engine swap adaptor plates

[steveo3002]

keep seeing build threads where folk fit another engine to thier old gearbox by means of a home made adaptor plate so they still bolt up

was just wondering how they deal with the gearbox being a inch or so further away with regards to the clutch /input shaft meeting up etc

 

[shed or dead]

Hopefully the gearbox would be over engineered by the manufacturer so that the forces acting on the spline were well within manageable torque transmission levels.

Personally I would have an adapter plate cnc cut by an engineering firm, and try to keep it 1/2" maximum thickness, but there will be plenty of other suitable adaptions.

Do you have access to milling equipment?

 

[AndyStobbs]

Maybe them shim the flywheel out too.

 

[steveo3002]

mr shed ...just asking as i was intrested , i dont have anything to convert

 

[DrNik]

They normally use a centre out of a clutch plate that fits the gearbox input shaft, and then a input shaft that fits the engine, knock these two up into a small adapter, and then a puck which slides over the adapter to increase the length of the release bearing so it can use the standard one, simple, oh and they cut the input shaft down so it's just long enough to catch on the spline on the clutch plate/adapter shaft

 

[mfletch]

The adaptor plates I've seen are only quarter inch thick {steel}

 

[shed or dead]

The adaptor plates I've seen are only quarter inch thick {steel}

Makes much more sense than to me now, especially as mass produced gearbox's are usually (once upon a time) over spec'd to account for the range of engine choices available in most road cars.

 

[normspanners]

Adapter plates only need to be 5mm ish, if you see the drive plate on an auto they are 2-3mm thick and take the full torque of some MASSIVE motors and through a MUCH smaller radii than bell housing radii.
Also some frontwheel drive cars dont have a spigot brg on the first motion so there is no problem with that if the clutch uses a concentric it is an easy job to make a spacer up to take the movement but that usually has to be done anyway when lightening the flywheel because the metal can be removed from the clutch face as well as the back of the flywheel but the first motions usually have enough leeway to accommodate this.

 

[711jrp]

That's the incorrect way of looking at it, a drive plate or flex plate only has to take torsional loads between the center hub and the torque converter, there are no bending loads in the plane of it's thickness,you could probably bend one in a vice by hand if it didn't have the ring gear on it, whereas a conversion plate has the weight of the engine and gearbox trying to bend it in it's weakest plane, these forces must be catered for especially in off road 4x4s where conversion plates are very common. The main reason you often don't see a spigot bearing in fwd's is because the the first motion shaft is sported with two bearings,one a either end.

 

[normspanners]

I dont think you would ever bend a 5mm plate as a conversion plate because the bell housing will be of a least big enough to cover the clutch and therefore cover most of the area of the two, so the actual force of the two separating through bending force will be minimal also due to the fact most engines and gearboxes are mounted in their longitudinal c of g ish, the weight loading is not that great. I obviously was talking in relation regarding to the torque developed where the greatest load is produced. many manufacturers adapter plates are only 5mm.

 

[Spark plug]

The plate will need to be thick enough to hold a decent thread and thick enough to countersink, it the plate needs to be bolted to the engine from the gearbox side.

 

[CompoSimmonite]

Conversion plates to attach different engines to, say, Land Rover gearbox are often 1" or more thick.

Paul H

 

[Wallace]

The thickness of the adaptor plate often depends on the application, it may need to be thicker as the flywheel is too big to fit in the bellhousing if mated closer. One aim of the adaptor plate is to save any mods to the engine or gearbox so either can be replaced without modifying them specifically for that vehicle conversion, it should ideally be all bolt together. I took an adaptor plate conversion off a rwd car recently and replaced it with a bellhousing conversion as an 1/8" gap had appeared where the weight was separating the engine & box, only 3 of the upper studs were left and they were bent. This wasn't a homemade plate, it's an imported kit with all the fittings, drive plate etc and the adaptor is a CNC machined 1/2" alloy plate with high tensile studs. Closer inspection showed the kit not to be at fault as the plate had sections cut away to clear the car chassis and the gearbox bellhousing was hacked up removing two of the lower mountings. From what I could make out this was done so the gearbox could be fitted from under the car instead of taking the engine out! The bellhousing conversion involved cutting the original off the gearbox as like many modern gearboxes they are cast with the main casing.