So I finally got the car onto a Dyno to see what the the actually put out. A fellow vintage race (he runs a 2.0 914) set up the time for a couple of us. The shop uses a Mustang Dyno which I'm told read a bit lower than the Dyno-Jet machines (supposedly around 12% lower). Also the Mustang Dyno is supposed to be more accurate.

The motor made 98 at 8000 rpm with a mind blowing 78 ft/lbs of torque at 6700. The torque curve is pretty level form 4300 to 6700 then tapers off down to 68 at 8000 rpm. Power is fairly level, 95 at 6500 to climbing up to 98 at 6900 and holding that through to 8200. From 6500 down to 6000 the power falls of to around 88, from there the power drops to 78 at 5300 rpm.

The specs on the motor is as follows:

1508cc
76.5mm JE forged pistons
11.89 compression.
14lb flywheel
Ported GX head with 37/30 SI narrowed stem valves with Isky dual springs
Delta 278 cam (280 advertised duration .420 lift).
4-1 header
39mm Keihin flat slide carbs

I was expecting slightly more out of the motor but it's running fairly rich; I'll need to drop done at least one size on the main jets. The jetting alone should net another 3-5hp.

Now for the fun part; during the process of installing the O2 sensor, I was drilling the hole for,it and discovers the exhaust has in effect a double walled tube. Some of you may remember back in 1998 I was running a motorcycle engined sports race and I'd actually sold the car to a racer friend, who then sold it on to a racer friend of his. Well the exhaust was redone during this time whoever did it must have used whatever they had lying around. The header ID at the collector flange is 1.75" but the pipe attached to the exhaust flange is 1.5", then there is a 3-4" length of 1.5" pipe stuffed inside the 2" exhaust. So basically I have an outlet restrictor. No clue how much power this is robbing but I'd venture to guess it's at least 4-5hp.

So all said and done between the jetting and fixing the exhaust flange there's probably 10hp to be had.

My reason for noting the power output at 5300 is that's where the rpm drops to when shifting from 2nd to 3rd with the 60 series 5 speed. Basically this results in a 20hp drop. I was having second thoughts about my plan to install a 63 series box but since it's possible to build a mid close (Z20 powered A10 gear set in A-series case). On small change in ratios may not seem worth it but the lesser rpm drop means the motor would only drop 10hp on the 2-3 shift. Further a close ratio would limit the power drop between gears to 3-4 hp.

Long term is to get the output near 120ATW.

On a final note my friends Porsche put out 101.6 HP, his friend brought a 9 liter 1979 Trans Am which putout 500hp with 560ft/lbs of torque.

Sounds good. That's what, about 120hp on an engine dyno?

Yeah I'd say it comes out to about 120 give or take a few horsepower. With the exhaust fix and perhaps a few minor tweaks we can get it up to 115ish. I've been contemplating ways to get beyond that, I may have to cave and perhaps install larger valves in the spare head.

280adv dur is a very tame cam for a race car, and if that's total/gross lift, it's also very small.

Get a real cam in the thing! :P Should be over 300deg adv and closer to .500" on a race motor

Harry it is indeed .420 valve lift so without a doubt it's really not more than a hot street cam. I was revving the A12 to 8600 and that wore it out in a hurry. On the A15 I'm trying to keep the revs below 8000 as that allows me to go several seasons between rebuilds. I have an extra A15 that I may at some point bore out to 78mm or 79mm in conjunction with larger valves and a more aggressive cam. The issue with doing this is two fold; I've just spent the past 6 months sorting various minor issues on the car so I want to just drive and enjoy the car. Secondly I have the single seater which at the moment I just use for autocross, if I'm going road race car with more frequent maintenance intervals I'm might as well run the single seater as obviously it's much faster (likely 20 seconds a lap). Granted with the 1200 I have more people to race with so I'll admit that my logic may be lacking.

Hi Tom from what I have read you have a very GOOD mild race motor with reasonable HP and good reliability which we are all after.
But saying that I have retired my 1322cc sceemer after 7 years of pretty troublefree racing.And have built a 1510cc whith all the things you listed that you could do to yours including 14.5-1 comp and E85 fuel.Dyno SAYS 119.3 HP at wheels but most important the mixtures are spot on for sea level.Let the fun begin.GREG

98 can be fun
Thats what we got back in about 05 the one time mine went on the dyno

Had a couple of changes since then... but it sure was fun to drive
I kept to a 7600 redline
Broke the original pistons and no-one seems to know why... no issues with the new ones except they are abit low comp... rebuild coming eventually for some more comp

Got a pic of your graph ?

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Chassis dynos can be inaccurate not like engine dynos but are useful for getting the tune correct and to show where torque and power band is.
This motor has lots more developement left in it if needed.
PS this motor is an A14

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I'll have to scan the dyno sheet, I just noticed run number 2 was actually 99 horsepower, my friend told me he saw 98 on the screen so I never looked at it closely.

Greg as for compression I have a local gas station chain that sells 100 octane fuel, so I try to work with that fuel. Also the rules don't allow for E85. I can up the compression with a head gasket change as I still use the 1.2 crush thickness one. Also my spare GX head was milled at some pout and the combustion chambers are only 27cc

As for Dyno sheets, yes they are simply a guide. One of the take away from this was as mentioned above is the gearbox. Ideally I'd want a box with ratios that only allowed a 1500 rpm drop between gears as that would keep the motor output between 95-99hp.

It would also be nice to see about fabricating a pressure wave termination box since I have to redo the exhaust at the header end.

Tom you are a bit luckier in USA for transmission choice.In AUS there is not a lot of choice i now use a Toyota T50 5 speed std ratios after blowing 3rd gear in my good 4 speed it kept the revs up to a manageable height.it's a shame you are not allowed to use E85 the HP gain is impressive for a small motor but you use a third more fuel. GREG.