Okay I'm stumped. This is what I have. I have a 350 block out of a 1991 pickup that was originally flat tappet. It has the provisions for the oem roller setup so I got a oem style roller cam from howards with the stepped nose. (180325-08). I currently do not have the rear cam plug in the block. The cam moves freely back and forth without the timing gear attached. This is the timing set im using Summit Racing® True Roller Timing Sets SUM-G6601 - SummitRacing.com. Its for an OEM roller setup for a NON vortec engine.
I know the last picture is a tad fuzzy but you can see the nose of the cam sticks out about an 1/8". The recess in the timing gear is about an 1/8th" as well.
Here is my problem.... It seems as though when I tighten down the timing gear it sandwiches the thrust plate between and draws the timing gear and cam together and eliminates any thrust clearance I have.
What am I doing wrong.... any ideas?
Thanks for your help everyone!
,Shane
Edit: Also this motor was run for about 50 miles with the clearance issues. Wear can be seen on the thrust plate and thrust surface on the timing gear.
What's it's doing in drawing the gear down to the thrust plate is correct, but the gear should bottom its hub (bolt circle) against the cam snout before it binds on the thrust plate. Some thin shim stock between the cam snout and the gear under the bolts should solve the problem by seating the gear before it clamps the thrust plate between it and the cam.
Is it common to have to install shims to get the thrust clearance correct? would a different timing set maybe fix this? If im pointing blame at the $30 timing set or the $300 cam im leaning towards maybe trying a new timing set. Any ideas?
Or lap the thrust face of the cam gear, but that's already been suggested.
If you decide to change the dimensions of anything, first use a straightedge to check the alignment of the cam gear to the crank gear. Then see if moving the gear forward (using shim stock) or moving it rearward (lapping the cam gear thrust face or lapping the retainer plate) brings the alignment of the two gears closer to perfect.
And yes, I know there's some alignment leeway in the width of the chain vs. the widths of the gears. But if you're going to do anything that will affect the alignment, do it to make it better not worse.
If I were you, I'd remove the retainer plate and inspect the other side where the cam nose contacts, and smooth the surface if its galled. It should show similar evidence of contact if the retainer is acting like the meat in a sandwich. If not, it would suggest that the cam was being pulled rearward by distributor, or pushed from front(wouldn't think so if there is enough timing cover clearance)?
You may want to remove the cam, and install the retainer between the gear and the cam for testing to see if there is adequate clearance. It may not be easy to turn the cam in the block and be certain that any resistance is from the retainer/gear/cam interference alone. Just a thought.
FWIW,
ssmonty
that makes sense. I will pull it apart this weekend and get you some pics of both sides and the cam face and do some measurements and assembly and see what im working with.
I had thought that with your gear bolted on, there was no clearance between the retainer plate and the back (thrust surface) of the cam gear. That would mean there was no "outside force" pushing the cam rearward, instead, there was a problem w/either the depth of the step on the nose of the cam (too short), or the thickness of the gear vis-a-vis the thrust face to the bottom of the bore that the stepped nose of the cam fits (too much), or the thickness of the plate (too thick).
In going over our previous conversation on this, I see you measured the cam retainer plate at 0.100", and the step on the cam nose at 0.260".
That leaves the step of the cam nose 0.160" proud of the retainer.
That means the depth of the cam gear has to be an amount less than 0.160" or there will be no clearance for the thrust surface of the gear to the retainer. I don't recall you giving the depth of the gear when we talked about this earlier.
Or to put it another way, w/the cam out and the retainer on the step and the cam gear bolted to the cam, the plate should be free to turn w/about 0.010"-0.015" clearance.
The face of the block doesn't matter as far as how far forward the face is, the cam will move to compensate because it's free to float fore/aft as needed (within reason, obviously). It should be square, however, and the wear pattern shows yours to be off a slight amount. But as long as there's some clearance between the gear and plate, the squareness being off a couple minutes really doesn't matter on a street build.
One thing I noticed is the galley plug face is flat, just as they are on Vortec blocks. Even so your block is a non vortec, it still could be possible that it will require a vortec type chain. I went and took a look at the face of both my Vortec blocks and they're identical to yours. When I looked at a older 305 block the galley face had the classic high low arrangement. Not saying this will solve the issue, but thought it maybe worth saying.
I wonder if its worth it to see if my machinist has a timing chain for a vortec that I could mock up real quick to check. I have only seen older blocks, vortec blocks and my block and I would definitely agree that mine looks like the vortec one. Idk what GM did differently between the flat tappet, the pre vortec rollers and then the vortec rollers.
Thanks for the input guys. Sorry took me so long to get back to you Ive been swamped with school and work.
Thanks everyone for the input. I am going to my machinists after work to have him look at everything and make sure I am not missing anything. When I explained the issue to him he mentioned just lapping the thrust plate until the correct end play was established but we will see what he says after I show him all the parts.
Today while cleaning up my nephew's engine which is a 1988 350 roller block and it's face is the classic high low arrangement. I'm not sure what year they changed it.
When I did my vortec build years ago Northern Auto Parts sent me a timing chain set in place of the Cloyes "Vortec" set as it was on back order and it was a Milodon double roller unit for OEM roller cam blocks. After installation was when I noticed it was making contact with the block. When I called back Northern the guy says "Says here not for VIN R" which is a Vortec block.
IIRC in this case the plug hasn't been installed yet. It's installed same as a flat tappet block when the time comes. All the fore and aft movement of the cam is controlled by the relationship between the step on the cam nose, the depth of the recess in the cam gear, and the thickness of the retainer plate.
hey everyone, sorry I haven't been on in awhile to update but i have been pretty busy. After talking with my machinist he thinks that between the assembly lubricant and the low temperature it was causing the cam to not move easily. I took it home threw the plate in the parts washer and after letting the shop warm up for a couple hours I ended up with .007" of end play. Thanks for all the input and help everyone. Im glad this turned out not to be as big of a deal as I thought it was going to be.
Thanks
Shane
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Hot Rod Forum
2.2M posts
175.7K members
Since 2001
A forum community dedicated to hot rod owners and enthusiasts. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!