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Old 11-29-2012, 05:20 PM
oldbogie oldbogie is offline
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Originally Posted by bj383ss View Post
Well made some headway today. Started the engine up to operating temps. Shut it down and starting pulling spark plugs and valve covers so I could adjust the valves.

I FOUND MY PROBLEM!
#2 cylinder has some issues.


Broken pushrod and 2 rocker arms off. No wonder it ran like crap. It also split the pushrod guide in 3 places. It marred the edge of the valve tip but I think it is ok. A couple of the other rocker arms on this side were very loose. SO I guess when I adjusted the valves I obviously did it incorrect. So I am going to pull the intake to get the rest of the pushrod.

I hit the intake valve using a block of wood and hammer and it went down and back up fine so I am hoping it is not damaged.

When I pull the intake I am going to pull each lifter out individually and see if any are damaged. Hopefully this will only need a pushrod and new guide.

Thanks to all those who have been giving advice.

Bret
This makes more sense, there wasn't anything about your build that otherwise would lead to unusual problems, by today’s standards this is really a pretty moderate build and the XE268 isn't all that hot of a cam. This combo should be a good sturdy street engine. I get the feeling you ride it pretty hard which will take the life out of the motor pretty quickly. I don't think your rocker selection was up to the task and perhaps other parts as well. I consider roller tip rockers with ball fulcrum to be a complete waste of money. The problem with rockers is the fulcrum more so than the tip. The ball and socket gets really hot with high spring pressures, valve float, and high RPMs. There isn't any way of really dealing with these temps and friction in the fulcrum other than a fully rollerized rocker. Grooved balls will let you push the edge a little but the XE286 does need a pretty good spring. You did match the Comp recommended (should be required) spring kit with this cam, didn't you? This is big time important and often overlooked when people buy aftermarket heads with an included "racer springs" by someone's definition who are selling the heads not the cam. My best recommendation when buying aftermarket heads it to purchase them bare, use a known good quality valve and use the springs and retainers sold by the cam manufacturer unless you’re sufficiently knowledgeable in the rocket science of valve train dynamics to go off on your own. I find there are damn few people building engines that are that good. This takes expertise and pieces of really expensive development equipment the average guy and many if not most equipment purveyors just don't have. This is a place where you need to pay like Goldylocks, not too soft and not too stiff, just right. Too soft will float the valve train which pounds the parts to pieces when they snap closed. Too stiff and the pressures just wear everything out too quickly. The XE268 does not need a fast leak down lifter, keeping these things tracking the lobe quietly is a problem. You're walking a really fine line between pumping the lifter holding the valve open or pounding the tappet into the lobe.

When you start getting up around .5 inch lift you also need to consider a stepped push rod guide to give more support closer to the rocker as that end with high lift is going to move a considerable distance from the point of support so any deflection of the push-rod will become increasingly magnified where it interfaces on the rocker as this distance increases. That will cause the rocker to want to wander off the side of the valve stem.

I'm not a fan of the simplified method of adjusting valves where you are skipping cylinder to cylinder and side to side doing multiple adjustments at certain crankshaft stations, this especially gets to be risky as the cam durations become longer simply because it is difficult to hit TDC accurately unless you go though the degree wheel and positive stop drill for every adjusting station which is a huge amount of work these simplified adjusting methods were developed to avoid for the flat rate mechanic. I highly recommend that one start at number one cylinder with both valves closed on the top of the power stroke and make you initial adjustments here then rotate the crank through the firing order in order and adjust each as they come up on the firing position. That insures the tappets are not on any part of a lobe. Where one uses older design performance cams with really long ramps leading to and from the action this is a big time problem to get accurate with simplified method. Cams like the XE, the Voodoo, and other similar modern cams where the ramps are short and the action quick are less likely to cause alignment problems on set up but if you're off TDC too much you will have big trouble as these cams come on the lobe really fast.

Bogie
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