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Old 11-04-2012, 05:50 AM
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sbc thrust plate

This is the first time I have posted a question on this site but really need to know. I'm building a sbc 421 and can't figure out the thrust plate deal. I guess I ordered the wrong one because I had to dremmel out the bolt hole to make it fit. This is my first time installing a factory roller cam.
My question is that I have about .125 forward end play (walk). What is the max end play I can have and is there something I can put on the end of the cam to take it up. I guess that's two question. Any help would make my day. Thanks, confused Charlie.

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Old 11-04-2012, 06:44 AM
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Charlie3030,
I know for certain that there are two types of cam thrust plates with different bolt center dimensions. If it were me I'd probably spring for the
for the other to make sure there is enough support for the bolts, but then again I'm pretty anal about those things. You will probably be ok as long as you make sure to install the cam, and adjust the plate from side to side to get it in the center without any contact with the sides of the cam surface before tightening the bolts, but like I said I'd get the correct one.
As far as front to back end play, it sounds like you may have the wrong timing set. The ones needed for a factory roller cam have a counter bore for the cam face to insert into about 1/8". When installing the timing gear, tighten the cam bolts slowly while turning the cam with the gear to see if it interferes with the block. It ussually contacts the center oil galley boss, and can be clearanced with a grinder. just be carefull not to go too far as to compromise the oil plugs fit.(see pic)
If you get a new timing set you may have to grind on the block for clearance, especially if its a double roller set. after you get the gear to clear you need to try to hang the chain on the gear without installing it on the crank gear to see if it clears as well.
Here are the two part numbers for the retainer plates:
GMP PN 10088128 retainer for 3.62" bolt centers
GMP PN 10168501 retainer for 3.294" bolt centers
Maybe I spoke too soon. I just re-read your post, and realized your making a 421. The plates I'm refering to are for a 1987-1992 factory block with provisions for a roller cam from the factory. I don't believe they made a 400 block with the same provisions, but I've been wrong before.
ssmonty
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Old 11-04-2012, 07:11 AM
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Here is the poor boy solution to your problem

Get a thrust plate from a factory SBC or 4.3 roller cam engine. Cut off the "ears" from the plate and install plate over the front of the roller cam. Install the CORRECT timing gear (small bolt pattern, small center hole) Use three allen or small button head cap screws (hardware store). then install assembly into block.

Take a regular aftermkt SBC thrust button and install it in the front of the timing gear. It will have to go in with the small end towards the cam. The large side will go towards the timing cover. Then trim length, off the big end, till you get proper end clearance. I usually shoot for around .005"

This works on almost all pre roller cam blocks. . I prefer to use the aluminum or nylon thrust buttons over the roller buttons. In this application.

Last edited by BOBCRMAN@aol.com; 11-04-2012 at 07:17 AM.
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Old 11-04-2012, 07:53 AM
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The GM 10088128 thrust plate is for a 4.3L V6 roller cam engine.
The GM 10168501 thrust plate is for a 5.7L V8 roller cam engine.

The camshaft end play should be .004" - .012". No thrust button is required with 1987-1994 GM V8/V6 roller cam blocks.

The correct roller tappet camshaft for GM V8/V6 factory roller blocks has a recess in the front cam bearing journal for the thrust plate whereas the correct roller camshaft for non-factory roller blocks does not have the recess.
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Old 11-04-2012, 09:58 AM
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thrust plate sbc

I have a Dart SHP block and all the rest is Comp Cams. Thank you guy's so much for your replys. Do I really need a cam bottom if I'm using a retainer plate. This is a factory roller cam from Comp.

Us gear heads must stay together, thanks again.
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Old 11-04-2012, 11:37 AM
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If the Dart block is drilled for a thrust plate. You won't need a thrust button. Just measure center to center on the retaining plate holes and get the correct plate. Bolt it in.

If retainer plate is not bolted to block, you need thrust button.
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Old 11-05-2012, 01:31 PM
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Quote:
Originally Posted by charlie3030 View Post
I have a Dart SHP block and all the rest is Comp Cams. Thank you guy's so much for your replys. Do I really need a cam bottom if I'm using a retainer plate. This is a factory roller cam from Comp.

Us gear heads must stay together, thanks again.
X2 on BOBCRMAN comments.

The SHP is intended to stand between the stock OEM style block and the race block using features of both such as the OEM type roller cam combined with priority main oiling of the out and out DART race block.

GM uses several sizes of thrust plates, you have to take your DART thrust plate bolt centers and go to your GM parts dealer to order exactly what's needed.

The GM 10088128 thrust plate 3.662 inch bolt center is for 1988 through 1990 90 degree SBC V8 roller cam engines and some other applications.

The GM 10168501 thrust plate 3.294 inch bolt centers is for 1991- 2000 roller cam engines and some other applications.

GM includes the provisio "measure first" which is to say that these rules aren't that hard and fast. DART just says uses SBC production parts which might be their way of adding "we're not consistent either".

The remainder would be that the timing set also needs to be that which will fit the OEM production roller cam block as well. These use a different thrust dimension on the cam gear to provide the space used up in the thickness of the thrust plate of the OEM roller cam blocks. A roller cam block, the DART SHP included can use a flat tappet cam in which case the thrust plate would not be used and the older flat tappet timing set would be used. You've got to be careful not to be mixing and matching parts between OEM roller cam configurations and those of flat tappet configurations.

Also, the thrust plate must use a round or pan headed fastener, there is not space behind the cam gear for a hex headed bolt, the proper fastener should come with or be purchased from GM parts when getting the thrust plate.

Bogie


You should not have anywhere near .125 forward end play, this needs to be about .005 to .010 inch. This kind of end play indicates something isn't correct and needs to be checked out.
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