Upgraded S65 Connecting Rods

[pbonsalb]

Not sure there is a poor man's semi built motor. If taking apart the motor for forced induction, why not run lower CR pistons. Unless you use E85, you are knock limited and can't safely run more boost on stock compression.

So much labor is involved in rebuilding. I assume if taking the motor apart to install aftermarket rods and new piston rings, I assume you would go one step further and replace the main bearings. Why not buy lower CR pistons? Might even get the rings included. And the ideal boost piston might have more than a ring gap change. The ring lands may change.

[GabeS]

Originally Posted by pbonsalb

Not sure there is a poor man's semi built motor. If taking apart the motor for forced induction, why not run lower CR pistons. Unless you use E85, you are knock limited and can't safely run more boost on stock compression.

So much labor is involved in rebuilding. I assume if taking the motor apart to install aftermarket rods and new piston rings, I assume you would go one step further and replace the main bearings. Why not buy lower CR pistons? Might even get the rings included. And the ideal boost piston might have more than a ring gap change. The ring lands may change.

That is a proven poor mans build on other engines, if they had money to do a full build it wouldn't be a poor mans build.
It does increase the engines capacity for higher boost over stock.
The piston rings are a lot of times the ones to go when there is issues with boosted engines and so are the rods

Lets say I have a SC and enough money to do the rod bearings, and I could possibly squeeze out another $1500-$2500 for upgraded rods and rings I would do it.. I wouldn't say "Oh I cant afford to do a full build so Ill just leave the motor more vulnerable for now"

[pbonsalb]

My point is that it's so expensive to get in there that the added cost for proper boost pistons is small. Doing the rod bearings is a piece of cake in comparison. I did mine myself. Doing piston rings and rods would be so much more work and expense because you are taking off the heads rather in addition to pulling the oil pan.

And again, with 12.0:1 CR your issue on pump gas with boost is not piston rings. It's compression.

Rod bearings and bolts and parts for the rod bearings might run $500-$1000 depending on what parts you use. Labor might be $1000 to $1500 depending on who you use. It takes about 8 hours.

Rods cost about $2100. They additionally require the removal of the heads, which means a lot of labor stripping down the motor and putting it back together new headgaskets and bolts. Timing the cams takes some work. Certainly while you had the pistons out, you could do the rings, but you have to buy rings sets for about $100 each times 8, and you have to spend time filing and fitting.

New, lower compression alusil friendly pistons will cost about $2800 and come with rings. And you can option the added benefit for boost on pump gas of lower compression, which probably also includes revised ring lands that are designed for boost. Getting into sleeving the block to use cheaper standard pistons would be much less cost effective since sleeving is expensive.

I am not an engine builder, but maybe one of the members who does this work can comment on the labor costs pull the heads and pistons.

If I was going that far, I'd pull the crank as well and do the main bearings. I would hate to spend a bunch of money and then have the front main bearing fail.

[GabeS]

Originally Posted by pbonsalb

My point is that it's so expensive to get in there that the added cost for proper boost pistons is small. Doing the rod bearings is a piece of cake in comparison. I did mine myself. Doing piston rings and rods would be so much more work and expense because you are taking off the heads rather in addition to pulling the oil pan.

And again, with 12.0:1 CR your issue on pump gas with boost is not piston rings. It's compression.

Rod bearings and bolts and parts for the rod bearings might run $500-$1000 depending on what parts you use. Labor might be $1000 to $1500 depending on who you use. It takes about 8 hours.

Rods cost about $2100. They additionally require the removal of the heads, which means a lot of labor stripping down the motor and putting it back together new headgaskets and bolts. Timing the cams takes some work. Certainly while you had the pistons out, you could do the rings, but you have to buy rings sets for about $100 each times 8, and you have to spend time filing and fitting.

New, lower compression alusil friendly pistons will cost about $2800 and come with rings. And you can option the added benefit for boost on pump gas of lower compression, which probably also includes revised ring lands that are designed for boost. Getting into sleeving the block to use cheaper standard pistons would be much less cost effective since sleeving is expensive.

I am not an engine builder, but maybe one of the members who does this work can comment on the labor costs pull the heads and pistons.

If I was going that far, I'd pull the crank as well and do the main bearings. I would hate to spend a bunch of money and then have the front main bearing fail.

Makes sense, I had no idea of how much all that costs on this engine!
I was thinking based of experience on SR/2J/Rb engines which cost much less

[deansbimmer]

Originally Posted by pbonsalb

My point is that it's so expensive to get in there that the added cost for proper boost pistons is small.

Generally I would agree with your post...But what you're proposing would result in a significant increase in cost to do properly by an engine builder. At that point it would basically be a full rebuild.

Personally I don't think it's economical to tear down an S65 just to upgrade the rods. At that point so much has to be done to do the job correctly, that you might as well install the rest of the goodies. But don't fool yourself into thinking that it's only going to add marginally to the job.

[Nugget]

Originally Posted by tdott

Sucks to hear, goodluck with the next engine.

How bad was the crank/journals for the main that failed? I'm assuming not salvageable with a new crank since you are going with another engine? If you happen to have pictures of the crank and main bearing journal that failed, I would love to see them. Just curious to see how bad it was.

Was pretty bad.

Originally Posted by GabeS

I have been contemplating doing aftermarket rods as an upgrade when I install my supercharger too, might as well upgrade the piston rings also, it'll give you a semi built engine setup which will allow for much higher boost than stock engine.
It's sort of the poor mans forged engine build.

