MCfan Posted May 28, 2011 Share Posted May 28, 2011 Been working on the Monte this week trying to knock a few things off my "to do" list before I head northwest for the summer. My primary goal today was to adjust the valve lash since a couple of the solid lifters were clicking louder than the others. But as soon as I got the first valve cover off, I couldn't resist the tempatation to try some metal polish on it to see if the cast aluminum would polish up. I tried Brasso, Meguires All Metal, Never Dull and Haggerty's 100 All Metal polish. The first three cleaned and polished but didn't remove much. Haggerty's, however, showed more promise. It looks, smells and works exactly like Semichrome polish which has gotten rather expensive lately (used to polish my brass in ROTC with that). So, I got out my old 9" angle polisher and went to work. A couple hours and some detail polishing by hand later, I had a shiny valve cover instead of the aged patina I had been tolerating since I bought the Monte over a year ago. I removed the other valve cover and snapped a picture of both for comparison. Set the valve lash (cold, iron bolck and heads, Sig Erson #120421 cam) to .024" intakes and .025" exhaust. At least three were quite loose (probably the noisy ones), three were a tiny bit tight and the other ten were either right on or a bit loose. Haven't started the engine yet, but don't anticipate any surprises. Final picture is the engine with the polished valve covers re-installed. I've never seen another pair just like these. They have a Chevrolet Towanda engine plant sticker in the center "window" but no other manufacturer's name on them. I think they were installed when the engine was rebuilt in 1974 so they've probably been around awhile. Does anyone recognize them? Were they possibly an aftermarket item from the GM performance shop? Here's the original condition "before" polishing. Here's the other valve cover "after" polishing. Here's the engine after adjusting the valve lash and re-installing the polished valve covers. Shoulda done it long ago! Oh, well ... now I need to tune the Edelbrock 650 (calibration kit is on order), get a taller K&N air filter, install an HEI distributor (with "correction" cap) and replace the headers. Some of that will have to wait until next fall. Quote Link to comment Share on other sites More sharing options...
Ian Posted May 28, 2011 Share Posted May 28, 2011 Looking good! I had a set of valve covers on mine, like that when I got it, they were Micky Thomson covers. I sold them on ebay a few years ago... Quote Link to comment Share on other sites More sharing options...
overdrive Posted May 28, 2011 Share Posted May 28, 2011 Nice job! They look so much better now. Dan Quote Link to comment Share on other sites More sharing options...
502ci Posted May 28, 2011 Share Posted May 28, 2011 Nice job, makes a huge difference... This reminds me I gotta do my valve covers before the Eastern Meet... Quote Link to comment Share on other sites More sharing options...
70mcarlo Posted May 28, 2011 Share Posted May 28, 2011 Nice job on the covers, Dennis! Your big-block looks great! Quote Link to comment Share on other sites More sharing options...
MCfan Posted May 29, 2011 Author Share Posted May 29, 2011 Set the valve lash (cold, iron block and heads, Sig Erson #120421 cam) to .024" intakes and .025" exhaust. At least three were quite loose (probably the noisy ones), three were a tiny bit tight and the other ten were either right on or a bit loose. Haven't started the engine yet, but don't anticipate any surprises. Well, maybe I SHOULD have anticipated a surprise or two .... I ferried my wife to the local Farmer's market today in the Monte because I wanted to see how she (the Monte, not the wife) sounded and ran with freshly adjusted valve lash. Sounded good - steady clickety click of solid lifters with no rowdy ones in the bunch. Ran fine .... once I got her moving .... But ... something happened to the formerly well-mannered idle. As soon as it came off the fast idle cam (at the end of the driveway - its' HOT here!), the idle speed dropped to 600 on the tach and the idle was more "lopey". Of course, I didn't want to show any concern to my wife and have her think I had screwed something up so I pressed on with the journey. Everything went fine but the idle was so lopey at every stoplight, the whole car was shaking slightly and I had to rev it a bit to get under way in first gear. I used the "opposing cylinder" technique to adjust the lash (i.e. when the #1 intake is fully depressed, adjust the #6 intake lash) so I should have avoided any false lash settings. Since I hadn't touched the carb or distributor during the valve lash adjustment, I wondered if I had accidently disconnected a vacuum hose but I found nothing at all amiss. Then I remembered what I had read in a website article about slightly altering cam timing and effective duration by increasing or decreasing valve lash just a few thousandths. Thinking back, at least ten of the sixteen valves had to be tightened to close to "cold" lash settings - three of them by quite a lot. According to the article (as well as common sense reasoning), tightening the valve lash setting effectively adds duration because the lifter engages the ramps on the camp lobes a bit sooner and stays on them a bit longer than a lifter with a looser lash setting. So, my theory is that by adjusting the lash on my valve train mostly tighter, the engine is behaving like it has more duration on the cam when actually nothing else changed. This would also account for a lower idle rpm at the same carb settings and the lower idle combined with the higher duration would produce a more noticable "lope" at idle. I presume that simply turning my idle screw up to 700 rpm will make this little change less noticable? I sure don't want to get back into the dieseling on shut down problem I fought for so long. Okay, all you highly respected (and rightly so) gearheads, what REALLY (or probably) happened to cause such a noticable difference in my engine's idle performance following the simple valve adjustment I described above??? Quote Link to comment Share on other sites More sharing options...
LuckyKenny Posted May 29, 2011 Share Posted May 29, 2011 Nice! I cant wait to see it in person Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted May 29, 2011 Share Posted May 29, 2011 They came out great Quote Link to comment Share on other sites More sharing options...
bigscaht Posted May 31, 2011 Share Posted May 31, 2011 those look great..nice work!!! Quote Link to comment Share on other sites More sharing options...
Winston Wolf Posted June 1, 2011 Share Posted June 1, 2011 A lash change of .004" is equal to 2 deg of duration at .050" lobe lift. Quote Link to comment Share on other sites More sharing options...
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