NWL – Project Concours Carmine Sprint

[SprintMWU773V]

Just our of interest have you weighed the original pistons?

[James467]

Harsh Jer, harsh!

Yep, covered in crud still but bare, with no rings there is a 2.7g difference between lightest and heaviest.

Probably closer to 1.5-2g cleaned up.

They are Mahle, it's printed on the underside of the crown!

And you'll want to remove the filings they've left before you fit the pistons in your engine.

Don't you worry about that!!

Haven't had a call from Rimmers yet, will chase them.

[Jon Tilson]

Remind me what was wrong with your original pistons?

Some would kill for Mahle's...

Jonners

[James467]

Cylinders 2 and 3 were scored, looks like it was from the thrust side of the piston skirt, on page 1 of the thread.

Too much to hone out unfortunately.

One of the bearing shells was scored as well, luckily it didn't damage the crank, I put that down to Wadham Kennings service department's lack of cleanliness who replaced the bearings at 60k!!

I still have the Mahle's though...

[SprintMWU773V]

They do tend to wear on the thrust side. To be fair yours are way better than mine were.

[James467]

Had an email from Nornda, the piston supplier in Oz this morning. If I tell them the weight of my pins and pistons they will send me a replacement piston with the closest matched weight to the rest free of charge as long as I pay the shipping.

I'm happy with that, hopefully if we can get a set within 2g of each other then I can get the weights down to 0.5g without too much trouble.

[James467]

Newsflash!

A complete new set of pistons are on their way........

Watch this space!

[James467]

A package arrived from a land far far away containing a set of these.....





Looking good so far! They are the new and updated versions of the ones I had.

but these jp look like some cheap boogie woogie pistons

Nope Jer, I am afraid not. I found out some things about JP Pistons, yes, they are cast but they make pistons for Rolls Royce and are highly regarded in the vintage Rolls restoration world. They also make pistons for a lot of vintage british bikes.

Their customer service has been second to none, they really have gone to the next level for me. I have a new set of pistons weight matched and all I had to pay was the shipping so I'm very happy.

Shall we see how close they are!









I'm happy with that, I don't need to touch them.

So all I did was to match them up with the rods and pins and hey presto...



The scales don't lie!









I think it's about time I got this engine built.

[soe8m]

Let's change it to funky pistons then.

Jeroen

[James467]

Shall we leave it until the first start and let the running of the engine do the talking?

I need to match the water holes in the new head to the block as well as smoothing out the ports a bit.

Jer, did you leave the little lubrication holes for the small end alone? I think mine need a bit more of a countersink on them but I dont want to weaken them. I assume thats there to catch spray and lubricate the small end.

The last question is it worth me getting a set of ARP bolts for it? I can't seem to find any for the head though.

[soe8m]

Yes only do countersink them when you did take material of the top of the rod. Never did enlarge the hole but sometimes it is needed to go through with a drill of the same dia because the hole of the small end bush does not line up ok. The countersink area is to collect oil. As for weakening the big bangs and compression stroke the forces are towards the big end.

Jeroen

[James467]

Thanks, holes are ok, it just need more of a countersink at the top to create a well.

[James467]

Looking at my project plan I am going to change the order in which I'm doing things. A new arrival is due in October and I'd rather not be outside in the cold welding through the winter, I'm getting too old for that and this seems like a more efficient way of doing things.

I am going to use the summer months to get the bodywork done and over the winter in the warmth of the workshop I can get everything else built up and refurbished. This way hopefully all I will need to do next spring is have the shell sprayed then I can put the car back together ready for the summer.

If I leave the welding until next summer it's going to be another year or so before she's back on the road, I'm welding the MG anyway so it makes sense to do it now. I don't need to assemble to engine now, everything is safely stored away and wrapped up so I can pick that up later on in the year.

[tonybsa]

James,dont worry about those JP pistons.I have had a set in my Sprint for 6 years,without any problems.I also had a set in a BSA A65 sidecar I used to race.My only criticism,is they are a little on the heavy side,but I guess it dont matter in road engines.Looks like you have had great customer service too

[PaulB]

I too have JP pistons,although the car deosn't do many miles it will have done say 5000 since fitted about 4 years ago with no issues.

But given the price, I wish now that I had used a set of forged JE instead as they don't cost much more.