My Tractor Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
1,315 Posts
Discussion Starter #1 (Edited)
thought some might find this interesting.

I've been wanting to up the HP on my 3813 to 14, and by using the parts catalogs at boats.net, had narrowed the differences in the two engines, down to the cylinder heads.

Dave4514 pointed me at the link to a copy of the 4514's svc manual online (can't believe honda hasn't sent their intellectual property attorneys at the guy), but in comparing the two manuals, i found they listed both the valve diameters and cam lobe heights for each engine.

both employ the same diameter exhaust & intake valves, but what becomes odd is the 13 hp engine actually has a taller intake cam lobe, than the 14 hp head.

neither manual lists the duration for the lobes (ie degrees of a circle it maintains that height) but it appears that the camshaft & muffler and carburetor jet are the key items for the additional 1 hp. I'd include the airbox, but i don't see any significantly larger filter area. The inlet snorkel tube on the 13 is much smaller, but that's easy enough to adjust by just removing the cover, and bolting direct to the filter.

I;ve got a 4514 muffler here w/exhaust manifold and there is no difference in the exhaust manifold between the 14 and 13 hp version- configuration and ID are the exact same. And considering the 13 has a higher intake lobe, it might actually produce slightly more hp with the 14 hp muffler.

And one seller has indicated the carb inlet diameters are the same.

here are the specs for each:

3813 valve diameters: intake 28mm
exhaust 22mm

cam lobe height: Intake - 26mm
Exhaust - 25.9mm


4514 valve diameters: intake valve 28mm
exhaust valve 22mm

cam lobe height: Intake - 24.96mm
Exhaust - 25.92mm

GX360K1 (3813) cyl head


H4514H cyl head


GX360K1 (3813) cam


H4514H cam



more in line with what i'd expect, on the carburator, the 13HP shows a "#88" main jet vs a "#92" jet for the 14 hp

Bore & stroke are the same (58 X 68MM) which suggests crankshaft & pistons are the same, as are compression ratios for each 8.5 : 1

again, on the odd side, intake valve clearance adjustments (.004" to .006") are identical but the 14 hp has more valve clearance (.007" .009") vs the 13's (.004 - .006") which means the 14's exh valve doesn't open quite as far - and that slight difference you can feel on a 240hp engine, so it will be discernible on a 14 hp engine.

Both btw, have identical ignition timing - 24 BTDC, and same ignition coils

I know this probably seems like a lot of effort for 1 hp, but my goal was to put the 46" deck back on my 3813 - the 13 was a little anemic when that larger deck hit thick grass (and my 13 is in pretty decent shape, power wise - compression is well above limit at 156-160 psi, new timing belt, iginition coil cleaned and checked with i put the belt on, and valves adjusted).
 

·
Registered
Joined
·
237 Posts
Another thing I noticed is that the 13hp has almost no intake manifold but the 14hp has about a 3inch long one. I would say that you could gain hp by rejetting and using a 14hp intake horn.
By looking at the valve lash data, I would say that the opening duration is longer. Think about it,they used the same cam but they had to turn it down to change the duration, which required a different valve lash clearance. At least that is the way I interpret it.
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #3 (Edited)
interesting about the intake manifold being longer - a longer intake would give it slightly more torque (never understood how or why, but i learned that when i saw the first early 50s chrysler with those long intake runners crossing over top the engine, with the carb on the passenger side feeding the driver side cylinders and vice versa). And a little more torque is what i'm looking form.

don't know if i agree about the cam lobe thing - they could have lowered that intake lobe from the 13's lobe hgt, but the valve clearance on the intakes stayed the same, according to their recommended adjustment (.004-006") - it was the exhaust valve clearance that was increased (exh lobe staying same hgt) - but you're right, it's possible they're increasing the duration of the valve staying closed to give the combustion process a nanosecond more time to burn in the cylinder
 

·
Registered
Joined
·
237 Posts
Looks like the intake may be staying open longer to take advantage of that ram charge effect from the intake manifold. The exh valve clearance just may be an allowance for the increased operating temp which may make the valve expand in length more. ???
I may be looking at it the wrong way too ???
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #5
man, you're waking up memory on details i haven't thought about since the early 70s and can't remember enough to sound intelligent on

and i just checked boats.net again for the cylinder head - the core head is the same - when i clikked on the part descript for the 3813 it went to a page showing all the applications of the head and the H4514H was on the list. Valve guides etc all show to be the same etc between the two engines - just the cams differ
 

·
Registered
Joined
·
231 Posts
Not to muddy the water, but Honda also used the same GX360 engine in the ES6500 and EX5500 generators. In those applications it is rated at 12 hp. So, you have the same basic engine rated at 12, 13 & 14 hp. I will be interested in your findings.
 

