[ho421]

Question. I'd like to replace the PRW stainless roller rockers in my 421 with Harland Sharp rollers. Will they fit under my stock valve covers? I'm using a 5/16" butler VC gasket currently. Thx in advance. Bob

[25stevem]

I have no direct experience with them on Pre 1967 heads, but I would think that as long as your heads are not fitted with longer then stock valves, then you will have adequate clearance.

[JLMounce]

I have the HS 1.5's on my KRE heads and a cheap set of stock style valve covers fit with a standard cork gasket. You may just need a thick or double gasket, depending on the differences in head depth.

[tom s]

WHAT valve covers?Tom

[25stevem]

With the early 20 degree valve inclination heads and stock valve covers it may be a question of how much lift you can run before the push rod end hits the valve cover.

[gpguy]

if this is any help...I put the Harland Sharp 1.6s on my 71 455 with stock chrome covers and thick gaskets and had to use short polylocks as they long ones hit the valve covers.

[ho421]

Originally Posted by tom s

WHAT valve covers?Tom

63 HO valve covers Tom. I have the polylocks now. This was the setup recommended by Dave Bisshop a few years ago when I built my motor. He worked my HO heads and supplied my stump.puller cam

[tom s]

I think it might be tight with 63 covers,the HOs have stacks which is the diff but no taller.The 69-70 stock covers work fine with 660 lift on H&S 1.65s with 5/16 gaskets.Tom

[b-man]

No matter what you’re going to need at the very least some thicker gaskets and quite possibly some thin spacers.

There are some pictures of how well the valve covers cleared the Crower rockers on my 421 HO linked here:

https://forums.maxperformanceinc.com...0&postcount=34

[ho421]

Originally Posted by tom s

I think it might be tight with 63 covers,the HOs have stacks which is the diff but no taller.The 69-70 stock covers work fine with 660 lift on H&S 1.65s with 5/16 gaskets.Tom

Probably why they pushed the PRWs. I suppose the Crowers would be fine? 1.52s

[ho421]

Originally Posted by b-man

No matter what you’re going to need at the very least some thicker gaskets and quite possibly some thin spacers.

There are some pictures of how well the valve covers cleared the Crower rockers on my 421 HO linked here:

https://forums.maxperformanceinc.com...0&postcount=34

Were those the shorter polylocks? Thanks for the reference by the way

[b-man]

Those must have been the same polylocks that came with the rockers, I don’t see any extra polylocks I bought in my list of parts.

[rwfisher]

You may also have issues with an end rocker rubbing the radius of the valve cover. I had to slightly grind my HS rockers on the corners for clearance.

[ho421]

Originally Posted by rwfisher

You may also have issues with an end rocker rubbing the radius of the valve cover. I had to slightly grind my HS rockers on the corners for clearance.

How much did you have to remove.. with 1/2" gasket, ps end rocker is making.contact with the oem ho stack valve covers. Sorta wishing I had gone with crowers at this point

[dhcarguy]

Originally Posted by ho421

Question. I'd like to replace the PRW stainless roller rockers in my 421 with Harland Sharp rollers. Will they fit under my stock valve covers? I'm using a 5/16" butler VC gasket currently. Thx in advance. Bob

I have HS 1.5 rockers on my 66 389 with 5/16 gaskets. I have the stock 65 covers with no issues

[ho421]

Originally Posted by dhcarguy

I have HS 1.5 rockers on my 66 389 with 5/16 gaskets. I have the stock 65 covers with no issues

I have these with 1/2" gaskets and they are making contact

[25stevem]

If it’s the push rod side of one of the end rockers it does not take much metal removal on the rocker to gain the needed clearance.

Pull a rocker cover remove all the oil from each end and then color it with a big marker and then reassemble everything.

Crank the motor a few times and you will then see where the issue is.