454 head question

[Axkiker]

So it appears that my heads are in need of a rework. They are Gen 5 casting 10114156. I found a guy local who has what he claims are to be low mileage takeoff heads of the same casting number from warranty return vehicles. Supposedly the heads only need to be cleaned and can be used.

If they are indeed good heads would it be okay to use my springs / rockers etc on the new heads. I assume I could not use them as is because the springs would not be correct for the cam that the boat runs. Also I assume the valves are the same since they are from the same casting ????

Any advice from others who have more engine building experience.

Thanks

 

[tpenfield]

Valve springs might be OK, since the marine cams are fairly mild. You could always just get new valve springs so that they are fresh. Valves and the valve seat angles should be ground.

What would prevent you from having the existing heads re-worked versus getting new heads?

 

[Scott Danforth]

unless your heads have a crack, it will be cheaper to redo your existing heads than to buy new ones. regarding the take-off heads, he most likely has the same heads with the same valves and springs if it is a truck motor.

 

[Axkiker]

So it appears that my heads are in need of a rework. They are Gen 5 casting 10114156. I found a guy local who has what he claims are to be low mileage takeoff heads of the same casting number from warranty return vehicles. Supposedly the heads only need to be cleaned and can be used.

If they are indeed good heads would it be okay to use my springs / rockers etc on the new heads. I assume I could not use them as is because the springs would not be correct for the cam that the boat runs. Also I assume the valves are the same since they are from the same casting ????

Any advice from others who have more engine building experience.

Thanks

These are 75.00 a piece, hence why I am interested. If they truely are low mileage heads that are perfectly fine it would be easier and cheaper for me to just buy them from him. Heck he said he would give me 25.00 per head as a core for my heads.


My concern is that the springs / valves are not compatable with the cam in the boat.

 

[Scott Danforth]

unless you put in a hot aftermarket cam, it is the exact same springs and valve that are on the truck heads. boat cams are really close to truck cams in lift and duration, with just a bit of lobe separation difference. most aftermarket cams are RV/Marine.

for $75 each, buy them, and run them.

 

[scoflaw]

Have them totally checked out before bolting them on, make sure they are in good shape. Lot of labor and parts to yank them off again, even if they are free.

 

[Axkiker]

So I ended up getting the heads. They look great but im still going to give them a good check prior to bolting on. I personally dont see why I wont be able to bolt them on and go.

I do have a question though. The springs on these heads do not have that round metal surround thing that is around the springs. Im not sure what it is or what its called. Anyone know if its necessary or was just discontinued after a certain year. I have them from my old heads I can use but honestly cant see what they are for.

thanks

 

[Axkiker]

After a little more research it appears the shield kinda things are called dampers. Any idea why some heads have them and others do not.

 

[Axkiker]

After a little more research it appears the shield kinda things are called dampers. Any idea why some heads have them and others do not. Any concern running them without

 

[Axkiker]

Another quick question. Can someone please tell me what the service stem clearance tolerance for a 454 is. I have the specs listed for this motor at http://www.perfprotech.com/blog/articles/mercruiser-bigv8-marine-engines-specifications and dont totally understand what the "service"limit is. I understand the production limits because they give a range. How are you to calculate the service limit? Do they mean .001 above production is ok????

Also im not sure what valve margin is. Any hints?

Thanks

VALVE SYSTEM

ENGINE MODEL	7.4L	454 MAGNUM	502 MAGNUM
Lifter	Hydraulic
Rocker Arm Ratio	1.70 to 1
Face Angle (Intake & Exhaust)	45°
Seat Angle (Intake & Exhaust)	46°
Seat Runout (Intake & Exhaust)	.002 (0.05) Maximum
Seat Width	Intake	.0300-.0600 in. (0.7620-1.5240 mm)	.03125-.0625 in. (0.79-1.58 mm)
Exhaust	.0600-.0950 in. (1.5240-2.4130 mm)	.0625-.09375 in. (1.58-2.38 mm)
Stem Clearance	Production	Intake	.0010-.0029 (0.0254-0.737)	.0010-.0027 (0.025-0.069)
Exhaust	.0012-.0031 (0.0300-0.0787)	.0010-.0027 (0.025-0.069)
Service	Intake	.001 (0.02)	.003(0.07)	.0037 (0.09)
Exhaust	.002 (0.05)	.004 (0.10)	.0049 (0.12)
Stem Diameter	Intake	.372 (9.45)
Exhaust	.372 (9.45)
Valve Margin (Intake and Exhaust)	.0312 (0.79)
Valve Lash (Intake and Exhaust)	Fixed Lash

