Re: Snapey's 1935 Racing Biposto
Posted by 55PackardGuy On 2011/6/25 15:14:53
Quote:
Could sinking one or both of the valve seats deeper in the head provide for greater width? Of course, this would result in "shrouding" and also affect combustion chamber pressure. But, remember the extra flow you'll get from the blower. You might be looking for a problem that you won't have.
Quote:
I agree, with your obvious skills and access to equipment, this will not be too hard. Multiple cylinder heads for in-line engines have already been used with good results. International Harvester did it on their crawler tractor engines. 6-cylinder in-line diesel (overhead valve) engines had two "3-cylinder" heads that were torqued individually to the block. The block, of course was over 4 feet long (I estimate), so a full-length head bolted to it would naturally tend to buckle and crack. In fact, the short heads were even prone to cracking. So, another reason for the split head design is maintenance. Possibly just one head needs repair and it's much easier to remove and transport 250 pounds at a time instead of 500 (not really exaggerating much because each included valves and rockers).
SO, separate 4-cylinder heads for a straight-eight automotive engine should be a strength, not a weakness. It's probably been done on other engines, I just happened to be personally familear with an International 6-cylinder in a TD 18 crawler tractor.
Now, about those 2-cycle engines and "scavenging" exhaust from cylinders during the downstroke, using crankcase pressure and ports in the cylinder walls, any old Lawnboy mower gives a great example of how well this works. As most of you know, plenty of other 2-cycle one or two cylinder engines use a similar design. The advantage is: no blower needed, eliminating moving parts and parasitic drag.
This leads back to my flathead. valveless engine... each cylinder could have a discreet crankcase that would used its own pressure on the downstroke to scavenge the cylinder of gases and re-fill with air/fuel mixture. Of course, some type of oil injection or oil-mixed fuel would be necessary in that case. Otherwise, a blower would be needed.
Next, to eliminate the ignition system as well... think gasoline powered engines for model airplanes and cars, but on a larger scale.
The downside to all of this is, of course, emissions. But on a race car, this is not an issue, and the whole point of posting these thoughts is to make sure you're using every possible crazy idea on this Biposto. It's beginning to look like this might end up being your bucket-list vehicle, after all, so it must make a complete statement of your personal values and tastes, or lack thereof.
Snapey wrote:
With what are relativly small valves (and without much room to increase their diameter) it means that to improve flow I will need to increase the valve lift. Also with the valves so closely spaced increasing the overlap could also become a problem.
Could sinking one or both of the valve seats deeper in the head provide for greater width? Of course, this would result in "shrouding" and also affect combustion chamber pressure. But, remember the extra flow you'll get from the blower. You might be looking for a problem that you won't have.
Quote:
http://clubs.hemmings.com/clubsites/wocv/willywilly/willyrac_07.htm ). I figure this will be pretty simple - just double a straight 4 cylinder design to get a straight 8 head... easy...
Actually it is easier than you might think
I agree, with your obvious skills and access to equipment, this will not be too hard. Multiple cylinder heads for in-line engines have already been used with good results. International Harvester did it on their crawler tractor engines. 6-cylinder in-line diesel (overhead valve) engines had two "3-cylinder" heads that were torqued individually to the block. The block, of course was over 4 feet long (I estimate), so a full-length head bolted to it would naturally tend to buckle and crack. In fact, the short heads were even prone to cracking. So, another reason for the split head design is maintenance. Possibly just one head needs repair and it's much easier to remove and transport 250 pounds at a time instead of 500 (not really exaggerating much because each included valves and rockers).
SO, separate 4-cylinder heads for a straight-eight automotive engine should be a strength, not a weakness. It's probably been done on other engines, I just happened to be personally familear with an International 6-cylinder in a TD 18 crawler tractor.
Now, about those 2-cycle engines and "scavenging" exhaust from cylinders during the downstroke, using crankcase pressure and ports in the cylinder walls, any old Lawnboy mower gives a great example of how well this works. As most of you know, plenty of other 2-cycle one or two cylinder engines use a similar design. The advantage is: no blower needed, eliminating moving parts and parasitic drag.
This leads back to my flathead. valveless engine... each cylinder could have a discreet crankcase that would used its own pressure on the downstroke to scavenge the cylinder of gases and re-fill with air/fuel mixture. Of course, some type of oil injection or oil-mixed fuel would be necessary in that case. Otherwise, a blower would be needed.
Next, to eliminate the ignition system as well... think gasoline powered engines for model airplanes and cars, but on a larger scale.
The downside to all of this is, of course, emissions. But on a race car, this is not an issue, and the whole point of posting these thoughts is to make sure you're using every possible crazy idea on this Biposto. It's beginning to look like this might end up being your bucket-list vehicle, after all, so it must make a complete statement of your personal values and tastes, or lack thereof.
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