Rocker Arms won't clear valve springs
08-26-2003, 05:45 PM
#1
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Location: so close I can taste it...
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Rocker Arms won't clear valve springs
A friend is putting his motor back together and was putting his rockers back on his heads when he came into a little problem.
The body of the rocker arm is hitting on the valve springs and won't even go down on the studs.
The heads are supposedly LT4 heads, but we don't think they are because the spring seats had to be cut for the bigger springs that were used. The springs are 8305 Isky's. Outside diameter is 1.510 according to Isky's site. Cam is a 236/242 comp XE.
The rockers are Crane non-self aligning for 3/8 studs for centerbolt valve covers that are shown in Summit.
Is there any reason that these rockers wouldn't clear the larger diameter springs if they cleared the smaller diameter springs that were on the heads before?
Any ideas?
The body of the rocker arm is hitting on the valve springs and won't even go down on the studs.
The heads are supposedly LT4 heads, but we don't think they are because the spring seats had to be cut for the bigger springs that were used. The springs are 8305 Isky's. Outside diameter is 1.510 according to Isky's site. Cam is a 236/242 comp XE.
The rockers are Crane non-self aligning for 3/8 studs for centerbolt valve covers that are shown in Summit.
Is there any reason that these rockers wouldn't clear the larger diameter springs if they cleared the smaller diameter springs that were on the heads before?
Any ideas?
08-26-2003, 06:25 PM
#2
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Join Date: Jan 2000
Location: Lockport, Illinois 60441
Posts: 487
Hey Dan hows it goin?
Well to start with you questions. LT4 heads came with the 1.265 outer diameter spring originally so it still is possible that your friend has LT4 heads. The bad news is the rockers he has will not work with the spring diameters he has. The Rocker part #crn-10751-16 (1.5) or 10758-16 (1.6) will not work on larger valve springs. These rockers are thinner so the body is made a little thicker around the pivot area. So it takes some clearance away from the spring. Not a problem for the stock diameter valve springs but when you go that large on the springs. You need to run a rocker number of 11752-16 (1.5) or 11755-16 (1.6) but then you also need to get different valve covers and the adapter plates which allow you to change from centerbolt valve covers to the old style which bolted on the edges. I had to do this with my buddy's car as he ran into the same problem. The only other alternitive is to find smaller diameter springs that have the same specs as the larger ones or at least for the cam he is using. When I did my LT4 heads on my 383, I bought the K-motion#kmo-k750 springs and the KMO-k-7500 retainers and locks 10 degrees. I would think these springs would work for him as well as they are rated for 600 lift. Hope this helps some. Total for the springs and retainers is about 180.00. Still cheaper then the other alternative I listed.
Well to start with you questions. LT4 heads came with the 1.265 outer diameter spring originally so it still is possible that your friend has LT4 heads. The bad news is the rockers he has will not work with the spring diameters he has. The Rocker part #crn-10751-16 (1.5) or 10758-16 (1.6) will not work on larger valve springs. These rockers are thinner so the body is made a little thicker around the pivot area. So it takes some clearance away from the spring. Not a problem for the stock diameter valve springs but when you go that large on the springs. You need to run a rocker number of 11752-16 (1.5) or 11755-16 (1.6) but then you also need to get different valve covers and the adapter plates which allow you to change from centerbolt valve covers to the old style which bolted on the edges. I had to do this with my buddy's car as he ran into the same problem. The only other alternitive is to find smaller diameter springs that have the same specs as the larger ones or at least for the cam he is using. When I did my LT4 heads on my 383, I bought the K-motion#kmo-k750 springs and the KMO-k-7500 retainers and locks 10 degrees. I would think these springs would work for him as well as they are rated for 600 lift. Hope this helps some. Total for the springs and retainers is about 180.00. Still cheaper then the other alternative I listed.
08-26-2003, 10:24 PM
#3
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Join Date: Jul 2001
Location: so close I can taste it...
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Hi Ron,
He called the shop today that did the heads for him and they told him about a new set of rockers that "should" work. Supposedly he has used them before with the same springs and said they cleared no problem.
Additionally, on Thunder Racings site they list Crane and Comp rockers that they say will clear springs up to 1.62 OD.
But I will definitely make sure he sees this thread! Thanks!
He called the shop today that did the heads for him and they told him about a new set of rockers that "should" work. Supposedly he has used them before with the same springs and said they cleared no problem.
Additionally, on Thunder Racings site they list Crane and Comp rockers that they say will clear springs up to 1.62 OD.
But I will definitely make sure he sees this thread! Thanks!
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