low horsepower

[356mal]

I have just had my formula ford on the dyno and it is only showing 74 horsepower
the engine builder is stumped and the mechanic at the dyno is stumped as well
they both have about 40 yrs experience each
the cam timing is correct , the carby and the jetting are correct , the valve clearances are correct . the motor is a kent motor and is new
the timing is set at 34 deg before tdc and the motor sounds sweet and crisp .
another kent power formula ford had a reading of 93 hp several mths ago
on this dyno
does anyone have any ideas where else we should look for the missing horsepower ?

thanks
mal

[Tim FF19]

I would do a leak down to confirm there are no problems with rings or valves seating. If it passes that test I would look at the carb again and maybe even put on a differnt carb that is know to operate properly. Does not seem like ignition (motor sounds crisp) but is still a possibility. I assume the dyno guy has calibrated the dyno load cell with a dead weight and the dyno output is not in question.

[Brian]

Cam timing needs to be 112 - 113 ATDC and ignition timing needs to be 38 - 39 BTDC for an iron head engine and around 40 for an aluminium head engine. 34 is nowhere close, based on what i know anyway. Which admittedly ain't all that much..

Brian

[Dick R.]

Engine or Chassis dyno?

Dick

[sracing]

Assuming the dyno is correct.. As mentioned do a leakdown. The 4 or 5 degrees of ignition timing won't make that much difference. (although you want it correct).

Also based upon your HP numbers, I have to assume this was done on a rear wheel dyno. So do the test and check your rotor temps. It doesn't take much drag to drop lots of HP. Then of course you have your trans in the loop also. If you are doing inertia chassis dyno runs you should be able to do them in 2 or 3 different gears. The HP should be close to the same on all runs. If they are radically different you have some thrust load trans issues. (If you are getting these nums on an engine dyno, you have a serious issue )

[Daryl DeArman]

must be my old motor

[Hawke]

Mal,

If your engine builder and dyno man set the timing at 34 degrees, then it is possibly time for new men.

That extra six degrees can make reasonable difference.

You may also want to check the accuracy of that setting. I have seen an engine that had the TDC mark 12 degrees out.

By the way, who's dyno did you use?

93 for an Australian Kent engine on a chasis dyno is pretty high.

[356mal]

it is a chassis dyno
the dyno bloke and engine builder know what they are doing
as I said they have about 40 yrs exp each
the 93 was one of the top nsw state championship cars
I dont expect mine to be that high but 74 is a bit low
I will check the brake rotor temps but the car is easy to push around
and runs down slowly
we will try a leakdown test on monday but the engine sounds
crisp when reved
mal

[Rick Kirchner]

check the gearbox. Easy to lose a ton of Hp there on a chassis dyno if things aren't right. Old Staffs boxes had to be bluprinted on delivery.

Put an oil temp gusge in the gearbox oil, especially if you have another car to compare it to.

[DaveZ]

Really dumb question (hopefully), but did you check for full throttle?? Might be worth a look...

[356mal]

dave z
yes we checked the throttle opening

max power 74.6hp @ 5500 @ 122 kph 3rd gear
max tourque 86.5 ftlb @54 kph
motive force 2047.2 N @54kph
we are going to pull the camshaft out to check the specs

mal

[stephen wilson]

You could check the lift at the valve, without having to pull the camshaft.

[Art Smith]

mal-

new cam or old cam? if old, were the lobes checked for lift before assembly??
new lifters or old lifters? if old lifters, were they numbered so as to get back to "their lobe"?
if old lifters and not not numbered, was camshaft break-in lube used and the camshaft broken-in with street springs for 30 minutes? if not, check camshaft lift at each push rod!!!

what was the camshaft timing set at?
what type of exhaust is being used and where was it tuned to make maximum power?
what are the exhaust gas temperatures you're seeing by cylinder?
what's the maximum EGT difference at expected maximum power rpm?
how much air is the engine ingesting (measured with a turbine flow meter) at maximum rpm?

what type and weight oil is being used?
what is the operating temperature of the oil?
what is the oil pressure at 6500rpm at operating temperature?
is the same scraper being used? was it checked for clearance?
what is the operating temperature of the cooling water?
what is the fuel pressure?

how were your new rings seated? if not on a dyno under minimal load, check leak down........................!!
what type and brand of rings are being used; top, middle, & oil??
what were the gaps set to; top, middle, and oil??
were the bores bored and honed or just honed? what surface finish (ie: Ra) was requested?

lots of questions I know. think of it as the likely battery of questions you'd get at the doctor's if you arrived and only said you didn't feel well................. when the questions were done the thermometer and needles would come out to get some objective metrics !!!

Art
artesmith@earthlink.net

ps: I'm not a doctor, didn't stay at a Holiday Inn Express last night, but have asked more than one engine to say ahhhhhhhhhhhhhhhhhhhhh

[Larry]

Leaking intake manifold?

Larry