Short block long stroke engine

[ill_will]

Finally found some time to start measuring up. Checked the micrometer against setting gauge and measured new JE pistons from Dave Bean, 1/2" up from base of skirt. They were very consistent at 3.2840-3.2841", and within 1 gram.

The bores should be 3.287" (83.49mm), so 0.030" clearance per the piston data sheet. Set the micrometer to size, and then zero'd the bore gauge at 0.00mm. It is quite confusing working with a mix of metric and imperial tools. The bore gauge also turns anticlockwise as the bore increases, to add to the fun.

In the thrust direction the measurements were coming out at between +0.01 and +0.02mm (~= 0.0008") over spec, which I am a little surprised by. But I don't know if Gosnays machined the bores with a plate clamped on to simulate the head. I will ask them. It also isn't the greatest bore gauge, although I tried a few tests against the micrometer, which I trust, and it behaved as expected.

While I was at it I measured the new 77.6mm Farndon EN19 crankshaft journals. These were also very consistent at 2.1256-2.1257" (across 20 measurements at various orientations) and 1.9373-1.9377" (across 16 measurements.) This should be good to 8000rpm, although I am aiming for 7500rpm, based on crack tested and balanced 125E rods with new ARP bolts. The plan is to use a single dowel to the flywheel, but I'm interested to hear about peoples experience on this as it sounds like often no dowel is used.

The crank assy was balanced by Gosnays - crank, flywheel, clutch diaphragm, pulley and bolts, in total 25.5kg. This is a heavy duty road/competition Helix unit and lightened steel flywheel. I was hoping to get a lighter flywheel but couldn't find one to suit the road clutch.

I took the opportunity to chase out all the threads in the block - I was hoping to fit the crank and check clearance to the block but found I didn't have the right bearings so will have to order them. The 701m block is 35.9kg with the jackshaft bearings, coreplugs, and (square) caps and bolts.

[1owner69Elan]

W The plan is to use a single dowel to the flywheel, but I'm interested to hear about peoples experience on this as it sounds like often no dowel is used.

As per Dave Vegher build.

[rgh0]

I would not worry about the nominal piston clearance of 0.003 inch / 0.076 mm giving a 83.49 mm bore versus what appears to be an actual bore of 83.50 mm. If anything a little extra clearance is good in a modified engine intended to spend significant time at full power.

cheers
Rohan

corrected to get the decimal points in the right place

[promotor]

I would not worry about the nominal piston clearance of 0.030 inch / 0.76 mm giving a 83.49 mm bore versus what appears to be an actual bore of 83.50 mm. If anything a little extra clearance is good in a modified engine intended to spend significant time at full power.

cheers
Rohan

I'd certainly be worried about 0.030" clearance!

[rgh0]

I would not worry about the nominal piston clearance of 0.030 inch / 0.76 mm giving a 83.49 mm bore versus what appears to be an actual bore of 83.50 mm. If anything a little extra clearance is good in a modified engine intended to spend significant time at full power.

cheers
Rohan

I'd certainly be worried about 0.030" clearance!

Yes you start talking in mixed units you confuse me. I am just a simple fellow and getting the decimal point a zero out is the least of my many problems

cheers
Rohan

[promotor]

I would not worry about the nominal piston clearance of 0.030 inch / 0.76 mm giving a 83.49 mm bore versus what appears to be an actual bore of 83.50 mm. If anything a little extra clearance is good in a modified engine intended to spend significant time at full power.

cheers
Rohan

I'd certainly be worried about 0.030" clearance!

Yes you start talking in mixed units you confuse me. I am just a simple fellow and getting the decimal point a zero out is the least of my many problems

cheers
Rohan

You and me both!

[ill_will]

W The plan is to use a single dowel to the flywheel, but I'm interested to hear about peoples experience on this as it sounds like often no dowel is used.

IMG_5982.jpeg

As per Dave Vegher build.

Good to know - thanks. It took a while with a rubber mallet to separate the crank from the flywheel, after balancing the whole assy but got it apart in the end.

[ill_will]

I would not worry about the nominal piston clearance of 0.030 inch / 0.76 mm giving a 83.49 mm bore versus what appears to be an actual bore of 83.50 mm. If anything a little extra clearance is good in a modified engine intended to spend significant time at full power.

cheers
Rohan

Thanks Rohan. Your experience knowing how much 'outside spec' you can go before worrying is always appreciated.

Since I last posted, I'd sent the 125E rods back to have them crack tested at Gosnays, as this job wasn't done when the small end bearings were honed and I wanted to be as certain as I could be that they were ok before taking them up to 7500rpm. Annoyingly the courier has lost the package, hopefully only temporarily, so trying to chase that down has been taking up time I could be spending doing various checks on the engine.

