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Old 06-13-2019, 05:37 PM   #1
roflcopter
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Default B20 Fuel and Power Limits

I mentioned this in my project thread but I thought it may have a bit wider of an audience here...

I have a car with somewhat unknown history, full on racecar, 1970 144. I have emails from a decade ago (previous owners and shops) saying the car was tuned for VP110 and some slightly more recently ones saying it was delivered with a mix of VP110 and pump gas in it, and also another stating it can be run on pump gas but 'reduced power' may be experienced. Reduced power to me sounds like they are flirting with some knock at that point.

I'll list off everything I know (read: think) has been done to it:

B20
Heavily ported head (not sure which one)
Isky Max Competition cam (vv101)
Chevy chomoly pushrods and valvetrain parts
11.0:1 compression (supposedly, not sure if pistons or shaving or what)
DCOE40s
KG Trimning header
KG Trimning intake manifold
Reworked distributor (supposedly 36-37btdc at wot/rpm)
Rev limiter set to 8000 currently
Lightened flywheel
4.27 gears
M40

Now my two big questions are:

A) does this motor need VP110 to be safe? Can it be cut to ~100 octane and be good?

B) and this will be answered tomorrow on the dyno, what kind of whp can be expected?

I'm mostly asking the power question so I can gauge how tired the motor is (if it is at all) and I'm curious what a setup like this is supposed to make. Numbers will be posted once I have them!
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Old 06-13-2019, 07:36 PM   #2
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Should be in the 180 at the crank range I'd expect. That CR isn't too far from what the Competition Parts kits were running. Also would help to now if the bore or stroke were changed.
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http://forums.turbobricks.com/showthread.php?t=224983

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Old 06-13-2019, 08:02 PM   #3
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I think that was left alone (other than maybe an oversized piston for block clean up purposes), I hope it’s making a bit north of that though.

What do you think typical drivetrain losses are with the M40? It has a clutch style LSD in it and most of the running gear seems pretty free moving.
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Old 06-13-2019, 08:04 PM   #4
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You might need bigger DCOE's on that. 45's or 48's.
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Old 06-13-2019, 08:05 PM   #5
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Quite possibly. That should be pretty easy to diagnose tomorrow... if the power shuts off then that’s probably why. It sure ain’t the cam.
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Old 06-13-2019, 08:10 PM   #6
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I would estimate around 15% or so power loss for the M40 since there's no OD or anything.

FWIW the Full tilt Competition Parts B20 was around 200hp at 12.5:1 with some serious head work, big bore kit, header, bigger carbs, etc. and that was back on better quality fuel.
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Old 06-13-2019, 08:12 PM   #7
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Crank or wheel?

And so far everything seems to be done ‘right’ on the actual engine build with this thing. I’m not worried about fuel quality since it’s getting nothing but race fuel for the time being.
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Old 06-13-2019, 10:03 PM   #8
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Too much cam, carbs too small and not enough compression. I think it'll make ~130-140 h.p. at the crank and ~110-120 at the wheels.

The stage IV engine was 2200cc, 11.7:1 with a special head casting, 45/38mm valves and custom port work and it only made 185 h.p. DIN.

Mill the head for more compression or use a thinner head gasket if possible if you're going to stay with that cam. It has more overlap than the Volvo cams so you're dynamic compression is less than 9:1 assuming the bore is close to stock.
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Old 06-13-2019, 10:18 PM   #9
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I looked back through the emails that were forwarded to me...

Supposedly bored 0.030" over with Mahle pistons, "big valve canadian head" milled 0.100" with porting/polishing/etc. Nothing else too telling in any of it.

I guess we will definitely see on power, quite the range being thrown out there for sure. Any thoughts on what fuel is really required in this thing?
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Old 06-13-2019, 10:31 PM   #10
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You can probably run 93 octane pump gas with a dynamic CR of 9:1 but I would back the timing down a bit and listen for detonation to be sure. Cast pistons won't tolerate detonation for very long.
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Old 06-14-2019, 12:46 PM   #11
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120whp as it sits, but there’s more on the table.

