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P51 heads with Kaase guide plate pushrod diameter

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Post  Axshun November 11th 2022, 4:57 pm

Building a 521 with Kaase P51 heads set up for a hydraulic roller, and I'm using Morel hyd. lifters. I'm noticing that the holes in the heads for the pushrods on the some of the cylinders are quite offset. Can anyone confirm that the guide plates that were supplied by Kaase are for 3/8" pushrods? If they are, some of those pushrods are going to come pretty close to the bottom of the holes in the head that they pass through. Going to a 5/16 rod gives me better clearance, but not sure if the 5/16 rod will work with the Morel lifters, or be too small for the guide plates on the heads.
Thanks for any advice from you guys who have run into this problem too.


Axshun

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Join date : 2018-10-02

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Post  supervel45 November 11th 2022, 7:47 pm

Look at the ends of a 3/8" pushrod. They taper to 5/16".

https://www.jegs.com/i/COMP-Cams/249/7928-1/10002/-1

If you go to a 5/16" and have 3/8" guide plates you will need to change them.

Here is a good picture of the pushrod angle. It's quite a bit on the exhaust side. It's worse with a Hyd. Roller.

https://www.ford-trucks.com/forums/1240901-rebuilt-460-losing-push-rods.html

Measure your guide plates.

Have you heard of running mechanical roller lifters on the Hyd. Roller Cams?

supervel45

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Post  Scott Foxwell November 12th 2022, 1:06 pm

Axshun wrote:Building a 521 with Kaase P51 heads set up for a hydraulic roller, and I'm using Morel hyd. lifters. I'm noticing that the holes in the heads for the pushrods on the some of the cylinders are quite offset.  Can anyone confirm that the guide plates that were supplied by Kaase are for 3/8" pushrods? If they are, some of those pushrods are going to come pretty close to the bottom of the holes in the head that they pass through. Going to a 5/16 rod gives me better clearance, but not sure if the 5/16 rod will work with the Morel lifters, or be too small for the guide plates on the heads.
Thanks for any advice from you guys who have run into this problem too.

"Coming pretty close" is not a problem. If they rub a little, you grind a little till they don't rub. They only need to not touch. I use a piece of paper as my "feeler gauge" around pushrods. If it slides all the way between the pushrod and head, that's plenty of clearance. Clearancing for pushrods is part of building a performance engine although I find it hard to believe that it's actually a problem with those heads. Even if you could, you don't want to use 5/16 pushrods. 1) they won't work with the 3/8 guide plates and 2) they're just wrong for the application.

Scott Foxwell

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Post  supervel45 November 12th 2022, 5:17 pm

Scott Foxwell wrote:
Axshun wrote:Building a 521 with Kaase P51 heads set up for a hydraulic roller, and I'm using Morel hyd. lifters. I'm noticing that the holes in the heads for the pushrods on the some of the cylinders are quite offset.  Can anyone confirm that the guide plates that were supplied by Kaase are for 3/8" pushrods? If they are, some of those pushrods are going to come pretty close to the bottom of the holes in the head that they pass through. Going to a 5/16 rod gives me better clearance, but not sure if the 5/16 rod will work with the Morel lifters, or be too small for the guide plates on the heads.
Thanks for any advice from you guys who have run into this problem too.

"Coming pretty close" is not a problem. If they rub a little, you grind a little till they don't rub. They only need to not touch. I use a piece of paper as my "feeler gauge" around pushrods. If it slides all the way between the pushrod and head, that's plenty of clearance. Clearancing for pushrods is part of building a performance engine although I find it hard to believe that it's actually a problem with those heads. Even if you could, you don't want to use 5/16 pushrods. 1) they won't work with the 3/8 guide plates and 2) they're just wrong for the application.



Or cut them in half?

https://www.429-460.com/t21587-guide-plates

supervel45

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Post  Axshun November 12th 2022, 9:33 pm

Thanks for the info guys. I do see how the 3/8" taper down. I definitely want to use what size Kaase designed the heads to use.

Axshun

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Post  supervel45 November 12th 2022, 10:54 pm

Don't forget the intake pushrods or shorter then the exhaust.

Motor Trend did a P-51 build back in 2007 with a mechanical roller and they where .3" shorter with a 8.950" and a 9.250". Yours should be shorter then that with the hydraulic lifters. You just have to get it together and see where you are at with an adjustable pushrod.

supervel45

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Post  Scott Foxwell November 12th 2022, 11:13 pm

supervel45 wrote:
Scott Foxwell wrote:
Axshun wrote:Building a 521 with Kaase P51 heads set up for a hydraulic roller, and I'm using Morel hyd. lifters. I'm noticing that the holes in the heads for the pushrods on the some of the cylinders are quite offset.  Can anyone confirm that the guide plates that were supplied by Kaase are for 3/8" pushrods? If they are, some of those pushrods are going to come pretty close to the bottom of the holes in the head that they pass through. Going to a 5/16 rod gives me better clearance, but not sure if the 5/16 rod will work with the Morel lifters, or be too small for the guide plates on the heads.
Thanks for any advice from you guys who have run into this problem too.

"Coming pretty close" is not a problem. If they rub a little, you grind a little till they don't rub. They only need to not touch. I use a piece of paper as my "feeler gauge" around pushrods. If it slides all the way between the pushrod and head, that's plenty of clearance. Clearancing for pushrods is part of building a performance engine although I find it hard to believe that it's actually a problem with those heads. Even if you could, you don't want to use 5/16 pushrods. 1) they won't work with the 3/8 guide plates and 2) they're just wrong for the application.



Or cut them in half?

https://www.429-460.com/t21587-guide-plates
That's usually done to help the rocker alignment with the valve. If that's OK, you don't want to move the guide plates around too much.

Scott Foxwell

Posts : 419
Join date : 2011-06-23
Age : 64
Location : E Tennessee

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