[joes455]

Purchased a set of yella Terra 1.65 shaft rockers a while ago and would like to know if it's possible to shift the pushrod over .090 a little less or more give or take to straighten out port at buldge.Any good machinist out there?

[steve25]

What heads do you have and what do they flow?

I went to Terra's web site and I don't even see where they offer a shaft mounted rocker system for a pontiac unless I missed it!

[Steve C.]

This will not be a specific answer. However if this involves the Edelbrock Performer round port heads I can report that years ago I bought a set of semi-machined heads with no intake pushrod holes. This for the purpose of moving the hole over to remove the pushrod bulge. Not a 'wide-port' design, but moved over only enough to completely eliminate the pushrod bulge, thus a straight port wall. I obtained, and still have on hand, detailed drawings with dimensions that point out the centerline for the placement for the holes as drilled by Edelbrock for the 'stock' location. These were used to help locate the new holes.

We used a T&D shaft rocker arm which was 0.170" offset. This 0.170" offset allowed us to accomplish the project, that said could it have been done with less offset I cannot answer that.

If memory serves me right the intake ports are about 1.250" wide and 2.300" tall. The intake runner volume was about 234 cc's. The airflow was at or near 230 cfm. They supported 700 hp at 7000 rpm on a 4.125" stroke / 450 CID engine.


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[Steve C.]

I suspect these are used for the "wide-port" design heads....

Pontiac .240" Intake Offset Shaft Rockers For Edelbrock Cylinder Heads

https://butlerperformance.com/i-3078...tp-yt6370.html

This brings up the subject of how much is the standard offset as delivered from Edelbrock. I do not have the exact dimension, but years ago T&D listed their shaft system part number for the Edelbrock heads as 9020.
If I'm correct T&D told me it used their number 100200 rocker arm on the intake. At that time that rocker arm part number was for a 0.080" offset. This should be verified.

Side note, when they first came out for the KRE High-Port heads it was stated it utilizes standard pushrod locations. It is my understanding as cast they were already 0.200" offset on the HP head.


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[Steve C.]

Correction. The 1.250" port width reported previously is incorrect, that was for another set of heads. Not the offset heads.

Sorry for the confusion.


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[steve25]

I think you mean 330 cfm Steve to support 700 hp?

I have reworked the E heads to 340 cfm without eliminating the buldge, but cutting it back & sleeving it with 1/2" Brass tube.
If the OP of this string has aftermarket heads that are not flowing more then 340 cfm then there should be no need to go thru the cost and gyrations of going for offset rockers.

[Steve C.]

Damn ! Yes, 330 and they are 2.150" dia on the intake. That was with titanium valves and they are now hollow stem stainless steel used on my current 505, with the change we lost some airflow because of the design of the valve.

We had the port work done on those heads about 18 years ago. Doing it again today, I agree no need to go thru the cost and gyrations of going for offset rockers.

Of interest, Porting push rod bulge

https://forums.maxperformanceinc.com...ghlight=cattle



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[joes455]

Okay first off these are the latest style CNC chamber design off the Edelbrock heads the problem I'm having right now ,the yella terras are slightly tapping the inner wall of the pushrod buldge holes with perfect alignment of rocker arm tip to valve stem .Signs of interference are on the pushrods.I need agood .040 offest to be safe and maybe a little extra .Buldge has pressed in tubes.

[Scott Stoneburg]

I haven't seen the YellaTerra rockers, but from what I have seen of aluminum rockers the pushrod cup is a steel insert. So wouldn't your rockers have to have the insert removed, weld up the existing location and then re machine them for an offset? I would look into just the purchase price of buying the intake rockers made for the offset. If Yella Terra still offers them. I imagine the cost of the machine work to move the pushed cup would be pricey. But I could be wrong

[Gary H]

Don't know if you're running hydraulic or solid roller. Offset roller lifters? If not, that's an option.

[BADDTA]

Joes 455

We have the exact scenario you are talking about. My son has the 350 cfm head from Ceralli. We have the Yella Terra shafts. Also have the brass tubes inserted. We needed a few rockers moved over. Can’t remember exactly but it was around .070. We had Todd Goodwin do that for us. They worked out perfectly. It was around $200-50.

Brian

[joes455]

Thanks Brian what was involved ?

[BADDTA]

Would have to call Todd. It was 4 years ago. I believe it was the way the rocker was attached to the shaft. He machined something and moved it over.

Brian