B6 100wheel/hp N/A

[Sam121]

Hello All,

I have a b6 8V carby I am swapping into my Mazda 121 (Australia) I am using the car for hill climbs/rally and wish to build an engine combo that is;

-Very simple, not too much wiring etc.
-Reliable
-and makes ~100hp at the front wheels

I haven't seen any write ups on this in the forum history. I wish to keep the engine carbied, not use too many aftermarket parts.

So, Is this possible?
What would the essential modifications be to achieve my goal on a budget?

I'm thinking along the lines of; Webber, port matched intake, polished/shaved head, FMS cam. That's about where I run out. I don't know anything about these motors and the 8V is a bit of a darkhorse. Still a rebuild on an 8 valve 4 cyl motor will be CHEAP!

[Roboskittle]

Good luck, if you find anything let me know. I have been searching google, here, other forums, and have had very minimal things surface as far as a N/A SOHC b6 build is concerned.

[TominMO]

I doubt that an 8-valve B6 would make 100 hp at the wheels with those mods. Stock Hp at the crank is 82; subtract ~15% for driveline losses to get wheel HP, and you have about 70 WHP. The mods you list will cost you some good money and maybe bring you about 20 HP; I would be very surprised to see 30.

Can you get your hands on a B8 (1.8L 16-valve) motor? Already has 100 crank HP (85? WHP), more torque, and is a fairly easy install. Sounds like your car won't have A/C, so that makes it easier still. You can sell the B6 to help finance this effort.

[Aaronbrook37]

I doubt that an 8-valve B6 would make 100 hp at the wheels with those mods. Stock Hp at the crank is 82; subtract ~15% for driveline losses to get wheel HP, and you have about 70 WHP. The mods you list will cost you some good money and maybe bring you about 20 HP; I would be very surprised to see 30.

Can you get your hands on a B8 (1.8L 16-valve) motor? Already has 100 crank HP (85? WHP), more torque, and is a fairly easy install. Sounds like your car won't have A/C, so that makes it easier still. You can sell the B6 to help finance this effort.

I completely agree. This is from Wikipedia:

"B8 - The 1,839 cc (1.839 L; 112.2 cu in) B8 is not just a bored and stroked B6. Rather, a new block with widened cylinder spacing. The bore is 83 mm and the stroke is 85 mm. This SOHC engine was used in various Australian Mazda 323s and the American 1990-1994 Mazda Protege. It came in both 8 (B8-E) and 16-valve variants (B8-ME)."

[leapin]

Quaddawg had pretty good numbers with his carbed B6. I think if I remember correctly he had about 100hp he said.

http://www.cardomain.com/ride/2474540

[FestYboy]

i see no issues with reaching your 100hp goal, as i too have a 100+ WHP goal for the B6 carb. in my experiance, your worst restriction will be your carb. at WOT, i still pull 2-3" of vaccum even with the FMS cam. secondly, the exhaust ports are a major restriction as well, as there is no short side radius, just a shelf with a 90* turn. your intake valve is shrouded on the short side as well and can be increased in size with a better designed valve. thermal coating and anti-friction coating are a good idea as well. and if you can add volume to the intake manifold directly under the carb, it should pick up some midrange power.

there's the option of using a twin carb Laser intake with an addapter (search bravekosack for that mod) but i'm looking into 1.6 escort carbs and early 12b rotory carbs (4bbl) as options as well.

[muscle_Car1]

Since he wants to keep it carby does the vacuum advance from the earlier carbys work on the B8? Your going to want custom manifolds on either side of the ported head. Get the race cam not the more sedate competition cam.

I think 100hp@wheels is possible look at whats being done with the b3= http://www.fordfestiva.com/forums/sh...ad.php?t=27805

[Roboskittle]

Does FMS still sell the B6 cam???

I think it is very possible to get the numbers he is after. If a honduh can do it so can we.

[bobbyspider]

yea for your goal you mite want to go with the race cam and raise the compression

[Evil D]

Mill the head down for compression, port the hell out of it and install bigger valves, custom intake/exhaust. It can be done with just about any engine if you have the money to make it happen. It'll have to breath and have to hold some highish RPM to make real usable power.

[getnpsi]

If there are custom pistons for the 1.6 miata they will go into the b6 per the swap info sticky. The head will limit your flow as stated above.

[blkfordsedan]

I agree that 100WHP is completely possible with typical "hot rod" mods.....they just have to be done correctly. My guess is with stock compression, a mild pocket ported head, mild cam, header and a good Weber carb, you'll be looking at around 100hp to 105hp @ the flywheel with peak HP around 5500 RPM and a nice flat torque curve. From what I've seen based on dyno pulls by other members, losses through the Festiva trans seem to be slightly less than the average 15%. I think if you mill the head to raise compression, get a good performance valve job and some thoughtful port work and a lightened flywheel, you should be able to get 100WHP. For hill climb (and also due to the sub-10:1 compression) you'll want to stay somewhat mild on the cam profile. You should have a nice flat torque curve with peak HP at a usable 5500 and make over 100FtLbs torque from 2500 all the way to 5500.

I would talk to Mattdickmeyer (member here). I think he has some custom cam profiles available and also a header kit.

OR, you could just go with a B8 SOHC, but the B6 will be slightly lighter and look stock.

[Sam121]

Thankyou everyone for your imput. It seems that the power levels I'm after will be attainable. There's only one way to prove it and that's to do it! When I've completed my build and dyno'd the car I'll post my method and results. I'm not going to get carried away with HUGE cams or anything as drivability and reliability are more important than +20hp. We shall see what this little motor can do!

[muscle_Car1]

Does FMS still sell the B6 cam???

I think it is very possible to get the numbers he is after. If a honduh can do it so can we.

AS long as its a early b6 then yes its the same as the festy & even has the carby fuel pump knob

[bobbyspider]

i have an early b6 with a fms comp cam in my dd and its fast i enjoy driving it alot thats why i suggested the race cam from fms because it mite be even more fun then the comp cam. word ha ha

dont know how much im putting to the wheels but im sure its not 100 but its still quick and fun and it still suprises people for sure