[2cams70]

Whilst the engine may run OK with bores bored 0.001" larger than they should be be aware that there may be some tradeoffs - eg:

1. Piston slap when cold (If you are sensitive to such noises you may notice a slight hollow rattling sound from the engine until it warms up) Unless really bad it's usually not noticeable from within the car but you can detect it when listening to the engine outside the car with the bonnet up). With new cars and engines that are so quiet customers are VERY sensitive to piston slap - even the non technical ones. With an ancient Twin Cam maybe somewhat less so !!

2. Reduced life between rebuilds.

With a nominal piston clearance of 0.003" an extra 0.001" is not an insignificant amount in percentage terms. At the very least I'd be talking to the engine machinist about what you found and see what their response is. Oh - and when you do get a response appreciate if you could report it back here (very rarely do people do such things on this forum unfortunately).

Regarding the crankshaft bearing clearance - best to supply your machinist with everything i.e Crankshaft, actual bearings you are going to use and the block and ask them to check the bearing clearances. If need be they can then adjust the clearances to a small extent by machining the bearing caps and line boring the block to reset the bearing crush and hence the bearing clearances resulting from that crush (or linish the crankshaft a bit depending on whether there's too little or too much clearance).

I forgot to add with this one - once you have established accurately what the bore size is on your engine and if it's deemed to be out of spec. by a significant margin I'd be contacting the piston manufacturer and seeking their opinion too. Their opinion is most critical as the clearance they set is based on their knowledge of the type of aluminium used (and hence it's thermal expansion characteristics) and also the type of skirt profile the piston has been ground to.

[ill_will]

Whilst the engine may run OK with bores bored 0.001" larger than they should be be aware that there may be some tradeoffs - eg:

1. Piston slap when cold (If you are sensitive to such noises you may notice a slight hollow rattling sound from the engine until it warms up) Unless really bad it's usually not noticeable from within the car but you can detect it when listening to the engine outside the car with the bonnet up). With new cars and engines that are so quiet customers are VERY sensitive to piston slap - even the non technical ones. With an ancient Twin Cam maybe somewhat less so !!

2. Reduced life between rebuilds.

With a nominal piston clearance of 0.003" an extra 0.001" is not an insignificant amount in percentage terms. At the very least I'd be talking to the engine machinist about what you found and see what their response is. Oh - and when you do get a response appreciate if you could report it back here (very rarely do people do such things on this forum unfortunately).

Regarding the crankshaft bearing clearance - best to supply your machinist with everything i.e Crankshaft, actual bearings you are going to use and the block and ask them to check the bearing clearances. If need be they can then adjust the clearances to a small extent by machining the bearing caps and line boring the block to reset the bearing crush and hence the bearing clearances resulting from that crush (or linish the crankshaft a bit depending on whether there's too little or too much clearance).

I forgot to add with this one - once you have established accurately what the bore size is on your engine and if it's deemed to be out of spec. by a significant margin I'd be contacting the piston manufacturer and seeking their opinion too. Their opinion is most critical as the clearance they set is based on their knowledge of the type of aluminium used (and hence it's thermal expansion characteristics) and also the type of skirt profile the piston has been ground to.

That is interesting information - thanks for posting. I will double check my measurements and then have that conversation with the machinist. I'll let you know how it goes.

[ill_will]

Whilst trying to find the missing con rods and deal with the bore, there were a few jobs I could make some progress on.

One item was a cartridge style water pump with front and back covers to suit, and I wanted to do a trial build to gauge what the fit was like between the two gasketless flanges at either side (where they normally leak.) The Burton design has a rubber o-ring at the front and back cover interface in the water pump area, but nothing at the two flanges. On a past build with original style covers I made up three gaskets which worked well (a la Brian Buckland) and a variation on that is one option here. You can see the rubber gasket in one of the photos.

Before the trial fit I checked the diameter of the timing chain (iirc?) oil passageway, location of holes, etc. Pump vane clearance was 0.020-0.025", so inside spec (0.020-0.030".) Clearance to the jackshaft pulley and bolts was ok.

I found I needed to temporarily put all the bolts through into the block before tightening the back cover to block, to make sure the back cover was aligned correctly. I'm hoping to make up a tool for centering the front cover seal housing on the crank - thanks for the tip Rohan in one of your build threads.

With the three bolts around the pump tightened, with feeler gauges I measure between 0 and 0.15mm clearance between the two covers, at various points along each flange. I'm tempted to try to find some very thin gasket paper (0.1-0.2mm perhaps?) and make up two gaskets, one for each flange, and rely on the rubber gasket at the central interface between the two covers. I'm not a huge fan of using lots of silicone.

One thing still to do is check the dipstick tube location, a quick search found this thread on the topic: viewtopic.php?f=39&t=34170&start=

Also need to dig out the alternator and brackets to check whether some of the bolts (the three upper right ones in the last photo) need to stick through the cover (I vaguely remember a banana shaped stiffening bracket attached on the back here?) The Burton design has threads in the back cover rather than clearance holes so there aren't nuts on the back for most of the bolts.

