Prototype Adjustable timing chain set

[jayb]

The pictures below are the top gear of a new adjustable timing chain set, being developed by Survival Motorsports.  At the PRI show Barry and I hounded Cloyes about doing something like this for the FE (Cloyes makes these already for other engines), in light of the availability of my two piece timing cover.  But Cloyes has been kind of moving slow, so Barry has been taking matters into his own hands.  Just to give them the basic idea and a prototype product, he has taken two of the top gears from one of the Cloyes premium sets, and machined them to make a single, adjustable top gear.  This is really going to be a cool product:







There is a +/- 10 degree range of adjustment on this gear, and it will come with the premium roller chain, making it a top end setup.  I'm not privy to all the arrangements Barry has with Cloyes, but my guess is that if they don't make this available soon, Barry will probably manufacture them himself. 

I can't wait to try one of these out on the next engine...

[ToddK]

Thanks to guys like you Jay, and Barry, things just keep getting better in the FE world. Well done.

[My427stang]

I like it!

[cjshaker]

Now this is what I was waiting on for the timing cover! It's the perfect combo. Simple, yet effective, and no need to mess with taking a gear or the chain off. I wonder if Cloyes has had any issues of movement with big cams and stiff springs? They probably won't bother making them until AFTER Barry does, if he does.

[plovett]

That looks really cool.  I hope to hear more about it when it's ready for market.  Looking forward to your test results on the prototype as well, Jay.

paulie

[KMcCullah]

I like it! From the looks of the machined finishes I'd say those sprockets are pretty hard. Since this is a new deal, how about adding an eccentric stud for gnats-ass adjusting? Turn the hole next to the timing dot into an up and down slot. Add a hole to the hub. Make a drop in eccentric stud with a 3/16 broach for a 3/16 allen wrench. Or start with 3/4 hex steel maybe... Pull the stud out after adjusting. Or make it integral maybe...

[1968galaxie]

Very cool!

Now we need a removable timing cover to go with the adjustable gear.

Cheers

[ScotiaFE]

Very cool!

Now we need a removable timing cover to go with the adjustable gear.

Cheers

Your joking, right.

[Barry_R]

I like it! From the looks of the machined finishes I'd say those sprockets are pretty hard. Since this is a new deal, how about adding an eccentric stud for gnats-ass adjusting? Turn the hole next to the timing dot into an up and down slot. Add a hole to the hub. Make a drop in eccentric stud with a 3/16 broach for a 3/16 allen wrench. Or start with 3/4 hex steel maybe... Pull the stud out after adjusting. Or make it integral maybe...

The sprockets are hard as all - you know...

Right now I am waiting on some studs to do a proper assembly.  We don't really have the "legal" amount of thread engagement on the rear hub but is enough to work.  In production I think we can thin the front sprocket some to gain an extra thread or two for a better piece.  We just barely have clearance in the back for the thrust plate mounting bolts, and just barely enough in front for a fuel pump eccentric and arm to clear.  But they DO clear....  Details....

Tried moving the cam with an eccentric on a Chevy hex-a-djust.  Not real smooth or easy on an assembled engine, although it works without the valvetrain installed.  On the other hand you just loosen the six fasteners a touch on an assembled engine and use the damper bolt to rock the engine - the cam stays in position and it happens almost embarrassingly easy.

Gotta be careful about piston to valve clearance when making big changes in cam advance.  It changes a LOT.  A real LOT.  I know this because....

[Lenz]

Very cool!

Now we need a removable timing cover to go with the adjustable gear.

Cheers

Your joking, right.

When worked out, this cam gear and Jay's covers will sell each other.  I see a kit with both right down to seals and gaskets, everything you'd need to complete the process.  Well done .  Cloyes can sit this one out, yes?

[Drew Pojedinec]

Not trying to be a doubter....
but do you think that 6 bolts in a large groove like that will hold timing over a few years and thousands of miles?

I'd be somewhat paranoid of the gear sliding a little bit over time.

Otherwise, awesome idea.  I love the idea of having a certain cam timing to drive to the track with and sliding the timing for a few runs at the track

[shady]

I'd imagine the most stress on it is when the starter is engaged. don't see a problem with it slipping, especially with a roller cam. I like it the way it is, easy to adj. no buttons, keys, eccentrics. KISS.

[Barry_R]

I had the same concerns a few years ago.  The exact same setup works on most every belt drive I've worked on - - you see them on Comp and Pro Stock cars.  I don't think there would be a problem on street use.

[Joe-JDC]

I know it is work, but what would be the possibility of drilling a set screw hole for each of the timing marks around the perimeter of the gear.  If the holes were spaced around the perimeter, the balance would not be affected, and no two holes would line up with a degree mark. Just an added safety by the set screw going through both halves and locking the gear halves in position.  Joe-JDC

[cjshaker]

Gotta be careful about piston to valve clearance when making big changes in cam advance.  It changes a LOT.  A real LOT.  I know this because....

Checking the clearance from one extreme to the other during mock-up would be a wise choice and eliminate any questions of how far is too far.

I wouldn't guess balance would be an issue unless extreme weight was added. Since it's half engine speed, so close to center and having the bearing immediately behind it, not to mention the harmonics that the springs/lobes cause, I'm guessing that it would be a non-issue.