Air Head II

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plmbcrzy
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Joined: Fri Aug 18, 2017 4:07 am

Air Head II

Post by plmbcrzy »

I was installing weaker springs to measure pushrods, when I put compressed air to hold valves closed there was air leaking out intake and exhaust not much but I would expect that if the valves were seating properly there should be no leaks so back to shop they went. Both heads got relapped, again same thing. Second time machinist did mineral spirit leak down test and went through them and again. when I pump them up (100psi) I have some air leaks (all 6cyl int and exh) ok that must be the way it is and I'm wrong thinking there should be no leaks but I got a leak down gauge and #1 was at 20% the others just under 15%. That's within range ok good.

Now I go to put the roller rockers on and they all hit off center of the valve tips. I snug up #1cyl to measure rod lengths and sure enough the witness marks aren't looking like what should be expected. I'm almost positive that the new guides got reamed slightly out of whack. That would account for all the problems .

So I'm asking all those of you still reading am I correct in my logic should be no leaks except ring gap and are the heads salvageable. I'm in SW Florida North Port. I'd go with another machine shop but I'm already over budget and would expect that shop should make good on the job.

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plmbcrzy
Posts: 35
Joined: Fri Aug 18, 2017 4:07 am

Re: Air Head II

Post by plmbcrzy »

plmbcrzy wrote:I was installing weaker springs to measure pushrods, when I put compressed air to hold valves closed there was air leaking out intake and exhaust not much but I would expect that if the valves were seating properly there should be no leaks so back to shop they went. Both heads got relapped, again same thing. Second time machinist did mineral spirit leak down test and went through them and again. when I pump them up (100psi) I have some air leaks (all 6cyl int and exh) ok that must be the way it is and I'm wrong thinking there should be no leaks but I got a leak down gauge and #1 was at 20% the others just under 15%. That's within range ok good.

Now I go to put the roller rockers on and they all hit off center of the valve tips. I snug up #1cyl to measure rod lengths and sure enough the witness marks aren't looking like what should be expected. I'm almost positive that the new guides got reamed slightly out of whack. That would account for all the problems .

So I'm asking all those of you still reading am I correct in my logic should be no leaks except ring gap and are the heads salvageable. I'm in SW Florida North Port. I'd go with another machine shop but I'm already over budget and would expect that shop should make good on the job.

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Machine shop swears by his work so my question is has anyone else had the roller rockers not line up centered on the valve tips? He told me he had the same issue with different engines where the roller rockers didn't line up. He has another pair of Corvair heads there and they do the same thing, not line up centered using the steel rockers.

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66vairguy
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Joined: Tue Dec 21, 2010 3:44 pm

Re: Air Head II

Post by 66vairguy »

I recall some years ago a discussion of the "Roller Rockers" found one type didn't work well. The other type did work and were from a FORD engine.

Not saying this is your problem, but it sounds familiar.

The other discussion took place on the Corvair Center Forum. Sorry for the lack of details, but if the shop has two sets of Corvair heads and the rockers don't line up it could simply be the rockers are the problem.
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bbodie52
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Re: Air Head II

Post by bbodie52 »

ImageImagehttp://corvaircenter.com/phorum/read.php?1,839374

:think: Click on the link below for a list of numerous informative links on this subject, including the one mentioned above on the Corvair Center and a YouTube video presentation...

:google: :search: http://www.google.com/search?safe=activ ... %20rockers

SOME FOOD FOR THOUGHT...The high expense, complexity, and possibly low reliability provided by roller rockers in a Corvair engine application caught my attention, and may be well-summarized in the following paragraph:

Image
Pros and Cons of Roller Rockers wrote:...Woody is pretty sure that he is heading back to GM original rockers, not roller rockers. Woody functions as our ‘man on the west coast.’ Many builders have met him this was and have had a glimpse of his racing background. Lots of people have had something to do with ‘race cars.’ On the other hand Woody has run a Ford GT-40 to the lap record at Brands Hatch and was McLaren’s rep in North America. He also has a lot of experience with roller rockers, and he isn’t going to put them in his plane. He ran roller rockers in very demanding situations and thought they required constant attention. He concedes that our application doesn’t stress them anywhere near that far, but his point is that the original GM rockers have a very long history of working, and he simply wants to move back and tap into that reliability. Nothing wrong with the ball design, it is just a question of who made the parts. To Woody, roller rockers are an answer to a question that our application is not asking. Today he is just looking through his collection of used GM original rockers from core engines to find 12 in good shape. We additionally spoke about looking at several different brands of grooved balls to see if they are made differently, but I pointed out that I have been using the ones from Clark's with GM rockers on all of our engines in the last 12-14 years, without issue...
:link: https://flycorvair.net/2014/08/13/pros- ... r-rockers/
Brad Bodie
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plmbcrzy
Posts: 35
Joined: Fri Aug 18, 2017 4:07 am

Re: Air Head II

Post by plmbcrzy »

bbodie52 wrote:ImageImagehttp://corvaircenter.com/phorum/read.php?1,839374

:think: Click on the link below for a list of numerous informative links on this subject, including the one mentioned above on the Corvair Center and a YouTube video presentation...

:google: :search: http://www.google.com/search?safe=activ ... %20rockers

SOME FOOD FOR THOUGHT...The high expense, complexity, and possibly low reliability provided by roller rockers in a Corvair engine application caught my attention, and may be well-summarized in the following paragraph:

Image
Pros and Cons of Roller Rockers wrote:...Woody is pretty sure that he is heading back to GM original rockers, not roller rockers. Woody functions as our ‘man on the west coast.’ Many builders have met him this was and have had a glimpse of his racing background. Lots of people have had something to do with ‘race cars.’ On the other hand Woody has run a Ford GT-40 to the lap record at Brands Hatch and was McLaren’s rep in North America. He also has a lot of experience with roller rockers, and he isn’t going to put them in his plane. He ran roller rockers in very demanding situations and thought they required constant attention. He concedes that our application doesn’t stress them anywhere near that far, but his point is that the original GM rockers have a very long history of working, and he simply wants to move back and tap into that reliability. Nothing wrong with the ball design, it is just a question of who made the parts. To Woody, roller rockers are an answer to a question that our application is not asking. Today he is just looking through his collection of used GM original rockers from core engines to find 12 in good shape. We additionally spoke about looking at several different brands of grooved balls to see if they are made differently, but I pointed out that I have been using the ones from Clark's with GM rockers on all of our engines in the last 12-14 years, without issue...
:link: https://flycorvair.net/2014/08/13/pros- ... r-rockers/
I looked at the pics and videos of Corvair's running roller rockers and was surprised to see that they don't run true to center on the valve tips either, must be a design flaw. I'm going to run them since I've spent the $ already. The pushrods hopefully will arrive today or tomorrow and it will be a week or so before I have everything back together and installed. I'm using a 4bbl intake and a Holley Sniper 2300 EFI, but for cam break-in and adjustment a carburetor to start.

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