BN4 Longbridge Oversized Valves?

[Csarneson]

I am just starting an engine rebuild on my gallery head bn4 engine. I have a couple engine experts telling me that I should have enlarged valve seats and valves put in. Has anybody done this? Theoretically there are performance gains to be made but I have no idea. I've read that performance on this head is primarily limited by the carbs but again I don't have a good grasp. Thoughts?

Chris

 

[BoyRacer]

Your performance is NOT limited by the carbs....it is limited by the head design. Get a 6 port head and don't waste your money on a galley head. There is a good reason why they changed to a 6 port head.

 

[Csarneson]

Thanks Richard. I don't plan to swap out the head anytime soon. I will probably just do a basic rebuild then. I appreciate your help.

 

[Randy Forbes]

The 2-port head has a very dismal inlet tract, and I agree with Richard that there's nothing to be gained by fitting larger valves__certainly nothing you'd feel in the seat of your pants! If you're planning to keep the car/car's engine in original appearance, then you're just going to have to suck it up and take what you can get.

When I built the Longbridge engine for the car that Jim, aka healeyblue, restored, I fitted it with a BJ8 camshaft (and also a raft of polymer coatings, but more in the name of efficiency & longevity, than performance gains); you might ask him for his opinion on how it runs today, but I am not sure if they ever got the chance to drive it before the engine was removed and sent to me.

I did manage to get a few pics of the galley head before I put the core-plugs back in, to give you some idea of what the intake charge__air/fuel mixture__has to thread its way around to reach the cylinders. It's not pretty! If you're not concerned for originality, don't miss the last pic...

And for the kill shot! Looking forward from the rear:

Down the galley itself, and you see the row of head-studs that bisect the corridor.

Same shot, but from the front of the engine.

From the induction standpoint of a Healey, this is everything that the 2-port head is not

 

[Csarneson]

Randy if I were to swap in a 6 port head does it have to be from a 100-6 or will a later 3000 work as well?

 

[Randy Forbes]

Except for a skight detail difference near the water temperature port, there is little difference, so yes, you can use either one. I'm 99.99% certain the valves/ports are the same size, but look the valves up in a parts catalog, and you can verify for yourself.