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

 

i would go with the 7.350 pushrod.
or you could shim the rockers.

steve frank

 

Thanks.

I will change the pushrods. Shims will change the rocker/valve geometry and I'd rather not mess with that.

Tim

 

I wouldnt bother with it. All that looks fine. Stock, your car had as much or more preload than that. 1.5 turns is just fine for your setup.

 

I agree with JMX Tim... My stock heads are milled .040 with gm lifters.. I am using 7.40 pushrods.....

 

I would use the 7.350 PR.
Good luck,
Chris

 

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>

 

Over 7k? That's up there.. By the way Tim.. The XE-R is that far off? I see that you posted bigger specs than the cam actually is..

 

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.

 

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

 

Thanks for the info Tim.. Maybe I should get my 232/226 cam doctored.. It could be bigger than I think..

 

I talked to Comp today... their preload preference was 0.030".

Tim