This is quoted from the 084 experimenters Yahoo group.

The engines were tested at TEN thousand feet at 107 degrees that they were
tested at.
> > These engines were run at full load for one thousand five hundred
> > hours, and THEN dynoed to insure that they pulled the rated power at
> > those conditions.
> > AFTER the dyno test, they were taken apart, and the parts were
> > measured for wear. If the sample engines did not BOTH make the rated
> > power, AND pass the wear test, the ENTIRE shipment of engines was sent
> > back.
> > It is safe to say that most of the members of this site know this,
> > but for the one or two absolute "newbies" that we may get in the
> > future, aviation engines are power rated at sea level, onder standard
> > temperature, (79 degrees I think), and pressure. This power falls off
> > as altitude rises. If you reverse extrapolate the power numbers from
> > the conditions that the engines were tested under, you will see that
> > the engines should pull between 40 and 45 horsepower at sea level.

Here is a pdf file of the 4A084A engine manual. You can either click on it a read it or left click and save it to your computer.

http://miniairboatassoc.com/084/4A084a.pdf (http://miniairboatassoc.com/084/4A084a.pdf)
http://miniairboatassoc.com/084/4A084b.pdf
http://miniairboatassoc.com/084/4A084c.pdf (http://miniairboatassoc.com/084/4A084c.pdf)
http://miniairboatassoc.com/084/OCR.pdf (http://miniairboatassoc.com/084/OCR.pdf)

a. General.
Engine Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 41084-2, -3 and -4
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 cycle gasoline powered
Number of cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4 (horizontally apposed)
Horse power rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20 at 3600 r.p.m.
Fuel pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diaphragm 3.0-4.5 psi outlet pressure
Air cleaner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dry models 4A084-2, -3 and -4
Spark plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Shielded
Gap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-.033 in. (.071-.083 cm)
Magneto contact
Gap, Fairbanks Morse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..015-.019 in. (.030-.48 cm)
Gap, Slick Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .008-.012 in. (.020-.030 cm)
Valve tappet clearance cold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..007-.009 in. (.017-.027 cm)
(Intake and exhaust)
Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Centrifugal
Oil capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 quarts (4 1/2 gts. with oil filter change)
Alternator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 volts alternating current (ac)
Starter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 volts direct current (dc)
Regulator-Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28.5 ± .5 volts at 1.5 amps
Firing order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..1-4-2-3
b. Dimensions and Weight Models 4A084, -3 and -4.
Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 20 in. (50.8 cm)
Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.50 in. (72.4 cm)
Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22.10 in. (56.13 cm)

New guy again. :)

I've saved the 4A084 pdf for future reference. Thanks.

You said:

"the engines should pull between 40 and 45 horsepower at sea level."

So I learned something. When I saw it listed as a 20 HP engine, I kinda'
put it on my "not interested" list. You changed that.

That makes me think that a 4A084 would not only be cheaper than a new
35HP Briggs, but be much stronger as well. (after a little looking, I see that 35HP Briggs don't come cheap)

(I told you that I was going to ask dumb questions, so here goes)

Being as it's an "obsolete" military engine, how difficult / expensive is it to find one, and how difficult / expensive is it to find parts?

When souped up, how much power can someone get from one for a reasonable cost? On a HP per dollar basis, how do you think it compares to a VW engine?

BTW, I don't have any problem with using an automotive engine. I don't care about what class my boats ends up in. I just want a fun toy.

I'm still reading the various posts that I find about the 4A084, and still learning.

Thanks,

Hey duane, read these, ( Papee's 084 ) and ( Bill's Mini ) and ( Ron and Robins 084 ). We have some of these in stock, 2 new ones and 3 used ones.
Thanks, Chuck

Thanks Chuck,

I'll do that, and be back. :)

viewtopic.php?f=52&t=258 (http://miniairboatassoc.com/phpBB3/viewtopic.php?f=52&t=258)

viewtopic.php?f=52&t=338 (http://miniairboatassoc.com/phpBB3/viewtopic.php?f=52&t=338)

viewtopic.php?f=16&t=294 (http://miniairboatassoc.com/phpBB3/viewtopic.php?f=16&t=294)

Thanks everyone.

I "may" have just screwed up, and if so, it's all you guy's fault. ;)

I found a 4A084, new in the crate on Ebay, and placed a bid on it.