15+ AFR through the midrange, not getting into the 13s until over 5500. We’ll go back with some jets and get her dialed in.
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Old 06-14-2019, 02:53 PM   #12
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Dang, that's it? I'm at 130whp at 9:1 on MS, with some random VPD cam I have virtually no specs on.
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Old 06-14-2019, 03:11 PM   #13
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Like I said, there’s definitely more in it with the fueling the way it is. I’m hoping it’ll liven up with some jets.
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Old 06-14-2019, 07:51 PM   #14
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A drag calculator suggests that my PV is around 160-ish at the wheels with some vaguely similar mods. I also have DCOE 40's, with 36mm jets (as large as they make for the 40's).

B20 with 92mm B21A pistons
Rsport head (Stage 3 or 4? - Double valve spring, lots of work on the ports, big valves that all but touch each other)
Isky vv81
KG Trimning roller rockers
Chevy chomoly pushrods and valvetrain parts
11.5:1 compression (dished pistons regaining some of the cc's lost to a *WAY* shaved down head)
DCOE40s - 36mm chokes
KG Trimning header - 4:2:1 - although the 160-ish WHP was with a crappy 4:1 Patriot header
Shorty DCOE intakes
Mallory dual point distro body with Crane optical ignition running an MSD box
No rev limiter but I keep it under 7500-ish
Lightened flywheel
4.10 gears
M41
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Old 06-14-2019, 09:23 PM   #15
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Do you know what main jets you’re on? This has 115s in it currently.
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Old 06-14-2019, 10:00 PM   #16
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I had to go look. 125's on F15 emulsion tubes. Forgot to look at the air corrector.
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Old 06-14-2019, 10:15 PM   #17
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Alright, cool. Thanks!

I’m going to get a kit with a decent range of jets, I’m hoping the chokes and all are correct.
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Old 06-14-2019, 10:18 PM   #18
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I tried the 36 chokes on the engine when it had a stock F head, and it didn't work well. It was only after the R-Sport head went on that the engine pulled enough air to make the 36s work.
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Old 06-14-2019, 10:57 PM   #19
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115 main jets are small but it depends on what size chokes you have.

Here's a jet chart with a bunch of different B20 carb/cam combinations for reference.

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Old 06-14-2019, 11:08 PM   #20
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It had a very suspect intake box/filter on it when I got it. I’m not running that anymore, maybe the jetting is because of that. I’ll figure out what the choke size is tomorrow.
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Old 06-16-2019, 02:12 PM   #21
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Friend bought B20 from well known Swedish Volvo tuner Timo Kormu, he passed away about 10 years ago.

It was Timos latest versions of B20. Somehow OHC engines weren't so popular among rallycross drivers in beginning, and it was late 80's when trend turned towards OHC.

My friend B20 stroker has 92 mm bore and 88 mm stroke.
Head is r-sport casting, but with welded exhaust floor. Valves 46x40 mm. 50DCD Weber's and MotorPuls intake. Cam has 8,5 mm lift. It has 8-bolt crank and M-rods. Pistons are 92 mm KS with std compression height. Pistons comes over the deck height, naturally, so head has space for pistons.

Power? Don't know. It is still in pieces. Has been about 30 years.
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Old 06-16-2019, 08:25 PM   #22
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Quote:
Originally Posted by OttoB View Post
Friend bought B20 from well known Swedish Volvo tuner Timo Kormu, he passed away about 10 years ago.

It was Timos latest versions of B20. Somehow OHC engines weren't so popular among rallycross drivers in beginning, and it was late 80's when trend turned towards OHC.

My friend B20 stroker has 92 mm bore and 88 mm stroke.
Head is r-sport casting, but with welded exhaust floor. Valves 46x40 mm. 50DCD Weber's and MotorPuls intake. Cam has 8,5 mm lift. It has 8-bolt crank and M-rods. Pistons are 92 mm KS with std compression height. Pistons comes over the deck height, naturally, so head has space for pistons.

Power? Don't know. It is still in pieces. Has been about 30 years.
Sounds fancy.
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