Hi there,

Did exact the same on my 1300 engine. Full and comprehensive rebuild of the entire engine. 1) Complete teardown/disassembly, 2) Complete reassembly

Pistons: JE Forged apple bite pistons
Rods: Carillo
Valve springs: Spruell suplied and new (upgraded from the standard kit)
Mains and Rods bearings: King bearings
Chains (Bottom and distrib.): IWIS race

All this supplied by Spruell (Very well composed kit of high quality, IMO)

When cold and start the engine is a bit noisy and knocky, and when hot no noise at all and it runs like a charm.

KR

Thomas

 

Hi there,

Did exact the same on my 1300 engine. Full and comprehensive rebuild of the entire engine. 1) Complete teardown/disassembly, 2) Complete reassembly

Pistons: JE Forged apple bite pistons
Rods: Carillo
Valve springs: Spruell suplied and new (upgraded from the standard kit)
Mains and Rods bearings: King bearings
Chains (Bottom and distrib.): IWIS race

All this supplied by Spruell (Very well composed kit of high quality, IMO)

When cold and start the engine is a bit noisy and knocky, and when hot no noise at all and it runs like a charm.

KR

Thomas

Hi Thomas,

thanks for your reply. Besides displacemant, your engine and mine seem very similar. It's comforting me that this is not an issue and due to engine modifications. I was wondering what oil grade you're running. I'm with castrol classic 20w50. As oil pressure is at max when cold, I was wondering if this may cause this noise. I'll try some lower cold ool grade and let you know if this changes anything.

As i was also fearing I'm getting engine knock, I tried to reduce (even cancel) ignition advance, but it has no impact on the noise. BTW, because of higher compression and much flatter piston head, and therefore different combustion chamber shape, no standard ignition curve really fitted the engine. After months of trial and errors, I ended up with a curve max 33 advance that pulls quite decently from 2500rpm. If you're interrested, I can provide you with the curve.

Finally, I see a swiss flag with your profile picture. despite an Irish flag next to mine (due to VPN), I'm in switzerland.

Ludo

 

I suspect it`s piston slap. Likely due to too much piston to liner clearance.

 

Hi Richard,

thank you for your return.

What’s the worst case scenario if this is a clearance issue?

it’s also what I suspected. Pistons and liners are new and came as a kit from Alfaholics. They have quite good products so I found it unlikely it’s the cause. Also, shouldn’t I get some piston wear if it was a clearance issue? Oil analysis returned 3ppm of aluminum.

Ludo

 

I agree w Richard on this. The "tell" for me was forged pistons. In Triumph's (having owned a couple dozen over the years), engines rebuilt using forged pistons are built using looser tolerances when using forged pistons as they expand slightly more then cast. At least thats my understanding over the last twenty something years....

 

I agree, at the skirt clearance shouldn`t be more than .003" Clearances above the piston pin will be wider as you get to the Ring Area.

 

Yep. Relax and drive on ...

Pete

 

Thanks all for your inputs! even if this noise comes from the piston / liner clearance, it seems it’s not having any other consequences, so I’ll keep Pete’s advice and relax

 

Thankfully your oil analysis came back good

Pete

 

NO IDEA WHY I HAD TO RE REGISTER WITH A NEW USERNAME!
I'm sure I've told the story before on this forum. A couple of years ago a client of mine ordered a full rebuild kit inc new Nural/ FM brand liners and pistons. During measurement, which I'm sure 99% of diy assemblers wont do.....I found 2 liners were out of spec by an unacceptable amount. One measured 84.03 and one 84.06mm! That would have placed piston to bore clearance at 0.10mm and 0.13mm. The other 2 were between 0.07 and 0.08mm. They were returned and replaced. My advice with spruell apple bite forged piston sets is check everything. The 3x sets I used in 1750 engines were again not fit for use. Piston diameters varied and supplied 81mm oversize liners were tapered as much as 0.05mm top to bottom. I suggest you measure everything. Even bearing shell thickness. On the std type king bearing shells it's all over the place. When boring liners I do them here locally now. I made a 1/2" plate based on a headgasket without water jacket holes. I clamp the liners in the block and get them bored and honed normally. I see a max of 0.01mm out of round & or taper, which is perfectly fine.
Btw the Spruell apple bites i used were high expansion 2018 forgings. They begin to knock when cold at around 0.16mm in the 81mm bore. Ask me how I know! I've coated skirts on these to bring them back to 0.10mm and 12,000km later on the street, no knock. CHECK ALL CLEARANCES BEFORE ASSEMBLY

 

NO IDEA WHY I HAD TO RE REGISTER WITH A NEW USERNAME!
I'm sure I've told the story before on this forum. A couple of years ago a client of mine ordered a full rebuild kit inc new Nural/ FM brand liners and pistons. During measurement, which I'm sure 99% of diy assemblers wont do.....I found 2 liners were out of spec by an unacceptable amount. One measured 84.03 and one 84.06mm! That would have placed piston to bore clearance at 0.10mm and 0.13mm. The other 2 were between 0.07 and 0.08mm. They were returned and replaced. My advice with spruell apple bite forged piston sets is check everything. The 3x sets I used in 1750 engines were again not fit for use. Piston diameters varied and supplied 81mm oversize liners were tapered as much as 0.05mm top to bottom. I suggest you measure everything. Even bearing shell thickness. On the std type king bearing shells it's all over the place. When boring liners I do them here locally now. I made a 1/2" plate based on a headgasket without water jacket holes. I clamp the liners in the block and get them bored and honed normally. I see a max of 0.01mm out of round & or taper, which is perfectly fine.
Btw the Spruell apple bites i used were high expansion 2018 forgings. They begin to knock when cold at around 0.16mm in the 81mm bore. Ask me how I know! I've coated skirts on these to bring them back to 0.10mm and 12,000km later on the street, no knock. CHECK ALL CLEARANCES BEFORE ASSEMBLY

That’s true I haven’t checked pistons and liners clearances…

 

Interesting!

 

to close the topic, I think we can summarize as follows: we all agree that knocking noise cold that disappears when engine‘s warm is caused by pistons and liner clearance. It‘s also seem not very worrying and don’t need an engine tear down. I also contacted Alfaholics about this, and they came to the same conclusion:” If it goes away hot then I would not be concerned, I have never seen piston slap cause any type of engine damage.”

ludo

 

Piston slap will increase your oil consumption because the piston has excessive rock in the bore and thus the rings will not sit flat against the cylinder. This condition can be barely noticable or in the extreme....very noticable.
Also excessive slap will polish the bore in the plane of the skirts and thus erode the cross hatch pattern.
Slapping also collapses piston skirts and thus progressively gets worse.
In a race engine that's torn down every season, it's not a big issue. For a long term road engine.... not good. I have seen cold piston slapping engines run for 1000's of miles without consequence though, so send it, and deal with it if it gets to be a problem.