Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Stage 3 Displacement Upgrade

I have seen a couple posts on stage 3 upgrading the displacment from 121 to 128. Is it reqired to upgrade the throttle bodies and heads? I am not trying to ring out every drop of power but the cost to increase the displacement (ie pistons and jugs) from S&S seems very resonable once you already unlocked the ecu and upgraded the cams. If you have to Buy new heads or port and modify the heads, it likely becomes very costly. Just wondering if anyone had thoughts on what is required. I have also reached out to s&s and krazy horse.

What is very reasonable cost?
I might be tempted.....

BTW, larger injectors might be required

I run a KH stage 3 and that has no increase in displacement. My understanding is you need new heads, my plan is to do this upgrade within the next few years and I have been given rough costs of £5-6k with an end power of just under 130bhp.

New injectors will be require as mine are running close to max now.

A cylinder bore increase of 1/8" will take a 121 inch3 engine out to 128 inch3.

May be a year or two out of date now but an S&S catalogue lists a 4.375" bore cylinder set (non polished pair) part # 910-0002 @ $611.95 and includes gaskets

Matching forged pistons part # 920-0003 @ $389.95 and include rings, gudgeon pin and circlips.

Catalogue promotes bolt on power with no mods required! The dyno charts shown are with 569 cams and 58mm throttle bodies though.

For the price of Stage 3, etc. At what point does dropping in a crate 128/132/etc make more sense?

If you're looking for some additional low end torque, the overbore to 128", or the appropriate cylinders/pistons, will do just that, more torque.

If you keep everything stock, your throttle response "should" be better. Couple the larger 128" with Phil's urethane Centa inserts, that should make a nice low to mid range stump puller. As been said, maybe slightly larger injectors will be necessary.

I did not see injectors listed in the S&S catalog so anyone know what part number or where to purchase them. I will also call S&S as email is not getting their attention. Even when I speak to them their knowledge is somewhat limited. It is clear x-wedge is not mainstream for them or anyone. It is a shame there is not a more wide adoption of the x-wedge engine as getting info and parts is pretty limited.

Related to the heads it is hard to believe that they would have an x-wedge version with smaller valves just for Morgan. If the upgrade is just jugs, pistons and rings the parts are about $1K which seems reasonable to me.

The same injectors are listed in both dealer and customer catalogues I have. Only one type though part # 55-5005 Fuel Injector assy, style B, 31.3lbs/hr @ 58psi - $83.95

ETA: If I've got my maths right that's around 19 litres/hour from each of two, which sounds plenty.