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Finally put the 1200 on a Dyno, survey says 98whp.


Tom1200

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We put the 1200 on a Dyno yesterday. The shop uses a Mustang Dyno.

 

My motor specs is as follows:

 

A15 1508cc

76.5 MM forged JE pistons

14lb flywheel

Ported GX cylinder head with SI (narrowed stem) 37mm intake 30mm exhaust & Isky duel springs

Delta 278 cam (280 advertised duration .420 lift)

4-1 header 1.75 ID collector

Keihin 39mm flat slide carbs.

 

The motor made 98HP at 8000 rpm and 78ft/lbs torque peak at 6700.

 

The torque curve is very flat making 76-78 from 4300 to 6700.

 

The powerband is also decent; making 95hp at 6500 and 98 from 6700 to 8200.

 

The car is running rich and I'll need to drop the main jets down probably two sizes which should net another 3-5hp.

 

The exhaust pipe at the header flange is jacked up; I'd sold the car back around 1998 when I was racing a motorcylce engined sports racer, the person who had the car then redid the exhaust and unfortunately it was not done well. Then header flange has a 1.75" ID but the ID at the exhaust flange is 1.5" and if that's not bad enough there is a 3-4" run off 1.5" pipe stuffed inside the 2" exhaust pipe. When I got the car back a few years later I had no reason to examine the exhaust, the only reason I discovered it now is that I was drilling the exhaust to fit an O2 sensor for an air fuel gauge (yes kiddies I was reading the plugs to check the jetting).

 

So there's probably an easy 10hp to be had between the jetting and "removing" the outlet restrictor. Long term the goal was to get the car around 120whp so a few small fixes will get it halfway there.

 

I wasn't expecting more than about 105 so the motor was pretty much in the ballpark. All in all it's pretty good for the level of tune. Also back in the day a top level A12 national motor put out around 100hp to the wheels so the performance is probably what it would have been back in the 70s

 

The bonus side is it feeds my driver ego; given I'm mixing it up with cars that while being as much as 300lbs heavier also have 50-85 more horsepower advantage. No wonder I'm having to drove the living snot out of the poor little car.

 

A friend also brought his 2.0 914 which made 101.6 whp, which makes his driving all the more incredible given his car is 2100lbs and he's going 3/4 of a second a lap faster than I am.

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Yes rear wheel horsepower. Becuase I'm cheap and lazy I shoot for about 75% of a full race engine as that's a nice comprimise between output and maintenance intervals. I remember Dave Patton's A15 was/is 156hp so my motor is at about 2/3rds at the moment, perhaps with fixing the exhaust and proper jetting it will get to the magic 75%.

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We put the 1200 on a Dyno yesterday. The shop uses a Mustang Dyno.

 

My motor specs is as follows:

 

A15 1508cc

76.5 MM forged JE pistons

14lb flywheel

Ported GX cylinder head with SI (narrowed stem) 37mm intake 30mm exhaust & Isky duel springs

Delta 278 cam (280 advertised duration .420 lift)

4-1 header 1.75 ID collector

Keihin 39mm flat slide carbs.

 

The motor made 98HP at 8000 rpm and 78ft/lbs torque peak at 6700.

 

The torque curve is very flat making 76-78 from 4300 to 6700.

 

The powerband is also decent; making 95hp at 6500 and 98 from 6700 to 8200.

 

I wasn't expecting more than about 105 so the motor was pretty much in the ballpark. 

 

That's very cool! My engine is similar (except Solexes and 11 pound flywheel) and I was hoping for around 100hp and 80 ft.lb. 

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Yes rear wheel horsepower. Becuase I'm cheap and lazy I shoot for about 75% of a full race engine as that's a nice comprimise between output and maintenance intervals. I remember Dave Patton's A15 was/is 156hp so my motor is at about 2/3rds at the moment, perhaps with fixing the exhaust and proper jetting it will get to the magic 75%.

That's something not a lot of people understand. You can have 100% built race motor, but it needs to be freshened every three races. Or you can have a 80% motor and go two seasons.

 

The A12 in my 320 pickup had 100hp at the flywheel, but the cam was pretty wicked and the valves needed constant adjusting.