·
Registered
Joined
·
237 Posts
Bob V the waters are certainly muddy on this. I suspect that there may be a difference in hp rating standards. There may also be a diff in the flywheel weights too (I don't know for sure). The 12hp gens may be rated at a diff rpm range too, since they run at a constant speed. May also be a diff in carb size. My head hurts !!! :)
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #8
Not to muddy the water, but Honda also used the same GX360 engine in the ES6500 and EX5500 generators. In those applications it is rated at 12 hp. So, you have the same basic engine rated at 12, 13 & 14 hp. I will be interested in your findings.
i was aware of the ES 6300 (or 6500)and Ev4010/ev6010 series - in fact one of my "projects", i've got the fan tower that bolts to the waterpump on either the EV series (or maybe it was a waterpump that honda offers with the GX360 engine), so i can put the fan on the backside of the engine and the radiator up under the dash in an attempt to keep it from picking up grass, debris etc and clogging the radiator screen - just haven't gotten around to it

you're correct on the different hp ratings but i found, iirc, somewhere in the 3813 owner's manual or svc manual, the engine is actually rated at something like 12.2 hp

and in the 4514 svc manual, on the spec page, it shows 13 hp, so i suspect the 14 hp was an advertising ploy or under advertising "license"

whatever it really is is not as critical as just having a little extra "oomph" for the 46" deck

was comparing the 3813 and 4514 mufflers in the garage a few minutes ago, and surprised to see the 14's muffler has a little less volume, maybe 20-25% less, with the same size outlet port, so it's not enjoying any freer flowing exh system. It will mount fine on the 3813 without the black shroud - with the stroud, i think the hood may need some trimming
 

·
Registered
Joined
·
231 Posts
Hi Roger,

I think that Larry may have opened up a real can of worms here. The information that you both put forward is fascinating. My first thought would be that they are all the same horsepower, but listed differently on paper. However, about five years ago I spotted a brand new GX360 (in the crate) that was listed on eBay for a Honda HT3813. The price was so reasonable that I had to buy it before I took another breath. It was a complete engine - pan to carb with igniton, charging system and starter. When I got it and open it up, I knew right away that it was not for a 3813 because the carb was different. It has the electronic fuel shut off on the bowl. Also the throttle linkage was that of a single speed engine. That is when I realized that it was for a generator. Still, I was delighted because I only paid $325.00 for it and that included shipping. I pulled the 13 hp engine out of my unit and put this one in, adding the necessary pieces and it has run like a charm ever since. The only difference is that it does not quite have the power of the original 13 hp engine. If you never drove the 13 hp, you would not think a thing about it. But, having driven the 13 hp engine for 20 + years, the 1 hp loss was slightly noticeable. The 12 hp will do any thing that I need done without any hesitation, but the 13 hp engine did it with just slightly less effort. I am like Larry, looking for that 1 hp???

I have my 13 hp engine sitting on an engine stand and am thinking about putting it back in this winter - not that Florida has a winter, but the grass slows down a bit. If you and Larry can figure out the difference between the 12 and 13 hp motors, I can make my 12 a 13 hp. I can tell you that the block, head, valves, intake, and carburetor are all identical on both. The only thing that I have not compared is the cam profile.

Hope that you guy are able to figure out where the 1 hp is hiding.

Thanks ~ Bob
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #10
is it possible that generator engine has a lighter flywheel? - doesn't seem like it would need a regular wgt flywheel if it's direct connected to the gen but i haven't seen how it's connected to the gen head
 

·
Registered
Joined
·
492 Posts
Honda rates the GX360K1 engine in the 4514 at 13 HP at 3000 RPM. In section 3-19 of the shop manual it states the standard maximum engine speed is 3300 +0, -100 RPM. At 3300 RPM the HP will be about 10% greater than at 3000 RPM or 14.3 HP.

Here is a partial copy of the sales brochure that Honda published when I purchased my 4514 in '92. At that time it was listed at 14 HP.



Sorry for the size, tinypic is not helping.
 

