K321 build questions- rods n cams

[Greentored 3,214]

Started a thread in the 'engines' forum for putting together a K321 torque monster build, read Brian Millers entire page multiple times, emailed him (no reply) and have researched online- a bunch. Seems theres just not a ton of info out there, so figured the puller crowd might be able to answer my two main questions. This is going in a C120 custom/plow dog/worker and play toy, and cant deny Id maybe hook it on a sled sometime for the heck of it. 4000rpm max, if I even spin it that high- looking for grunt.

1. Aftermarket factory replacement rods- trying to find a K341 rod as theyre supposedly thicker, and seems the listings say 'K301-321-341'. Regardless, will these rods hold up to heavy use, a boost in compression, and 3500-3800rpms?

2. Cant seem to find any budget 'cheater' cams that folks talk about. Am I handcuffed into dropping 225+ if I want a decent grunt cam in it?

Again, this is not a serious, class specific puller looking to squeeze every ounce of power out of it, but I do want it to run as strong as it can.....

Thanks in advance fellas!

[oilwell1415 563]

I'm not very familiar with these engines, so this may not be possible, but since you don't want to radically change the rpm range have you considered having larger valves installed and running the stock cam?  This achieves the same thing as adding a cam with more lift, but leaving the duration the same.

[oliver2-44 9,752]

I've "heard" of Pullers using having the K341 bored to fit a Chevy 327 piston with the popped up are on the top of the piston which would increase compression.  I wonder if the  stroke and crank dia is the same and they use a racing 327 rod?? 

[oilwell1415 563]

I think the 327 piston in a 321 is a little optimistic.  But you could probably do some welding in the combustion chamber or offset grind the crank a little to increase the compression a bit.

 

Another option might be a small supercharger.  That actually wouldn't be that hard to do.

[ebinmaine 67,503]

[Greentored 3,214]

This is what I needed- real world experiences- thanks fellas!

  Dont know if Im going to get into offset grinding the crank and/or stuffing a small block chevy piston in one haha, although that IS very tempting as I have all the equipment to do it other than grinding the crank. Maybe one day.

Coming from a life of building engines, looking at the cam lobes on a stock Kohler versus even a very mild aftermarket cam makes it very hard to not upgrade. So much more 'area under the curve'. The 'RV' cam swaps in a V8 make a decent difference, and a 'bolt in' cam in a Harley or even 6.5hp 'clone' kart engine makes an unbelievable difference, right from idle on up. However, these are all OHV engines, so perhaps these flattys dont respond as well? 2-300 bucks for a "I THINK its stronger" is not money wisely spent, especially on a toy.

....and as far as Miller- wow, looked it up, and thank you for the heads up! Wont be spending money there.....

 

[ebinmaine 67,503]

I've got a half-decent basic understanding of what it takes to make an engine breathe better which of course is what it takes to make one increase power.

 

Please do correct me if I'm wrong here but I was always under the impression that the later model flathead V8s from the 50s really couldn't compete against a similar cubic inch overhead valve v-8. I suppose it makes sense that a single cylinder engine wood offer the same.

 

For my practical application in the work that I do on my own property I have absolutely NO good reason whatsoever to build an engine that has more torque than I already do.

It doesn't mean I wouldn't do it. Because I want to....

 

The question-and-answer information about the science of engine building has always fascinated me to no end and this is doing the same.

 

One of the things I do remember from my youth when I was messing with Chevy V8 305 to 350s.

If you did five things to an engine that were fairly minor and each one increased your horsepower by 5, you didn't get 25. You got 40. Because each one would complement the next one exponentially.

 

So perhaps changing a camshaft is something that would be a good compliment to several other modifications.....?

[Greentored 3,214]

@ebinmaine bingo!  Theyre just a big air pump- the more air you can move through it, the more power itll make, period. Obviously, flattys cannot move anywhere near the amount of air an OHV can, or at least not without incredible mods- no doubt someone has done it haha.

Pretty sure any big block Kohler in stock form will do more than id ever ask of this tractor, but it would be fun to have people say "damn, that thing pulls for a little 14hp!"  That, and the fact that I cant leave anything alone and always try to improve it 'while im in there.'

[ebinmaine 67,503]

4 minutes ago, Greentored said:

the fact that I cant leave anything alone and always try to improve it 'while im in there

That's a good enough reason for me

[oilwell1415 563]

As with most things with engines, adding power to a lawn tractor is rarely the best place to spend time and effort.  Even my 552 has more power than can effectively be used without doing other things.  Right now the front end is in the air at the slightest hint of pulling a load.  So I need to add weight to the front end.  Then I'll have a traction problem.  But tinkering with the engine is fun to do and there's just something about an engine that runs perfectly that sounds so good and makes the time and effort worth while.

[Greentored 3,214]

23 hours ago, oilwell1415 said:

....... tinkering with the engine is fun to do and there's just something about an engine that runs perfectly that sounds so good and makes the time and effort worth while.

