Lifter preload on my new setup...
Thread Starter
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Joined: Jan 2002
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From: Orlando, FL
Lifter preload on my new setup... Here is the configuration...
-stock heads with 0.015" milled off - the combustion chamber volume measured in at 64.3 cc so the milling is accurate
-GM lifters
-XE-R 224/228 (actually 226/230 measured)
- 7.400" pushrods
Tonite I installed the rockers and gave the lifters time to bleed down (about 20 minutes). I checked the lifter preload on both #1 intake and exhaust. I got about 1 5/8 turns on the intake and 1 1/2 turns on the exhaust from zero lash.
With the bolt having a 1.25 mm pitch this equals 0.049" per turn. So I'm looking at 0.080" and 0.074" preload respectively.
1) Am I missing something here in the calulations
?
2) Should I go with 7.350" pushrods or keep the 7.400" pushrods? I'm leaning towards going to 7.350" pushrods.
Tim
-stock heads with 0.015" milled off - the combustion chamber volume measured in at 64.3 cc so the milling is accurate
-GM lifters
-XE-R 224/228 (actually 226/230 measured)
- 7.400" pushrods
Tonite I installed the rockers and gave the lifters time to bleed down (about 20 minutes). I checked the lifter preload on both #1 intake and exhaust. I got about 1 5/8 turns on the intake and 1 1/2 turns on the exhaust from zero lash.
With the bolt having a 1.25 mm pitch this equals 0.049" per turn. So I'm looking at 0.080" and 0.074" preload respectively.
1) Am I missing something here in the calulations
?
2) Should I go with 7.350" pushrods or keep the 7.400" pushrods? I'm leaning towards going to 7.350" pushrods.
Tim
Thread Starter
TECH Regular
Joined: Jan 2002
Posts: 414
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From: Orlando, FL
Re: Lifter preload on my new setup... Well in theory if a lifter were to pump up it can pump up to an amount equivalent to the preload. This would be a very very bad scenario if it were to happen.
I'm going to go to the 7.350s. Pumping up is still a possible scenario but I'd rather take my chances with 0.030" rather than 0.080".
As far a stock goes... GM never intended the engine to rev upwards of 7K.
Thanks for the responses.
Tim
<small>[ November 26, 2002, 10:12 PM: Message edited by: TimZ28 ]</small>
I'm going to go to the 7.350s. Pumping up is still a possible scenario but I'd rather take my chances with 0.030" rather than 0.080".
As far a stock goes... GM never intended the engine to rev upwards of 7K.
Thanks for the responses.
Tim
<small>[ November 26, 2002, 10:12 PM: Message edited by: TimZ28 ]</small>
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Re: Lifter preload on my new setup... I had always heard that the aftermarket cams are about 0.030" smaller base cercal.
With that taken into consideration, with your heads having been milled 0.015", you are still 0.015" UNDER the factory preload.
With that taken into consideration, with your heads having been milled 0.015", you are still 0.015" UNDER the factory preload.
Thread Starter
TECH Regular
Joined: Jan 2002
Posts: 414
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From: Orlando, FL
Re: Lifter preload on my new setup... Vince,
Yes the cam measured larger than spec'd 226/230 vs. 224/228. The advertised durations (@0.006") were 274/280 vs. 273/277.
I said upwards of 7K not over <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I will probably be shifting around 6600-6700 atleast on the 1-2 shift.
Yes the preload may be ~0.015" less than stock but that doesn't mean it is right for this application. In a stock situation you won't exceed 6200 RPMs where there is really no risk of pumping up.
Tim
Yes the cam measured larger than spec'd 226/230 vs. 224/228. The advertised durations (@0.006") were 274/280 vs. 273/277.
I said upwards of 7K not over <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I will probably be shifting around 6600-6700 atleast on the 1-2 shift.
Yes the preload may be ~0.015" less than stock but that doesn't mean it is right for this application. In a stock situation you won't exceed 6200 RPMs where there is really no risk of pumping up.
Tim
