How big a pistons in a WC block?

Is 4.625 as big as you can go? Thanks,JM

can the block bores be offset to increase clearance for bigger sleeves? What is the biggest bore we can get?

JM wrote: can the block bores be offset to increase clearance for bigger sleeves? What is the biggest bore we can get?

  Yes .boring bar has to be offset away from cam side a 1/8 inch or more depending on the sleeves outside diameter and overall length. Sleeve will be right up against the outside head bolt holes.

Edited by mlpankey - 13 Jan 2011 at 6:05am

Lonn wrote: mlpankey wrote: No I am kicking around cutting two blocks and welding them back to increase the deck height  so the sleeve don't have to protrude past the camshaft and going into  2 cylinder jd size. In my magic ball I see 491 ci in the future. Say that again? Why not just make a spacer and use two head gaskets? Maybe I'm not following or does it have to look like a block and not a block with a spacer?

The problem is the sleeve outside diameter 5.125 and the length of the sleeve it takes to have a piston moving up and down in a sleeve with 6.250 stroke. If any of the sleeve at that od protrudes out the bottom the cam cant turn. most clubs have a rule on two head gaskets or spacer . The problem is getting stuff strong enough to handle the power . Any of them making over 150 hp no matter the cubic inches seam to be trouble.

Edited by mlpankey - 13 Jan 2011 at 8:52am

one of them ready to hone.

I've got about 120 runs on my engine that is apart, the cylinders are out of round about .006 or a tad more now, and we honed them quite a bit.  Piston skirt clearance is getting to high, the liners are hard, remade from a diesel application, but wear has taken it's toll.

Edited by wi50 - 14 Jan 2011 at 4:14pm

short rods are good at limeting power output of an engine.  They bend, or the crank breaks.  I've got friends that think the shorter the better, same story all the time, bent or broken parts.  Monkey see monkey do, again and again.  I see people wonder why the crank broke or a rod bent, but the answer is alwayse the same.  It was to weak, but the same rod in a better ratio is stronger.

 

It's nice to see a 1.5 to a 1.8 ratio, above a 1.8 and things are likely going backwards.  I wouldn't be afraid of a 1.4 but I wouldn't go any less than that.  I'll sacrafice stroke any day for an engine that has some durability and more ablility to perform in a wide powerband.

 

I can't think of how many times the rod ratio horse has been beat to death, but I've seen enough to know and will keep my opinions.

it's all in how it's fed.  Piston speed is good to a point and after that, it's just negative horsepower.  If a head is choked (which all these heads are) , and the cylinder is drawing air at a higher rate, the vaccuume goes up.  The higher the vac. the more power being robbed.

Engine Bore:	< value=4.8 size=6 name=bore>
Engine Stroke:	< value=4.5 size=6 name=stroke>
RPM:	< value=6000 size=6 name=rpm>
Port Area (CSA):	< value=1.96 size=6 name=csa>
Number of Cylinders:	< value=4 size=6 name=cyl>
Piston Speed: 4,500.00 feet per minute. Piston Speed: 75.00 feet per second. Average Port Velocity: 692.43

Engine Bore:	< value=4.75 size=6 name=bore>
Engine Stroke:	< value=6 size=6 name=stroke>
RPM:	< value=6000 size=6 name=rpm>
Port Area (CSA):	< value=1.96 size=6 name=csa>
Number of Cylinders:	< value=4 size=6 name=cyl>
Piston Speed: 6,000.00 feet per minute. Piston Speed: 100.00 feet per second. Average Port Velocity: 904.10
< value=Calculate =submit name=submit>

Edited by mlpankey - 14 Jan 2011 at 7:48pm

how realistic is 6000 ft/min piston speed?  half that or less is more realistic in a lot of these tractor engines.  I know a few that going over 4000 ft/min.

Edited by wi50 - 14 Jan 2011 at 8:12pm

heres why piston bore out performs stroke at a given piston speed

Engine Bore:	< value=4.75 size=6 name=bore>
Engine Stroke:	< value=6 size=6 name=stroke>
RPM:	< value=4500 size=6 name=rpm>
Port Area (CSA):	< value=1.96 size=6 name=csa>
Number of Cylinders:	< value=4 size=6 name=cyl>
Piston Speed: 4,500.00 feet per minute. Piston Speed: 75.00 feet per second. Average Port Velocity: 678.08
< value=Calculate =submit name=submit>

if you look at the 4.8 bore you will see it out performs the 4.75 bore at 4500 fpm of piston speed but if you ran both at the same rpm then the stroke kicks its tale in port velocity which makes more overall lugging power as well as more horsepower in the higher rpm range.. 

GBACBFan wrote: I gotta tell you, Pankey as much as I worry about you on a couple of subjects, you are smarter than the average bear on these hot rod tractors.

I am glad you care enough to worry but you really shouldn't  on a trivial me.

Thats what they say and even the computer says that but real world my engine turned 2000 rpms more than the computer said it would for a rpm on the tattle tale tack of 6000rpms.You know when pulling you generally want to take the rpms above where peak occurs and pull back down into peak power rpm range. I would rather have a computer for checking my thinking than going head strong and blind into a project.  I would definitely need a computer when designing a head. Could get the velocities and swirl off bad without a computer and flow bench.  Just for kicks when you reach 200 hp till me how much over 194 cfm at 28 inches of depression your head is running?  No doubt your a talented guy . So I leave you with a quote from Grumpy Jenkins . When you run into that engine that runs better than you think it should its time to change your way of thinking. It happens to me to.

Edited by mlpankey - 16 Jan 2011 at 8:36am

I believe it takes airflow in the form of cfms to produce the btus to convert energy into horsepower . I believe that the cfms to produce power have a effect on the rpm in range at which a engine produces this power number from. Cfms of air flow is based on the cubic inch size of the engine the cylinder head is on.  I believe it takes 194 cfm at 28 inches of cylinder head flow to produce 200 horsepower .now a 226 ci  engine with this head flow is capable of making the 200 hp if it is spun to the rpm that's required . I believe a 400 ci engine will do it at a significantly lower rpm.  Here is what I have learned by doing and observing tractor pulling . The small engine that gets its breath to produce power at a high rpm is dependent on the mechanical advantage of gearing to keep it in its breath. The large engine that is in a taller gear and spun past peak rpm and pulls down into peak and past it to the point of snuffing the engine out will be farther in distance than the engine which a lower gear held its  rpm but spun out.  First  reason the large engine in taller gear generated more ground speed and a object in motion stays in motion till a force equal stops it. Reason two the tractor that pulls higher gear and lugs his engine down is hooked to the ground and loosing rpm due to it.This engine is always the winner. The 15 percent difference in readings you talk about is people wanting best numbers and not using corrected numbers to obtain the standard but the formulas are out there for a standard no matter the elevation or barometric pressure may be at time tested . Do you really believe what you write ? You just typed you believe velocity is better than shape but in a above post wrote velocity can hurt horsepower . Qoute Wi 50 The higher the vac. the more power being robbed. Unless your running a charger or turbo how do get air to move to fill a void without vacuum

Edited by mlpankey - 16 Jan 2011 at 2:23pm

Steve M C/IL wrote: quality air beats volume air any day

yes if it didnt nitrous oxide wouldn't be a power adder now would it? A larger volume of air will have more avaliable oxygen when talking natural aspiration.