Change 5.7 engine from Reverse rotation to Standard rotation

[JGP]

Bondo or Don Please help

I put a rebuilt 1985 GM 5.7 270HP (Casting # 14010207) in my I/O boat it was suppose to be a standard rotation engine,but it is a reverse rotation engine,The motor came out of a inboard set of motors the guy was suppose to send the standard rotation to me and he has sent the reverse rotation , So how I know this is when I put a starter on the engine it is turning over correct but will not fire up and the distribitor is rotating counterclockwise. i pulled the timing cover and it is gear driven.
The marine mechanic that is working on this said we can change the cam out and timing gears to timing chain drive and that will correct the problem? He said the tcrankshaft P/N and they are the same for L/H or R/H and
I have heard from another forum with conflecting reports.

1. You need to rotate the pistons AND the rods 180 degrees because of the way the pin is offset for the thrust, If you do not you will have Piston slap? if the pistons are not turned around, the skirts will tend to crack also?

2. The rear main and front main seals need to also be changed? But the motor is suppose to have new seals in it and the motor was never ran in reverse since the rebuild only turned in Standard rotation So Are there different seals for Rev or Std engines. I hope not and maybe it will be OK?

3. A 5.7L GM engine doesn't know or care what
direction it runs. The cam shaft- starter
rotation - timing and firing order are changed.

I am confused now any help will be appreciated, My thought and hope is to get this engine running correct since I just paid to have installed. I hope I can just do the cam and timing and the seals could be OK since they are new and never been run ???
John
:'(

 

[Don S]

Re: Change 5.7 engine from Reverse rotation to Standard rotation

The crankshaft part numbers (From Mercruiser) are different between the LH and RH rotation engines. So is the cam.
Rod and pistons are the same.

Click here and see for yourself.

 

[JGP]

Re: Change 5.7 engine from Reverse rotation to Standard rotation

Thanks Don,
This engine came out of a 1985 Wellcraft twin engine and I not sure if it is a mercruiser because I could not find any Serial # or tag? Thye sticker on the Valve cover says Model 270 ?

 

[Bondo]

Re: Change 5.7 engine from Reverse rotation to Standard rotation

Hi JGP,......

Though I can't Absolutely answer your Question,.....
I still have the Question I left for you over at boatered,.....

$1500.??????

That's going to be Cheap,.... Compared to Rebuilding it In the Boat...........

To change the Cam,... The Timing Cover has to come Off,......
To Properly install the Timing Cover,.... The Oil Pan has to come Off,.....
And you want to do all this IN the Boat,..??..??.....

I don't deal with Righthanded motors,+ have only seen a Few,.......
But,....
I Do Know that motors of that vintage Most Definitely have to have the Pistons hung on the Rods in the proper orientation,....
So,... Yes, they'll probably be Backwards,......

Also,... The Seals are Different,... It doesn't matter if the motors been Run or not,...... That's listed in the link Don posted......

I Know it's Not what you want to Hear,.... But,....
Pulling it,+ Negotiating with the guy that Sold it to you IS still your Best Option........

Btw,...... It really doesn't Matter if it's originally a Mercruiser, or somebodyelse's motor,.......
Their All SBCs to Start.......It's just the Dressings that change........

 

[Don S]

Re: Change 5.7 engine from Reverse rotation to Standard rotation

I used Mercruiser as an example, the basic engine comes from GM, and that includes the crankshaft and the cam. It may be something as simple as the key slot for the crankshaft pulley is in a different location, or it could be all the throws are differnet, I never really compared them side by side or tried to change an engine direction and I doubt few people have, unless they tried it on their own engine.
Take your old engine apart and start comparing parts. As long as you ask questions on forums, you WILL in most cases get conflicting reports on everything. Especially when you try to do something that people just think about and answer, compared to actually doing it and reporting the outcome. There is a big difference in what actually works, and what people think SHOULD work, aka WAG.

 

[DHPMARINE]

Re: Change 5.7 engine from Reverse rotation to Standard rotation

back in the '80's and before,GM had two small bock engines.One had a timing chain,the other was gear to gear.

One had an internally balanced crankshaft.The other was externally balanced and the flywheels didn't swap over.

I doubt this can be corrected by spinning the engine in the opposite direction.

DHP

 

[tunahuntr1]

Re: Change 5.7 engine from Reverse rotation to Standard rotation

Hello JPG,I am writing to you because I very recently ordered a standard rotation engine brand new in crate.It is a 5.7 litre gm merc.Problem was is that I needed a reverse rotation as I found out after outfitting it in my Mako.I was able to tell by the timing gears as you did.This type of enging can easily be changed to a normal rotation engine by changing your rear main seal,cam shaft,and timing chain.If you want at this time you can also change out your lifters to solid roller lifters and push rods.This is exactly what I had to do to make my engine turn backward.After this change out the engine is running purrrfectly fine backward.By the way the reason that the rear main seal is different is because the machining pattern on the rubber seal has directional ribs facing left or right depending on engine rotation....If you have any questions feel free to ask...Good luck and happy boatingd