1275 crank problem.

Side valve, 803, 948, 1098., 1275 and Vizard mods

1275 crank problem.

Postby Gman 63 » Tue Jan 01, 2019 11:22 am

Rebuilt my engine a little while ago. After a few miles it started to develope a knock from the bottom end while on a run. Had the car recovered. Stripped it down and the big end shell on number 3 had cooked itself. Me and the engine machine shop put it down to somthing getting into the shell. Had my crank reground, rods circled back out. All new acl mains, big ends and rod stubs. Before i put it all back together I ensured the block was super clean, all the oil gullys pressure cleaned, made sure everything was as it should be and reassembled it. Got it started, ran for maybe 10 minutes while i set the timing and got it running right. Took it for a drive and noticed instantly that it still had a bottom end knock....

Oil pressure seems to be high, this could be down to my cheep gauge but i felt it needed mentioning.

My guess is that the shells are not getting oil?

New oil pump on it and oil gullys are clear.

Any ideas?

Thanks in advance.

Gman.
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby MM » Tue Jan 01, 2019 2:40 pm

Did you prime the oil pump, and establish that it had good oil pressure (60 psi or so, say) when spinning it over on the starter (with the ignition switched off) prior to running it?
Maurice, Kent.
1970 Trafalgar Blue Traveller

http://retrorides.proboards.com/index.c ... read=37056
User avatar
MM
.
 
Posts: 3705
Joined: Tue Jan 25, 2011 11:15 pm


Re: 1275 crank problem.

Postby Panky » Tue Jan 01, 2019 2:43 pm

Did you blow the oil ways in the crank through as well?
Could it be something hitting the oil pick up pipe
Image
User avatar
Panky
.
 
Posts: 1146
Joined: Sun Mar 22, 2015 6:00 pm
Location: Cheshire

United Kingdom (uk) UK England (.g)

Re: 1275 crank problem.

Postby Gman 63 » Tue Jan 01, 2019 3:18 pm

Yes to both. All oil ways on block and crank confirmed. Pump primed and oil pressure confirmed before start up.
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby Panky » Tue Jan 01, 2019 3:30 pm

Crank pulley bent or splitting maybe. Is it definitely bottom end and not a rocker hitting the rocker cover.
Image
User avatar
Panky
.
 
Posts: 1146
Joined: Sun Mar 22, 2015 6:00 pm
Location: Cheshire

United Kingdom (uk) UK England (.g)

Re: 1275 crank problem.

Postby Gman 63 » Tue Jan 01, 2019 4:59 pm

Crank pully looked good when fitted. Im sure its the bottom end. Its that unmistakable shell knock at about 2.5k rpm
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby MM » Wed Jan 02, 2019 11:27 am

Very strange. :? I presume the crank was checked for straightness while being reground? And what bearings are you using? They do vary in quality, and if too soft would tend to wear quickly.

Maybe the block needs to be line-bored to ensure all main bearing housings are aligned...
Maurice, Kent.
1970 Trafalgar Blue Traveller

http://retrorides.proboards.com/index.c ... read=37056
User avatar
MM
.
 
Posts: 3705
Joined: Tue Jan 25, 2011 11:15 pm


Re: 1275 crank problem.

Postby Gman 63 » Wed Jan 02, 2019 12:55 pm

Yea, crank was ballanced so all is good there. All acl bearings and studs. I folked out for the expensive ones after the first time the crank went.
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby Panky » Wed Jan 02, 2019 12:58 pm

Just a thought, when you fitted the oil pump was the gasket correctly positioned - possible the outlet port was partially blocked.
Image
User avatar
Panky
.
 
Posts: 1146
Joined: Sun Mar 22, 2015 6:00 pm
Location: Cheshire

United Kingdom (uk) UK England (.g)

Re: 1275 crank problem.

Postby Gman 63 » Wed Jan 02, 2019 1:31 pm

Yea i was concious of that after it went the first time. Ensured the gasket lined up spot on. To be honest i am leaning towards it being an oil pump/gasket issue as im just not sure what else it could be.
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby MM » Wed Jan 02, 2019 10:29 pm

Out of interest, which variant of 1275 is it - Marina/Ital or MG Midget/A-H Sprite, and is an A-series or A+ with the ribbed block?

Some early Marina 1275s were known for crank rumble issues; I gather the solution was for BL to fit a large crank damper pulley.
Maurice, Kent.
1970 Trafalgar Blue Traveller

http://retrorides.proboards.com/index.c ... read=37056
User avatar
MM
.
 
Posts: 3705
Joined: Tue Jan 25, 2011 11:15 pm


Re: 1275 crank problem.

Postby Gman 63 » Thu Jan 03, 2019 11:02 pm

Its the a+ block.
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby MM » Fri Jan 04, 2019 10:49 pm

And which crank pulley are you using - a Minor one, or the correct one for the 1275 A+?
Maurice, Kent.
1970 Trafalgar Blue Traveller

http://retrorides.proboards.com/index.c ... read=37056
User avatar
MM
.
 
Posts: 3705
Joined: Tue Jan 25, 2011 11:15 pm


Re: 1275 crank problem.

Postby Gman 63 » Fri Jan 04, 2019 11:45 pm

Ill be honest im jot 100% on the difference. The 1275 came from a moggi and i just pulled it out and rebuilt it. Do have a picture of the differences between the two pullys?
Gman 63
.
 
Posts: 38
Joined: Wed Mar 08, 2017 5:24 pm
Location: Surrey

Great Britain (GB) UK Wales (.l)

Re: 1275 crank problem.

Postby woodywoodchipper » Sat Jan 05, 2019 7:00 pm

images.jpg


its called an harmonic damper pulley common to A+ 80's minis and metro + others
Image

When its done its done (for now)
Derv Turbo Power (Joosed)
User avatar
woodywoodchipper
.
 
Posts: 3796
Joined: Sun Nov 07, 2010 5:11 pm
Location: up to my neck in dudu
Awards: 7
Contributions 2011 (1) Contributions 2012 (1) Contributions 2013 (1) Contributions 2015 (1) Contributions 2016 (1)
Contributions 2017 (1) Contributions 2018 (1)

United Kingdom (uk) UK Lancashire (lk)

Next

Return to Engine



Who is online

Users browsing this forum: No registered users and 0 guests