Overhaul a B3; bore & stroke? Etcetera

[bobstad]

I'm thinking about overhauling my B3, and wonder if either the motor's bore and stroke can be enlarged?

That would seem a better way than an used motor,* of not only making sure the engine were reliable; but, feasibly adding advantages of either the B6 or B8 too?**

I'd also welcome any general tips on the B3 overhaul; including those using after-market advantages, as available.

And, is there anyone who sells overhauled engines; ready to use? If so, what's the general and/or specific opinion on those?

*Nice to find a sweetheart deal, of course. **Not to mention the motor has recently gotten a new water pump, timing belt, alternator, timing belt tensioner, and alternator belt; so pieces a person wants to reuse.

[gergorian]

Sure the bore can be increased. I am running .030 over pistons in my b3, as well as a bunch of custom work done to the cylinder head. If you ever plan on boosting your little B3 then you should know that ARP head studs for a B6 work fine on the B3. As for changing the stroke, short of custom rods im not sure if parts from another mazda b series engine will work to stroke/ de-stroke the B3. I have a writeup in the Garage called Project Phoenix if you would like to see what I have done to my engine.

[FestYboy]

Bob, the B3 and B6 both use the same stroke at 85.3mm and unless you want to pay $2500 for the stroker crank, leave that bit alone. as for the bore question, do you really want to pay for machining the block? unless the bores are scored, i'd leave that alone as well. which leads me to the next question: are your front and rear main seals leaking? nessisating their replacement? if no, then i suggest you do what i'm currently doing: top end and reciprocating overhaul. simple tools and solvent are all you really need here. i'll be posting the build shortly once i have enough to show.

[Bert]

Bobstad: if you enlarge the bore enough you'll wind up with a B6! If more umph is what you're looking for then it might be better/cheaper to spend the money on a used B6 engine with all the necessary enlarged manifolds, valve train etc. The fancy new distributor you have for the B3 will fit right on that engine too.

[FestYboy]

^ can't do that, the b3 block won't support that much overbore; you'll run into water jackets and they don't like to hold cylinder pressure. a B6 block is a different casting that allows for the larger bore by siameesing(sp) the cylinders.

[Bert]

^ can't do that, the b3 block won't support that much overbore; you'll run into water jackets and they don't like to hold cylinder pressure. a B6 block is a different casting that allows for the larger bore by siameesing(sp) the cylinders.

That comment was largely in jest. But if I understand correctly it the external dimensions of a B6 and a B3 are identical. Sort of like figuring you can make a GM 400 ci out of an old GM 283 (same basic block) merely by reaming out the cylinders.

[FestYboy]

^ in theory, yes. just making sure you were aware of the differance

[blkfordsedan]

It all depends on what you want for results and what condition the motor is in. You really won't know until you tear it down. The Mazda blocks tend to fair pretty well...usually a basic hone of the stock bore will yield acceptable results. If the pistons are still good you can reuse them. You may also get by with just polishing the crank as well. On the flip side, it may need bored and the crank ground....it just depends on the current condition and what compromises you're willing to make. I don't know your budget, but if it's like mine, it's almost nonexistent. If I recall, your motor has high miles, so it's hard to say what condition the valve guides, cam journals, etc. are in. It may be more cost effective to find a low mileage b3 or b6 that runs good and just do a swap.

[bobstad]

stroked against my grain!

Bob, the B3 and B6 both use the same stroke at 85.3mm and unless you want to pay $2500 for the stroker crank, leave that bit alone. as for the bore question, do you really want to pay for machining the block? unless the bores are scored, i'd leave that alone as well. which leads me to the next question: are your front and rear main seals leaking? nessisating their replacement? if no, then i suggest you do what i'm currently doing: top end and reciprocating overhaul. simple tools and solvent are all you really need here. i'll be posting the build shortly once i have enough to show.

Damn! That sounds like big bucks for the stroker crank...a JEGS catalogue, which is nearly all for old Detroit cast iron stuff; lists a budget Chevy 355 long-block with valve covers for $2895.99 that includes aluminum heads and a nice list of other comparable speed goodies, in a two year-old catalogue. The most expensive crank offering is $725.99 for a large block Chevy, while stock cranks start at well under $200.

The seals behind the timing belt on both the cam and crank were replaced recently, that had leaked heavily enough the alternator was affected and failed; though the engine now seems to use even more oil, if a small enough increase I'm not really sure there was a change.

I've found a place here in town which subsequent to the work to change those two seals, did some front end work whose charge was less than half the quote of the shop which changed the seals. Thus I'm excited about perhaps finding people here who I've found likable, willing to work for me at prices I can afford ; which is what has me thinking more seriously about my Festiva's engine. While I'm also shocked at the difference between the two places; where the far less expensive place bases their fee on $75/hour shop rates. The only problem with them is that they apparently only do front end work; while my notion is perhaps they'd be able to refer me to another place, able to do other work also affordable within my budget.

Anyway, easy to imagine is that the least expensive aftermarket speed parts are those made for old-school hot rods; since they've been around the longest and have sold the most paraphernalia, so have the lowest overhead: While basing the whole shebang on low-cost petroleum, as a facet of super power world domination; too.