Different Heads on the same motor
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Senior User
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From: Graham, Wa.
Different Heads on the same motor
I found a real nice replacement 390 for sale, but when looking at it it appears to have different series heads on each side. One side has D2TEAA and the other is C8AE-H. I am assuming that this is not a good thing?
Post Fiend
Joined: Mar 2004
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From: Union, Washington
Same head just different vintage. The C8 (1968 version) is a late 60;s version and I would assume the head was rebuilt and had hardened valve seats installed. The D2 (1972 version after lead was removed from gas) head is just the same head with hardened valve seats to start with.
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From: Graham, Wa.
So I went and bought this motor and it has new .40 over pistons (can't tell what type), looks like the heads have been completely redone with new valves and springs. I took the cam out and it is a stock cam, which is really not what I would prefer to run.
I ordered a comp 268 and a new set of lifters for it, but then got concerned about if the springs would take it and since I don't know for sure what pistons were put in, I don't know the compression. I also don't know if I can assume that I can use the new pushrods or I have to get into that also.
I have searched through a lot of posts and it appears that this combo will work OK with the other stock components, but I would like to get any more information I can. Part of me is thinking I should just put the stock cam back in and run it, but I really want the rumble of the 268.
Suggestions?
I ordered a comp 268 and a new set of lifters for it, but then got concerned about if the springs would take it and since I don't know for sure what pistons were put in, I don't know the compression. I also don't know if I can assume that I can use the new pushrods or I have to get into that also.
I have searched through a lot of posts and it appears that this combo will work OK with the other stock components, but I would like to get any more information I can. Part of me is thinking I should just put the stock cam back in and run it, but I really want the rumble of the 268.
Suggestions?
Fleet Mechanic
Joined: Nov 2010
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From: Axtell, TX
There's no reason why you can't run the 268H with the stock springs. It only has .494" lift so you don't need a spring change. What does the top of the piston look like (flat tops w/valve reliefs, dished, etc.)? Have the heads been milled? and What head gasket are you using? This will help figure out what kind of CR you have.
Once you have the cam in you'll need to check the valve clearance to know if you need longer or shorter pushrods. Here's a link FE's That Bend Push-rods, A Dirty little Secret .: Articles for checking that. I'd advise to check them before you run it so that you don't have to use tool T58P-6565-A to bleed the lifters down. Once it's run and the lifters pump up there's no other alternative.
Once you have the cam in you'll need to check the valve clearance to know if you need longer or shorter pushrods. Here's a link FE's That Bend Push-rods, A Dirty little Secret .: Articles for checking that. I'd advise to check them before you run it so that you don't have to use tool T58P-6565-A to bleed the lifters down. Once it's run and the lifters pump up there's no other alternative.
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From: Graham, Wa.
Based on the numbers on the top of the pistons, they appear to be Sealed Power 381P's which are dished and have valve cuts. Info says they run 8.2:1. My son talked to the Comp Cam guys and they said that I did need to switch the springs out (but of course they are going to say that, they want you to buy more stuff).
I have not pulled the heads off yet so I can't tell what gasket was used and I don't know how I would tell if it was milled. The motor has not been fired since it was rebuilt so I did not want to tear it all down if I did not have to, but I also don't want to sell my self short from the start.
I do appreciate the info from those of you that have been there and are willing to share it.
I have not pulled the heads off yet so I can't tell what gasket was used and I don't know how I would tell if it was milled. The motor has not been fired since it was rebuilt so I did not want to tear it all down if I did not have to, but I also don't want to sell my self short from the start.
I do appreciate the info from those of you that have been there and are willing to share it.
Fleet Mechanic
Joined: Nov 2010
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From: Axtell, TX
From what I've seen the stock valve springs max out at about .510" of lift. Anything under .500" is good for sure. The factory GT/CJ cam had .491".
There's not much you can do with the low CR (1.67" compression height) pistons. With standard Fel-Pro .041" gaskets yes you'll have 8.2:1 static CR. You could bring that up to 8.6/7:1 by using steel shim head gaskets. It won't be a huge gain in power (maybe 15hp) or efficiency, so you'll have to decide if it's worth it to you to tear it down.
It's not my time/money, but I generally take anything I get (especially "rebuilt") apart and at least inspect it just so I know if it's right and what is in it. Taking the top half off is a cinch anyways....unless you still have a factory cast iron intake.
