Using a car B21 ?s

[Handegard]

My AQ120B has poor compression, 30-30-155-90. I'm going to rebuild it, but in the mean time, I really want the boat on the water.

I've been offered a B21 from a '81 240.

Now, I know I'd need to swap all the obvious external stuff.

But I read something about swapping the camshaft?

Any other "gotchas" I need to know about? I'm planning only to swap the long block, going to keep my oil pan and valve cover.

Oh, and the boat will only see fresh water.

 

[cr2k]

Re: Using a car B21 ?s

Not familiar with car models, however if you use the carb form the car ( oh problem, it's not a marine carb.) you should have no problems with the cam.

if you are going to use the marine carb, changing the cam may not be a good idea as far as "drive ability" issues.

 

[Handegard]

Re: Using a car B21 ?s

I will be using the boats carb setup, only planning to use the block/head/internals from the car.

I read something about "reversion"? (sucking water in the exhaust valve) when using a car motor without swapping cams, but I believe I was reading about a GM V6, and don't know if it's something specific to that model (the guy that had done the swap was having no-such problems with his car cam)

So I just wanted to make sure.

I'm sure I can get it running with the car cam, but I'd me real annoyed if I dropped it in the water for the first time, and something cropped up...

I'll measure the cars cam lobes when I get it and comepare. Hopefully it's the same cam profile...

 

[ken_23434]

Re: Using a car B21 ?s

Reversion deals with the overlap the camshaft has that can cause the engine to suck exhaust (and hence water) back into a cylinder on it's intake stroke.

Having both the intake and exhaust valves open for a short portion of the engine cycle is not that uncommon for an automobile. This overlap is one of the things that causes the old Hot Rods to have such a distinct idle (lots of overlap).

However, the overlap in a marine environment could cause the engine to suck the water into the cylinder through the exhaust. On a car, it would just be sucking air and exhaust in (not a problem like water would be).

 

[Handegard]

Re: Using a car B21 ?s

That about sums up what I had heard in bits and pieces...

I wonder if this would be a problem on a Volvo, they don't exactly have the same "meaty" cam profiles as a 350 or 302

I'm all set to go get the motor on Monday it looks like. My goal is to have the boat running by the 10th of July, I want it out for my birthday weekend!

 

[cooter2506]

Re: Using a car B21 ?s

Isnt the B21 a mazda engine? Sorry disregard this I realized after I posted you meant a 240 VOLVO car. My wifes uncle would have smacked the daylights out of me for saying mazda. He is a Volvo tech!!! LOL So good luck to ya. Happy boating!!!!!!!!!

 

[Handegard]

Re: Using a car B21 ?s

He he, you're thinking Mazda B2200 probably, which had F2 motor.

I wish this took a Mazda F2. I've got a half dozen of those around. I just built myself a all-new F2T for my daily driver not long ago, and it's old F2 is still in good shape (I'm hunting for a MX6 with a bad motor to put it in)

Sadly, I know nothing of Volvo. I own mostly old Fords/Mazdas. I work mostly on Japanese cars for money, and I used to be a German car tech. I don't know nothing of these Swedish motors