head swap questions
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5th Wheeling
Joined: May 2006
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head swap questions
Strange swap but necessity dictates it. Have an 89 truck with 302 roller cam- the cam gear came loose(bolt backed out). it trashed the valves and pushrods. I had a set of 1974 302 heads that were good. Bolted them on- had to use the pushrods out of the 74 also. The rocker arms have a ridge where they go over the valves so I THINK the alignment will be OK there. Took three tries but with a double set of gaskets finally got the EFI intake to quit leaking water. I can't get it to fire though. Any suggestions?? Do I need to put the flat tappet cam and lifters in out of the 74?? Money is limited and I need this vehicle running- driving an emergency backup vehicle that has a rod knocking and won't last long. (three quarts Lucas and 3qts 30w has kept me going for a week but won't last long- I live in the boonies and drive 60mi a day to and from work. HELP
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
I was gonna say, if you used the '74 pushrods the valves would never close. An '89 truck would not have a roller motor, so that must be a retrofit. What firing order did you connect the plugs? Have you done a compression test? All sensors and vacuum lines connected?
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5th Wheeling
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its a roller, everything is connected, uses regular 302 firing order though- had that issue when we replaced the rods and mains a couple of years ago- ran fine till bolt backed out. if you use the HO firing order it would barely run popping out the intake and exhaust.
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5th Wheeling
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only 60psi per cyl. think I'll flip the old heads upside down, pour some gas in them and see how bad they leak.....
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5th Wheeling
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have checked and plunger depression is .015- is this to much for a roller lifter?? this is an OK amount on normal lifters but maybe rollers are different and holding the valves open a little is why my compression is so low. don't thik an engine will run with only 60psi compression. did the gas test on the old heads- many, many bent valves. maybe time to pull the '74 heads off and get the valve grinding compound out. anyone know off hand if the valves are interchangable?
Postmaster
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How did you come up with .015 preload.....??
also the valves are not the same...the valves for the 74 heads if they are setup for rail type rockers should have a longer stem for the rail to work. The newer heads should have shorter stems..the valve tips are almost at the same height as the retainer....If you use the rail rockers on the newer heads the rails will push the retainers down before the rocker hits the valve...not good.....
also the valves are not the same...the valves for the 74 heads if they are setup for rail type rockers should have a longer stem for the rail to work. The newer heads should have shorter stems..the valve tips are almost at the same height as the retainer....If you use the rail rockers on the newer heads the rails will push the retainers down before the rocker hits the valve...not good.....
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5th Wheeling
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visual estimation- but couldn't tell on all because the valves depressed on some of the cylinders- should I try loosening the rockers? I did this on an earlier engine years ago and just double nutted them to keep them from loosening.
Postmaster
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DUDE.......if it's got a roller cam and lifters and you are using flat tappet pushrods you got problems......does the block have the spider in the lifter valley held in with 2 5/16 bolts....that hold the lifters from turning.
Hotshot
Joined: May 2003
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From: south louisiana
Valve stem length is the same for all mid 66 to the end of production, so the roller pushrods are fine with the 74 heads. The only heads with different stem lengths were the E6SE heads, but these have the same elevation as pertains to pushrod length in the heads.
Postmaster
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Originally Posted by baddad457
Valve stem length is the same for all mid 66 to the end of production, so the roller pushrods are fine with the 74 heads. The only heads with different stem lengths were the E6SE heads, but these have the same elevation as pertains to pushrod length in the heads.
I don't think so.......I have seen rail type rockers like I posted on e7 heads with the factory valves.....and they would not work.....the rail on the side of the rocker pushed down the retainer before it came close the the tip of the valve.....take a look at some factory e7 or even some of the early heads that had pedestal (sp) mounts. the tip of the valve is real close to the retainer...no where's near as tall as the ones in my pic.....
and I believe he said he is running a roller cam and lifters with 74 flat tappet pushrods.....or am I totaly off here.......