B6 hiding behind a B3 engine stamp, quite boring really

[Santos]

Hey all,

A couple of months ago i bought a Mazda 121 Funtop then promptly damaged my left hand during an oil change
Since then the suspected head gasket problem manifested itself(which is good really as it is helping me with contesting a speeding ticket, there is no way i can do 80km's an hour at 3500rpm running on two cylinders :shock: )

I am picking up a '92 festiva (Aussie carb'd) which is out of registration and pulling the motor out of it and dumping it into the Mazda so it runs and i have time to do my thing with the original block (matching engine numbers on chassis on block is always a plus with the authorities)
:angel4:

So i now have movement on my hand and will be rebuilding the block :roll:I am going to Bore it out to 1.6 to give it a little more kick. Maybe somewhere around 85hp+ (i want kick and zip not kamikaze red-line). Wherever ever i have the option i would like to take torque over ponies :wink:

Here's my thoughts
-Light port and polish to the head

- high compression pistons (sourced from a newer model 8v engine) as it only be running on 98, do i need to bother with this ? (like will the smaller head have a smaller combustion chamber?)

-Twin Carb intake manifold (heaps of old 85-88 Mazda 1.5l have these) OR switching to EFi (aftermarket would be cheaper here) OR fabbing up a custom intake manifold to run quad-carbs from a 1100cc bike (if the carbs flow enough fuel for a 1100cc bike at 9000rpm then they should be able to flow a 1600cc at 6500rpm right?

is there anything else i should do?Cams? Valves? :?

I want to keep it basic as i am keeping an eye out for 85-88 B6DE engine, which eventually i will rebuild the block once more with the forged internals and Twin-cam head
:idea:

So things like extractors and muffler will prob be counter productive to the budget, it's also going to be driven by my younger sister so I'm staying away from forced induction. (i do however like to know she driving a responsive vehicle so she can accelerate out of the way)

Best of all if the engine number is the same i can say i didn't know the internals weren't stock (which will last me as an alibi until i bolt on the b6DE head )

All input welcome

[Rumnhammer]

plans

Your plans sound good as long as the authorities bother to check for matching #s, otherwise it would easier and cheaper to just swap in a SOHC B6, they look identical to the B3 in a passing glance, so that could pass muster. Of course in OZ you likely have access to stroker kits etc, that we don't get here, so if that could be done cheaper there, and make you feel more comfy then go that way.

Cams would be a good idea especially if you add better carbs, the ones for performance we have here come from Australia, so being able to source them should be a piece of cake for you.

You mention a twin carb manifold, if that is something easily sourced for you, you could likely pick up some nice change snatching those up from your wreaking yard and selling them in the states, since we did not get them here, and one of the top complaints for people with Carbed festivas here is when the stock carb craps out, stock replacements are hard to find so most people just replace it with a single downdraft weber, if the type of manifold you describe is for side draft webers, or even twin downdrafts, it would be a nice performance option for carbed guys here.

good luck
Chris Rummel

[Safety Guy]

Since there are sometimes different coolant passage hole patterns from one B engine to the next, would it be smart for him to maybe send a gasket for that twin carb intake mani to one of us to check for compatability? Just a thought.

Also, isn't boring out a B3 to a 1.6 questionable? I was under the impression that the blocks are slightly different and boring a 1.3 out will not leave enough "meat." Or are the blocks really the same except for cylinder holes?

Karl

[aithanmier]

i doubt you would be able to get 1.6L with enough wall thickness, the b6 doesn't just have a larger bore it also has a longer stroke to give it the extra .3L....might get 1.5L on one though without going too thin...then again it's all up to how long you want it to last.

[Santos]

as far as i'm aware the b3 and b6 have the same stroke :?

like a b3 is 1324cc with a 71mm bore
and the B6 is 1598cc with a 78mm bore

For those keen to reverse this in maths you get 83.6mm stroke
(sorry lads but metric is simplier, just let it go )

To me the early B6 where just a bored out 1.6 by design, when they decided to go BP/B8 they streched it to bore it futher and that's when you can say you ran out of meat.

interestingly enough is the B1 and B5 share the same stroke too!
B1 is 68x78.4 = 1138cc and the b5 is 78x78.4 =1498cc (b5 to me seem like a good ratio)

Anyway to answer the questions


Same block number different internals
rebuilding would prob cost the same as buying a mid-k's motor if i do it myself, but the flip is i know the motor was 'done right' . Something good for another 200 000kms if needed and then i could go out and get a 1.6 overbore piston :lol: an unknown engine can be inspected and tested but at the end of the day it may last 5000 or 50000 :roll:

Also police officer patrol vehicles are equipped wth a little part number computer that let's the officer put in the part number and find out if it was available on that vehicle from the factory. Police don't have to be qualified mechanics in a court of law to defect :lol: The first thing they do is look out for turbos, intercoolers and extractors if they see those and you haven't got an engineer's certificate you haven't got a chance.

