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Old 10-25-2006, 10:18 AM
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Valve train issues.

I have a question for you guys. Iíve got a very mildly built 305 that has had the following done to it. Block zero decked, Speed Pro flattop pistons, Mallory HEI distributor and plug wires, Comp Cams hardened pushrods with guide plates, and Performer cam, lifters, and carb (6oocfm). Now I took this thing over to a local dyno shop to give it a good tune up and it made decent numbers. 322 Lb ft of torque and 287Hp, about what I expected. What I didnít expect was that it wouldnít turn over 5400rpms before fluttering out. The dyno guy said itís the lifters. I would think the lifters that came with the performer cam would be able to turn to 6K without trouble. Iím thinking itís the valve springs myself since they were just the old reused original ones. What do you guys think? Replacing the springs would get it to go to 6K?

Mike

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Old 10-25-2006, 10:33 AM
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Sure sounds like the springs......Were they checked?

Replace the springs and try it..........they probably need replacing anyways.
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Old 10-25-2006, 10:39 AM
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Nope, unfortunately the heads ended up being a rush job (long story here but me and this machinist parted ways over the head job). What do you think about the lifters? Could they also cause it or not likely?
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Old 10-25-2006, 10:40 AM
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The performer cam is only advertised good to 5500 anyway. Pulling it passed that won't gain you anything. I don't see the lifters being the problem. The cam/springs/heads are.
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Old 10-25-2006, 10:43 AM
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springs

If they are stock springs then there is a good chance there are junk.. I doubt it's the lifters..

Even if you swap the springs out don't expect much above 5000 rpm with that cam and a set of stck 305 heads...You may be able to spin it to 6000 with new springs but there is no reason to.

Keith
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Old 10-25-2006, 11:14 AM
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Yeah, I didnt expect to get a high revving motor out of this but I did kind of hope for up to 6K. The heads are 416s and have had the standard 1.84"/1.5" valves replaced with 1.94"/1.6" valves and had some deshrouding done. The HP was max at 5400 rpm and then the floating at 5500 so I was thinking that maybe if I could get it to turn a little more then I could squeek a few more ponies out of it. Wishful thinking? lol Well, I tried.
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Old 10-25-2006, 01:21 PM
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Your dyno guy should be able to tell from the EGT and A/F mixtures.


If it went stupid rich, the ignition probably broke down.

The EGT will spike when the valves are floating.
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