[2cams70]

On a past build with original style covers I made up three gaskets which worked well (a la Brian Buckland) and a variation on that is one option here. You can see the rubber gasket in one of the photos.

No - definitely don't do that!! Despite what Buckland may say this is not a good engineering solution. All you need to worry about is using the correct amount and type of sealant and tightening things up evenly to the correct torque.

I posted a few years ago about the Burton front cover. Suggest to look it up in a search.

Amongst other things you need to check when fitting the Burton front cover (aside from checking it thoroughly for manufacturing defects) are:

1. Check that there is clearance between the head of the front of block 1/4" NPT oil gallery plug and the Burton backplate. If not the backplate won't sit flat on the block and you'll get a leak.
2. Check the fan belt alignment across the front pulleys (Crankshaft front and water pump drive) during trial build. Once you have pressed the water pump pulley in position on the water pump shaft so that things are in alignment you may find that you now have no clearance between the inside of the pulley and the water pump cartridge mounting bolts. If so you may need to change to a lower profile style of fastener in order to gain clearance.
3. Use low strength loctite on the threads of the countersunk set screws that secure the tensioner pad to the inside of the front cover otherwise you'll get an oil leak from oil seeping through these threads.

There's lots of nuances to getting it all together properly. Feel free to send me a PM if you want. I can't be bothered tapping the keyboard here. I spend most of my working life tapping keyboards.

[ill_will]

Amongst other things you need to check when fitting the Burton front cover (aside from checking it thoroughly for manufacturing defects) are:

1. Check that there is clearance between the head of the front of block 1/4" NPT oil gallery plug and the Burton backplate. If not the backplate won't sit flat on the block and you'll get a leak.
2. Check the fan belt alignment across the front pulleys (Crankshaft front and water pump drive) during trial build. Once you have pressed the water pump pulley in position on the water pump shaft so that things are in alignment you may find that you now have no clearance between the inside of the pulley and the water pump cartridge mounting bolts. If so you may need to change to a lower profile style of fastener in order to gain clearance.
3. Use low strength loctite on the threads of the countersunk set screws that secure the tensioner pad to the inside of the front cover otherwise you'll get an oil leak from oil seeping through these threads.

That's a good list of things to check, thanks. The kit I have has 3 hex head bolts which have been machined slightly (a kind of anti-countersink, if that makes sense) which should give a bit of extra clearance to the pulley.

I'm interested to hear you are against a gasket - in the case of a Burton cover I'd agree, as you'd end up with a slight misalignment between outer and central faces if you keep the o-ring arrangement, but in the case of a 'normal' cover it doesn't seem like too bad a solution to me. I had a look and 0.15mm gasket paper is available, so the front cover wouldn't be offset by much. What's your thinking behind your comment?

[ill_will]

One other issue (of many, it seems) that has cropped up is the big end bearings that I ordered from QED. On opening the packet it looks like the box has been dropped at some point, and two shells are now closer than they would be in their original state:

So one has been opened out slightly, or one closed slightly, or some combination of the two. Has anyone fitted a shell that this has happened to and/or should I worry about it? It feels like the crush from the bearing housing and resulting circumferential compression should sort it out, but that is just a guess.

[promotor]

One other issue (of many, it seems) that has cropped up is the big end bearings that I ordered from QED. On opening the packet it looks like the box has been dropped at some point, and two shells are now closer than they would be in their original state:

Engine15.jpg

So one has been opened out slightly, or one closed slightly, or some combination of the two. Has anyone fitted a shell that this has happened to and/or should I worry about it? It feels like the crush from the bearing housing and resulting circumferential compression should sort it out, but that is just a guess.

You may find that the bearings involved have damage on the bearing material itself - Mahle's packaging standards have slipped as the shrink wrap is no longer shrunk on as well as it should be which holds the bearings in position better (I'm not saying it's impossible for the problem like yours to exist even with good packaging, but I believe it's more difficult when packaged correctly).
I bought some Mahle bearings not too long ago (different seller) and they were the same where the bearings had been jiggling around in the loose wrap and had ruined a few on the material itself. I was told that if in doubt don't open the package / shrink wrap and return them for replacement. The problem is will the next set be the same?

The replacements I had sent were individually wrapped in bubble wrap!

As for the sufficient "pinch" I can't say, firstly you'd have to measure the affected one(s) against a known good one and see how they compare on how much they have closed down, if at all.

I would ask for replacement and that they only send ones that are packaged properly out to you. This damage could well have happened before they were even sent to you. Hopefully any sellers affected by this will be passing this issue back up the chain to let Mahle know about it (and provided that enough end users complain maybe they will listen).