Cam thrust button

[Heatseeker]

I'm done degreeing the cam and I'm setting up to check cam end play. I go to install the cast aluminum timing cover(which was machined in the button area previously) and it won't sit flush to the block. The cam thrust button is too tall. Like an 1/8". Using a straight edge, it appears that the srockets are in properly aligned. What should I do? Machine the button down?
The timing set is a Manley that came with the Torrington bearing behind the cam sprocket and the front thrust bearing.
Help!

[Blown 472]

Maybe the rear freeze plug is in too deep??? and pushing the cam forward?? hell I dont know I work on ferds.

[Heatseeker]

472, I haven't put the plug into the back of the block yet. I was going to put the indicator on that end of the cam to check the end play and then install the plug.
Thanks though.

[Fiat48]

If the cam and crank sprocket are aligned, then evidently this type of chain setup doesn't require machining the block to accomodate the thrust washer. If that is the case, then machine the thrust button down. I do know there is more than one length of thrust button available, long and short.
On another note: A racer has just contacted me and said his Cloyes timing chain is actually broken, the motor destroyed. Never heard of such a situation. I'll go look at whats left of the motor tonight and try to determine the cause.

[Infomaniac]

The rod came up and stopped the cam. Broke the timing set.

[Heatseeker]

Looking at the original timing cover on the old engine, I noticed that the cover has a bubble in it, at the center of the cam sprocket. This cast cover I'm using is flat. I think I've figured out how much to machine off of the button. I'm going to make a dummy first, so I don't cut the original down too far.
Thanks for the replies, I'll let you know how it turns out.

[Fiat48]

Infomaniac:
The rod came up and stopped the cam. Broke the timing set. Pretty accurate diagnosis from 2000 miles away. Next time I won't give you so much "Infomation". :D Looks like #5 and or #6 rod bearing spun, rod broke, so much damage it's hard to tell what went first. But it's obvious the chain breaking was after the fact. I have no rod breaking experience as we all know I change them one run before they break. :rolleyes:
[ April 14, 2003, 11:07 PM: Message edited by: Fiat48 ]

[wfodude]

Hey john...Fiat is correct there are 2 different length buttons in a needle thrust assy. I had to machine mine down to fit also. It was no problem and still works perfectly.You can also get the solid aluminum button and machining them is simple.Put the gasket and cover on it and measure how far open it is with a feeler gauge then cut appropriately.you have to be careful to keep it even and square. take little cuts and check it several times as you go. You can do it in your garage with simple tools ...a lathe makes it much easier.

[Blown 472]

I was just reading about this last night in my Smokey Yunick book, he makes up some deal on the back of the water pump to push agianst the timming cover, said something like .002 to .006"
clearance tween the cam and the cover, when the cam moves around it throws the timming all over the place.

[Heatseeker]

WFO, Figures I got the long button assy! Just my dumb luck. I kind of figured I didn't have a choice but to machine it down. I just made a dummy to get an accurate reading. That way I don't trash the supplied piece. I'm getting .020" with the dummy.
Blown, I know why Smokey reienforces the cover. I have a cast aluminum cover and I can get .003" deflection by just leaning on the back end of the cam.
What do you guys set the end play at?

[Fiat48]

No more than .010.

[Heatseeker]

Thanks Fiat!
I'll turn down the button tonight at work.

[wfodude]

When I got done with mine I had .004 clearance...keeps things nice and straight as well as your timing rock solid

[Heatseeker]

Well, I shortened the button, first by turning it down close to finished size and then finished it with a surface grinder. I'm getting about .0025 without any real pressure on the cam. If I give it a light tweak, I can squeeze .004 out of it.
Too tight, or just right?
Thanks to all you guys. Without you and this board, I'd be freakin' lost on this rebuild!!! It's nothing like throwing together a small block for some shitbox that I'm forced to drive around in.
This one really matters!!!

[TIMINATOR]

The cam thrust is only important that it doesn't wear out the sides of the chain and sprockets or that the chain doesn't hit the front cover,if it is too excessive it can cause small changes in the ignition timing because the distributor and cam gears are ground at an angle and as the cam walks back and forth it advances and retards the timing at idle and LOW engine speeds ONLY. Once the engine rpm gets above about 1500 rpm, the oil pump creates enough drag that it keeps the cam pulled to the rear of the block. If your button clearance is too tight, the cam gear is forced into the block and will cause excessive wear there. Notice that when the engine is idling, the cam and button will walk back and forth slightly and when it moves toward and touches the timing cover it makes a whirring noise,with open exhaust you probably won't hear it. It is normal and harmless and once again, when the rpm climbs,the noise disappears. We build and run LOTSA roller motors! Hope that explains it!

[wfodude]

I know its too late John but when I did mine I machined a small groove from the cam bearing housing to the front of the block...it fed pressurized oil to the back of the timing gear...no wear baby.. BBC are notorious for the lifter bores being out of whack. Sometimes they will create a tremendous force forward ..other times it will push the cam into the block wearing it away....My cloyes set had a needle bearing on the back as well as my needle thrust bearing.The groove on mine just kept the needle well lubed but on others without the needle bearing it really seems to help keep the wear down.I'll do the same on my new summer bros set as well...

[Heatseeker]

WFO, my timing set is a Manley. It has the bearing behind the cam sprocket also. Where did you put the oil groove exactly It seems like the valley drains right above the cam would provide plenty of oil washing over that bearing. But I'd like to see exactly wht you did. It's never too late...At least not until the engine goes in!

[wfodude]

well I figure acceleration would push that oil back.I also have my valley screened which would slow the return somewhat.Under the cam bearing I machined a small groove from the oil hole to the front of the block.when the cam bearing is in you cant even tell its there.I figure I want my stuff built for overkill.cover my bases before they're loaded so to speak.

[Heatseeker]

Oohh, under the cam bearing. You're right, it's too late.
What about a pin sized hole in one of the front galley plugs? wouldn't that ensure a steady flow of oil to that bearing too?
And what do you mean about acceleration throwing the oil back, away from the valley drains? Aren't you running a V-drive? :D :D :D

[wfodude]

On hydraulic lifter motors that used to be a GM applied fix. The lifters would lock air in the galley and not pump up. Yes a teenie tiny hole would put a nice spray in there to keep things well lubed and cooled.I used to do it on all my rebuilds in our shop on small blocks too...Hey has Ric given you a ride yet????

[wfodude]

Oh yeah...when I first built this thing it was in a brendella tunnel as a jet. The one now known as the black bear racing black mamba...One hell of a ride...Surprised a lotta v-drives at CFW in that time...

[Heatseeker]

No ride in your former hydro yet! Ric was busy last weekend with something, and it was raining anyway. This weekend, he's got Easter plans. Next weekend, he's off to Nascar in Fontana(without me this time!Bastard!!!)I'm hoping for the weekend after that!!!

[wfodude]

Oh yeah...I got DTD awesome thanks so much...My little puppy was a tad over 1300 hp...I like it...