Watch that 250 pushrod length!

I can stare at this fresh build of mine all day and it doesn't change the fact - The pushrods are too long! The adjustable rockers from RAU only thread in a couple of threads when properly adjusted and that leaves way too much unused (weak) adjuster. I should mention that I only milled .060 off the head and made some of that back with the new gasket. Talking with Larry over at Clifford and he told me he is starting to hear more of this recently. We verified the rod length. It is at least possible that something had changed with the adjustable units, or some of them, from RAU. Gary over there is awesome and he is cutting me down a set of shorter rods to exchange with these. So, maybe I just got unlucky but heads up in case it helps. See you all...

all ways take 'an adjustable' PR and measure B4 orderin.
I'd suggest that now rather than some guy (no matter how experienced) remotely developin a set.

Can U know just from how much has been 'decked' off?

I couldn't fine one of those cup end adjustables but probably didn't know where to look. If the set that comes in doesn't have me on the valve right where I want to be I will consider making one. This "package" was supposed to be tried and true. The new rods are going (that's the plan anyway, right?) to be .020 shorter which will let me engage several more threads on the adjuster. Even though I had 060 milled, I definitely need more than that off the rod length. that's why I posted this - something is just plain wrong here. With the rods in place I have almost 1/2 inch of unused rocker adjusting end! Not confidence inspiring. thanks a bunch for your comments Chad!

There is actually a more involved process to determine the correct pushrod length and rocker geometry than just subtracting what was cut off the head, block or valve tips and eyeballing the thread adjuster protrusion. You can end up with excessively worn valve tips and damaged rocker arms if you don't exercise the correct method for checking this. Its also not a 1:1 relationship between pushrod length and how much you cut off the deck surfaces, because these deck surfaces and the pushrod are at angle to each other. Add to this the aftermarket rocker arm makes this not a simple as that. :nono:

chad":2ibxly55 said:

Can U know just from how much has been 'decked' off the block?

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Ask & ye shall recieve…dair U go, help waiting in the wings.

So wasss the answer besides use of the 'adjustables'? Assemble and measure…
Where, when, how, what, etc?

I'm a humble guy because there is always someone out there far more knowledgeable than I and probably more interesting too! The geometry on this valve train is beautiful. Rather than say that my pushrods were too long, I might have said that perhaps they were perfect and the rocker adjusters are too long!!! All I know is that three threads of the adjusters are not enough for my hot rod. So, I am going to shorten the rods and watch the geometry and see if I can live with it. I would discourage using the head mill dimension as a consideration in pushrod length. I mentioned it so as to discount it; .060 gained mostly back by the gasket, and with the angle to boot is barely relevant. I agree CNC Dude!

When it comes to recommendations on engine packages, "Trust but Verify"!

This has been the case even with stock adj rockers on the 250. There was a member who ran into this with his Ranchero 250 build. He had custom rods made, there is a thread about it. He tried the standard length and said he doubted the CI -1/8" ball/cup 250 pushrods would work either. Iirc his were 8.9"? I do remember he used http://www.pushrods.net/ in OR to make his good pushrods.

... and I thought I was crazy , I could fault my machinist if I didn't trust him for @ 30 years.

here's pics of a 250 I built with UNCUT D7DE head and modern composite gasket ( @ .045). I specifically had machinist work the valves and springs but not mill the head to get a low static compression ratio for turbo setup. After assembly the rockers hit the valve cover ! . I measured EVERYTHING and finally had a custom shortened Pushrod set built ( Thanks RAU - I asked if they had a promo sticker for my car ).





.. crazy ..




have fun

powerband":pls4wz02 said:

... and I thought I was crazy , I could fault my machinist if I didn't trust him for @ 30 years.

here's pics of a 250 I built with UNCUT D7DE head and modern composite gasket ( @ .045). I specifically had machinist work the valves and springs but not mill the head to get a low static compression ratio for turbo setup. After assembly the rockers hit the valve cover ! . I measured EVERYTHING and finally had a custom shortened Pushrod set built ( Thanks RAU - I asked if they had a promo sticker for my car ).





.. crazy ..


have fun

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Hope those are pictures of the valve train before you purchased the shorter pushrods.
Those adjusters are just about ready to come out of the rockers.

Hope those are pictures of the valve train before you purchased the shorter pushrods.
Those adjusters are just about ready to come out of the rockers.

Yes, I had those pics to prove to machinist I wasn't crazy - at least about the PR lengths. .

