Hey Guys,

It has come to my attention that my mysterious timing retard issue is possibly cam walk. I've yet to the pull off the cover and get a dial indicator on the cam to see exactly how much end play there truly is.

The engine is a:
86-95 four bolt mains, roller cam block, 350ci .040" over
Patriot 'Vortec' heads, 2.02"int/1.6"exh valves, 185cc Int runners
Comp XR276HR-10, 26918 springs, Proform 1.6 roller rockers
.535"Int/.544"Exh
224/230 dur @ .050"
110+ as cast 4
Balanced ZZ4 rotating assembly
H345NCP-40 pistons, .004" in the hole @ TDC.
10.7-1 compression
Professional Products Hurricane Plus single plane Int mani
Speed Demon VE 650cfm
Summit billet aluminum distributor, machined to ideal cam/dist gear mesh
125hp wet shot NOS


When I did the Comp cam & Patriot heads a few months back I installed the cam, bolted down the cam retaining plate, used a new single roller chain and just put her back together. Not even giving thought to the camshaft end play, now that I've been daily driving the engine and finally diagnosed a major hesitation under acceleration to an awkward ignition timing retard issue. It finally dawned on me the cam must be walking...

My question is this, I only see two different thicknesses of shims available. One for .031" and a bushing for .150", I don't really have any intention to use a torrington bearing unless it's mandatory. What kind of space should I expect to eat up, so I can order the right parts, should I order a couple .031" shims and one .150" just in case? can these shims be stacked to get the correct end play? These suckers are pricey @ $12.00 each before handling.

Thanks guys, Cheers ~Mykk

 

I've got a cam button you can have nib. What are shims for?

Sometimes I miss those old head-scratchers

 

Thanks, but no thanks. I'm using a plastic vortec L31 timing cover on my SBC. I'm afraid a cam button would put to much stress on the cover. The shims go behind the cam gear, between the cam gear and retainer plate, just to eat up space.

I've got the shims on order, two .031" and one .150". Hopefully they will arrive in time for me to tear it down this weekend.

 

any dyno numbers, speedo vids....

Do you have to run 91 octane full time with that much compression (I'm assuming the patriots are aluminum heads right)?

How to you like the new heads and cam. Any noticable improvements? I was wondering since the vortec's are so torquey off idle is that enough to off-set a bigger cam (the one above is on the big side for a 350 to me) Do you need a stall?

Sorry for all the q's I'm trying to put all the pieces together for a vortec headed 406 sbc build in a 99 2 door tahoe.

 

Mykk have you talked to Comp? They are always great about helping with crap like that. I talked to my bud and we're both at a loss. I do think that even .031 worth of walk would goof up your timing.

But I'd call Comp for sure. If you don't have the right dist gear mesh you'll get metal shavings all over and ruin the gear.

 

Yes I do run 91 pump gas, the heads are iron. I think the patriots are an 'ok' budget performance head. I do like the cam, I do run a 3200 stall. I have not had a chance to race it, I haven't really put my foot into yet until all of these little bugs are resolved.

Here's a short little video:

http://vimeo.com/6503426

I have sent an email off to comp tech, the response I received was very vague and didn't touch on my cam walk issue.

This is pretty much all it is:


"Many engine builders prefer these thrust washers instead of the trick roller bearings because if the roller bearing falls apart, the bearings will end up in the engine. The washers measure roughly 0.030 inch and prevent cam gear wear on the block"
(from Chevy High Performance Magazine)

 

that shim will only prevent the cam gear from eating nto the block. they wont stop cam walk.... what kind of dist gear did you install??? With a roller cam you are supposed to use abronze dist gear. just a thought

 

I would call Comp, not email. The same vagueness your recieved is the same vagueness they got from you. Its always much better to be able to have a back and forth discussion about your issues and you can end up with different ideas or solutions than you thought when you talk it out.

How much end play do you have? It seems as if you dont even know yet, your assuming "the cam must be walking".

 

I pulled the front end of the motor apart, the issue is not cam walk. The camshaft endplay is spot on. I'm glad I can rule that out. The dist gear has is a dead center wear pattern too. However, does this single roller chain appear to have too much slack?



I am really hoping to find this weird ignition timing retard issue.


Do I seem vague to you?

 

Are you using a mechanical or vaccume advance? MSD? Accell? Sounds like its you ignition box or icm