Milling a head .020”?

[Pullstart 62,786]

I found this thread about taking .040-.050” off a K-301 head, but there seems to be a little left to be answered.

 

I am cleaning up the head on the K-241 from our new 953.  I have the Bridgeport here.  Rebel’s main priority will be pulling a plow in the field.  Would I benefit from a mild mill of the head without adverse effects on reliability and longevity?

 

1. What is the compression ratio of a stock K-241?

 

2. This bored is .020” over.

 

3. I have other heads if I screw it up.

 

4. I’m all ears, I can keep sanding on the flat plate too and just call it good, but in all reality milling then sanding a touch might be quicker!

 

 

[WHX?? 48,770]

I don't think I would worry about it Kev. I have never even glassed a head on any of my rebuilds and never had a problem. Unless you need some practice on the mill. Just use a quality gasket and proper torqueing. How does it look with a straight edge? I think compression is around 8. & some change?? 

Edited April 24, 2020 by WHX24

[Pullstart 62,786]

2 minutes ago, WHX24 said:

I don't think I would worry about it Kev. I have never even glassed a head on any of my rebuilds and never had a problem. Unless you need some practice on the mill. Just use a quality gasket and proper torqueing. How does it look with a straight edge? I think compression is around 8. & some change?? 

 

I haven’t even checked it with feelers yet Jim, I figured I’d clean it up first before that step.  Would .020 bump the compression enough to even notice?  If not, I might just do it for the fact that I’d like to learn how!

[PeacemakerJack 10,738]

gonna sit in on this one for sure...

[Pullstart 62,786]

@richmondred01 @prondzy @953 nut ... I know you guys have been into engines for a day or two.  Thoughts?

[ri702bill 8,283]

Kevin:

 

Two things come to mind -

The Holding setup. Since the head is irregular in shape, I assume you are going to use the tee slot clamps and blocks instead of the vise? The setup must be rigid and hold the surface to be cut dead parallel to the table.

The cutter. Are you planning to use a center cutting endmill about 5/8 " or 3/4" in diameter versus a fly cutter? Both have advantages. The endmill will miss your clamps, but you have to walk it around the pattern. A wide enough fly cutter would allow a better finish in one pass and if you have an X axis power feed, your final .005 or so cut could look like a mirror. Clamping can be a challenge though.

 

Bill

[prondzy 3,881]

9 minutes ago, pullstart said:

@richmondred01 @prondzy @953 nut ... I know you guys have been into engines for a day or two.  Thoughts?

Kev, dont waist your time milling the head. The info you read about is for pulling, where every last bit counts. Milling that much will raise compression, possibly requiring a fuel change/timing etc. As far as pulling a plow your biggest gain will be switching to a 12hp or bigger. There is a noticeable power gain from 10-12hp the only real change being the length of the stroke from the crankshaft. To answer your next question you cannot just put a k301 crank in a k241. The crank is not balanced to the piston and you are likely to grenade the whole engine. Just sand the head flat and leave it be, or change engines all together.

[ebinmaine 67,268]

19 minutes ago, PeacemakerJack said:

gonna sit in on this one for sure...

Yep. Me too.

[Pullstart 62,786]

9 minutes ago, prondzy said:

Kev, dont waist your time milling the head. The info you read about is for pulling, where every last bit counts. Milling that much will raise compression, possibly requiring a fuel change/timing etc. As far as pulling a plow your biggest gain will be switching to a 12hp or bigger. There is a noticeable power gain from 10-12hp the only real change being the length of the stroke from the crankshaft. To answer your next question you cannot just put a k301 crank in a k241. The crank is not balanced to the piston and you are likely to grenade the whole engine. Just sand the head flat and leave it be, or change engines all together.

 

‘Nuff said.  Thanks Mike!  

[WHX?? 48,770]

I'll second Mike's comments. I am running heads that probably should have been thrown in the scrap bin. So far no problems and if I do run into problems in the field I know guys with a tow strap! Leave the head milling to the pro pullers. I went with a couple of pulling tips on a recent rebuilt but wasn't worth the effort. 

[Pullstart 62,786]

13 minutes ago, ri702bill said:

Kevin:

 

Two things come to mind -

The Holding setup. Since the head is irregular in shape, I assume you are going to use the tee slot clamps and blocks instead of the vise? The setup must be rigid and hold the surface to be cut dead parallel to the table.

The cutter. Are you planning to use a center cutting endmill about 5/8 " or 3/4" in diameter versus a fly cutter? Both have advantages. The endmill will miss your clamps, but you have to walk it around the pattern. A wide enough fly cutter would allow a better finish in one pass and if you have an X axis power feed, your final .005 or so cut could look like a mirror. Clamping can be a challenge though.

 

Bill

 

Bill, it would be endmill only.  After Mike’s comment, I imagine I’ll just leave this one be.

[Mickwhitt 4,584]

From a  engineering point I would either fly cut once I had sorted the clamping requirements, or I would put it in my shaper and use a finishing tool which can produce a near mirror finish.

But as others have said it's probably taking things too far for such use.

I cleaned mine up with a board and aluminium oxide paper which is exactly what our mower department at my local council used to do. 

I guess a bit of a rough texture would allow the head gasket to grip or seal better than a really perfect surface. 

