B8 w/350 cfm 2-bbl carb, cam & headers?

[bobstad]

I got the new JEGS catalogue in the mail a few days ago, which I always go through daydreaming of my days driving " 'Merican Iron."

I've noticed there are two different 350 cfm two barrel carburetors sold, one by Holley and the other called Road Demon.

I was wondering if I could put a B8 motor with the less radical of the two FMS cams and a FMS set of headers, with one of these 350 cfm carbs; to achieve some sort of torquey and powerful yet highly tractable engine for the Festiva?

I keep thinking about towing something, and how having the extra power to do that would be useful. Not to mention just fooling around driving for entertainment; with the better suspension I've already installed, as well as the Aspire brake upgrade I'm half through, and maybe even some wider rims and tires too when the current set of skins are dust.

I'd seen someone with a Mazda GTX motor in a Festiva, with 132 hp, dual cams and fuel injection; and wondered if using a B8 and a two-barrel set-up might be a more leisurely yet worthy approach.

Realizing this as a fantasy for perhaps the next millennium; but, attracted since my 289 '67 Mustang fastback used to have a Holley two-barrel, I'd driven my first few years as a college student during the early seventies, with Monroe Load-Leveler shocks on all four corners and the then new and revolutionary SEARS steel-belted radial tires too, and the three speed stick.

I also wonder what the difference is between the two carbs in JEGS?

[bobstad]

My BADD!?

In thinking further about the time I spend looking at things not of wild interest; the notion came that someone has mentioned or perhaps I've read; that the modern fuel-injection systems are mostly what is responsible for the greatly increased longevity of automobile motors nowadays.

This is due to the fact there is so much less fuel in the combustion chamber, other than at the exact moment of ignition, thus the cylinder walls are free for the most part of the lubrication defeating effect of fuel washing off the oil from the crankcase which keeps the rings from scrubbing directly upon metal.

Thus, to have a carbureted engine would defeat that effect, is my theory at least?

Can anyone comment about pre-injection Festiva motors lasting for fewer miles, or any other clarification?

[TominMO]

350 cfm is WAY too much airflow for a 1.3 - 1.8 motor IMO. The Weber DG or DF 32/36 carbs that people put on small four-cylinder motors flow something like 250 cfm I think; I will try to confirm that. Basically, sticking a Weber 32/36 on a Festy carbed motor will approximate the better power and fuel mileage of an EFI Festy motor, assuming proper jetting.

Properly jetted, the carburetor will flow about the same amount of fuel as EFI, so too much fuel on the cylinder walls is not a factor; it will all be consumed in the combustion cycle.

The Weber 32/36 is even used on Jeep 4.2 liter motors. With 1300cc, Festys have a combustion chamber volume of 325cc. The 6-cyl Jeep's chamber volume is 700cc and uses the same aftermarket Weber carb as the Festy. So 390 cfm is just too much. Stick with EFI. I have bought three new Webers for different 1.8 liter cars, and the supplier always sent the Weber 32/36.

The B8 is EFI, so just use EFI. Overall it's better than a carb--for example, no fuel starvation at high altitudes, for a carb jetted for sea level. One reason carbs have to be jetted a little lean is to make them more usable from 0 - 9000 feet.

The 100 HP of the B8 will be plenty for towing.

Edit: Here's a good writeup on the Weber carbs we are discussing: http://datsun1200.com/modules/mediaw.../36_Carburetor

[festivaWES]

Good luck fabbing up an intake manifold for the once EFI setup. I think all b8's are 16 valve variants here in the states. There are however, 8 valve 1.8's overseas.

The FM cam won't work...

[Aaronbrook37]

350 cfm is WAY too much airflow for a 1.3 - 1.8 motor IMO. The Weber DG or DF 32/36 carbs that people put on small four-cylinder motors flow something like 250 cfm I think; I will try to confirm that. Basically, sticking a Weber 32/36 on a Festy carbed motor will approximate the better power and fuel mileage of an EFI Festy motor, assuming proper jetting.

100% right... here are the rough peak flow numbers naturally aspirated at 6000RPM.

(Displacement (Cu. In.) x Max Revolutions)/3456

1.3L Motor = 140CFM.
1.6L Motor = 170CFM.
1.8L Motor = 195CFM.

[TominMO]

100% right... here are the rough peak flow numbers naturally aspirated at 6000RPM.

(Displacement (Cu. In.) x Max Revolutions)/3456

1.3L Motor = 140CFM.
1.6L Motor = 170CFM.
1.8L Motor = 195CFM.

Nice!

[bobstad]

0KAY, BUTT, is my theorizing about longevity accurate?

[bobstad]

Sexagesimal

Like Gandhi, one wonders where the shot might come next?

Though as in my sixtieth year now. the question still arises; is any carb-application, going to be "untoward" as far as the motor's longevity?

The JEGS catalogue offers also some older one-barrel Stromberg type carbs, too. Though here is a link to their 350 cfm Holley carbs [http://www.jegs.com/webapp/wcs/store...50cfm%2F2-bbl]

[Aaronbrook37]

Nice!

I've done a lot of work with turbo mapping and air flow, for 1.3/1.6/1.8. This was step one in that set of calculations. My findings were:

1) An intercooler that cuts air temperatures in half (250* to 130*) adds roughly the equivalent of 0.3L of displacement to a turbo car between 1.3 and 1.8 liters.

2) As such, it is more beneficial to B3 or B6 turbo cars to intercool, run meth on, or cryo their cars than to swap out for larger motors.

3) A B3 running 8PSI with an intercooler flows better than a B8/BP running 5PSI without one.

