Idle musing
Posted: Sun Sep 25, 2005 4:25 pm
What follows below is a purely hypothetical question, an exercise for the grey cells only. So please don't jump on me for being sooo stupid and naive, I know it ain't realistic. I wish it were tho.<br>
<br>
I've been asked to overhaul two Stag lumps, both of which have been laid up for years. I'll probably tap this mine of wisdom about something or the other on them later. Anyway, this got me thinking about the old 8 pot and the eternal question of weather Triumph ever planned a 32 valve version. I concluded years ago that they did not, it can't be done. Here's why:<br>
<br>
Imagine you have a Stag block with a sprint head on one side and an exactly mirrored head on the other. Picture in your mind the three main timing gears, crank and 2 off cam. Run an imaginary chain round them and rotate this lot in your mind. All three timing gears rotate the same way, clockwise or anti-clockwise, I can't remember and it doesn't matter. On the standard head all is well because the cam lobes are travelling from exhaust rocker to inlet cup. On the bass ackwards imaginary head the cam is rotating the same direction but the positions of the buckets and rockers means the exhaust opening would follow the inlet opening. I'm pretty sure about this but the only time I've ever attempted drawing it out has been in the pub on the back of beer mats. Somehow I doubt my drawing were up to much.<br>
<br>
So why am I asking this? Because after at least 14 years of drunken pub coversations it still bugs the hell out of me from time to time. But more to the point I thought with the number of people on this forum with more motor industry knowledge and experience than I'll ever have someone might have come across the solution. Triumph can't be the only ones to want to economise on timing gear this way and 2 valves per pot seems pretty rare these days. Even on a Ford. I'm pretty sure there are other single overhead cam and rocker straight engines now.<br>
<br>
I've mused a few theoretical and all highly improbable 'solutions' over the years: A cam layshaft (might as well use 2 cams), improbable chain paths with the reverse cam on the outside of the chain (would be less improbable with double sided belt), cam over exhaust valves (fine except the cam timing wheel sticks out the wrong side of the head). All unworkable I'm sure.<br>
<br>
So to sum up in one question; has anyone ever come across a V format multivalve engine that uses only two cams plus rockers?<br>
<br>
Go on, you can laugh now.<br>
<br>
Any vestige of creadbility shredded, Tinweevil.<br>
<p>1978 <!--EZCODE LINK START--><a href="http://www.triumphowners.com/704">Dolomite Sprint</a><!--EZCODE LINK END--><br>
1968 <!--EZCODE LINK START--><a href="http://www.triumphowners.com/705">GT6 II</a><!--EZCODE LINK END--><br>
1972 Spitfire IV<br>
39 anorak points on the Nicholas scale<br>
</p><i>Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... nweevil</A> at: 25/9/05 4:50 pm<br></i>
<br>
I've been asked to overhaul two Stag lumps, both of which have been laid up for years. I'll probably tap this mine of wisdom about something or the other on them later. Anyway, this got me thinking about the old 8 pot and the eternal question of weather Triumph ever planned a 32 valve version. I concluded years ago that they did not, it can't be done. Here's why:<br>
<br>
Imagine you have a Stag block with a sprint head on one side and an exactly mirrored head on the other. Picture in your mind the three main timing gears, crank and 2 off cam. Run an imaginary chain round them and rotate this lot in your mind. All three timing gears rotate the same way, clockwise or anti-clockwise, I can't remember and it doesn't matter. On the standard head all is well because the cam lobes are travelling from exhaust rocker to inlet cup. On the bass ackwards imaginary head the cam is rotating the same direction but the positions of the buckets and rockers means the exhaust opening would follow the inlet opening. I'm pretty sure about this but the only time I've ever attempted drawing it out has been in the pub on the back of beer mats. Somehow I doubt my drawing were up to much.<br>
<br>
So why am I asking this? Because after at least 14 years of drunken pub coversations it still bugs the hell out of me from time to time. But more to the point I thought with the number of people on this forum with more motor industry knowledge and experience than I'll ever have someone might have come across the solution. Triumph can't be the only ones to want to economise on timing gear this way and 2 valves per pot seems pretty rare these days. Even on a Ford. I'm pretty sure there are other single overhead cam and rocker straight engines now.<br>
<br>
I've mused a few theoretical and all highly improbable 'solutions' over the years: A cam layshaft (might as well use 2 cams), improbable chain paths with the reverse cam on the outside of the chain (would be less improbable with double sided belt), cam over exhaust valves (fine except the cam timing wheel sticks out the wrong side of the head). All unworkable I'm sure.<br>
<br>
So to sum up in one question; has anyone ever come across a V format multivalve engine that uses only two cams plus rockers?<br>
<br>
Go on, you can laugh now.<br>
<br>
Any vestige of creadbility shredded, Tinweevil.<br>
<p>1978 <!--EZCODE LINK START--><a href="http://www.triumphowners.com/704">Dolomite Sprint</a><!--EZCODE LINK END--><br>
1968 <!--EZCODE LINK START--><a href="http://www.triumphowners.com/705">GT6 II</a><!--EZCODE LINK END--><br>
1972 Spitfire IV<br>
39 anorak points on the Nicholas scale<br>
</p><i>Edited by: <A HREF=http://p206.ezboard.com/bthetriumphdolo ... nweevil</A> at: 25/9/05 4:50 pm<br></i>
