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#1
07-31-2006, 07:48 PM
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strange pushrod issues
have 72 Lemans 455 with 65 389 heads, two pushrods bad closed over oil hole on rocker end, One more bent nothing else seems damaged rockers all in good shape investigated buying new pushrods but with no set of mics these measure 8 and 11/16 all poncho pushrods I've seen are 9.1 or 9.6 with a set of mics scared to buy and install might cause big problems I did not build this motor bought car in 96, 97 drove to high school ran like scalded dog please help I don't know cam specs or anything kind of in the dark help help sos
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#2
08-01-2006, 01:08 AM
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Yes, 8 11/16" pushrods are quite short for a typical Pontiac V8. One possible reason would be roller lifters (aftermarket, either solid or hydraulic), which are typically quite tall. Have you had the valley cover off to see what type of lifters it has?
The only way to know for sure that pushrod length is correct, is to check the geometry of a rocker arm tip against its valve tip. During an open/close cycle of a valve, the contact of the rocker arm should remain very close to the center of the valve tip. If you search these forums' archives, you'll find lots of discussion of checking geometry. If you have solid lifters, you can definitely check geometry with no more disassembly than a rocker cover off. However, with hydraulic lifters, you would normally need to substitute a solid lifter (same length as your hydraulics) or make one of your lifters into a "temporary solid", by packing the inside with aluminum foil or whatever (requiring removal of intake manifold and valley cover). You could, of course, get real lucky and locate one of your hydraulics that has a very slow bleed-down rate, and check geometry of that one (avoiding pulling anything apart). |
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#3
08-01-2006, 07:55 AM
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The 389 heads used shorter pushrods, under 9" long. The 455 short block may have a cam in that has more lobe lift than the valve train can accomodate, & is bending pushrods. Check that the the springs are not coil binding, the retainers are not hitting the seals/guides. Do the 455 pistons have the valve flycuts in the correct location for the 389 heads?
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#4
08-01-2006, 06:57 PM
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Quote:
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#5
08-02-2006, 04:45 AM
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389 heads on a 455 huh? Don't see that too often. Looks like Jack and Geoff have you on the right track.
Definitely check for spring bind. Should be at least .050 between the coils at full lift. My suggestion would be to read this page on determining valve train geometry http://www.pontiacstreetperformance....traingeom.html You will need an adjustable pushrod like this : http://www.compcams.com/Technical/Cu...g/HTML/293.asp One more question - Do your 389 heads have the bottleneck rocker studs or the straight ones? The latter type would make things much easier.
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1969 GTO hard top ~ Std bore 400, '70-RA3 block, 670 heads, Bal. & Blue... M22, 12-bolt w/3:55s Last edited by GRX; 08-02-2006 at 04:50 AM. |
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#6
08-04-2006, 12:12 AM
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she has bottle necks and poly locks still puzzuled just found damage drove car every day in 97 then made it car # 2 in garage drove here and there seems like something would have thrown in the towel a whole lot sooner then here recently but still going to ck geo and look into adj pushrods ,only former problem was getting hot and then hard starting won't do much this week street rod nats in town in Louisville going to check out some old stuff still would like to cruise mine n show off some muscle but since it broke I'm learning alot always cool to know more guess I'll go brag race
Last edited by MEANASS455; 08-04-2006 at 12:18 AM. |
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#7
08-04-2006, 01:32 AM
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Quote:
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#8
08-05-2006, 12:10 PM
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yes I know just one.... typing too many letters needed to go to bed that day wore out
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