... It did run like that but it was a concern until the shorter custom set was installed.

have fun

w/cut PR's :

Cup and ball pushrods are required when moving to adjustables. No US 250 's came out with adjustables, and Aussie M codes from 1971 to 1975 were a different block deck height.


Powerband

Did you use the blue print 8.920" pushrods, or 8.813"

78 granada, what did you use.

Previous discussion on this had three other selections.


/viewtopic.php?f=1&t=71383&p=549672#p549672

62Ranchero200":16kagkoe said:

xctasy":16kagkoe said:

xctasy":16kagkoe said:

Did you use the 8.920" pushrods?

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What rod length did you use.

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I ended up ordering 8 13/16" (8.8125") pushrods from Smith Brothers. These are 1/2" shorter than "stock length" pushrods. I think I could have made slightly longer pushrods work, maybe up to 9".

The "stock length" CI cup and ball pushrods were 9 5/16", and the -1/8" CI cup and ball pushrods would have been 9 3/16" (3/8" longer than the Smith Brothers pushrods), definitely too long for the style of adjustable rocker arm that I have. Haven't finished adjusting valves because my battery died and I have to replace it so that I can bump the engine over ... can't get to the harmonic balancer bolt now that the fan is installed.

Thanks
Bob

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The ones I have in there are 9.300 which is essentially the length of the stock rods I took out. There may be a margin of error going to the cup configuration I suppose. Looking at going to a 9.100 length which will give me a lot more thread all things being equal. What would be cool is if someone offered different dimension adjustable rocker ball ends!!!!!!!!!!!

xctasy":2dusyiix said:

/viewtopic.php?f=1&t=71383&p=549672#p549672

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yeah that's the thread

When I worked for Headrick, one of his business partners bought a pushrod manufacturing company that was going out of business. On thing his partner learned is that not all pushrod tips and cups are the same. Each company has is own patent on ball radius and the radius inside the cup, so no two brands of pushrods will allow the ball on the rocker arm to seat at the same height, and alter each ones engagement differently brand to brand. This will also affect the overall length slightly from brand to brand depending on how deeply the ball seats into the pushrod cup.

CNC Dude is right on the money.

78 granada":17vuynrl said:

The ones I have in there are 9.300 which is essentially the length of the stock rods I took out. There may be a margin of error going to the cup configuration I suppose. Looking at going to a 9.100 length which will give me a lot more thread all things being equal. What would be cool is if someone offered different dimension adjustable rocker ball ends!!!!!!!!!!!

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That is also the truth.

Adjustment balls and the pushrod cups and pushrod types are variable. Some are oil through for some roller rocker applications.


See the pictures Bob the builder supplied between the CI and other types.

Not knocking Yella Terra, they have reaqlly done the hard research work, but for example, replacement Yella Terra adjustment balls are different to the stock worn 1960 to 1966 144/170/200 adjustable shaft balls.

Talking the 1.666" shorter 7.803" tall crank to head gasket deck 200 cubic inch block as an example over the 250's 9.469" deck.

Way back when, Rick Smol had problems with them in his 250 2V M code 170 HP head on his 120 hp 200 1-bbl block engine in his Mustang. The ball adjusters were sheared with just a moderate lift Schnider split duration cam. It wasn't the came that dislocated the pushrod, it was a adjuster ball to pushrod cup issue.


The recommended Aussie 250 2v head swap actually uses 186S General Motors Holden pushrods and roller rockers, but they require a 302 Windsor hydraulic lifter, and the US 250 is a few thou taller than the Aussie 250. Rciksmol had to find some other pushrods to suit his Yella Terra rockers and rocker shaft, and it failed to work with the adjusters.


He just took the stock rocker gear, and reverted back to non roller rockers, and it worked with the stock pushrods.


Down here, we used 2-bbl 1968-1971 Holden 186S adjustable rock pushrods, which were used on some 2650/ 3050 Torana and Monaro two door coupes in 161, and 202 engine sizes as well, some with triple carb XUI GTR Toranas. They have been known to shear off the adjustment balls if they don't match.

Gary over at RAU just sent me a set of rods he cut down for me at no charge to get this thing straightened out. Awesome guy Gary! They are at 9.1" now. That with the fact that the cup end is slightly deeper will give me a lot more adjuster thread to engage in the rocker.. .200" plus. Now just got to get the head back off because of that rocker I pulled out and tipped over and away we go!