Bingo!  When guys can successfully yank a plow with 6-8hp tractors, theres no need to build a hopped up 14hp to do it......but its fun.

...and Lord knows ive pee'd away more time and money on plenty of other senseless things in life haha.

[ebinmaine 67,503]

18 minutes ago, Greentored said:

ive pee'd away more time and money on plenty of other senseless things

Really?

 

Not me..

 

Nope....

 

 

[oilwell1415 563]

5 hours ago, ebinmaine said:

Really?

 

Not me..

 

Nope....

 

 

I have to plead guilty.  I spend half my money on airplanes and women.  The rest I just waste.

[Greentored 3,214]

On 6/10/2020 at 1:31 PM, oilwell1415 said:

I have to plead guilty.  I spend half my money on airplanes and women.  The rest I just waste.

Mine was beer, hotrods and Harleys. The majority that was spent on past women was indeed a waste.

....but it sure was fun!

[fast88pu 3,324]

On June 8, 2020 at 8:41 AM, Greentored said:

Started a thread in the 'engines' forum for putting together a K321 torque monster build, read Brian Millers entire page multiple times, emailed him (no reply) and have researched online- a bunch. Seems theres just not a ton of info out there, so figured the puller crowd might be able to answer my two main questions. This is going in a C120 custom/plow dog/worker and play toy, and cant deny Id maybe hook it on a sled sometime for the heck of it. 4000rpm max, if I even spin it that high- looking for grunt.

1. Aftermarket factory replacement rods- trying to find a K341 rod as theyre supposedly thicker, and seems the listings say 'K301-321-341'. Regardless, will these rods hold up to heavy use, a boost in compression, and 3500-3800rpms?

2. Cant seem to find any budget 'cheater' cams that folks talk about. Am I handcuffed into dropping 225+ if I want a decent grunt cam in it?

Again, this is not a serious, class specific puller looking to squeeze every ounce of power out of it, but I do want it to run as strong as it can.....

Thanks in advance fellas!

If your not gonna spin it past 4k or pull with it your just wasting your money on a cam. Stock rod will hold till 4500. Port and polish it and shave the head. It would be the most gain for the least money.

[fast88pu 3,324]

Yup this guy just said it lol

[ebinmaine 67,503]

3 hours ago, fast88pu said:

shave the head.

How much can you shave the head?

[oilwell1415 563]

20 hours ago, ebinmaine said:

How much can you shave the head?

I don't know how far you can go, but to increase the compression ratio by one point you'd probably have to take around 0.10" off and that's a lot.  That can cause valve clearance problems, especially with the later head with the plug directly over the exhaust valve.  I'm not sure there's enough gain there to make it worthwhile strictly from a power production standpoint, but a compression increase really helps at part throttle which is where a governed engine spends most of it's time.

[fast88pu 3,324]

On July 6, 2020 at 6:17 PM, ebinmaine said:

How much can you shave the head?

30 thousands

[Greentored 3,214]

Thanks for all the advice guys

[RandyLittrell 3,877]

On 7/6/2020 at 5:17 PM, ebinmaine said:

How much can you shave the head?

 

I have a stock K301 with the head shaved about .050 and have no trouble running 91 octane no ethanol fuel.

You could really feel a seat of the pants difference after I had it milled.  

 

 

 

Randy

[ebinmaine 67,503]

5 minutes ago, RandyLittrell said:

 

I have a stock K301 with the head shaved about .050 and have no trouble running 91 octane no ethanol fuel.

You could really feel a seat of the pants difference after I had it milled.  

 

 

 

Randy

Boy that's quite a lot. Was there a need two notch relief for the valves?

[RandyLittrell 3,877]

1 minute ago, ebinmaine said:

Boy that's quite a lot. Was there a need two notch relief for the valves?

 

No I didn't, but its a stock cam and head gasket. With a bigger cam or copper gasket, you may need to check clearance but its pretty common to mill .050 off for stock pulling. It takes just enough off it doesn't get into the combustion chamber, so its still legal for a stock class. I have also ran an LP head on a stock 12 and it feels like more compression than a newer milled head. I don't know the CC difference though. 

 

 

 

Randy

[ebinmaine 67,503]

4 minutes ago, RandyLittrell said:

have also ran an LP head on a stock 12 and it feels like more compression than a newer milled head

I'd believe it.

 

Seems like I remember reading you can run 2, even 4, points higher compression on LP

[Redneckdavis 308]

More carburetor is going to be a necessity. I'm not sure what all was done to my 321 but it placed well enough in stock classes that they pulled it before anyone tore it down. Idled too smooth for a cam. And even after buying it the guys wouldn't tell me what was done. 

I can tell you at 4k rpm the gravity tank wouldn't feed it. The carb jets had been drilled out. I had to add a pump.