|
|
|
|
| Author |
|
|
Rosco_NZ
|
Valve replacement required??
Hi Pelicans,
So I’m building a 2.7RS+ engine for my ‘72T restoration, replacing some parts (upgrade to 7R cases, Nikasil cylinders, mod-S cam, upgraded valve springs/ retainers) while modifying / retaining others (CNC ported heads, inlet stacks, T to 019 pump, standard rods, cross-drilled crank) My question relates to the valves .. appears the engine had a top end rebuild sometime, the valves likely replaced as they’re in spec .. But I’m guessing all valves are not created equal, and they can be a risk item, failing & dropping into the combustion chamber. How much is in reusing vs new valves? How much does quality change different price points? What makes a better valve? Thanks all. Regards from down-under. Ross |
||
02-23-2020, 09:32 AM
|
|
|
Registered
Join Date: Jun 2009
Posts: 1,242
|
Mich the stems, and if they are in spec and the lip of the valve still has good margins, have the valves ground and use them. New valves are nice, but may not be necessary and put that money toward what you really require. Bob
|
||
|
02-23-2020, 01:06 PM
|
|
|
Registered
Join Date: Oct 2008
Location: Nash County, NC.
Posts: 8,503
|
+1 on in spec valves.
Bruce |
||
|
02-23-2020, 01:45 PM
|
|
|
Rosco_NZ
|
Thanks to those responding. I guess I’m concerned that this engine designed rev ceiling 74-7500 rpm. Would hate to drop a valve into the new ($$$) engine ... But you seem to be saying rest easy ...
|
||
|
02-23-2020, 01:47 PM
|
|
|
Ingenieur
|
The price of the engine and the rev range makes some sort of non-destructive testing worth a look. Valves are subject to thermal and mechanical fatigue. It is only $100 or so.
|
||
|
02-23-2020, 02:41 PM
|
|
|
Registered
Join Date: Oct 2008
Location: Nash County, NC.
Posts: 8,503
|
New things self destruct, too
Modern quality isn’t necessarily guaranteed. Spec is spec Bruce |
||
|
02-23-2020, 05:05 PM
|
|
|
|
Registered
Join Date: Jul 2001
Location: mt. vernon Wa. USA
Posts: 8,714
|
+1....in spec is in spec
__________________
[B]Current projects: 69-911.5, Previous:73 911X (off to SanFrancisco/racing in Germany).77 911S (NY), 71E (France/Corsica), 66-912 ( France), 1970 914X (Wisconsin) 76 911S roller..off to Florida/Germany RGruppe #669 http://www.x-faktory.com/ |
||
|
02-27-2020, 08:33 AM
|
|
|
Rosco_NZ
|
Valve replacement required??
I figured this was going to draw responses from both sides .. thanks all for your thoughts .. here are mine ..
Firstly in the aircraft world, parts have an hourly life which when exceeded means the parts are retired & replaced, regardless of spec. Results are catastrophic if parts fail .. Given the the use will be Touring, D/E event days, Club Days & occasional track. Even with the rpm limit of 74-7500, the engine won’t live there often. I’m building this 2.7 as much for torque as HP & therefore despite the relatively low cost of new valves, I’ll give these parts another go around. Rolling the dice .. |
||
|
03-03-2020, 02:28 PM
|
|
