modifying 866

[ducky698]

Hi, so has any one played with firing order changes on the V8? I am looking at converting this one to the same firing order as a ford cleveland 1,3,7,2,6,5,4,8 instead of the 1,5,4,8,6,3,7,2 the reason is for less load on the crank pins from 1 an 5 then making the back end of the crank do all the work 4,8 the flex and stress on the crank must be huge.

am also fitting E9 pistons and liners tot he 866 block due to lack of 866 liners. this will give it a piston size of 5 n 3/8 inch instead of the 5 n 1/4

Grant

[Rob]

Hi, so has any one played with firing order changes on the V8? I am looking at converting this one to the same firing order as a ford cleveland 1,3,7,2,6,5,4,8 instead of the 1,5,4,8,6,3,7,2 the reason is for less load on the crank pins from 1 an 5 then making the back end of the crank do all the work 4,8 the flex and stress on the crank must be huge.

am also fitting E9 pistons and liners tot he 866 block due to lack of 866 liners. this will give it a piston size of 5 n 3/8 inch instead of the 5 n 1/4

Grant

Custom ground cam profiles and firing order? Sounds like a whole wheelbarrow of money gonna be spent to make this happen?

Rob

[Olivetroad]

Grant - that is a great project - keep us posted - post some photos if you can, I don't have the gonads to try something like that - so I need to experience it through you!

Custom ground cam profiles and firing order? Sounds like a whole wheelbarrow of money gonna be spent to make this happen?

Rob

Yes, and this is not 1920 Germany either - this is wheelbarrows of money that is actually worth something!

[ducky698]

Hi, turbo is not a drama, many sizes out there. liners, well the machineing is so close that it appears to be a fairly simple exercise. the piston pin height on the 866 to E9 is the same so this makes it more of a reason to do it. the cam regrind is not a problem, Ivan Tighe engineering can do this to any profile i want. the firing order is the curious one, engineers predict a 30% gain in just switching to the new firing order. its hard to explain but #1 fires then all the power that #1 just made is working to get #5 up the bore for it to fire, then this is cylinder is working to get # 4 up there. the new fireing order when number 1 has fired # 3 is all ready on its way up due to crank configuration. this will give a smoother running engine thats under less torsional stress.

how ever in saying that, why did Mack use the fireing order they have? BMW also run the same fireing order as Mack.

Ford windsors in the 60s ran a 1.5 firing order but later changed to the 1,3 firing order due to harmonic issues etc

Grant

[Olivetroad]

\how ever in saying that, why did Mack use the fireing order they have?

Grant

That is always my first thought whenever I want to "improve" on something that some more intelligent than me engineer figured out in the first place. I wonder if those guys are still around or if the Mack Museum could shed some light on that?

[bullhusk]

Hi, so has any one played with firing order changes on the V8? I am looking at converting this one to the same firing order as a ford cleveland 1,3,7,2,6,5,4,8 instead of the 1,5,4,8,6,3,7,2 the reason is for less load on the crank pins from 1 an 5 then making the back end of the crank do all the work 4,8 the flex and stress on the crank must be huge.

am also fitting E9 pistons and liners tot he 866 block due to lack of 866 liners. this will give it a piston size of 5 n 3/8 inch instead of the 5 n 1/4

Grant

Grant,

Put a V12-71 in your truck, this way everytime the the piston comes to the top it fires!... Problem solved! LOL!! don't comma lookin for me!!

[ducky698]

Hi, thought about the v12, but the 866 is more favourable because I have one. trying to find old engines here is crazy, they still want 15,000 for a E9 that the cant gaurantee.

I spoke to someone last week that wants 3000 for an 866 crank shaft for an engine that reality is its to old, no one really uses because parts are to hard to get for it. yet they still want the earth for it.

where to find E9 pistons and liners is the next thing.

Grant

[Mack Doctor Jr.]

Francise Engineering is the place to go. Dale has everything.

The only hard part about changing the timing I can see is the fuel pump itself. But its just a money thing there. I always wanted to get rid of the cam and use a soleonoid to move the vales. The cam and push rods are the only hold up for high RPM's.

[ducky698]

Hi, 351 clevelands spin to over 7000rpm with pushrods and lifters. will try the engineering place, thankyou. the fuel pump isnt a problem, I can do it 2 ways, new cam in the pump or re route the fuel lines. am still unsure on firing order swap yet, would like to here from some one at Mack who may know why they chose that firing order to begin with.

does any one know the lift/duration and all the cam specs on the 866? I dont have this in the book.

Grant

[Rob]

Francise Engineering is the place to go. Dale has everything.

The only hard part about changing the timing I can see is the fuel pump itself. But its just a money thing there. I always wanted to get rid of the cam and use a soleonoid to move the vales. The cam and push rods are the only hold up for high RPM's.

Connecting rods and piston weight play a lot into the equation also. A lot of centrifugal forces acting upon one another. I've often wondered how a composite connecting rod comprised of aluminum, and cast, or forged steel would hold up to increased rpm's. If the actual bearing surfaces were of the heavier material for durability against deflection, the aluminum would lighten them overall. Also wondered about a needle bearing supported crankshaft through the mains rather than sleeve type bearings currently used.

