Adjustable rocker arms needed

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Oct 12, 2011 | 08:20 PM

dbculprit

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Adjustable rocker arms needed

I am work on a 1985 4.9L. I have larger valve in the head 1.84 intake and 1,60 exhaust the problem I am having is I need adjustable rocker arms because of the longer length of tht new valves. Any suggestions on which way is best to do this without spending another $350 on the head. Comp cams offers alum rocker for about $350 then I need guide plates and screw in studs etc...

Oct 12, 2011 | 08:53 PM

f100jim

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If the new valves are longer, you will need longer pushrods to correct the valvetrain geometry in addition to the adjustable rocker arms.

Oct 12, 2011 | 09:30 PM

dbculprit

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I am not to sure how longer push ros will help me. that would mean that the rocker arms would be even farther off the head because both the valve stem and now the push rod are longer. I read that someone used 390 pistons in a inline six. I am looking for a short cut like that for my rocker arms along with any "learn from my mistakes" type information. Thank you for the reply.

Oct 13, 2011 | 08:30 AM

f100jim

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If your valve stems are longer, you need longer push rods to get the correct rocker arm geometry. Yes, that moves the rocker arms even further up away from the head, and yes, they need to be adjustable.

If the valve stems are not TOO much longer, AND you are using a cam with stock or near stock lift, you MIGHT be able to get away with the stock push rods by simply using adjustable rocker arms. But, you would need to put it all together and turn the engine over by hand and check to make sure you don't run into problems with the rocker arm angle and interference between parts.

As to which adjustable rocker arms to use, it will depend on which head you have, or more precisely, which type of rocker arm mounting your head has.

Oct 14, 2011 | 05:47 PM

F-250 restorer

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From: Near Los Angeles

First of all, I hesitate because so many people don't want to hear what they are being told, and I think you are one of them, but I will continue anyway with hope that it might save you a bit of grief.

I installed the sbc 1.94" oversize valves. They were .095" longer than oe ford valves. That was the beginning of my troubles. Having adjustable rockers is not going to solve your problem. If I were you I would contact a company called S.I.valves, if they are still in buss. They make the 1.94 and 1.60 valves in oe ford length. Maybe they have or can make a set of the diameter you need.

BTW, the guy that said you need longer p.rods was right. Crane makes them. If you think you will find a cheap, easy fix, think about how quickly those rockers are moving on the freeway. When you play with the oe geometry things tend to fly loose. Usually when they fly it is like a little gernade in your engine--not pretty. And definately not cheap or easy to fix.

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9; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} </style> <![endif]--> A pedestal mount 300 head can use stud mount rockers if you use a pushrod guidplate conversion kit. I have intsalled it on my 90 cyl head and it all works just fine. Crane part number 36655-16 will give you 3/8 studs and guideplate for 5/16 pushrods. If you go this route hardened pushrods are not required becuse the kit has nylon inserts in the guidplates. I had to mix a couple of kits on mine cause I needed 7/16 studs for BBC rockers I already had. It is best for long life of the nylon inserts if you polish the pushrods to make sure there are no burrs on them. This is easy to do in a drill.
This conversion kit will also make your valvtrain adjustable.

Good luck.