Question on DART Cylinder Head
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
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From: Tampa Bay FL
Question on DART Cylinder Head
When having the valve train hardware installed for my retro roller cam conversion, I had new bronze guides and steel inserts installed in the valve seats of my DART Iron Eagle cylinder heads (the heads had 'hardened' valve seats which did not last more than 30K miles).
When I set up the push rods and rockers, I noticed that the rockers for the exhaust valves are at a slight angle from the intake; they are not perfectly parallel from pushrod, stud and valve head.
The heads have guide plates and hardened push rods.
Is it normal for the center of the exhaust valves to be slightly off-set from the rocker stud when compared side-to-side to the intake?
When I set up the push rods and rockers, I noticed that the rockers for the exhaust valves are at a slight angle from the intake; they are not perfectly parallel from pushrod, stud and valve head.
The heads have guide plates and hardened push rods.
Is it normal for the center of the exhaust valves to be slightly off-set from the rocker stud when compared side-to-side to the intake?
Last edited by TedH; Jul 29, 2013 at 07:04 PM.
Race Director
Joined: Jul 2004
Posts: 12,707
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From: Scottsdale Arizona
I don't think it's normal at all but noted some thing similar with my iron eagle heads. I thought that the guide plates were off. I also had issues with the studs coming loose. Fixed that with red Loctite.
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Look at the point the rockers contact the valve stem. It should be centered on both the intake and exhaust. If not, you're side loading both the valve AND the rocker stud, plus loading the valve to one side of the guide. IMHO, not a ticket to longevity.
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
I did not. The heads were rebuilt by a shop and the guide plates were 'set' when they re-installed the screw-in rocker studs (I assumed they removed when they installed new guides and valve hardware). I assumed they would take the time to align the guide plates so that I would not have to loosen and re-torque the rocker studs... I will see if the guide plates are correctly installed and the correct application.
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
I am reading some DART literature that says they move the intake valve away from the exhaust; that results in the I/E rocker separation being greater when viewed side-to-side at valve tip.
All to aid intake port airflow and accommodate larger valves.
I will see if adjusting the guide plates is an option to keep the rocker centered over the valve tip on each valve.
All to aid intake port airflow and accommodate larger valves.
I will see if adjusting the guide plates is an option to keep the rocker centered over the valve tip on each valve.
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Yeah, sort of bummed the cylinder head rebuilders didn't seem to set the guide plates according to location of the valves. Will verify this evening.
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Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
I probably should have when I installed the heads the first time; perhaps the premature valve guide wear resulted. Going to open 'er up this weekend and check it out. I would appreciate any detailed instructions on proper guide adjustment. The plates are single-piece, flat. I will get the PN # this evening.
Drifting
Joined: Jun 2013
Posts: 1,269
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From: Cocoa FL
This cannot be done until the heads are installed and the lifters, push rods and rockers are in. That's when you make the final adjustments. Unless they installed the heads, lifters, push rods and rockers there is no way they could know exactly where the guides need to be.
Le Mans Master
Joined: Mar 2008
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From: Oxford MA-----You just lost the game!!!!
This cannot be done until the heads are installed and the lifters, push rods and rockers are in. That's when you make the final adjustments. Unless they installed the heads, lifters, push rods and rockers there is no way they could know exactly where the guides need to be.
It's the truth. If you think about it, it's pretty obvious. How are you going to be able to tell where the pushrod is going to be until it's installed?
Scott
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
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From: Tampa Bay FL
The rockers are Comp Ultra Pro Magnum 1.52 ratio (not self-aligning). I think I did not see the difference with the positioning with the stamped rockers since they are one-piece and cover more of the valve tip side-to-side. With the rollers, I could see how the exhaust roller tips were centered where the intake tips were not
The flat, one-piece guide plates were installed by Indy Cylinder heads on the DART heads when I purchased from them around 2000. Strange they did not include any instructions about adjusting the guide plates. They are name brand (I need to pull a valve cover to get the part numbers). The push rod holes in the heads are oversized compared to the stockers' narrow slots.
Are there written instructions on how best to adjust the guide plates? I don't want to mess up the exhaust valve rocker location to valve tip.
Last edited by TedH; Aug 2, 2013 at 06:54 PM.
Drifting
Joined: Jun 2013
Posts: 1,269
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From: Cocoa FL
I have used the one-piece guides and a few times I've had to cut them in half to get the rockers to line up correctly. Install the rockers and set the guides to where it all lines up correctly. Then set the initial lash and manually turn the motor over and recheck. If all looks good go ahead and start it up and properly set the valve lash on it. Then check again for proper alignment.
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
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From: Tampa Bay FL
OK. The guide plates are Manley 42151's. I found that I am able to 'move' the rocker tips a little on the valve tips to make them sufficiently line up over the valve tips; they do not have a lot of side-to-side travel and they are not at risk of dropping off the valve tips.
When I pulled the driver's valve cover, there were only two that were slightly off-center. One was intake another was exhaust. Most were ok.
Perhaps I overreacted given I can make the rockers line up perfectly on the valve tip with just a small nudge. And not all of the intake rockers are out of alignment.
I'll take a look at passenger side tolerances.
When I pulled the driver's valve cover, there were only two that were slightly off-center. One was intake another was exhaust. Most were ok.
Perhaps I overreacted given I can make the rockers line up perfectly on the valve tip with just a small nudge. And not all of the intake rockers are out of alignment.
I'll take a look at passenger side tolerances.
Drifting
Joined: Jun 2010
Posts: 1,781
Likes: 15
From: Oxford Ohio
This cannot be done until the heads are installed and the lifters, push rods and rockers are in. That's when you make the final adjustments. Unless they installed the heads, lifters, push rods and rockers there is no way they could know exactly where the guides need to be.
Exactly. They would be set in relationship to the lifter.