Rob

[ducky698]

2 stroke motorcycles are needle roller big end and little ends, mains are roller bearing with a pinned crank. alloy conrods are used in high performance V8s but they do stretch eventually and forged pistons are used over cast pistons also stoking engines is not uncommon these days, scat do a crank for a 351 that sends it out to a 408. the Mack V8 is no differant just bigger.

Grant

[Rob]

2 stroke motorcycles are needle roller big end and little ends, mains are roller bearing with a pinned crank. alloy conrods are used in high performance V8s but they do stretch eventually and forged pistons are used over cast pistons also stoking engines is not uncommon these days, scat do a crank for a 351 that sends it out to a 408. the Mack V8 is no differant just bigger.

Grant

I've built a lot of bikes in the past but they do not exert the downward thrust onto the crankpins that a diesel engine does. Roller bearings on the rod journals would not withstand the forces as there would be so little shear film of oil to cushion the force of the curvature of the bearing itself. This is why the conventional sleeve bearing is used here. The mains now are simply a rotating member with much less force applied although there is still some.

I don't think a large diesel engine will hold together due to torsional stress induced by rotating masses and resulting harmonics which can be devastating at high rpm. I do think a Mack V8 would survive at 4500-5000 rpm with very close tolerance machining and precision fitment of parts.

I had a 6.9ltr IH engine in a 1983 Ford F250 that blew up on me although it ran really well. When I rebuilt the engine I had the rotating assembly precision balanced, and the new pistons weigh matched. Also had the crank turned to match the bearings with the caps, (rods and mains) torqued. I put this engine back together and it had much less than 1/2 the shake or buzz it had before being rebuilt. After installing a new ATS turbocharger kit onto the truck, it really woke up too. I had the governor recalibrated to 4800 rpm as the valves started to float much above, and it really ran like a scalded dog.

Rob

[Phase 1]

I do not think that roller bearings on a crankshaft offer any advantages. The reason they are used in two strokes is that plain bearings would not live in the limited lubrication of two stroke oiling. It has been done in four strokes, but as I remember, in an oil circulating engine the rollers have a tendancy to slide and not roll, and the pushing of oil by the rollers decreases performance. Roller bearings would have a shorter life and be more expensive. Oil lubricated plain bearings have very low friction.

[ducky698]

yes, it was just a point. this thing will be getting a balance, I balance all engines, E9 piston/liners the heads rebuilt, new cam with a differant grind. the blocks going in today to get the tunnel looked at today as it has an issue with one main cap.

the firing order is what I am still unsure on as the harmonics on the firing order Mack have must be huge.

Grant

[skip]

There isnt a lot of clearance between the bore and the outsiide wall of an 866. An E9 liner is only 1/8" bigger OD but I would be concerned wiith that area of the block. It might also be a bit of a drama to cut a bigger fire ring recess in the 866 head surface. Ive looked into the possibility of doing the same thing to an 865 Ive got. Ive got a set of pistons and liners for an E9 if you want that have done low kms, but if you are going to the trouble of all that machining then use new parts. The bottom of the block around the o-ring grooves will also need inserts made up, as the bigger liner will have a different sealing area. I admire what you are doing but it wont be cheap. I had similar work done to my 864 and it was a long way from affordable! But keep me posted and let me know how you go mate. Skip

[theakerstwo]

I may be missing somthing but if you grinding down the liners and get them in there how will the piston pins work in the 866 rod? And what will the compression ratio be?

[ducky698]

Hi, the block is machined, not the liners. an 866 and E9 have the same head bolt spacings, the fire rings are thinner on the E9 and can either use E9 head gaskets or the 866 gasket. cyl head fire rings are an easy machine job as its the same mod as fitting them to a blown engine.

866 an E9 pistons have the same pin hieght from top of piston, comp will be higher wich can be off set with a cam shaft grind and if need be shaveing the top of the pistons a little.

the block at the bottom is also machined out and the use of E9 seals are fitted.

the distance between the new liner and side of the block is going to be closer by 1/16 so I wouldnt think it would be enough to cause a problem.

all this is fairly easy machine work, what I would like to know is why Mack chose the firing order they did? both front cylinders fire then all the way down the back to the rear 2. why did they go with this? the torsional stress on the crank is massive. I have not found a reason yet to keep it the same Mack firing order. 351 cleveland firing order is looking real good.

Grant

[Olivetroad]

Grant - I really hope you figure out why they ran the firing order the way they did. I have asked a couple of older Mack mechanics and no one seems to know. Let us know what you find out.

[ducky698]

Hi, I got they did alot of research from 1 Mack guy, another Mack guy said they did it that way for a reason why would you want to change it? someone else said it will blow up in a short time. my guess is they didnt do alot of research, they just copied something else. it is differant to the scania v8. am not sure of the cat v8. the only reason i can think they used this firing order is torque related, yet to me it looks like it would be robbing the engine of power rather than produceing it.

all i know is Ford changed the firing order of the windsor due to harmonic issues and Mack have alot of harmonic issues in the v8s.

it has other problems any way, there telling me the block is unserviceable due to the counter bores been cracked for the piston liners. what causes it to crack here? liners moving?

Grant