a good possibility of interference though I'm speculating at this point.

 

[dan filipi]

Joe I measured a 1200 intake valve diameter against an 1100 intake and that IS 3 mm smaller. Same for the intake port itself at the carb bolts.

Could that be the 3mm your talking about?

 

[slabghost]

I haven't measured them but I've run mine with 1100 heads and early 1000 cam and run it past 8 grand quite often and never took out any valves.

Keep in mind I have run mine for several thousand miles on a early 1000 cam in the right side I didn't know I had.
That to me proves at least the early cams work in an 1100.

That reassures me a lot. I just bought a pair of 1000 cams for my 1100. :yahoo: :thanks:

 

[joedrum]

im sorry guys ....dan your right the lift is almost the same ....and yes your probably right dan 3mm was me mixing the figures from one place to my head and then post and it all changes ....just like my post about the exhast vavle being smaller when it was the intake valve sorry guys ....

but this i do know the 75-77 1000piston cutout is deeper than 78 and later yrs .....give me a day or two and iwill know exactly how close it is......im just saying with bad springs could maybe float over the top and might be a problem

its just my opinion but springs need to be address when using these cams for confidense and complete throughal mod..... :mrgreen:

 

[scdmarx]

im just saying with bad springs could maybe float over the top and might be a problem

its just my opinion but springs need to be address when using these cams for confidense and complete throughal mod..... :mrgreen:

I gotta back ya on this one, Joe. This thread having come this far, I don't think I'd feel comfortable installing a hotter cam without a NEW set of springs. And if yer go'n that far, might as well take a look at the valve stems and guides, too.

Dan, since you've already been running a 1000 cam on one side with no problems, (that's great news) just for grins and giggles, you outta put some play doe, or silly puddy, or something on top of a piston, bolt the head back on and roll it through one time, remove the head and measure just how much clearance there really is left between the piston top and the dent the valve left in the play doe. You know, just to see it with your eyes.

 

[dan filipi]

I agree new springs are a must.

After I try out the 1200 cams I have on the way I'll decide which grind I'm going to use.

These early 1000 cams are nice in 5k+ rpm range but less low end torque concerns me.
I didn't like how it struggled that hill on the test ride today.

 

[scdmarx]

If you go with the 1000's, I wonder if it would be possible for the machine shop to grind them about 2 or 4 degrees advanced when they're doing the work? That would move the whole power band farther towards the low end.

 

[joedrum]

im going to test fit a 1000 and cam on a 1100 short block i have ....and find out how much clearence were talking about here when using 75-771000 cams.... :mrgreen:

 

[dan filipi]

If you go with the 1000's, I wonder if it would be possible for the machine shop to grind them about 2 or 4 degrees advanced when they're doing the work? That would move the whole power band farther towards the low end.

Just trying to understand what you mean,
Would that be like moving the belt a tooth, or maybe like half a tooth?

 

[joedrum]

hes talking about them grinding to new specs ....dont even think about one thooth off with these cams ....these cams are the most likely piston hitters with there longest open time of all the cams oh2: :mrgreen:

 

[dan filipi]

My question was looking for an example Joe, of course you don't want to move a tooth off.

 

[slabghost]

Probably safer and easier to adjust ignition timing advance.

 

[dan filipi]

I'd like to set the record straight about the whole aspect of cam lift, duration and degree at which all of this takes place and the risk (if any)
of valve interference if that's possible with the information we have.

Unfortunately Clymer is very well known for wrong information but the GL1000 service manual does also list this information.
Both are in the Gallery.

Since ALL years opening of the intake happens at 5 degrees BTDC,
and ALL years closing of the exhaust valve is 5 degrees ATDC,
AND the lift is virtually the same among all years 1000 and 1100,
(Clymer and the service manual both say the same at 5 degrees so I think we can be pretty sure this is correct)
I don't believe there is ANY risk of valve heads bumping the piston if I'm understanding this right
as long as the valve spring is keeping the valve under control.

If that valve floats then all bets are off.

 

[dan filipi]

Probably safer and easier to adjust ignition timing advance.

I agree.
If these were not interference engines, lift, timing, and all this would be a non issue.
Maybe with new springs and cams the valve would be better controlled but since we know the follower is floating off the cam the risks are high.
The unknown is how much room do we have to play with.

We already know that one tooth off on the belt may not damage a valve, I've done it myself intentionally to see but I didn't ride it or run up the rpms.

 

[scdmarx]

2 - 4 degrees is nowhere near a tooth off. This is usually accomplished with a bushing kit. On the back of the cam gear where the alignment dowel from the camshaft goes, you would drill that hole to accept a bushing. The bushings are offset. You can use a 2 degree bushing, or a 4 degree bushing, etc. They can be installed to advance or retard, depending on what it is you're wanting to do. I really doubt there happens to be a bushing kit available for an old GW motor, and figured if these cams offer desireable results, maybe the shop could do a custom grind, to tune the cam timing. I don't know, you'd have to talk to them when you're gonna get the work done. Adjusting ignition timing serves a whole different purpose.

 

[joedrum]

those specs you quoted are where the exhast closes and intake opens ....and what it means is there is a 10 degree overlap where both valves are open at the same time the duration lenath would be 50 degrees past ABDC ...after bottom dead center for 75-77 cams and then less on 1100,1200,78-79 1000 ...with the 78-79 1000 cams having the shortess open time....the longer the duration the closer the piston gets to it during its stroke.... :mrgreen:

 

[dan filipi]

The 1200 cams came in and I put in the left side.

As before the knock is gone on the left side, still loud on the right.

I have to work myself up to swapping the right cam, a lot has to come off because the alternator crank pulley is in the way to get the inner belt cover off which means the radiator has to come out to put the impact on it, do the swap then put it all back together :fiddle:

The buzz in the bars is back and throttle response is slower than with the 1000 cams but it's the smoothest and quietest I've ever heard this engine run.

 

[slabghost]

Seems like you might have the cure once you get the right side done. Well you may still need to fine tune as far as valve clearances and ignition timing.

 

[dan filipi]

My last discovery finds that a 1200 right cam is indexed differently than the 1000 and 1100 right cam which causes compression readings up over 200 lbs. so testing with a 1200 cam aint gonna happen. :crying:

This is a major disappointment in my quest to find this knock.

Wah!
Time to eat some of Santa's cookies.