counter rotation chevy 350 rebuild help

[captseasick]

ok, so I have my 270 xf and need to rebuild the counter rotation motor... anyone have any material on rebuilding one... or know of a good place to get a rebuild kit.. need cam and crank. Would love some stuff to read up on, so I know if acces. need to be counter rotating and so on... anything would be great... not having much luck on google....

[seabob4]

Looks like some good reading here...http://www.hotrodders.com/forum/marine- ... 14118.html

Oh, and the one guy who comments in that thread, Bondo?  Know him well from iboats.  Crotchety old F, arrogant...but knows his chit...

[captseasick]

hey You cant teach experience... learned that the hard way in the ocean lol but hey you live you learn

[captseasick]

ok.. so let me see if I have this correct.... the reverse rotation motor has a different crank, cam, rods, and the pistons are turned 180... you use a gear instead of a chain to turn the cam the proper "standard way" but its a reverse rotation grind to go with the reverse rotation crank..? which makes for a reverse rotation firing order.... but seeign as the cam is turning the "standard way" the oil pump turns the correct way to provide oil but you put a reverse cam gear on the distributor to turn counter clock wise... again for the fireing order..... what about water pump and alternator? and raw water pump?... seeign that I am goign with crank mounted pumps..... dang this reverse thing is un-natural to me lol

[GoneFission]

ok.. so let me see if I have this correct.... the reverse rotation motor has a different crank, cam, rods, and the pistons are turned 180... you use a gear instead of a chain to turn the cam the proper "standard way" but its a reverse rotation grind to go with the reverse rotation crank..? which makes for a reverse rotation firing order.... but seeign as the cam is turning the "standard way" the oil pump turns the correct way to provide oil but you put a reverse cam gear on the distributor to turn counter clock wise... again for the fireing order..... what about water pump and alternator? and raw water pump?... seeign that I am goign with crank mounted pumps..... dang this reverse thing is un-natural to me lol

Well CSS, not exactly...  Often the reverse engine only has a different cam and a few other parts...  The crank, pistons, and big parts are often the same.  The distributor may be the same with a different pickup setup, or some run the same distributor and just twist it around to get the right timing.  Water pumps are sometimes the same - they just pull off different sides of the engine to make the rotation work, or switch the inlet and outlet ports to fit the rotation.  The firing order is reversed, but that's just common sense - you can't change the sequence of the piston firing on a V8 without getting into serious balance problems.  Check the specs on your pumps and you may find most of them offer inlet/outlet options depending on rotation.  

[captseasick]

ok, I thought the crank was drilled differently for reverse rotation ( the oil holes) and also thought I read somewhere that the rods were  offset different as well, but if not that would be great so I could order eagle rods for both engines with no issues.... so when you turn the pistons 180 deg. it doesnt change the rod settings or angle? it seems that information is limited when i google counter rotation/reverse rotation marine engine... and have yet to find a reverse rotation engine build site..... again all information is welcomed! and thanks to all for sharing.

[seabob4]

Capt., even though counter rotators have been around for years, there seems to be some sort of "mystery" about how they are built.  All O/Bs and I/Os achieve reverse rotation of the prop via the gearcase, not the motor.  It would be nice, on an I/B, to run a transmission that does the same thing.  That way, you don't have to worry about all the engine crap, just bolt a standard motor up to the tranny and go...

[captseasick]

it would jsut be all tooo easy to have the tranmission reverse it with an extra gear wouldnt it....... but thats a lot of lost money in cams and alternators and sooo on.....

[captseasick]

ok.. so getting my self confused with more reading.... so in the reverse rotation motor the camshaft turns the " standard way".... do you need to put a reverse roation gear on the distributor or leave the standard one on??   What way do you want the distributor turning?? hope this isnt a stupid question...

[seabob4]

Pretty much what I read as well.  Obviously, the firing order is reversed, but with changing the timing chain to a timing gear set, the cam will rotate as normal (proper intake and exhaust sequence, oil pump operation), basically opposite the crankshaft rotation...

Seasick, I believe you're here in FL, correct?  All up and down each coast, particularly in the SE area are excellent marine engine shops.  I'd stop in one of them and ask some questions.  Just like most "boat people", they're usually pretty happy to share their knowledge...

[wingtime]

We converted a standard rotation crate long block to a counter rotating for one of my boats.  It was pretty easy.  I don't remember all the details but I know we swapped out the timing chain for a gear driven set,  I also seem to remember something about swapping out the crank seals or something like that due to the reverse rotation.  The crank, pistons rods etc were left as is,  also the cam stayed the same since it was still rotating the standard direction due to the gears.  I think the firing order stayed the same too...  think about it the piston compression stroke was the same.... just the bottom of the was going the other way.... the top was still pushing up at the correct time.  the valves were opening and closing the same as standard.... the oil pump was turning the same way due to the cam rotating the standard direction etc etc.  only the crank was going backwards.   The engine water pump may have to go backwards, but that depends on if you ware using V-belts or serpentine belts.   The transmission had to have the pump reversed to work with the CR motor.

[GoneFission]

ok, I thought the crank was drilled differently for reverse rotation ( the oil holes)
Nope - the cranks are the same

and also thought I read somewhere that the rods were  offset different as well, but if not that would be great so I could order eagle rods for both engines with no issues.... so when you turn the pistons 180 deg. it doesnt change the rod settings or angle?
The pistons mount the same - you don't turn them

it seems that information is limited when i google counter rotation/reverse rotation marine engine... and have yet to find a reverse rotation engine build site..... again all information is welcomed! and thanks to all for sharing.

A counter-rotating V8 really has very few changes compared with normal rotation.  Look at the repair manuals for Crusader or Mercury marine engines and you will see very few parts that are different for the counter-rotating engine.  I've had boats with counter-rotating inboards for over 30 years and you almost never have to specify which engine when buying parts.  Again, things like the seawater pumps get the ports reversed due to different rotation.

It's really not very complicated - good luck!

[captseasick]

ok so I have read on mulitiple sites that you turn the pistons from front to rear to prevent piston slap due to the reverse rotation... you have been the first to say otherwise..... not saying that you are right or wrong... just saying your the first to say leave them in the normal postion.... so now im more confused lol...
So im looking at manifolds and risers... anyone using GLM manifolds..... have good or bad things to say.....

[GoneFission]

ok so I have read on mulitiple sites that you turn the pistons from front to rear to prevent piston slap due to the reverse rotation... you have been the first to say otherwise..... not saying that you are right or wrong... just saying your the first to say leave them in the normal postion....

Many 4-stroke V8 pistons don't have a front or back - they are symmetric.  Where there is a front/back, it's normally due to valve clearance, and you will hit the valve(s) with the piston if you reverse the piston...