4) A B3 running on more than 6-8 PSI Intercooled will outflow a stock B8/BP.

5) A B3 running 10PSI with an intercooler essentially is like having a 1.9-2.0L engine in terms of flow.

6) A B6 running 10PSI with an intercooler essentially is like having a 2.6L engine in terms of flow.

7) A B8/BP running 10PSI with an intercooler essentially is like having a 2.9/3.0L N/A engine in terms of flow.

8) A B3 Turbo 10PSI with an intercooler flows 196CFM, which is more than a stock B8/BP.

9) A B8 Turbo 10PSI with an intercooler flows 271CFM... so even if you're cranking out near 200HP (calculations put this setup with a medium-sized turbo at 190HP) you still would find that it's smaller than 300CFM.

If you've worked with Excel before, I can send you the raw calculations if you're interested.

My more accurate method puts the B8/BP at 170CFM, factoring in PV=nrt calculations for a standard engine. The B6 at 146CFM, and the B3 at 122CFM. All still at 6000RPM. The biggest variable is of course intake air temperature. It would be fair to call a 1.8L engine between 165-205 depending on the time of year.

IN SUM - if you are not running an engine larger than 3.0L N/A or 2.0L boosted at 10-12PSI, a 350CFM carburetor isn't necessary, and will prove to do more harm than good.

For a stock B8, you should search for a carburetor that flows 200CFM for a 1.8L.

At 10PSI with meth, winter air, and an intercooler, a B8 would flow 313, but only when you were WOT at 6000RPM...

[TominMO]

0KAY, BUTT, is my theorizing about longevity accurate?

I know that old carbureted Corollas and Subarus could get over 300,000 miles no problem, so I would have to say that carburetors have no negative effect on engine longevity.

[Aaronbrook37]

Also according to my calculations, getting a Festiva to 130HP requires either:

10PSI + Intercooler + Small Turbo on a B3

8PSI + Intercooler + Small-Medium Turbo on a B6

8PSI + Medium Turbo on a B8

5PI + Intercooler + Medium Turbo on a B8

For the Mitsu guys and gals, consider medium a 14B Eclipse turbo. Consider small a 9B 3000GT turbo.

The 9B is perfect size for a turbo B3, but it would spool really really quickly thanks to a 0.41 A/R ratio. At high boost with an intercooler, the B3 tops out around 225CFM and 13.52 LBS/min of airflow. This would be theoretically 135-140HP at the crank, but I would worry about the head gasket and strength of internals. Basically a deathtrap without a good build.

For B6's, you need either 10PSI without an intercooler or 6PSI with an intercooler to hit 130HP. Turbo estimate is an 11B/13G Mitsu. Manageable, but VERY feisty.

On the same front, a turbo B8 can accomplish this with either 8PSI or 5PSI with an intercooler using a 13B. Very conservative and safe build.

Bob - skip the carb craze, and build a B8 car. Then, if that's not enough, throw a turbo snail on it and run low boost with an intercooler, some high flow intake/exhaust materials, and a good tune. You'll want at LEAST some 185 performance tires and some suspension/braking as you've mentioned already. That puppy will run 130-150HP at the crank all day and night no problemo... I feel for your clutch already. I would also say it could run 15's or maybe even 14's in the quarter mile with the right grip, tuning, and driver skillset.

[TominMO]

Thanks for all the info Aaron! My B6rt falls very nicely within your figures, with 111 WHP. I'm guessing your figures are crank HP.

[Aaronbrook37]

Yep... I do need your turbo's information as well though to really get you mapped out. Tell me your specific turbine (I'll track down the compressor map), and I'll get back to you with the hypothetical numbers after you give me your PSI and intercooler setup in terms of flow. But yes, from what I see, 111WHP is right on the mark if you're running 6-8PSI with an intercooler turbine pending.

[gorgonheimer]

Dude do my setup. I'm building a bp with a ct26 Turbo from a 91 supra. Ill be running 15-18 psi, 440 cc injectors.

Need any more info?

[Aaronbrook37]

Dude do my setup. I'm building a bp with a ct26 Turbo from a 91 supra. Ill be running 15-18 psi, 440 cc injectors.

Need any more info?

15 PSI no intercooler - 73% efficient compressor, estimate of 187CHP.
18 PSI no intercooler - 75% efficient compressor, estimate of 206CHP.
15 PSI good intercooler - 76% (literally perfect) compressor, estimate of 225CHP.
18 PSI good intercooler - 76% (literally perfect) compressor, estimate of 250CHP.

Note that your injectors won't be too happy with much more than 230-240HP... they'll be running high on the duty cycle, so this will slow you down from reaching theoretical maxes. Look into 660's for your needs. Also look into getting some 999/10-R14 tires for some traction.

Bank on 190-200WHP on 15PSI, and with 18 PSI and a giant intercooler, I would expect to see about 210-220WHP depending on your transmission. Really try and hammer down your IAT's and you'll see huge power gains at 18PSI. Use phenolic spacers, meth, and heat shielding and venting. You can do it.

Food for thought... if your ceramic turbo can last that long, it'll hypothetically flow really well for your purposes up to 25PSI, which would be 300BHP intercooled, or maybe 260WHP if you could keep it strapped down to the dyno. HAHAHA!

For anyone else interested, I can provide you with all of this information with the following data:

Engine, Turbo, PSI, Intercooler.

I can't be doing this for the whole forum, but if you are actually doing a build, I will give you a reasonably accurate power and efficiency quote. Don't ask me about random turbos... I have to track down the compressor maps, which is a pain already.

EDIT: See the third link in my signature if you want a quote or mapping done!