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Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 6:47 pm
by RBrown
I replaced both distributors on our 454 Crusaders with Delco EST kits two years ago. I have one reverse rotation engine and I thought that I needed two different distributors. I looked at the original distributors and they had two different model numbers. The difference in the model number indicated that one was that one was for a reverse rotation engine. After several years of on and off research I found out that both engines use the same distributors. The difference is that one engine has a timing chain and the other has a timing gear set. If you go the the Marine Parts Source website you can find your engine and look up the exploded parts diagrams for your engine. My diagrams had part numbers for LH & RH engines. The distributors had the same part number.

I am very happy with the EST distributors. The engines start better and idle much smoother. I must have had the old points distributors set and operating optimally since there is no measurable gain in performance of fuel economy.

Rob

Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 7:35 pm
by EWRice
The cams do spin clockwise in both engines by means of chain in one and gear to gear on the other as stated, however, I believe the cams are different between the two. I will have to double check my sources on this.

Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 9:42 pm
by Leviathon
I think the cams are different. The gear on the reverse rotation engine camshaft is ground so that the distributor still turns the same way. Also on the tranny, model is important. I am working on 2 crusaders to replace my tired 360 Chryslers, and the trannys turn opposite the input shaft. So, starboard engine is standard rotation, tranny is reverse rotation. Port engine is reverse rotation and tranny turns prop standard rotation. I am interested to see how everything is going to line up going from Chrysler to Crusader in the engine compartment.

Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 10:04 pm
by EWRice
Just checked the book. RH is different than LH cams. Distributor gear is b the same on both.

Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 10:52 pm
by carl
BigM

Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 11:01 pm
by TinLizzy
It is also possible that someone could have two of the same direction engines and full reversing transmissions, i.e. zf hurth transmissions. Meaning that the transmissions can take full power all day long in either direction. I do not know if there is a velvet drive that does that.

Re: Twin Screw Engine Rotation...

Posted: Tue Jan 31, 2017 11:40 pm
by RBrown
Oops. Thanks for setting me straight on the cams. I don't know what I was thinking. I went back and removed my comments about the cams.

Rob

Re: Twin Screw Engine Rotation...

Posted: Wed Feb 01, 2017 5:29 am
by carl
BigM

Re: Twin Screw Engine Rotation...

Posted: Wed Feb 01, 2017 10:52 am
by john26
Hi to everyone.Maybe a little off subject but, what rotation is normal for a single screw looking from flywheel end?I should know this..My motor is listed on ID plate as a 255R so does the R possibly indicate reverse rotation or maybe reman.Ford 255 Mercruisers were only made for a couple of years 73-74 ish..very little info available.
Thanks for any help..
John

Re: Twin Screw Engine Rotation...

Posted: Wed Feb 01, 2017 11:10 am
by Fastjeff
Usually reverse rotating.

Jeff