- See more at: http://www.perfprotech.com/blog/art...e-engines-specifications#sthash.ODrhqIcb.dpuf

 

[alldodge]

~~

Another quick question. Can someone please tell me what the service stem clearance tolerance for a 454 is. I have the specs listed for this motor at http://www.perfprotech.com/blog/arti...specifications and dont totally understand what the "service"limit is. I understand the production limits because they give a range. How are you to calculate the service limit? Do they mean .001 above production is ok????
Also im not sure what valve margin is. Any hints?
Thanks

Valve dampers are used to control harmonics, they also assist it keeping the springs straight. They also add to the overall spring height which is a measurement used to determine if the spring is usable. If they are removed from a setup which was installed with, the tension is reduced. In short, if they came with, do not just remove. If you want to build without them check spring height.

Stem clearance is the space between the guide and the stem. Your chart indicates, Intakes at .0010 -.0029 and exhaust at .0012 - .0027

Comment on your first post indicating the heads were take offs because of warranty work. If they were taken off by warranty, something caused it. Need to find out why they were taken off before I would just put them on and run.

Think of service limit as a brake rotor, you can only grind on it so far before you reach the serviceable limit

 

[Axkiker]

Here is what I know as far as the story of these heads. The company I purchased these from takes all the warranty returns for I think NAPA and resells them. They take in the entire long block, pull the heads and pan then do a quick inspection before resell. I picked these heads from a pallet of probably 30 heads..

I have removed the springs and valves from one side and have found the valve stem clearance to be within production specs. Valve seats look great along with the valve seat faces. Valve stem and length measurements all match up to my original heads so all seems well there. These heads could not have many miles on them. So far for the price I am very very pleased.

One of my few concerns is that these heads didnt come with that damper. I guess since it didnt come with it ill just run them as is. Im just curious how 2 sets of identical heads would be different in that aspect.

Other than that im tickled to death with them. Based on the measurements im doing im staying within production limits... Im still confused regarding the service stem clearance limits. They list intake as .001. Do they mean you can measure .001 above the max production limit and still be within spec??? Doesnt really matter since im under that but im curious non the less.

This company also has short blocks that are returns. I looked at a couple which had been verified as standard mains and they literally look new. Im almost tempted to try one of those and just roll with new rings and bearings... I need to do some measurements on my current motor first though.

 

[alldodge]

Here is what I know as far as the story of these heads. The company I purchased these from takes all the warranty returns for I think NAPA and resells them. They take in the entire long block, pull the heads and pan then do a quick inspection before resell. I picked these heads from a pallet of probably 30 heads..

I have removed the springs and valves from one side and have found the valve stem clearance to be within production specs. Valve seats look great along with the valve seat faces. Valve stem and length measurements all match up to my original heads so all seems well there. These heads could not have many miles on them. So far for the price I am very very pleased.

One of my few concerns is that these heads didnt come with that damper. I guess since it didnt come with it ill just run them as is. Im just curious how 2 sets of identical heads would be different in that aspect.

Other than that im tickled to death with them. Based on the measurements im doing im staying within production limits... Im still confused regarding the service stem clearance limits. They list intake as .001. Do they mean you can measure .001 above the max production limit and still be within spec??? Doesnt really matter since im under that but im curious non the less.

This company also has short blocks that are returns. I looked at a couple which had been verified as standard mains and they literally look new. Im almost tempted to try one of those and just roll with new rings and bearings... I need to do some measurements on my current motor first though.

The stem clearance is the clearance between the stem diameter and the valve stem guide. The stem production diameter is .372, just find out what the guide ID is and there should be no more then .0010 - .0029 clearance. To much clearance allows for wobble. to less does not allow for expansion

 

[Axkiker]

The stem clearance is the clearance between the stem diameter and the valve stem guide. The stem production diameter is .372, just find out what the guide ID is and there should be no more then .0010 - .0029 clearance. To much clearance allows for wobble. to less does not allow for expansion

I understand what you are saying but what is the service limit. It says stem clearance service limit of .001. Does that mean .001 above the production limit ??? Just curious.

 

[Axkiker]

Any takers ?????