Don Terrill’s Speed-Talk

The Joe Gibbs 10W30 XP3 Racing Oil may have marginal Zinc and Phos, but look at the Moly - 1,125 ppm. That's a lot of Moly and maybe that's what they're using to compensate. I noticed the Mobil 1 SN oils you listed have quite a bit of Moly now also, which I don't believe they had before the Zinc and...

Actually this is part of their prep for all cam break-ins. Apparently they are putting on a better finish and they say this has helped reduce the failure rate on flat tappet cams.

I was reading the Joe Gibbs Oil web site. They use their oil, of course. But they also said they polish the cam lobes and lifters. They recommend you use a tape of chemical polisher to improve the RA finish of your cam and lifters prior to break-in. What is a tape of chemical polisher? Do any of you...

I'd return the Comp and buy Mike's cam.

That is essentially the advantage of modern cams over older designs. More lobe area within a given duration and max lift results in more air flow which helps - but only if your engine needs it and the valvetrain remains stable. Lift-rule cams are a good example of what you are asking about. They pro...

Here's a chart that may help. Even though it doesn't have the 30-30 cam specs, it has the L79, LT-1 and others. The 30-30 cam was 254/254 @.050 with .485 lift, 114 LSA and 112 ICL. Duration was around 346 at 'lash point', and this cam had very long lash ramps. I think it was about 314 with lash at ....

I'm certainly glad some of you with many years of engine building experience are sharing this kind of information. My machinist also told me he won't use Eagle anymore. He also got tired of the 'generous replacement' offers where he paid the shipping every which-way, and kept getting something worse...

What type of oil and bearing clearances do they use?

You're right Mike. And if the .050 numbers are correct the ICL would be 123. These are the specs I copied from the article. I doubt the ICl is 130 and I read somewhere else it is really 123. That gives us IO 15 and IC 81 and if the LSA is 122 the overlap is 42. That sounds a little more 'normal'. Th...

Here are the valve events for the LS7: @.004 IO 8 BTDC IC 88 ABDC ICL 122ATDC EO 81 BBDC EC 35 ATDC ECL 119 BBDC Overlap @.004 = 43 @.050 IO 18 A TDC IC 48 ABDC EO 53 BBDC EC 3 B TDC Overlap @.050 = neg 21 The intake closings are late for the short duration because the ICL is set 12 to 18 degrees la...

That's very true. The article mentioned their computer software to develop the LS9 and the actual engine performance ended up within 3.5% of the computer's prediction. But it's around 100 times the power and complexity of any of the desktop programs most of us would have.

That makes sense. But I'm still wondering why these engines run as well as they do. Obviously, its the combination as always, but with a different application of physics and airflow.

Eric

I found some detailed cam specs for the LS engines. I knew they had wide LSA's, but didn't realize how late the intake center lines were. They run from 118 to 122 degrees ATDC. Intake openings @.004 are from 7-9 BTDC and 18-19 degrees AFTER TDC. Exhaust events look fairly normal. So it seems GM's wi...

The key words are "meets and exceeds" manufacturers specs and requirements. That does not mean it is API approved, so it could have the higher Z and P levels. If an oil is in fact API approved it will have their starburst logo. Many good oils meet and exceed but have not sought the API app...

I think the API limits are down to around 800, and 1,200 is about as low as you want to have for a flat tappet engine.