Mick 

[richmondred01 2,237]

39 minutes ago, prondzy said:

Kev, dont waist your time milling the head. The info you read about is for pulling, where every last bit counts. Milling that much will raise compression, possibly requiring a fuel change/timing etc. As far as pulling a plow your biggest gain will be switching to a 12hp or bigger. There is a noticeable power gain from 10-12hp the only real change being the length of the stroke from the crankshaft. To answer your next question you cannot just put a k301 crank in a k241. The crank is not balanced to the piston and you are likely to grenade the whole engine. Just sand the head flat and leave it be, or change engines all together.

 I agree with everything prondzy said.

 

[bds1984 1,429]

58 minutes ago, prondzy said:

- or change engines all together. -

No replacement for displacement!  

[Greentored 3,201]

Compression= torque, but not much in the hp department, which in our cases grunt is where its at. Not sure if youd feel .020, and like Prondzy said, if you did enough milling to make a difference, timing, jetting, even cooling and longevity will come into play.

When I was playing with the 'run whatcha brung' oval race karts a few years back, I would grab those 6.5 Predator 212s (yep, same ones you guys are stuffing in the Horses for a repower) change valve springs, strip the governor, bore the carb, jet, bump timing, throw a pipe on them, toss the .050 head gasket for a .010 shim steel, then whack .070-.100 off the head- most times lose the first cooling fin haha. Wed fill em with Mobil 1 5-30 and turn them 5500-6000 all weekend long, for months- stock rod, plastic cam gear and all.

Everyone did these mods, but only a couple of us got silly with milling the heads- the engines had a much more noticeable 'pop' to them, and on the green flag, we would walk away from the other guys.

  So yes, it helps, but you wont feel it unless its a drastic change and you do the supporting mods as well.

 

PS- thats another shameless plug for those Harbor freight Predators. If any of you have doubts about a 99.00 pressure washer engine, dont. They are an excellent little powerplant, and will handle a LOT of abuse. Just keep em under 6000rpms or you could have flywheel parts in your face. That part I am very serious about.

Edited April 24, 2020 by Greentored

[PeacemakerJack 10,738]

Where’s @Achto with one of his many awesome wheelie pics on his Ray Rod?  I know that he has some mods on his little Predator!  

[WHX?? 48,770]

1 hour ago, PeacemakerJack said:

 Ray Rod?

He renamed it?!?!? 

[clueless 2,976]

4 hours ago, ri702bill said:

Kevin:

 

Two things come to mind -

The Holding setup. Since the head is irregular in shape, I assume you are going to use the tee slot clamps and blocks instead of the vise? The setup must be rigid and hold the surface to be cut dead parallel to the table.

The cutter. Are you planning to use a center cutting endmill about 5/8 " or 3/4" in diameter versus a fly cutter? Both have advantages. The endmill will miss your clamps, but you have to walk it around the pattern. A wide enough fly cutter would allow a better finish in one pass and if you have an X axis power feed, your final .005 or so cut could look like a mirror. Clamping can be a challenge though.

 

Bill

Yea, that's what I was thinkin 

[Pullstart 62,786]

1 hour ago, WHX24 said:

He renamed it?!?!? 

 

Not one thread can keep away from going down the drain... huh?  Where’s Plunger when we need him?  

[ebinmaine 67,268]

34 minutes ago, pullstart said:

 

Not one thread can keep away from going down the drain... huh?  Where’s Plunger when we need him?  

[Stormin 9,981]

  Skimming of heads isn't worth doing unless badly warped imo.

  Many years ago I used to tune up a couple of Triumph 650cc twins for a mate who raced. Never skimmed the heads. Just polished the combustion chamber to a mirror finish. The majority of the mods were gas flowing the ports, mainly the inlet. The exhaust was not all that important. Plus high lift camshafts and lightened and balance con rods. Pistons with slightly more domed crowns. Put the compression up to 12 to 1 from 10 to 1 if memory serves. Can't remember the BHP increase. Could have gone further, but we wanted reliability.

 Those engines ran for four full season without any problems, till rebuild time during each winter. My mate had good results as well. 

 

 

  

[SALTYWRIGHT 859]

I PLANED THE HEAD ON MY RAT ROD 0,60 AND GOT 8 MPH MORE TOP SPEED.  (42 MPH ON A WHEEL HORSE IS FAST)I ALSO PORTED THE HEAD AND INTAKE. I HAVE CUT ABOUT 40 HEADS OVER THE YEARS. SOME TIMES I HAD TO CUT THE BLOCK AND CUS THE PISTONS.

[953 nut 55,068]

In my teenage years I would read articles in Hot Rod and other magazines that showed how much HP could be gained by porting and polishing the intake and exhaust runners of a Ford Flathead V8 and then adding dual exhaust, shaving the Edelbrock heads, changing out the cam to a high performance one and adding a manifold with twin Stromberg 97s. and so on.  I had such an engine, and the day I replaced it with a Buick 401 Nailhead my Flathead days were over!

9 hours ago, bds1984 said:

No replacement for displacement!  

[Shynon 7,459]

13 hours ago, pullstart said:

 Would .020 bump the compression enough to even notice?

Nope, when you see what the Boss is plowing with this year your still gonna be left out 

[Achto 27,502]

I'm with @prondzy on this subject. Unless you are building a full blown puller or drag race engine shaving the head will not be felt on the seat dyno. Porting & polishing to me is fruitless unless you have a flow bench.  Example : On a Harley Shovel or Evo engine one of the first steps with the heads is to close off part of the intake  port in order to increase flow. Then again an increase in flow will only give benefit at high RPMs, so again not much good for a worker. Recently you opted for boost over displacement, but if you actually want to work some thing... I'll say it again "No replacement for displacement"