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| OHC! A fun mental exercise. https://slantsix.org/forum/viewtopic.php?t=26059 |
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| Author: | slantasaurus [ Sat Dec 01, 2007 12:39 pm ] |
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MindforRent, actually Dakite brought up the fact that the dist and oil pump are cam driven (it kinda slipped past me), I made the point about crank trigger and dry sump. Here is another thought to debate. Dan brought up the Pontiac OHC engine. What is the bore spacing and head bolt pattern like on that engine ? Might it be easier to make that work on the slant if it's close enough. It would save a lot of the work changing the slant head. The link for the OHC slant does seem to show it's driven from the rear.....as to how, I'm scratching my head on that one too. It looks like it bolts onto an existing slant head as first sugested though. This is certainly a more constructive discusion than the "Power Pipe" thread though !!!! |
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| Author: | CARS [ Sat Dec 01, 2007 1:53 pm ] |
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Here is a PDF http://clubs.hemmings.com/clubsites/pontiactn/ohc6.pdf that has some good drawings for the Pontiac OHC6 engine. No dimentions but maybe someone can see something to spark an idea. Those crazy inliners have a forum too!! http://p075.ezboard.com/bsohcsix If someone is bored enough to join, maybe a few dimention questions could be answered? |
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| Author: | SlantSixDan [ Sat Dec 01, 2007 2:31 pm ] |
| Post subject: | Re: Ok then. |
Quote: Slantasaurus- thank you, I didn't know that the cam drove the oil pump and distributor. EDIS and a dry sump would be a walk in the park compared to this.
True. One could also solve the ignition issue by driving the distributor right off the end of the camshaft, or with a gilmer belt.Quote: I'm surprised that Chrysler stopped work on an OHC program
Sixes just weren't where the North American premium-engine market was focused in that timeframe. Gasoline was cheap, so V8s were the easy and cheap way to have increased power and extra profits.Quote: I like those cam followers, I wonder if that would work for what we're theorizing here.
Well, perhaps one could cut up some 2.2/2.5 cylinder heads and weld them together...Quote: You mentioned the oiling system on a '81+ hydraulic set up, how did that differ from the older set ups?
Higher-volume oil to the top end.
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| Author: | slantzilla [ Sat Dec 01, 2007 3:01 pm ] |
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If you could make a plate like a Jesel belt drive you could still drive the cam and oil pump with the original cam, and run the OHC cam off of a second sprocket on the front of the cam sprocket. That would only add about 1-1/2" or so to the length.  I wonder what the guy did to rear drive the cam on his conversion. Maybe a spacer between the bellhousing and block, and a gear between the crank and flywheel? It appears he left the stock cam in place for the oil pump and distributor too. 
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| Author: | MindforRent [ Sat Dec 01, 2007 6:12 pm ] |
| Post subject: | More insight, thank you. |
I liked the pdf for the Pontiac OHC, that was actually quite useful for my own edification. It seems to show a gilmer belt driving the cam I wonder about the efficacy of converting the head design over to ours though, if any does join their forum, please do ask them about the dimensions. Dan, I can certainly understand why they stopped from that perspective, the v8's simply made them more money. As for the heads, I sure some people over at turbododge would sell their heads, er....you know what I mean. I like the idea of using a blank or ground down cam to maintain the oil pump and distibutor. it would also keep the oil flow path maintained. That would certainly solve that problem. Slant6Ram mentioned that it might be necessary to relocate the water pump, any reason why? |
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| Author: | slantasaurus [ Sat Dec 01, 2007 7:43 pm ] |
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As for using a 2.2/2.5 cylinder head, why. The 2.0's in the Dodge Neon are avalible in SOHC and DOHC flavors and flow much better. Although it is a crossflow design...... |
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| Author: | Joshie225 [ Sat Dec 01, 2007 7:44 pm ] |
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The Pontiac OHC Six head will be too long to fit a slant. The bore spacing of the Pontiac and Chevy sixes is 4.40" if memory serves. The Pontiac OHC engine was the first auto engine to use a rubber timing belt. The 2.2/2.5 K-car engine heads won't work without lots of cutting and splicing because Chrysler siamesed the cylinder bores so the bore spacing is closer than that of a slant even though the bore is slightly larger. The K-car engine uses a timing belt driven auxiliary shaft to drive the distributor and oil pump. I don't think we're going to find an OHC head that comes close to bolting on to a slant as our cylinder bores are quite small for our bore spacing. |
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| Author: | 68barracuda [ Sat Dec 01, 2007 9:34 pm ] |
| Post subject: | OHC Versus pushrod |
OK now for some gas on the fire  OHC sounds nice and the mental exercise is good the big advantage would have been if one could do a full blown DOHC HEMI crossflow - but we are sort of Slanted out of that game So I was thinking in the line of the Australian 245/265 Hemi - I kwow it is not a true hemi but what does the bolt pattern and and borespacing look like on those beasts?  The most radical aftermarket cylinder head I have ever seen is the 32 Valve Hemi head discussed in How to Build High Performance Mopar engines - or some such name - Frank Adkins... and it uses the std Push rod layout 
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| Author: | SlantSixDan [ Sat Dec 01, 2007 10:19 pm ] |
| Post subject: | Re: OHC Versus pushrod |
Quote: I was thinking in the line of the Australian 245/265 Hemi - I kwow it is not a true hemi but what does the bolt pattern and and borespacing look like on those beasts?
