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Triumph TR3 - TR3A to TR4A Engine Swap

OK, I have a TR4A engine to swap into my TR3 with the seized motor. They are the same engines but with some differences in installation.
The front engine mount is different but one can switch the mounts after pulling the timing chain cover and the cam gear. I have it all apart and this will work.
The exhaust manifolds are different but will switch.
The intake manifold is different but will switch or I guess I could use it if I wanted to.
My problem is at the clutch. The two clutches are different. The TR4A clutch is a Borg and Beck as is, I believe, the TR3A clutch. But they are different; the 4A clutch is 1 inch thinner than the 3A clutch with many fingers. The 3A clutch has only 3 fingers. I can't easily swap them from flywheel to flywheel. The bolt patterns are the same but they are pinned differently.
So my question is: will my old throwout bearing in the clutch actuator be adjustable enough to actuate the thinner 4A clutch? Or, should I buy a 4A throwout bearing and install it on my trans in place of the 3A? The catalogues sell a different bearing for the two engines but the trans is the same. Or, should I get the 3A clutch installed on the 4A engine one way or another? If anybody has been over this ground before I would appreciate any information on the subject. And, am I in for any other unforseen trouble????

Howard Petri

I did the same switch that you are looking at doing but with a tr4 engine. If I remember correctly, the tr4a pressure plate is different than the one used on the tr2-4. However, you could probably switch out the crank from your tr3 and use the tr3 flywheel,etc. The engines are near identical with the major exception being the piston size. My goal for the switch was for the bigger pistons. I was able to buy the engine for $50 at a junk yard...cheaper than buying the components from a supplier.
Mike Parkhill

I know you're probably trying to do this on a budget, but it sounds like you have enough parts to do the switch. You could pull the heads and pans on both, pull the TR4 pistons and sleeves and put them in the TR3 motor. If the rod journals on the 3 are good, splurge a little and fit new rod bearings of the same size. They should be marked. (Mark the pistons 1 2 3 4 front to back and refit in the same hole) Clean the piston ring grooves with a piece of the rings you take off. You'll need a minimum of headset and figure 8 and pan gaskets. Have a valve job done. Probably change the timing chain (another gasket and seal).

Sounds like you have the tranny separated to look at the clutch. Don't tighten the bolts until the transmission is touching the engine, and then go a little at a time. You could break the bellhousing flange.

You'll regret not doing thngs now, you don't want to pull it again for a while :-)

Tom from Nebraska - Welcome to this BBS.

If you have the head off, change all the valves and guides for lead-free gas and have inserts machined in for the 4 exhaust valves to prevent valve seat recession. I had mine done 35,000 miles ago and check the gaps every 3000 miles. In that time, I've never had to re-set the valve clearances.

Don Elliott, Original Owner, 1958 TR3A

In 2001, I convoyed alone (a convoy of one - if that's possible) to VTR in Breckenridge, Colorado and while I was crossing Nebraska (2-lane highway #30), I "raced" from Chapman, NE with a Union Pacific 4 Diesel - 100 container cars for 150 miles to North Platte along beside me. We tooted and honked all the way. After a village, my speedo read 95 mph to catch up again.
Don Elliott

I know the route very well. Chapman's not far from me and I live on hwy 30. Those dam towns always seem to let the train catch back up again. And there's one every 10 miles thru there. The trains honk for every crossing. Reminds me of the old cartoons where the little car races and just barely makes it in front of the train each time. Occasionally a steam train will come through. The TR's big headlights make them seem animate like that, you should get some static cling pupils for the eyes when you show yours, hehe. And they seem to bend in the middle around corners like those old cartoon cars, too.

Not related to this thread, I took a brake drum off the '58 tonight to find both linings separated from the shoes. No wonder that wheel didn't want to turn!

Progress Report
I have installed the TR4A engine in my TR3A. The clutch problem I referred to above wasn't a problem. I just used a TR4A throwout bearing and throw out bearing holder. There seems to be no excess slack in the system although it hasn't been tested under operating conditions yet. I am still doing the plumbing and accessory bolt on work but I may be able to start it soon. I also still need to check valve clearances and rebuild the SU's. More later.
Howard Petri

Way to go, Howard. Can't believe we didn't think of the simple way to do it. Keep us posted.

This thread was discussed between 18/03/2004 and 15/04/2004

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