7.500" pushrods in an LT1 head???
10-07-2008, 07:43 PM
#1
Registered User
Thread Starter
Join Date: Apr 2000
Posts: 1,444
7.500" pushrods in an LT1 head???
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)
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)
10-08-2008, 09:17 PM
#4
Banned
Join Date: Oct 2006
Location: Goochland, Va.
Posts: 4,974
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
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
10-08-2008, 09:26 PM
#5
Registered User
Thread Starter
Join Date: Apr 2000
Posts: 1,444
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.
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.
Last edited by James Montigny; 10-08-2008 at 09:28 PM.
10-08-2008, 10:54 PM
#6
Registered User
Join Date: Oct 2007
Posts: 220
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.
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.
10-08-2008, 10:55 PM
#7
Registered User
Join Date: Oct 2007
Posts: 220
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.
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.
Last edited by 1989TransAm; 10-08-2008 at 10:58 PM.
10-08-2008, 11:04 PM
#11
Registered User
Join Date: Oct 2007
Posts: 220
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.
10-09-2008, 11:22 AM
#13
Registered User
Join Date: Oct 2001
Location: SoCal
Posts: 2,525
They are great to work with too. I highly recommend Terry and his crew.
