Hi wondering if you guys think a rebuild is worth it. I've got a spare 12a engine that I was planning on rebuilding it and putting a street port on it and carbs for a bit extra power and putting it into my current FB so there's minimal downtime with the engine swap..

Anyway the engine has 90K miles on it and I've been warned on other forums that if I take it apart the hole engine might be completely unusable due to wear and tear but if I keep it in one piece it would act as a spare for a few thousand miles.

What do you guys think?

 

90k miles is nothing. I wouldn't worry about tearing it down and rebuilding unless you really wanted to port it or if there is something clearly wrong with it (bad compression, bad coolant seals, etc.). Add a nice carb and exhaust and just enjoy it for now. Later you can rebuild and port.

 

I'm going to have to give the opposite advice as Kent did. If your goal is more power through porting, a lower mileage engine is a good place to start as they usually have fewer surprises once opened up. Before you even crack the keg, have a plan in place, including carb, fuel pump, fpr, etc.. It helps to have and view one of the rebuild vids before even starting the tear down. There is also a porting vid out now days too.

 

Thanks guys, I've broke down my current FB (chassis is rotten) and got the engine and gearbox and rad as well as a few other bits and bobs I'm keeping for spares.

I have another FB on the way should have it in a few weeks its pretty clean but needs a new radiator (thats why I've kept the other one).

My initial plan was to get a new triple rotor e-shaft made up but its proving a bit more complicated than I first thought (that was my logic for keeping the spare 12A in the first place).

Anyway back to the point I feel a bit more comfortable breaking the higher mileage engine (less to loose and less work) If the housing and rotors are at an acceptable standard to be reused I'll clean it up and look into getting a new triple rotor e-shaft made up, if its not too costly or to much hassle.

If it is too much bother/expense I'll port the intake and exhaust ports and rebuild the engine with better seals and tips, maybe give it a lick of paint too then it should be a simple engine swap

Just to clarify both of you think the housing and rotors should be OK if I break the engine, if not I could just keep it as a spare or sell it on should have around 25K miles left in it. Would this last point be accurate?

 

Nothing wrong with it think the compression might have dropped a bit, when you turn the ignition key you need to hold it for about 5 seconds before the engine starts to kick in. Would that be a correct diagnosis?