Gen V or VI ???
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Gen V or VI ???

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    Default Gen V or VI ???

    I`m working on a big block crate engine with the casting no. of 12550313. It does have the provision to mount a mechanical fuel pump. Mortec says 12550313, "454....91-up....4 bolt gen v crate motor, gen vi 4.25" bare block, fuel pump boss". I`m not getting enough oil to the rocker arms. About half are getting very little oil and the rest, none. I replaced the cam, lifters, chain and rockers with Comp equipment for gen iv. The cam is XE-274H-10. Lifters 812-16 and stainless roller tip rockers. Pushrod lenghts are intake 8.280 and exhaust is 9.250. The pushrod guides have gen v stamped on them and were installed by the previous owner. I`m the second person to try and fix this problem. I never checked the casting number until today. Does the gen vi use different lifters and/or cam? What generation engine do i have? How can i tell the difference?
    Last edited by Richard Till; 10-09-2013 at 12:56 AM.

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    Quote Originally Posted by Richard Till View Post
    I`m working on a big block crate engine with the casting no. of 12550313. It does have the provision to mount a mechanical fuel pump. Mortec says 12550313, 454....91-up....4 bolt gen v crate motor, gen vi 4.25" bare block, fuel pump boss. I`m not getting enough oil to the rocker arms. This was a good engine until the owner wanted a cam change. The problem ever since has been that its not getting enough oil to the rockers. About half are getting very little oil and the rest, none. I replaced the cam, lifters, chain and rockers with Comp equipment for gen iv. The cam is XE-274H-10. Lifters 812-16 and stainless roller tip rockers. Pushrod lengths are intake 8.280 and exhaust is 9.250. The pushrod guides have gen v stamped on them and were installed by the previous owner. I`m the second person to try and fix this problem. I never checked the casting number until today. Does the gen vi use different lifters and/or cam? What do i have? How can i tell the difference?
    No Gen 5 has a fuel pump boss. Gen 6 crate and service blocks do. Gen 5 timing covers LOOK like MK IV but are different at the pan seal. Gen 6 timing covers only have 6 bolts. Gen 5 and MK IV have 10,
    The lifter bores on the Gen 6 are approx. .300 taller than MKs and Gen 5. When you installed the flat tappet lifters the tops of the lifter should have been below the tops of the bores when on the base circle of the cam. The front of the cam has a step and uses a retainer plate behind the cam sprocket.

    Comp Cams nor anybody else I know of, sells a flat tappet specifically for a Gen 6. They sell MK flat tappets without the nose step, and you use a MK timing set. If the timing chain was a double roller, you shouldn't have been able to use the stock timing cover.

    If this is a crate engine, it would have come with a hyd roller. I understand the owner wanted more thump in it, BUT WHY DOES IT HAVE A FLAT TAPPET!!!! What did the first guy do with the roller lifters that came in the engine? Keep them??? Somebody should take a flattened trashed flat tappet camshaft and beat that idiot with it. Does the owner KNOW that the engine originally had a roller in it and now has a POS flat tappet?

    Other than helping you ID the engine, I know none this is of much help. But if the thing has reasonable oil pressure, there is not reason the thing shouldn't oil to the top.



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    Thank you very much Sir. You have been a BIG help. I`m convinced that i must have a gen 6 engine. Evidently when the previous owner had the cam changed he installed pushrod guides with gen V stamped on them and thats what i thought it was. I need to turn my back side to an ass kicking machine.

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    Quote Originally Posted by Richard Till View Post
    Thank you very much Sir. You have been a BIG help. I`m convinced that i must have a gen 6 engine. Evidently when the previous owner had the cam changed he installed pushrod guides with gen V stamped on them and thats what i thought it was. I need to turn my back side to an ass kicking machine.
    Pretty sure those are the original plates to the engine. I think all GEN plates are stamped GEN V regardless which GEN engine they are used in. It just IDs them as different than MK plates.



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    Quote Originally Posted by Richard Till View Post
    I`m working on a big block crate engine with the casting no. of 12550313. It does have the provision to mount a mechanical fuel pump. Mortec says 12550313, "454....91-up....4 bolt gen v crate motor, gen vi 4.25" bare block, fuel pump boss". I`m not getting enough oil to the rocker arms. About half are getting very little oil and the rest, none. I replaced the cam, lifters, chain and rockers with Comp equipment for gen iv. The cam is XE-274H-10. Lifters 812-16 and stainless roller tip rockers. Pushrod lenghts are intake 8.280 and exhaust is 9.250. The pushrod guides have gen v stamped on them and were installed by the previous owner. I`m the second person to try and fix this problem. I never checked the casting number until today. Does the gen vi use different lifters and/or cam? What generation engine do i have? How can i tell the difference?
    I have always found Motec to be pretty good, but as Bob stated, there are differences between the Gen 5 and Gen 6 blocks, so I would have to say they made some sort of mistake with their listing.

    OK, to be clear, it had the same oiling problem prior to you installing the new cam, correct?

    Are the three 1/8" pipe plugs installed in the valley? Did you consider running an oil priming tool when you had the intake off?

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    Yes, the engine had the problem prior to my installation of the new Comp Cam parts. Its in a 1962 Chevy station wagon. Owner no. 1 wanted a cam change. Thats where the problem began. No. 1 said to heck with it and sold to owner no. 2 . I couldn`t figure out for no. 2 why it had the poor oil supply while holding 50-60 lbs. pressure. The new owner asked if a new cam, lifters, pushrods, roller tip rockers, springs and timing chain would fix the problem? My dumb ass said hell yes, what else is left? Thats what i would do. I talked to the owner today and confessed my ignorance. You have a 6 instead of a 5. He`s going to call Comp and seek a remedy. I don`t know if hydraulic flat tappet lifters are available for it or not? He may be out for a whole new roller lifter valve train. The saga continues.

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    Pipe plugs, i don`t recall any. Where should they have been? Might it have oiled if they were there?

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