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Many years ago while picking up some suspension bits from Neely he offered up a built A12 at a really good price. I snatched it up without thinking and only later learned that the 9000 rpm wonder needed going through every six hours. Fortunately I was able to sell t on for the same price I paid for it.

 

My last Dyno visit was 73whp; that was a otherwise stock GX A12 with ported head and the flatslide carbs. The motor was on 10th season, I rebuilt it with the roarty cam and that 8600 rpm wonder wore out very rapidly. Based on the top speed difference I'd guess that it was making 7-8hp more. Not worth the bother, it was a bear to load onto the tilt trailer, it did nothing below 4500 rpm and the mid close ratio box barely kept it in the powerband. It acted like a carbureted Formula Atlantic or my old 125cc GP bike.

 

Running vintage GT-lite (under 2 liter) and being in the small bore group the car only needs to put out 120-125 to win overall. By contrast if I get thrown in with the B-sedan the car needs to be putting out 150-160whp. The BMW 2002 are allowed 2085lbs with driver and those are putting down 170-180whp. The 510s 175-190 at 2085 to 2185 depending on motor. I'm way to cheap to spend 9-12K on a motor plus the cost rebuilds at the end of every season. Did I also mention I'm lazy?

 

I also have a morbid fascination with driving underdog cars.

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Tom Neely? I built a few of his GT4 motors when I was at Rebello.

 

You're not lazy, you are fortunate in remembering that it's supposed to be fun. One of the main factors in keeping me from racing again is that I know I will eventually want to be competitive, and that takes the fun out of it.

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My old friend, Kent Stacy, used to charge $1000 per second, meaning he would tweak on your suspension and then lap your car and charge $1000 for every second gained in lap times.

 

At some point, your bravado takes over and it just becomes madness. That bravado can cost thousands upon thousands of dollars...and for what?

 

My favorite times on the track we're when I remembered to have fun.

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Yes, Tom Neeley. He had a shop in Burbank then.

 

As for keeping it fun, I struggle with that as well, when I ran 10-12th overall out of 30 cars it was easy not to get carried away. Now that I run top 5 in the small bore group it's a bit harder. I've lead the first 3/4 of the open lap several times but get out motored down the back straight.

 

Of course it would also help if I stop giving pointers to my competitors as to where they're losing time. Last February at Spring Mtn Steve Link followed me around in his B-sedan 510 for a few laps, he was very complimentary about my driving and for sure got him up to speed very quickly. I believe his exact word were "your driving the living $hit out of that thing" When I have to run with the B-sedan cars it's brutal, there's a 10-15mph speed differential at the end of main straight. The front running cars 6-9 seconds a lap faster. A friend drove Nitkowski's (sp) 610 and was almost 11 seconds faster, nothing like a 190whp.

 

Now that Spec Miata is allowed in vintage that would probably be the way to keep things cheap. For someone who's an engine builder the cost would be low because the motors for them cost more than the rest of the car. 115 hp at the rear wheels would be enough to keep it competitive. Ironically the 99whp my car is belting out is equivalent.

 

I've raced a Miata and it's one of the few cars I find as fun as the Datsun but there's something about that skatey slip sliding leaf spring car that is the 1200 that I really enjoy. If I really wanted to go faster I have the 87 Novakar Formula 500 in the garage, it's chassis number 3 and has a bit of history so it would easily be accepted. Ironically the Rotax motor is probably good for 100whp, of course in a 735lb car it does result in "slightly" better acceleration (not going to find a Datsun that does 0-60 in 3.5 seconds).

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Spec Miata is vintage? Boy, I am getting old. I remember when they were in showroom stock classes. Who were those two brothers that raced showroom stock Miatas? They were big guys out of the south bay and were affiliated with Toyo. Name's on the tip of my tongue.

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I know who you are talking about but can't remember their names either. I bought Eric Moorhouse's SSC Miata in 95 and ran it regionally for the 2 years it was eligible. After that I took the cage out and all the graphics off taking it back to just a plain street car. When I bought the car my son was a toddler, he turns 24 next month.

 

I remember when Datsun parts were stupid cheap and a 240Z with 170 rear wheel horsepower was F@&&ing amazing!!!!

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