Stock cam question

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jestang5

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Dec 17, 2007

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Jan 3, 2009

#1

• Jan 3, 2009

• #1

I swapped a stock 87-93 cam in my stock 86 long block but when I tighten the rocker arms back down, I believe it is hanging the valves open. Motor just free spins when I try to crank it. Anyone ever had this problem? Am I doing something wrong in adjusting the rocker arms? I simply torqued them all down to 20ft-lbs when the respective valve was in its closed position. Any help would be much appreciated here. Thanks.

 

J

jestang5

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Dec 17, 2007

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Jan 4, 2009

#2

• Jan 4, 2009

• #2

Anyone?

 

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Brian@PAR

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Sep 15, 2008

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Phoenix AZ

Jan 4, 2009

#3

• Jan 4, 2009

• #3

Well you may need to start over in setting the rockers. Put the lifter on the base circle and then hand tighten the rocker until you get to zero lash (where the PR will not easily spin with your fingers). Then torque them down but you must get to full torque in 1/2 to 3/4 of a turn. If you have to go further then you'll need shims under the pedestal.

I would put a compression pressure guage on it first. If you're building compression then the valves are not hanging open.

Also, a 180 out distibutor sounds a lot like a free wheeling engine.

 

Maryland Stang

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Aug 21, 2002

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Greenville, NC

Jan 5, 2009

#4

• Jan 5, 2009

• #4

What cam did you take out? Can you pull one of the pushrods out and measure it's total length?

 

J

jestang5

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Dec 17, 2007

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Jan 5, 2009

#5

• Jan 5, 2009

• #5

Brian ... do u know if the 86 model came stock with rocker shims?

Maryland Stang said:

What cam did you take out? Can you pull one of the pushrods out and measure it's total length?

Click to expand...

I was running a tfs head before with the tfs stage 1 cam and different pushrods. I am putting the car back stock now but I didnt have the 86 cam I originally removed so I put in a stock cam out of an 87 mustang and I am using my stock 86 heads, rockers, pushrods, etc. Pushrods measure to be about 6.27" I believe. I measured them yesterday but will recheck when I get home. Thanks for all the help everyone.

 

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Brian@PAR

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Sep 15, 2008

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Phoenix AZ

Jan 5, 2009

#6

• Jan 5, 2009

• #6

jestang5 said:

Brian ... do u know if the 86 model came stock with rocker shims?

Click to expand...

Sorry, I've taken a couple apart but I can't recall. What you are experiancing, if it is too long a push rod, is surprising. The lift difference between an 86 and 87 cam is pretty small so I'd be surprised if the PR's would change much since you are using the original 86 heads.