Could valves be floating?

[wild85]

As some of you have read in some of my past posts, when my engine hits 4500 rpm it seems like it is hitting a wall, bad performance passed that point. Could the valves be floating because my heads suck(882\'s),and I have 2\" exhaust(also sucks) and just cannot flow enough? The cam is made to pull till 6000 and the valve springs are matched to the cam etc. carb is 670 and intake rpm air gap.So could this be a reason for my bad perf. passed 4500?

[my454s10]

just becuse the springs are matched does not mean it is good..they have to be set up right with the correct shims...if they are set up right than the problem is else where...maybe the lifters are pumpping up...this will cause the same thing...

[wild85]

it was done professionally by an engine builder so it should be shimmed right.

[my454s10]

it may be the heads..882 are smog heads...but i would think that even stock heads would be ok till at least 5500 ...what kind of ingition set up do you have....if it is a stock hei that may be the problem..stock hei will go to about 4500 and start loseing spark big time...

[Scotty_S-15]

I\'d say that the answers to your questions are: No, no, no, no, and no. http://www.s10v8.com/images/smilies/icon_razz.gif

........ But seriously, if you\'ve got new valve springs and installed properly (height), not likely that that\'s the problem. Exhaust should be plenty fine, 2\" duals. The carb is big enough. So............

......... Are you sure the vac. sec. are opening? Go lighter on the spring until you can \"feel\" it, then go back a little.

........ I probably asked you this a dozen times, have you checked TDC, and, if cam is \"straight up\"? Are all the lobes as tall as they used to be? http://www.s10v8.com/images/smilies/icon_mad.gif

......... And of course, fuel might be an issue, and so might ignition. Got that total timing back down to 36 or so?



Oh, and BTW, this is what happened to me when my timing somehow got too far advanced... think it was a slipping balancer \"thing\", but I\'ll never know for sure, the outer ring fell completly off, rubbing on timing cover.



busted piston (http://s10v8.com/members/Scotty_S-15/piston_04-99.jpg)



Looks like a piece of the busted top ring was bouncing around in the chamber for a few revolutions. That was my original engine in the S-15, busted in 3-99, that\'s when the ZZ4 short block went in.

[wild85]

nope, (yikes) still the same. but the truck is parked now, was just thinking about it today! So I thought I would see what you guys thought. Its like the engine has to work real hard at 4500+, it all of a sudden is like an additional load is put on the engine at that rpm. The distrib is hei, has a 50000 volt coil, new module, rotor ,cap, light spring curve kit etc. I have a proform dist. at home with msd cap, rotor. The plastic wire harness is f\'d up though so whenever my engine torqued the cap would touch the cleaner and the timing would go retarded, so I pulled it. It also still has the cough and sputter when you use throttle, except under wot.

[Scotty_S-15]

For what it\'s worth, the engine looked mighty powerful in your burnout video.....

....... So it\'s laid up for the winter? If so, we\'ll have plenty of time to hash it out.... and double check all the details.

[wild85]

Yep shes laid up for the winter! Wondering if i should take the engine apart and see whats up. Or sell it!or do the 383.

[Scotty_S-15]

I\'d say that if you\'ve got the time, just go thru the whole thing, leakdown test, check TDC (again) degree the cam, check fuel flow, check for potatoes in the tailpipeshttp://www.s10v8.com/images/smilies/icon_biggrin.gif , etc.

.......... Not that a 383 is a BAD thing.... http://www.s10v8.com/images/smilies/icon_razz.gif

[riotpolice75]

that or destroke a 400 block. big ass bore, short stroke. ridiculous compression. and you can still run 87 in it.







smith