|02-13-2013 06:27 AM|
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.
|01-31-2013 04:33 PM|
|cobalt327||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.|
|01-31-2013 07:32 AM|
|gearheadslife||ok then how would you set the core plug depth in the rear of the block.. I'd think that matter (never rebuilt a roller block|
|01-31-2013 06:29 AM|
|cobalt327||The plates are different only in the spacing of the bolt holes that attaches it to the block. The two do not interchange.|
|01-31-2013 12:46 AM|
|gearheadslife||doesn't gm have 2 dfferent design thrust plates.. for the genI sbc|
|01-30-2013 09:48 PM|
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.
|01-30-2013 10:40 AM|
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.
|01-29-2013 01:18 PM|
Still there is no harm in trying different gears to see if a better clearance can be had.
Generally the configurational difference between non roller, roller, roller optioned but flat tappet equipped are:
- Flat tappet blocks have no provisions for a roller i.e. no spider mounting bosses (3), no face machine or drillings for the thrust plate, low height lifter bores, flat face on cam. Thrust is taken between the backside of the cam driven gear and the block face. The cam will always have a fuel pump lobe.
- Roller blocks have three bosses on top of the main oil galley to mount the spider, the block face is machined to accept two mounting bolts for the thrust plate, there is a thrust plate, the lifter bores are raised to provide support for the longer lifter, the lifters are tied in pairs by a gadget called the dog bone, the cam has a stepped face that protudes about 1/4 inch forward of the flat tappet cam so it can pass through the thrust plate, the cam gear is modified in the hub so it can accomodate the thickness of the thrust plate which it now reacts against instead of the block face. The cam may or not have fuel a pump lobe. The push rods are shorter to accomodate the taller roller liftesr.
- Roller provisioned blocks with a flat tappet cam have all the unique provisions for a roller cam but use a standard non roller cam with the flat and short face. This uses standard length flat tappets with the older standard length (longer) push rod. It uses the older timing gear that reacts thrust aganist the block instead of a thrust plate. The cam may or not have a fuel pump lobe.
- The Vortec block used in the L31 Vortec is the same as the preceeding roller blocks whether those blocks had a roller or flat tappet cam. The Vortec block (880) actaully was used in late 1995 production and some 1996 Vans with a flat tappet or roller tappet cam, sheetmetal timing cover, Swirl Port or L31 Vortec heads, with Throttle Body Injection (TBI). Where the L31 in pickups starting with 96 production all used Central Multi-point Fuel Injection, L31 Vortec heads (two versions), a plastic timing cover which drives a unique timing gear and chain set for clearance (narrower gear teeth and chain) because the plastic timing cover accomodates often but not always a built in crank seal and always a crank position sensor.
As you can see where the roller provisioned or equipped and the L31 blocks are concerned there is a lot of interchange between them and they can use the flat tappet cam, lifters and timing set from older Gen I engines when all this stuff comes in a set of equipment. The L31 Vortec plastic timing cover does require a unique narrowed timing set as it uses up space for the crank position sensor. If you're using an L31 Vortec with carb or TBI it's simple back date the engine to use the sheetmetal or even a cast aluminum timing cover from the earlier engines.
|01-29-2013 11:42 AM|
To help w/the diagnosis, the timing set currently being used is SUM-G6601. Application is '85-'99. It says "For factory roller camshaft Gen 1 motors, except 1996 and later Vortec. Will not fit behind stock plastic timing covers."
The timing set that was mentioned as a possible replacement for the Summit timing set is Cloyes p/n 9-3145. Application is '85-'99. Says "For factory roller camshaft motors. Will not fit behind stock plastic timing covers."
The camshaft is a Howards OE roller.
I have heard of double row cam gears requiring the block to be clearanced, and it's common knowledge the plastic timing covers are a problem. I've also heard the steel cover may need to be replaced or use doubled gaskets for clearance, although I've not had that problem on any I've dealt with. But if the retainer plate is being pinched between the cam gear and the step on the nose of the cam, something's just not right (obviously). It seems like measuring the length of the cam nose step, the depth of the bore in the back of the cam gear where the cam sits, and the thickness of the retainer plate should show what's wrong.
|01-29-2013 05:16 AM|
Thanks for the input guys. Sorry took me so long to get back to you Ive been swamped with school and work.
|01-26-2013 12:14 AM|
|DoubleVision||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.|
|01-25-2013 08:57 PM|
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.
|01-25-2013 11:22 AM|
|01-25-2013 10:07 AM|
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.
|01-25-2013 08:50 AM|
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