·
Registered
Joined
·
237 Posts
Guys, my experience with Honda Motors is that they usually don't push the figures. They are one of the few mfrs of generators that actually put out the advertised watts. So by saying that I think that the 14's,13's,12's actually do exactly that. When it comes to ratings Honda is very conservative across the product line. And no I do not work for them. I believe that the diff is in the carb mix,manifold and most importantly the cam. It just has gotta be. Everything else is the same. I even checked flywheels and the 13 and 14 are the same.
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #13 (Edited)
roger - if you're talking about honda generators, i agree - but honda got caught a few years ago with overrating their V-Twin series engines for generators - i've got one that was billed as 20HP, and some sort of lawsuit ensued, and i think the FTC got involved - all i noticed was for awhile you couldn't get a hp figure from honda, and now, the engine i've got (came in combo with a Northstar 13,500W gen) is now described as 18 hp

really hp isn't the important number, torque is - remember it was carroll shelby that said, "HP sells cars on Monday, but Torque wins races on Sunday" and i suspect that's what honda was relying on when they offered that engine as suitable for 13.5KW. Sometime back when i visited their web, even their recommendations had been removed, ie leaving it the responsibility of the Gen mfgr or user/fabricator.

on the subject of whether they're 12, 13 or 14 hp, i tried to find some torque/hp curves i had, from honda, but can't find them.

I did find these pages in the honda svc manuals for the 3813 and 4514. Honda is claiming here the 4514 is maxing out at 13 at 3000RPM, and in the 2nd page, to not exceed 3300RPM
while the 3813 is maxing at 13 HP at 3600RPM which i don't run my engine at. I generally run mine in the 3200-3250 range, so i'll guess mine is running somewhere in the 11.5-12hp range at that rpm.

but i'll try to find the torque / hp sheets, cause i swear the 3813 was showing 12.2 hp at 3600 and the 4514's torque was showing maxing at 2800 rpm, not the 2500 showing down below

but i'm starting to think it's the combo of cam, carb jet and muffler that are dictating the 4514's power curve. It occurred to me this afternoon, before i spend $107 on a 4514 cam, the cams appear to be close, and if anything, with the 3813 cam having a higher profile intake lobe, i'm going to try the 4514 muffler and the #92 carb jet to see how she feels.

4514




and last, fm the 3813 manual


and on page 63 of the GX360 owner's manual at http://www.ultimatewasher.com/download/honda-engines/gx360.pdf it shows max power at 12.3 at 3600RPM - sorry couldn't get the page to print into pdf
 

·
Registered
Joined
·
237 Posts
I think you are right on Larry. Don't forget that I have a 14hp cam if you are interested. If you haven't already purchased one.
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #15
i'll keep that in mind but i've got some optimism the muffler/carb jet are going to give me some extra "oomph".

if it's handy, might be interesting to see a trace of intake and exhaust valves.

i haven't pulled my valve cover off in awhile, but if it's possible to cut a "U" into a pc of cardboard, enough so that you could slip it down over the cam and up against each lobe, and then trace the lobes onto that cardboard (thin cardboard like you see or used to see as "stiffners" inside of brand new shirts),

it'd be interesting - if you scan and post (if you have a scanner), i'll do the same when i've got the valve cover off. If you don't have a scanner, if you could mail em to me, i'd scan both and post em
 

·
Registered
Joined
·
237 Posts
Larry I have tried that and it ain't that easy. I think the cam will have to be pulled and I don't have time to do it today.
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #17
that's alright then, don't worry about

if you're like me, you've got a "honey-to-do" list longer than my arm -
 

·
Registered
Joined
·
1,315 Posts
Discussion Starter #19
to make things a little more confusing to decipher, i went to boats.net to order the #92 carb jet (remember, in the 3813 the stock jet is #88) and found as optional jets for the 4514, honda offers both a #88 and a #90 jet.

That doesn't add any confusion, as dealerships would adjust the jetting in carbs for elevation - the higher the elevation of the area that the engine would be run, the leaner the fuel mix or the smaller jet that would be called for. Higher elevation = thinner air. So i can see them offering a couple of leaner jets.

but then going over to the 3813 parts page, they show the #90 & #92 jet as optional jets with the #88 as stock.

The confusion is, why would they offer richer jets as substitutes on 3813?
 
1 - 20 of 23 Posts
Top