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Chevy oe roller cam questions.

General engine tech -- Drag Racing to Circle Track

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Bill Chase
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Chevy oe roller cam questions.

Post by Bill Chase » Sat May 02, 2020 9:17 am

When you have proper crank end play, and proper cam end play but the crank gear stands proud of the cam gear by about. 015"

Do you just lightly mill the back of the crank gear?

I checked the radius of the crank gear and compared to the crank. there is no problem there.
The other thing is the thrust plate is brand new, new short block also, so will it just wear in with time?

Also the car is a manual trans so there will be some wear there upon break in.

Am I splitting hairs here, or should I center the cam within the endplay I have, do the same for the crank, then correct any alignment issues by milling the back of the crank gear?

It is a brand new Cloyes hex a just set for factory hydraulic roller cam setups. What would you do in my situation?

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Re: Chevy oe roller cam questions.

Post by BillK » Sat May 02, 2020 12:19 pm

Sounds like you have the wrong timing set. What part number is it ? I dont have number handy but I have always used the Cloys set and never had an issue. Also, are you comparing the faces of the gears or the actual chain alignment ?? I dont know the face of the gears lining up really means anything.
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Re: Chevy oe roller cam questions.

Post by Bill Chase » Sat May 02, 2020 2:13 pm

It is literally the only cloyes hex-a-just part number for 86-96 tpi/lt1 engines.

Cloyes Hex-a-just 9-3145a for factory roller cam with stepped cam face.
The gears where the chain rides are exactly the same thickness.
The cam gear is 0.015 back from the crank gear, I have checked it with endplay back, fore, and centered for crank and cam. And the cranks thrust clearance is right on, the cam end play is a little to the tight side of the spec, but it will definitely wear in, all the parts are brand new, not reconditioned, not used.

Seems my choices are to lap the cam thrust plate slightly, or take a little off the back of the crank gear.

But this brings up the question of how much the thrust end play of the crank will increase upon break in, I could see them both wearing a few thousandths once break in is complete? It is a manual trans so it should wear in slightly?

I have access to a Bridgeport mill at the shop, I have a small assortment of fly cutters and can easily take 5-10 thousandths off the crank gear where it mates to the crank once it is pressed on, as I mentioned I did check the radius of the crank and gear prior to assembly.

Does anyone know what the step in the cam face is supposed to be nominally for a 350 oe roller cam? It is a sadi core, being soft maybe it is machined tight so once break in occurs thrust to the front will increase slightly?

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Re: Chevy oe roller cam questions.

Post by BillK » Sat May 02, 2020 3:04 pm

Bill,
I can measure a few things first thing Monday for you. I have an LT1 sitting on the engine stand right now. It is not going to have a Hex-Adjust, just a stock single roller chain. I would not mess with the cam retaining plate, it is what sets the camshaft end play. Are you sure the crank gear is sitting flush to the crank face ? I have seen some cranks with a pretty big radius and if the radius on the sprocket is not enough it will keep it from seating.
I still am not sure if comparing the sprockets is the right thing to be doing. It would require a bit of rigging but I would try to measure the actual face of the chain when installed compared to the block face. Or maybe measure from the face of the chain to the front of the sprockets to see if you really have an issue.
Like I said, I will gladly measure some things Monday AM. I have several new and used step nose cams and a couple of different timing sets. I have one customer who builds nothing but LT1's and I can ask him if he has ever had an issue. I dont know what timing sets he uses.
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Re: Chevy oe roller cam questions.

Post by racear2865 » Sat May 02, 2020 7:09 pm

Many times per year, we have to make shims to shim bottom gear out or vice versa at the top. You have to watch how the sprockets enter and exit the gears. You will be surprised how awful it can be.
reed

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Re: Chevy oe roller cam questions.

Post by MadBill » Sat May 02, 2020 9:54 pm

Haven't checked for myself, but I have a vague memory of being told that the nominal position of an SBC crank gear face (at least with non-roller cams) is slightly rearward of the cam gear's, to exert a thrust force on the latter to reduce axial movement and the resulting spark scatter. :-k

BTW, if anyone doubts the need for end play control with a roller cam, I once worked on a prototype Olds 307 that had a roller cam but no forward end play location and the spark timing would drift around randomly by +/- 5° or more...
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Re: Chevy oe roller cam questions.

