No, I'm not crazy ... at least no more so than usual.

We put the new Dart Pro 1 heads on the motor yesterday and we were setting
up the valvetrain today. While measuring the pushrods, we found that a 7.500"
produced the best pattern. That seems extremely long to me, but there aren't
a whole lot of setups to compare to.

I'm running +.100" length valves
I have Comp Promag rockers on ARP 7/16" studs and Comp 850-16 lifters.
I thought the Dart castings would use stock length pushrods.
The heads are actually milled to get the chambers down to 56cc.
The lifters looked fine me.

Has anyone seen anything like this on their setups?

(and no, no one slipped LS1 castings in by mistake LOL)

 

At first glance that PR length does appear long, but it is what it is if you measured it correctly.

 

Yeah, as long as the springs are compressing the lifters I'm fine.
I'll double-check tomorrow.

 

long compared to what? stock.....

well aftermarket head, lifters and a longer valve........I wouldn't say it long, if you check it right then right is right. You don't have stock parts anymore so can't compare apples to bananas

 

I agree, it just seemed odd.
But I don't know anyone running stud-mounted rockers on Dart heads so I have nothing to compare to.
For whatever reason I had it stuck in my head that the Dart casting geometry should be just like a stock casting.
All of my paper napkin sketches and calculations become somewhat worthless now heh ... oh well.

We double-checked today, it is in fact 7.500" and the lifters are fine (not collapsing during the test)
So the new pushrods are on order and the old 7.150" ones are for sale.

Just paranoid with the build getting closer to being done I guess.
Lots of little issues, but each has been easily resolved. So I'm happy.
Once the oil pan gets back from the fabrication shop (moving oil level sensor away from headers), we can continue with the project.
Might actually get this motor in the car before November and make a pass at the track before it snows.

 

I currently have Dart Pro One 200cc heads with .100" longer valves and that is the push rod measurement I came up with using the "mid-lift" theory. However with mine the center of the sweep was closer to the exhaust side of the valve tip than I liked at that point.

The minimum sweep was at .031" with a .576" lift. I wound up backing off the length of the adjustable pushrod to 7.365" and the sweep increased to around .043". However the center of the sweep was back off the edge of the valve into an area more to my liking. So I went with the 7.365" pushrod. This is on an L-98 motor.

 

I currently have Dart Pro One 200cc heads with .100" longer valves and that is the push rod measurement I came up with using the "mid-lift" theory. However with mine the center of the sweep was closer to the exhaust side of the valve tip more than I liked at that point. The minimum sweep was at .031" with a .576" lift.

I wound up backing off the length of the adjustable pushrod to 7.365" and the sweep increased to around .043". However the center of the sweep was back off the edge of the valve into an area more to my liking. So I went with the 7.365" pushrod. This is on an L-98 motor.

With the new motor I'm building I'm going with the AFR 195 Comp heads and "standard" valves. I will be interested to see what length pushrod I come up with.

 

Great info, thank you. It's good to see that I may not be completely off my rocker (no pun intended)

 

I thought you could only get pushrods in .05's

 

There are other lengths available, I'm not sure if EVERY .005" is out there but
I've seen quite a few non-.050" increments at Summit.

 

I went with Terry Manton custom pushrods. They are available in .005" increments and not that expensive. I was surprised for such a quality pushrod. I wanted the strongest pushrod I could get. With my new motor I will go with Terry again.

 

Smith Brothers is where I went for my custom 6.125 pushrods. Very reasonably priced.

 

They are great to work with too. I highly recommend Terry and his crew.

 

With a +.100" valve, I'm not surprised at all. After doing the extensive checks I did on mine, a longer valve is what would solve the problem of the stock head/geometry.

 

Very happy with my Smith Brothers rods as well.

7.000" on stock LT1 heads using Caddy Racing lifters, Pro Mags, and a normal GM487 cam. short? sure... compared to stock, but if the pattern fits..