On that note a quick search came up with this:


Pauter: http://pauter.com/shop/rods/bmw/bmw-s65-b40-m3-rods/

Carillo: https://store.vacmotorsports.com/cp-...t-8-p2744.aspx

Cp Pistons: https://www.carid.com/cp-carrillo/co...65540s-00.html

Strokers:

Pure: https://www.pureperformancemotorspor...onnecting_rods

I have a set of custom Carillo Rods on the way that I no longer need. Can save you the 6 week wait if you want them.

[deathbunny]

Originally Posted by pbonsalb

My point is that it's so expensive to get in there that the added cost for proper boost pistons is small. Doing the rod bearings is a piece of cake in comparison. I did mine myself. Doing piston rings and rods would be so much more work and expense because you are taking off the heads rather in addition to pulling the oil pan.

And again, with 12.0:1 CR your issue on pump gas with boost is not piston rings. It's compression.

Rod bearings and bolts and parts for the rod bearings might run $500-$1000 depending on what parts you use. Labor might be $1000 to $1500 depending on who you use. It takes about 8 hours.

Rods cost about $2100. They additionally require the removal of the heads, which means a lot of labor stripping down the motor and putting it back together new headgaskets and bolts. Timing the cams takes some work. Certainly while you had the pistons out, you could do the rings, but you have to buy rings sets for about $100 each times 8, and you have to spend time filing and fitting.

New, lower compression alusil friendly pistons will cost about $2800 and come with rings. And you can option the added benefit for boost on pump gas of lower compression, which probably also includes revised ring lands that are designed for boost. Getting into sleeving the block to use cheaper standard pistons would be much less cost effective since sleeving is expensive.

I am not an engine builder, but maybe one of the members who does this work can comment on the labor costs pull the heads and pistons.

If I was going that far, I'd pull the crank as well and do the main bearings. I would hate to spend a bunch of money and then have the front main bearing fail.

Wouldn't you also need to have the cylinders honed or w/e they do with alusil so the new rings can seat properly?

Does anyone know if the harrop design puts less stress on the front main bearing than the various centrifugal setups? It sounds like it doesn't extend past the normal pullies like the other systems do.

[pbonsalb]

Honing is not a big deal. The labor is in getting in there. If I was voluntarily disassembling the motor to make it stronger for FI, I would do rods and pistons and main bearings.

You can get 600 rwhp on the stock bottom end. It's a lot of money to get another 150 rwhp.

[Green-Eggs]

Originally Posted by deathbunny

Wouldn't you also need to have the cylinders honed or w/e they do with alusil so the new rings can seat properly?

Does anyone know if the harrop design puts less stress on the front main bearing than the various centrifugal setups? It sounds like it doesn't extend past the normal pullies like the other systems do.

Some superchargers use their own 3rd rail (more load on the nose of the crank), while others use the factory 2nd rail (less load on the nose of the crank). It would be nice if there were a list of which kits use a 3rd rail and which use a factory rail. We did bearings on an ESS kit car a few days ago and it used the 2nd rail. Next time we install an AA kit, I'll take a look at what it uses.

[pbonsalb]

What do you mean by "rail?" Aren't all the S65 supercharger kits, whether centrifugal or positive displacement, using the factory belt drive location to drive the supercharger, and thus their brackets are bolted to the front of the motor? I do recall some S52 and S54 kits that used an extended crank pulley with a third forward pulley for a dedicated supercharger drive, but don't recall seeing that on any S65 kits.

[Green-Eggs]

Originally Posted by pbonsalb

What do you mean by "rail?" Aren't all the S65 supercharger kits, whether centrifugal or positive displacement, using the factory belt drive location to drive the supercharger, and thus their brackets are bolted to the front of the motor? I do recall some S52 and S54 kits that used an extended crank pulley with a third forward pulley for a dedicated supercharger drive, but don't recall seeing that on any S65 kits.

The factory crank pulley is two rails. Evolve and Gintani make a modified crank pulley with three rails and drive the supercharger off the third (front-most) rail. ESS uses the factory crank pulley. Can't seem to remember what what Harrop or AA do.

[Nugget]

Originally Posted by M.Hagen

The Harrop kit replaces one of the two serpentine belts with a longer one that wraps around the SC snout. It does not change the crank pulley.

There is extra drag on the crank/engine (as with every supercharger), but the added length to the belt does not increase the moment on the crankshaft.

.

[deathbunny]

Originally Posted by Green-Eggs

The factory crank pulley is two rails. Evolve and Gintani make a modified crank pulley with three rails and drive the supercharger off the third (front-most) rail. ESS uses the factory crank pulley. Can't seem to remember what what Harrop or AA do.

Thanks, I didn't realize the ESS used the factory pulley, I assumed all the centri kits would be setup the same.

Just based on pulley layouts between the different kits does anyone know or have an opinion which setup would put the least amount of extra strain on main bearing 1 or are they all going to put it at the same amount of risk?

Sorry for thread jacking, I bought the car with full intentions of SCing it but after reading through the spun MB threads im having serious second thoughts about adding one.

Best of luck to OP on getting back up and running

[Doc Oc]

If you look at the crank and pulley as a lever, with the #1 mb kind of being the fulcrum, the leverage will be increased the further away the from the fulcrum the force is applied.