Post by Bill Chase » Sun May 03, 2020 3:59 am

mad Bill, I have the opposite, crank gear is standing proud of the cam gear.

ill pull it and double check the radius of the crank snout and gear.

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Re: Chevy oe roller cam questions.

Post by Bill Chase » Sun May 03, 2020 4:02 am

BillK wrote:
Sat May 02, 2020 3:04 pm
Bill,
I can measure a few things first thing Monday for you. I have an LT1 sitting on the engine stand right now. It is not going to have a Hex-Adjust, just a stock single roller chain. I would not mess with the cam retaining plate, it is what sets the camshaft end play. Are you sure the crank gear is sitting flush to the crank face ? I have seen some cranks with a pretty big radius and if the radius on the sprocket is not enough it will keep it from seating.
I still am not sure if comparing the sprockets is the right thing to be doing. It would require a bit of rigging but I would try to measure the actual face of the chain when installed compared to the block face. Or maybe measure from the face of the chain to the front of the sprockets to see if you really have an issue.
Like I said, I will gladly measure some things Monday AM. I have several new and used step nose cams and a couple of different timing sets. I have one customer who builds nothing but LT1's and I can ask him if he has ever had an issue. I dont know what timing sets he uses.
keep in mind, this is a stroker crank with 1 piece rear seal block. it is a late model roller block, but not an lt1. it is going into a corvette. so it could have the old crank radius from years gone by. i knew to check it. it seemed fine, the crank gear goes flush to the flat face where the radius is. but i could have missed it.

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Re: Chevy oe roller cam questions.

Post by BOOT » Sun May 10, 2020 4:31 pm

BLP use to have cam gear shims/spacers
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Re: Chevy oe roller cam questions.

Post by Bill Chase » Sat May 16, 2020 10:29 am

BOOT wrote:
Sun May 10, 2020 4:31 pm
BLP use to have cam gear shims/spacers
For the stepped nose factory roller cam stuff? Got a link?

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Re: Chevy oe roller cam questions.

Post by MikeB » Sat May 16, 2020 12:37 pm

I have used this GM timing set on several roller cam blocks with zero issues. No, it's not a whiz-bang double roller, but it's not your father's SBC timing set either. And it's good enough for many of the high performance crate engines.

https://www.gmperformancemotor.com/parts/12371043.html

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Re: Chevy oe roller cam questions.

Post by BOOT » Sat May 16, 2020 2:11 pm

Bill Chase wrote:
Sat May 16, 2020 10:29 am
BOOT wrote:
Sun May 10, 2020 4:31 pm
BLP use to have cam gear shims/spacers
For the stepped nose factory roller cam stuff? Got a link?
Doesn't appear they have them in stock anymore, they prob make em in house so if yah call they'd be able to answer if they will work but good question! https://blp.com/cart/index.php?main_pag ... ath=75_161
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Re: Chevy oe roller cam questions.

Post by turbo camino » Sat May 16, 2020 3:56 pm

It would have to be a shim that went between the thrust plate & block to change the cam sprocket location. A shim between the cam nose & sprocket would only increase the cam endplay.
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Re: Chevy oe roller cam questions.

Post by Bill Chase » Sun May 17, 2020 8:19 am

I have a different cam coming, I'll mock it up with the distributor and see if the contact mesh is right, but shimmying the thrust plate would be easy enough. If contact mesh looks good I will just spot face the crank gear

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Re: Chevy oe roller cam questions.

Post by BOOT » Sun May 17, 2020 12:39 pm

turbo camino wrote:
Sat May 16, 2020 3:56 pm
It would have to be a shim that went between the thrust plate & block to change the cam sprocket location. A shim between the cam nose & sprocket would only increase the cam endplay.
I bought one when I ordered some carb stuff a few yrs back cause I was curious and if I rem right it was large enough to go around the cam. But yah between cam & gear to locate cam, between block and gear to line up gears. idk if the shim was for between the cam plate & block or for a torrington thrust bearing type gear. It was cheap n I was curious.
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