If this turns out bad, I'll blame it all on you guys. :)

BTW, he has 2 more, if anyone is interested.

Hey Duane where are you located Chuck has 2 new ones at the shop we also have 2 new belt drives for them that we can do a good deal even the o84 engines on call him up 353-330-1015

Thanks David,

I'm in Wilson, NC. About 40 miles East of Raliegh.

I guess that I jumped the gun a bit by bidding on ebay for the motor, but I just couldn't help myself. Shame on me. I bid what I thought that it was worth to me. Damn. I'll probably get it anyway. :)

If I "win", I am pretty sure that I will be looking for a belt reduction drive, etc. etc.....

I have created a monster. :(

Does anyone know what the valve adjustment is for the 084? I have looked thru that @#%!&^%(*&^%$$ TM until i'm mad. That brings back some old memories of working on military equipment. And i don't miss it.

Thanks

I know it's there LOL, I had a hard time finding it also and just saved the page with that stuff on but now I can't find it. Great now I'm looking for two things. I'll never get ahead :lol:

Airhead and Papee,

I think you will find that the 084 lifters are hydralic, and require no adjustment. Correct me if you find out that I am wrong.

Dave

Buster, Airhead, and Papee,

I've done some searching myself, with very few results. The best I've come up with is that they are hydraulic, like Buster said. Even so, it seems like there'd be some target clearance when the lifters aren't pumped up.

I'll keep my ears open for more info....

Thanks,

Duane

Duane,

If you pull off one of your valve covers, you will not find any adjustment screws. That is how I determined that they must have hydraulic lifters.

Maybe your engine is different than mine, but I don't think so.

Dave

Buster,

I don't have any oil leaks YET, and ain't going to try starting one. ;)

As it turns out, as I was about to reply to YOUR post, I got this reply from Les Smoot.

Duane,

Hey there! I am in China for a bout 3 more weeks, I have
been in and out of several hotels ...internet is spotty!

You are spot on!

NO valve adjustment ...hydraulic lifters. If you are getting
valve noise it's because of a worn lobe on the camshaft or
the lifter itself is NOT puming up. This problem starts to
pop up when an engine has been rebuilt many times over
and the same lifters and camshaft are re-used vice replaced.

If the engine noise is only there when cold but clears up as the
engine gets to temp it's likely a bad lifter .......

Hope to be home by mid September ..........

Cheers,
Les

BTW, Buster, I never said you was wrong. I was just trying to get the answer from someone who's been into these engines many, many times.

Thanks,

Duane

Airhead,

See above. ;)

Thanks,

Duane

Duane,

I checked the lifters from a parts engine i bought and they are definately hydraulic :) NO ADJUSTMENT REQUIRED :D This makes sense because of what they were used for 8-)

Sorry guys I read right past that one. I knew this because I have already replaced a head on mine. I thought he was asking for torque specs.

Anyone know what the timing is for the 084? The TM says line up the marks :mrgreen: Now, i cant do that :o I thought i had found 19* BTDC in the TM, but i don't know for sure. And 19* sounds like really too much.

Thanks

I looked through the TM again and still cannot find the timing. I looked at the original flywheel and the timing mark says TDC. So i must assume that is the timing. Just want to clear up the 19* business, i don't know where i got that unless i was thinking about point gap.

If anyone has something different, please post.


Jim

Airhead,

There is a how-too on the Yahoo Experimentor's group.

Here's a link to it.

http://groups.yahoo.com/group/A084Exper ... the%20084/ (http://groups.yahoo.com/group/A084Experimenters/files/Timing%20the%20084/)

Let me know if you can't access it, and I'll get it to you some other way.

Duane

Duane,

I looked back on the site and all i could find was how to find the tdc and timing. What i need to know is, what does the timing set on. From what little i can figure it is tdc. I don't think this has anything to do with my problem, but it does need checking.
I think my main problem is half checking, so this next week i will be more thorough.
Thanks anyway and if i missed something, lett me know.

Jim

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Please report these posts so I can delete them and ban the user. Don't reply to it just report it, replying makes more for me to clean up.

Other specs I have run across during my ignition conversion:

Timing advance: 28-degrees before TDC (confirmed with a degree wheel)
Compression Ratio: 6.8:1