It's ok to have the same engine from another car so if your block dies you can get one out of a festiva or 121 so long as it's from a same year or later model (pollution gear being same or better) but if it wasn't available for that make (like b6 and b5 being in the 323 and not 121) then that's a defect too! (but if the numbers match up to the 'factory' and it looks stock he's going to skip over the engine and look at tyres and other easier targets which are easier to clear)

NB: A police office can demand to open up the engine to check boring and such, but this is rare for fear that if they are incorrect it cost theirdepartment a lot to rebuild it to the owners sastisfaction and compensation for inconvinience incurred. Prob only if he was a chevvy motor buff and knew very inch of the inspected engine

Twin Carb Intake

By easy i mean there is always a few pop up every now and then. Not to certain if i could conjure a steady supply. mostly because every guy who wants performance ou of there ford laser or mazda 323 have long since gone for JDM twin cams and efi .If they wanted stock ones i could post them in boat loads.
:idea:

I think they litterally are two 1.6 carbs feeding two cylinders each. the actual air fiter housing looks like an elongated b1.6. If i could get one off the mid 80's 1.5l 323 it would be sweet as the big faded mazda logo would be excellent cammoflauge. It is for some reason hader to get the metal airbox with the carb for some reason.

Still i'm liking this idea better and better as the bike carbs would be better but more hastle to get right (hey but fuel economy and response awsome) and at a later date i could go twin tbi if i give up on my Twincam dream to work on my Suzuki's (yeah plural i know) :twisted:

I'll keep an eye out for surplus manifolds, after all maybe the carby festivas of the states want a bit of the action too

[Rumnhammer]

rules

Man, your cops sound strict. In the states you can put any motor into any car you want as long as it is newer then or the same year as the one being replaced, and has all the emissions intact. Even in California.
Most states just have an emissions check if anything, anything pre 96 just gets sniffed, the later cars get an OBDII plug in. Very few states have a visual inspection, California is one I know of. They get uptight there with stuff not normally on the engine turbos etc, unless it has a CARB sticker, but like I stated above, as long as the engine is one that was imported and used in this country and as long as all the emissions gear is in place, it doesn't matter what car you stick it in.
I had no Idea that they were that strict in OZ!! that sucks.

I would love to do up a B6 DOHC with bike carbs! would be really fun.
Chris Rummel

[Santos]

oh i can put a BP JDm turbo engine in a 121 here in Australia, it's just requires a engineer certificate.

Not cheap as it would require brakes, emission testing and tuning, several vehicles test chassis stiffening may be required etc etc once I've done that i can get a plate exempting from said parts to be defected
any further mods or changes would then have to go through the same process

I can't however exceed a certain capacity regardless of mods in other areas (so no V8 under the bonnet or anything bigger than like a 2.5l )

In someway it's good because i know that high-powered vehicles that ridiculously exceed national safety standards are culled to a minimum

If i do find a cheap pair of motorcycle carbs I'm pretty sure i could tuck them away under the air box to keep them hidden from sight

[festivagt]

...

Have you given any thought of just cutting the number pate off of your stock engine and remounting it on whatever you decide to mount in your car? It's not a black art or anything. It would be a bit illegal but as you say the cops are just going to have to read the numbers, just make sure when you reweld the plate onto your engine you take some time to 'hide the welds or grind them down. Cast iron can be welded, takes a bit of a decent welder that has some experience with cast iron.

[Santos]

Yes i have. About as much work as boring.

Two reasons why i have disregarded the idea.
a) whatever block i get i wan to rebuild it well, so I'm saving steps here
b) The cylinder walls would be like a new b6 if you started off from b3
c) Finding a welder who would be skilled enough and at the same time willing... well I'm not really going there

[Santos]

oh guys i got a mirror topic going on a mazda 323/Ford laser forum in Aus where i have the pics of the gaskets of a b3 and b6 8v and showing how similar they are

http://www.fordlaser.com/forum/viewtopic.php?t=34015

Just don't tell them it's for a 121