There's not much you can do with the low CR (1.67" compression height) pistons. With standard Fel-Pro .041" gaskets yes you'll have 8.2:1 static CR. You could bring that up to 8.6/7:1 by using steel shim head gaskets. It won't be a huge gain in power (maybe 15hp) or efficiency, so you'll have to decide if it's worth it to you to tear it down.
It's not my time/money, but I generally take anything I get (especially "rebuilt") apart and at least inspect it just so I know if it's right and what is in it. Taking the top half off is a cinch anyways....unless you still have a factory cast iron intake.
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From: Graham, Wa.
My reluctance to take the top off was more about the fear of the unknown, but we took them off last night and pulled the springs out and they appear to be used factory springs. I think we will opt to replace them with stiffer ones just to be safe. The decks are really smooth and look like they may have been touched up a bit, is there a way to check if they have been milled?
My son suggested that while we are in there we should replace the timing chain with a double roller and new retainers as well. These are not high dollar items anyways and I really don't want to have to go back into it later.
Do you have a suggestion on the head gasket? Looks like Mr. Gasket has one that compresses to .030, would that be a better choice to lift the CR a little?
My son suggested that while we are in there we should replace the timing chain with a double roller and new retainers as well. These are not high dollar items anyways and I really don't want to have to go back into it later.
Do you have a suggestion on the head gasket? Looks like Mr. Gasket has one that compresses to .030, would that be a better choice to lift the CR a little?
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From: Graham, Wa.
I am having a heck of a time figuring out what the dish volume is on that piston. Based on the info on Summit, the diameter of the dish is 2.62" and the depth is .097", but every time I try to calc it I come up with a different number of CC's to enter into my CR calculation. My last one was 8.5cc's which give me a CR of 8.19. Is this how you came up with your 8.2/1 Sleepy?
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Fleet Mechanic
Joined: Nov 2010
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From: Axtell, TX
yeah that is how I got the 8.2:1. I figured the swept volume and converted to cc's. I just made it an even 9cc.
I was thinking the springs would be new on the "rebuilt" engine. See what I mean. You never know what the extent of rebuilt is until you see for yourself. Springs and new timing set aren't that much $$ and you sure don't want to have to tear it down again.
I wouldn't worry about how much the block or heads have been milled with the pistons you have. It can only help. The NOS B9AE-6051-A (.015 thick) and C8AE-6051-B (.020) I believe can still be found. Or you can go with the Mr Gasket 720-1132G (.020), or if you have to have the best, you could go for a set of copper Husseys.
My figuring on an 8.6/7:1 was based on a .020 x 4.220 gasket (Mr G listed above). With a mill it might be .1 or so higher depending on how much was taken off.
About 9.5:1 would be perfect with the 268H but there is no way to get there as is. I'd try to get as close as possible if it were me. The thin head gasket gets you alot closer.
I was thinking the springs would be new on the "rebuilt" engine. See what I mean. You never know what the extent of rebuilt is until you see for yourself. Springs and new timing set aren't that much $$ and you sure don't want to have to tear it down again.
I wouldn't worry about how much the block or heads have been milled with the pistons you have. It can only help. The NOS B9AE-6051-A (.015 thick) and C8AE-6051-B (.020) I believe can still be found. Or you can go with the Mr Gasket 720-1132G (.020), or if you have to have the best, you could go for a set of copper Husseys.
My figuring on an 8.6/7:1 was based on a .020 x 4.220 gasket (Mr G listed above). With a mill it might be .1 or so higher depending on how much was taken off.
About 9.5:1 would be perfect with the 268H but there is no way to get there as is. I'd try to get as close as possible if it were me. The thin head gasket gets you alot closer.
Elder User
Joined: Feb 2011
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From: west sacramento ca
sleepy445fe is rite on about the stock lift. if your running the stock rockers and all. the springs on the rocker shaft eventually failed causing all sorts of stuff to happen.
kurt
73 f250 highboy fe390
kurt
73 f250 highboy fe390
Needsmorecoffee.
Joined: Oct 2004
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From: CT
DSC sells the C8 and Mr G shim gaskets. DSC Motorsport Ford Racing Parts the C8 427 shim gaskets have a 4.390 bore size and also have the reinforced compression ring. Mr G's are a bit smaller on the bore size and not sure of the exact size. Those are just a stamped steel gasket no reinforced compression ring like the C8 427's. $30 pr for the C8 and $28 for the Mr G's.
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