Utterly, totally, completely incompatible.
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| Author: | DionR [ Sat Dec 01, 2007 10:43 pm ] |
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Based on the size of the cam pulley on the OHC slant, I would guess he is using the flywheel as the crank pulley. |
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| Author: | emsvitil [ Sat Dec 01, 2007 11:51 pm ] |
| Post subject: | water on the fire........ |
long stroke engines aren't know for high-rpm abilities..... OHC engines primarily benefit high-rpm...... (esp with 4 valve heads) So you'd end up wasting a bunch of time and money with not much rewards......... |
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| Author: | slantzilla [ Sun Dec 02, 2007 5:27 am ] |
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Quote: Based on the size of the cam pulley on the OHC slant, I would guess he is using the flywheel as the crank pulley.
That is very possible too. 
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| Author: | Sam Powell [ Sun Dec 02, 2007 6:14 am ] |
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Very interesting. Of course a hemi combustion chamber, with cross flow design and spark plug in the middle would be wonderful, but are pretty much out of the question for our small numbers and wallets. You kind of wonder why Chrysler, with their early, and very successful hemi V-8 production did not put the spark plugs on top, and the exhaust ports where the spark plugs are now on the slant six. Maybe hood clearance was the issue. Chrysler did lower the hood on all their cars in 1957 with their "Forward Look" which caught GM and Ford absolutely flat footed in the design wars. Then again, maybe putting the exhaust on the passenger's side would have made right hand drive for those few backwards countries out there difficult somehow. Another, perhaps more practical discussion would be one on combustion chamber design. I have been told the slant combustion chamber is bad, but dont; know why. What can be done to change it? How hard would that be? Do you weld it up,and then grind to suit? What can we do to existing heads that is somewhat cutting edge, short of trying to redesign the entire thing with hemi shape, cross flow, and canted valves. Any thoughts on this? Sam |
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| Author: | Matt Cramer [ Sun Dec 02, 2007 6:29 am ] |
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Quote: Very interesting. Of course a hemi combustion chamber, with cross flow design and spark plug in the middle would be wonderful, but are pretty much out of the question for our small numbers and wallets. You kind of wonder why Chrysler, with their early, and very successful hemi V-8 production did not put the spark plugs on top, and the exhaust ports where the spark plugs are now on the slant six. Maybe hood clearance was the issue. Chrysler did lower the hood on all their cars in 1957 with their "Forward Look" which caught GM and Ford absolutely flat footed in the design wars. Then again, maybe putting the exhaust on the passenger's side would have made right hand drive for those few backwards countries out there difficult somehow.
I'm guessing the issue would be where to put the distributor, although they could have put it at the front of the engine. I've sometimes wondered about a crossflow head for the slant myself. I've sometimes been tempted to measure the bore spacing on a BMW M20 or other small inline six. Of course, every time I suggest that to the local BMW shop, they ask why I don't just transplant in a BMW motor. Sam 
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| Author: | Sam Powell [ Sun Dec 02, 2007 6:39 am ] |
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Quote: I've sometimes been tempted to measure the bore spacing on a BMW M20 or other small inline six. Of course, every time I suggest that to the local BMW shop, they ask why I don't just transplant in a BMW motor.
It's questions like that which make fooling with the slant sooo appealing. They just don;t understand, and there is no way they can ever know why. It is our secret shared by the slant Illuminate.Sam |
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