Switching rockers, unknown to Scat 1.25

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Switching rockers, unknown to Scat 1.25

Post by Leatherneck » Thu Jun 01, 2017 8:51 pm

I am switching Rockers from an unknown to Scat 1.25 well it seems that my pushrods are to long. Is there a way to check correct pushrod length without taking apart the stinking engine?

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Re: Switching rockers, unknown to Scat 1.25

Post by 66brm » Fri Jun 02, 2017 7:18 am

Just get an adjustable push rod and use that to determine the correct length needed for your setup, no need to strip the engine down

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Re: Switching rockers, unknown to Scat 1.25

Post by Piledriver » Fri Jun 02, 2017 9:45 am

In a lot of cases it helps the rocker geometry to shim under the rocker mounts.
They sell kits for this with shims of various thicknesses for correcting rocker geometry.

You may find it gets you in the proper adjustment range...
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Re: Switching rockers, unknown to Scat 1.25

Post by Leatherneck » Fri Jun 02, 2017 7:52 pm

Thanks for the info guys, If I get rid of shims and make new pushrods I shouldn't need shims if done correctly right?

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Re: Switching rockers, unknown to Scat 1.25

Post by Piledriver » Fri Jun 02, 2017 8:55 pm

Leatherneck wrote:
Fri Jun 02, 2017 7:52 pm
Thanks for the info guys, If I get rid of shims and make new pushrods I shouldn't need shims if done correctly right?
MmmmNo.
Search for "rocker geometry".

Non trivial, but not hard to do, just time consuming.

You need to do that first to find the best fit shim stack and pushrod length, THEN make up the new pushrods.

At least if you want your valve guides to last.

If these are the stock type 1.25s the Porsche style swivel feet work well, but change the geometry.
They are more forgiving as to guide wear, available in 8/9/10mm thread depending on the rocker.
The "real" Porsche adjusters only come in 8mm, but for the cost of one of those you can get a set of the Bugpacks, which at least used to be made in the US.
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Re: Switching rockers, unknown to Scat 1.25

Post by Leatherneck » Fri Jun 02, 2017 9:42 pm

Ok, I'll start all over again with new rocker geometry. Thanks!

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Re: Switching rockers, unknown to Scat 1.25

Post by Leatherneck » Wed Jun 28, 2017 8:10 pm

Ok, I am back at this. So I have stock lifters with elaphant foot adjusters, I am installing Scat 1.25. These have lash caps, with lash caps installed I have not pushrod play at all, with lash cap removed I can adjust lifters. Do I have to use the Lash caps?

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Re: Switching rockers, unknown to Scat 1.25

Post by Piledriver » Wed Jun 28, 2017 9:02 pm

The rocker geometry with the elephants foot is completely different than with the finger style rocker.
I would run the lash caps, as the finger style rockers tend to chew the ends of the valves.
(They usually do no favors to the guides, either)
Put some shims under the rocker stands to get some adjustment and see where you are.
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Re: Switching rockers, unknown to Scat 1.25

Post by Marc » Wed Jun 28, 2017 9:21 pm

Scat offers both their "Pro Street 707" (P/N 20188S, ~$125 a set including "solid" shafts) rockers which are similar to stock 1.1:1s and their "Pro-Comp 765" (P/N 20196, ~$230) that are the "finger" style with the adjuster at the pushrod end....so you need to be more specific than just saying you have "Scat 1.25s".

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Re: Switching rockers, unknown to Scat 1.25

Post by Leatherneck » Wed Jun 28, 2017 10:31 pm

Pro-Comp 765" that are the "finger" style with the adjuster at the push rod end

Put shims under, got adjustment but it made the geometry hit high on the valve.

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Re: Switching rockers, unknown to Scat 1.25

Post by Piledriver » Thu Jun 29, 2017 2:06 am

Leatherneck wrote:
Wed Jun 28, 2017 10:31 pm
Pro-Comp 765" that are the "finger" style with the adjuster at the push rod end

Put shims under, got adjustment but it made the geometry hit high on the valve.
That's less important than what it does over the full stroke.
Those have a big radiused contact patch that can do ~anything depending on where you put it, including having the valve tip dig into it. The larger area, harder lash caps reduce the possibility...

I tried to use some generic 1.4s like that awhile back on a WBX, ended up relieving where the adjuster screwd in quite a bit to get reasonable geometry. but those were WBX head etc so not quite T1.

Ended up digging up some ancient factory T1 1.1s and put 911-style adjusters in it, that can be made to work right.

I have considered taking the TIG and a mill to a set to make high ratio stock-style rockers that actually work properly..
I freely admit I have little experience making the "hipo" T1 rocker setups work, but the one time I really tried I failed.
OTOH I expect >200K miles out of a rebuild. YMMV.
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Re: Switching rockers, unknown to Scat 1.25

Post by Leatherneck » Sun Jul 02, 2017 4:14 pm

Well I installed them, started it up and ran for a bit, went to the back and there was oil underneath both covers, the rockers are hitting the covers and lifting them up each stroke. GGGGRRRRRRRR>

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Re: Switching rockers, unknown to Scat 1.25

Post by Piledriver » Sun Jul 02, 2017 5:08 pm

(Ball Peen) Hammer time...

They also make taller aluminum clip on valve covers/bails for T1s that work OK.
(only use contact cement to secure the gasket, RTV ends up in the oil pickup)

Not a fan of the bolt ons, they tend to leak no matter what you do at the through bolts, plus the attaching hardware is made from recycled bean cans.

They can be made to work but it required finding or making cap nuts with integrated oring seals.
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Re: Switching rockers, unknown to Scat 1.25

Post by Ol'fogasaurus » Sun Jul 02, 2017 5:21 pm

I have had good luck with my cast AL bolt on valve covers over the years but a lot of people just do not like them. The seals did give me a pain once but I found an ersatz solution to that which, so far, has held well. If interested...

VW clip on valve covers are either a yes or a no with most people; I have had bad luck with those but I didn't spend a lot of time making sure the contact area was flat and straight either.

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Re: Switching rockers, unknown to Scat 1.25

Post by Piledriver » Sun Jul 02, 2017 5:31 pm

Ol'fogasaurus wrote:
Sun Jul 02, 2017 5:21 pm
I have had good luck with my cast AL bolt on valve covers over the years but a lot of people just do not like them. The seals did give me a pain once but I found an ersatz solution to that which, so far, has held well. If interested...

VW clip on valve covers are either a yes or a no with most people; I have had bad luck with those but I didn't spend a lot of time making sure the contact area was flat and straight either.

What's your solution for the bolt on covers?
Last time I cured a leak in a set I used 8mm cap nuts with orings underneath (made that way), and put a stud in to inside nut. IIRC I had 5/16 and drilled/installed 8mm x 1.25" helicoils as I coudn't find SS metric sealing nuts at the time.

Some of the covers come with mixed metric/SAE threads with SAE for the hold down, YMMV.
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