Topic: Why 11 hp Head..!!!!

[roger]

I was just woundering, but why would you want to put a 11hp head on a 12hp motor.....Just asking?? If it is for more compression why not deck the 12 hp head...???? Thanks...Roger

[George Herrin]

Thats a GOOD question. I havn't run a 12hp head in several several years now!!!!!

[cycloneracer]

I've run both.  Certain combinaitions work better together.  Some times I run a 11 hp head, and on other engines I run a 12 hp head.

Just need to do some testing and see which one runs better.  It is a easy swap.
Your port job, carb, and cam make a big difference in making this decision.

Paul

[texasmower5]

I've run both.  Certain combinaitions work better together.  Some times I run a 11 hp head, and on other engines I run a 12 hp head.

Just need to do some testing and see which one runs better.  It is a easy swap.
Your port job, carb, and cam make a big difference in making this decision.

Paul

If you run a stock cam and only a stock cam, run a 10hp head (22).  You will definately see the difference.  Ran one for 4 years now!

[Hitch]

12 hp head is better if properly machined,some welding,milling & a correctly cut fire slot.I've tried the 11 hp head but not as good for me.The combination of other things play a big part as to which one to run.

[Ty]

I have been running a 11 hp head,works for my set up.

[cycloneracer]

12 hp head is better if properly machined,some welding,milling & a correctly cut fire slot.I've tried the 11 hp head but not as good for me.The combination of other things play a big part as to which one to run.

Interesting!  I've always thought of doing that, but was concerned with the weld sticking.  Are you using NEW briggs heads so they are clean?  Or are you just cleaning up the used ones.

My local machine shop (VERY good one) won't weld on used alum becasue it just won't stick.  The oil in the pores of the alum creates problems, or so they tell me.

Been thinking about buying a spool gun for our welder and trying some alum welding.  But I'm not sure I want my "experiment" to be on a brand new engine!  I can see using a 12 hp head and cutting a nice "port" from the valves to the pistion.

Paul

[Hitch]

I have welded both new & used of course new is better but if you clean it good (let it soak in carb cleaner about an hour & bead blast after that) it'll stick.I prefer tig welding but a spool gun will work.


I'm not saying a 11 hp head won't work alot depends on cam,port work,carb. & deck height,just try both if ya want.

[cycloneracer]

 

Good stuff right there!!!!!  Hope ya'll are reading.


Now to explain to the wife that I NEED a spool gun!  Guess I have to break something alum that I use on the farm, then she will understand!

Paul

[Ty]

To my understanding,people are using the 12 hp head for more flow and others are using 11 hp head for compression.Didn't think there was anymore to it than that.

[cycloneracer]

You are correct.  But different combinations like different heads.

When I started running stock ungoverned stuff, we all put 11 hp heads on and advanced the timing.  Made a big difference, but everything else was stock.

Once I started modifiying stuff, I started experimenting.  One engine I run a 12 hp head, it don't like the 11.

My 28 I run an 11 hp head, but it isn't stock.

On my "backup" engine I run a stock 11hp head, it just doesn't like the 12.  But the port job isn't as good.

But I also do some work to the block between the valves and the piston.  That is how I get away with running the 11 hp head and make it run so good.  If you are going to do this mod, be prepared to ruin some blocks.  There is a fine line of how much to grind off.  If you have seen Don G's engine video it is the same thing he does, I just go WAY farther.  That is why if I can weld the head up, I can see making a "port" to control the flow to the center of the piston.

Paul

[Hitch]

Now ya got the picture give it what it wants.

[Ty]

Well I do have enough blocks to wreck .

[Mowerpar]

I've heard a rule of thumb for "relieving the valves" is to go no more than a little above the 1st ring on the piston.  If you have access to a machine shop have them do the first cut then blend in to your desire with a dremel

[mowpower]

Not to be a smart a** which 11 horse head are you guys talking about. I have 3 11 horse heads that came off 11hp 28 cid engines. I put one on my 12 and saw no difference. I even CC them the 12 head had a smaller combustion chamber then the other 2 I had gotten. Or are you talking about the 25 heads instead of the 28 heads?