Why is a top end rebuild $7,000?
04-03-2010, 01:14 AM
#61
RL Technical Advisor
Its been my distinct pleasure to be able to offer you something constructive and useful,...
Indeed, you can send heads (and anything else) here for a properly done valve job. People do this all the time and I've had folks send me heads as far away as Bahrain,....
In addition to our own P-B guides that are hand-honed to fit (they will last far longer than the OEM ones), the valve lengths are maintained to ensure proper hydraulic lifter travel. This prevents buying the expensive oversize lifters,....
Anyone can just call or drop me a line and I can fill in all the details,....
04-03-2010, 01:21 PM
#62
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If valve guides are replaced and any ovalised seats have the required reworking, how would the correct hydraulic lifter clearances then normally be maintained...are the standard length lifters adjustable? I had previously assumed that the oil pressure would take up the difference in effective valve stem length. I have heard of some instances where the longer lifters have been wrongly put in causing the dreaded tapping/ticking.
Thanks,
Carerra Cup
04-03-2010, 03:27 PM
#63
RL Technical Advisor
Please excuse my lack of knowledge...
If valve guides are replaced and any ovalised seats have the required reworking, how would the correct hydraulic lifter clearances then normally be maintained...are the standard length lifters adjustable? I had previously assumed that the oil pressure would take up the difference in effective valve stem length. I have heard of some instances where the longer lifters have been wrongly put in causing the dreaded tapping/ticking.
Thanks,
Carerra Cup
If valve guides are replaced and any ovalised seats have the required reworking, how would the correct hydraulic lifter clearances then normally be maintained...are the standard length lifters adjustable? I had previously assumed that the oil pressure would take up the difference in effective valve stem length. I have heard of some instances where the longer lifters have been wrongly put in causing the dreaded tapping/ticking.
Thanks,
Carerra Cup
First, whenever a valve job is done, the seats are remachined (3-angle) and the valves are ground. These procedures place them slightly deeper into the seat which repositions the tips of the valves closer to the lifters. Given their narrow operating range (due to size), can force the use of the very expensive oversized lifters. These lifters are not adjustable and thats why Porsche makes them in 3 sizes: standard ($97/each), with 2 oversizes ($220/each).
To assure the use of a standard lifter, one compensates for these changes by making very precise measurements of the installed assemblies, individual valve lengths and then slightly grinding the tips to maintain the exact same dimensions. This assures that a standard lifter can be retained.
The only reason I can think of where lifter noise ocurred after a valve job may be due to a failure to follow the procedures listed above, the improper use of an oversized lifter, or perhaps lifter failure (not uncommon after a lot of miles).
Hope this helps,
Last edited by Steve Weiner-Rennsport Systems; 04-03-2010 at 04:09 PM. Reason: Edited for syntax and clarity
04-03-2010, 03:34 PM
#64
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Thats an excellent question.
First, whenever a valve job is done, the seats are remachined (3-angle), the valves are ground, and this places them slightly deeper into the seat. This repositions the tip of the valves closer to the lifters and given their narrow operating range (due to size), can force the use of the very expensive oversized lifters. These are not adjustable and thats why Porsche makes them in 3 sizes: standard ($97/each), with 2 oversizes ($220/each).
One compensates for this by making very precise measurements of the installed assemblies and individual valve lengths and slightly grinding the tips to maintain the exact same
dimensions. This assures that a standard lifter can be retained.
Hope this helps,
First, whenever a valve job is done, the seats are remachined (3-angle), the valves are ground, and this places them slightly deeper into the seat. This repositions the tip of the valves closer to the lifters and given their narrow operating range (due to size), can force the use of the very expensive oversized lifters. These are not adjustable and thats why Porsche makes them in 3 sizes: standard ($97/each), with 2 oversizes ($220/each).
One compensates for this by making very precise measurements of the installed assemblies and individual valve lengths and slightly grinding the tips to maintain the exact same
dimensions. This assures that a standard lifter can be retained.
Hope this helps,
04-03-2010, 05:21 PM
#65
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[QUOTE=Carrera Cup;7452006]You ARE the man [/QUOTE
I agree. Steve has helped me numerous times with tech help and parts.
He's a good soul...
When my valve job is needed...I'm heading up to Portland!
[/QUOTEI agree. Steve has helped me numerous times with tech help and parts.
He's a good soul...
When my valve job is needed...I'm heading up to Portland!
04-03-2010, 05:46 PM
#66
Drifting
Thats an excellent question.
First, whenever a valve job is done, the seats are remachined (3-angle) and the valves are ground. These procedures place them slightly deeper into the seat which repositions the tips of the valves closer to the lifters...
First, whenever a valve job is done, the seats are remachined (3-angle) and the valves are ground. These procedures place them slightly deeper into the seat which repositions the tips of the valves closer to the lifters...
04-03-2010, 06:05 PM
#67
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