tight roller cam

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tight roller cam

Post  glenevans on July 31st 2015, 1:31 am

I have finally started to put my new roller cam, p-51 headed 545 together, but have a problem with installing the cam. This is my first roller cam engine so maybe I am doing it wrong. When I tried to install the cam in block, it would only go in to the middle bearing, then would not go in any more/ was bound up. (.760 lift) I finally got it out by using a dead blow plastic hammer from the rear cam plug. So then we (my 13 year old Carson was helping me) tried my old solid flat tappet cam, and it went right in like all the other cams I have installed.......so is the cam bent somehow???? I got it used from a member on here, but it doesn't look beat up ....????? Any ideas??? thanks - glen

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Re: tight roller cam

Post  supervel45 on July 31st 2015, 2:17 am

Put it on a known flat surface and see what it looks like. It sure sounds bent from what you describe.

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Re: tight roller cam

Post  maverick on July 31st 2015, 7:37 am

More likely it's the cam tunnel. Tight cam bearings are not unheard of in BBF's. Check the bearing bores...you may need to hone a bit. And be sure the cam spins freely on install or bigger problems can result.
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Re: tight roller cam

Post  DaveMcLain on July 31st 2015, 7:52 am

maverick wrote:More likely it's the cam tunnel.  Tight cam bearings are not unheard of in BBF's.  Check the bearing bores...you may need to hone a bit. And be sure the cam spins freely on install or bigger problems can result.

No, most likely it is the roller cam that's the problem. If you mic the journals you will probably find that they are very large when compared to the ones on your flat tappet core. I've seen them about .001 over the top end of the spec. You can put the cam in a lathe and polish the crap out of the journals and get it to work if you're careful.

This is a common problem.

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Re: tight roller cam

Post  dfree383 on July 31st 2015, 9:49 am

Or your can actually put it in a crank grinder and undersize it too.... Its more accurate than polishing if you have it available.
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Re: tight roller cam

Post  rmcomprandy on July 31st 2015, 10:27 am

DaveMcLain wrote:
maverick wrote:More likely it's the cam tunnel.  Tight cam bearings are not unheard of in BBF's.  Check the bearing bores...you may need to hone a bit. And be sure the cam spins freely on install or bigger problems can result.

No, most likely it is the roller cam that's the problem.  If you mic the journals you will probably find that they are very large when compared to the ones on your flat tappet core.  I've seen them about .001 over the top end of the spec.  You can put the cam in a lathe and polish the crap out of the journals and get it to work if you're careful.  

This is a common problem.

YEP ... for some reason, some new billet roller camshafts come through with as much as .0008" over the HIGH limit ... I have seen this at least 20 times.. This and being bent more than .003" are not unusual.

I happen to know a crankshaft grinder who has taken a thou off many cam main journals for me.

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Re: tight roller cam

Post  glenevans on July 31st 2015, 10:48 am

Thanks for the ideas, I will check the journals and roll it on the table.

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Re: tight roller cam

Post  glenevans on July 31st 2015, 12:11 pm

Well on my "highly accurate" harbor freight caliper, they both seem to be 2.123 journal diameter, but I don't have machinist quality tools so will have to get it measured at the machine shop to get definite size difference.

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Re: tight roller cam

Post  maverick on July 31st 2015, 12:40 pm

I'll bow to the masters here. I spoke from personal experience several years ago. My problem was the tunnel. Glad I heard about the oversize cam deals. I'll keep an eye out for it. Cool
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Re: tight roller cam

Post  gt350hr on July 31st 2015, 1:11 pm

The 523 I just finished for myself was fine with a Comp hyd roller core. But my 302 RDI block ( with common size needle cam bearings) was tight. i did like dfree suggested and had my cam grinder grind the journals .001. That did the trick and the cam spins freely. One well known aluminum block Ford builder said not to worry that a little tight cold was ok , but I couldn't do it. A babbit bearing can never be run tight , failure will be the result for sure.

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Re: tight roller cam

Post  cool40 on July 31st 2015, 2:19 pm

Quality imported products ! Rolling Eyes
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Re: tight roller cam

Post  gt350hr on July 31st 2015, 4:49 pm

cool40 wrote:Quality imported products ! Rolling Eyes

?? what would be imported? Not the cam core or cam bearings .

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Re: tight roller cam

Post  Lem Evans on July 31st 2015, 5:34 pm

glenevans wrote:Well on my "highly accurate" harbor freight caliper, they both seem to be 2.123 journal diameter, but I don't have machinist quality tools so will have to get it measured at the machine shop to get definite size difference.  


2.1248" = high side
2.1238" = low side

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Re: tight roller cam

Post  glenevans on July 31st 2015, 5:46 pm

Cam is in !!!!!! I took it to machine shop and they honed the journals with a polishing belt to the same size as my flat tappet cam and now it goes right in !!! Thanks for the help guys, much appreciated !!!!!!!

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Re: tight roller cam

Post  Lem Evans on July 31st 2015, 7:34 pm

1] maverick is correct...it can be a small housing bore but, even when they are it's one or two that are.

2] Randy and Dave are correct that a given cam can have over the high side journals. But, what bites most people's ass is that most  are ~ at the high side at the journal & if the block has a tunnel that is at the low side it could be a sad deal. Polishing the journal even .0003" can made a deal work.

3] Randy also mentioned bent/run out. ...It should be checked. He said you may see .003"....which you could.... .0015" seems to be what one would have to live with.

4] If you have to install the cam with a hammer...STOP. If you are doing an engine with big roller springs and the cam with light oil and it does not spin like it's on a roller bearing please rethink the deal.

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Re: tight roller cam

Post  glenevans on August 1st 2015, 1:14 am

It spins very freely now, we got it stuck when trying to install just by pushing/twisting. Thanks again for all the help Smile

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