Saw this photo in 'vintage shots of days gone by'. Question: What is the performance advantage of having the air/fuel mixture moving in the 'reverse' direction? Also, does the crank still turn in the same rotation? Youth [in mind] wants to know !
I can see maybe the benefit of long straight intake runners and 8 carbs not jammed together, although these are close. The valves and passages would have to be modified quite a bit. Is there a benefit of side drafts?
[QUOTE="ned5049, post: 11160274, member: 81953". Is there a benefit of side drafts?[/QUOTE] Yes if it's straighter path to the intake valve...Like motorcycle and inline engines...Other than tunnel ram type manifolds most auto engine have down draft because of engine compartment size.
I have seen a few with reverse flow mostly on Salt Flat cars but if there were any real advantages there would be more of them.
All engines are designed with exhaust valves and ports about 80% the size of intakes because that works best. Reverse flow, I don't see how it can work with too small intakes. It has been done for a novelty but I can't see it performing better unless supercharged or turbocharged. The engine does not need to run backwards but it does need a special cam with the lobes relocated.
It's not a performance deal. It's a "Look at me" deal. I believe that GM has single drive geared cams for racing and marine use. I also believe that if you used that gear drive so that the cam turned backwards, the intake and exhaust ports could be reversed. Once the distributor and oil pump were situated it should run. On Bonneville flathead engines with reversed flow. Ron Main used the intake ports for exhaust because of the very convoluted exhaust ports on a flathead Ford. He cut into the block and made new intake ports. The original exhaust ports were not used .
I was just thinking about this a little more. It seems to me that if you wanted to reverse rotation of your engine but not the air flow, All you would need would be a direct gear drive to rotate the cam the opposite direction from the crank,. And a starter that turned the other way. Nothing to do with reverse flow. But tied in with where you can get direct drive gears for your reverse flow engine.
NO...it was NOT a novelty. It was just people thinking for themselves, right or wrong. It stemmed from the desire to go faster than the next guy. There were many that tried that "trick" over the years. On one hand, it beats me as to the "why's" of this change (small exhaust valve). On the other hand, they should be applauded for thinking outside the proverbial box. That's what it takes to win, doing things that others have not, otherwise...you'll always just follow. Mike
Hmmm...carb icing on one hand, and hot exhaust happy to rise on the other! The carb's would have lower entrance air-pressure, at speed.
Bruce Crower built one, their was a detailed article on it in Hot Rod magazine in the mid 60's. His did not use stock ports. It was for Indy I believe.
If you think this engine was built with reverse flow as an attempt to improve performance over a more conventional port location, I have some real good speed parts you might want to buy. Outside the box is good. But you still have to deal with physics. It's an eye catcher. It does it's job well.
December 1970. A good read; all I could find is a link to the cover. https://www.google.com/search?q=hot..._vj_5v1xwIVVTKICh3-fgWH#imgrc=YJQBMEChwzPjNM:
Yup. No amount of port work, and valve work is going to make this an improvement over the conventional arrangement. It is very cool to look at. It has to be just a special cam. Marine reverse rotation engines have a conventional crank, but a starter that turns it backwards. The timing set turns the cam counter to the crank rotation, as opposed to the same direction, so the do NOT have special oil pumps, or distributors. On both of a matched pair of marine engines, the cams turn the same way. The cams are matched in profile, but are special for the application. Reverse: Standard:
if you look closely at that cover pic the ports are not reversed, he moved the intake ports to the outside of the head
Yes. As i pointed out. A special cam would work. But so would running the cam reverse. But as I also said, you would need to situate the distributor and oil pump. Sort of the "More than one way to skin a cat". If you look at the front of my Plymouth engine here. You can see an easy way to deal with distributor rotation. Or you could always go with a crank trigger deal. I once made a twin distributor, reverse rotation ignition for a SBC. Also the oil pump here is going the correct was regardless of cam rotation. I have an idea that Crower cast the heads shown in the HRM piece. You should have seen what he did to a 32 Nash straight eight. I heard alot about the twin cam 4 valve head he was making foe a Packard 8. But never saw that one.
Got to comment the willingness to try absolutely everything to squeeze out more power, in an age before credit cards, websites, and CNC mills.
I didn't even have to look I knew what article he was referring to. And MAN did he miss the boat! AFR did a similar set of BBC heads, NOTHING to do with using the exhaust ports as intakes. I'm surprised some rodabilly hasn't used the DOHC indy ford as an "example"...
And having seen Rich's shop it appears he has tried just about everything... As mentioned above I see this as a potential Ford Flathead advantage if anything. Valve sizes are equal, at least on my 60. With boost the exhaust ports would be OK for intake and the intakes wouldn't heat the block like the exhaust does.
I've never seen it, but I shared a round-trip to Bonneville with him. I am not sure I will live long enough to match the experience that he has had. I fear that the era of true innovation has passed. Now you can just buy horsepower and torque. I envy the guys that had no choice to build it, and did. Now, I mostly try to listen and learn. I can make 1000hp with a credit card and electronics. It doesn't move me in the slightest.
My Dodge Bros has 4 exhaust ports and 1 only, cast in intake port. Now I have been converting it to OHV. But if I was going to run it as a flathead, I would definitely reverse the ports. Four intakes and cut into the cast in intake and make one very large rectangular exhaust port. I might keep the original intake port and use it as a second, cross flow, exhaust port. That would make this guys Chevy look normal.
And unlike doing this to a sbc (or any other domestic v-8 made in the last 50 some odd years), actually have a valid line of reasoning behind it.
I have seen a couple of Model As that used reversed cams. 4 intake ports. 2 exhaust. Seemed to work OK. But I was told they cracked after a while. Seems that the foundry dosen't put as much iron in intake ports as exhaust. Because they shouldn't need it. So when you switch the port walls are to thin for the hot air pounding out of the cylinder. So I am told.
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