A bit rough at high revs

[AJT]

Hi All,

Are all 1098 engines a bit rough at high revs? mine had a new crank, shells, timing chain 2000 miles ago, oil pressure is 35psi at hot idle, 40-60psi when in gear (according to revs).

The noise is a quieter version of the racket it made before the crank was changed. Only noticeable under load at higher revs i.e 2nd gear up a steep hill or pulling away sharpish. I'm guessing normal: forget it & just drive?!

Thanks

[bmcecosse]

They are not the smoothest of engines - although mine revs very willingly! Your oil pressure is 'ok' - but not fantastic. Did it get a new oil pump with the crank? Sure it's not pinking going on detonation ?

[AJT]

I'll check the timing to ensure it's not too advanced.

The specialist who did the crank didn't think changing the pump was worth it as he believes they don't really wear.

Slightly worried that you think the pressure isn't great: I thought the cut out was 60psi when hot so all good & fine?

[cadetchris]

i would of had the oil pump changed, as they do wear and when they give up the ghost, it means the engine has to come out, clutch off as well as flywheel, abit of a faff, hence its always a good idea to change them when the engine is in bits

[bmcecosse]

Some 'specialist' if he thought the pumps don't wear!! But don't panic - it's ok - just not fantastic. I don't think your roughness will be crank related.

[swithland]

Im still getting a grinding / rough noise on my 1098 engine. Its now done 1,000 miles since the rebuild and mine had everything replaced or reconditioned at the time. I did play with the timing and discovered that if I advance the timing, I get a lot more power up the hills, but a lot more grinding / roughness at higher revs. I found retarding the timing made the engine much smoother ( although it still grinds at high revs...but not quite as much ) but not as powerful.

I have tried to strike a happy medium on the timing between smoothness and power but it is a bit irritating when the engine grinds when at higher revs, especially when at speed.

I was reading another post earlier from a chap that had a noisy water pump....im wondering if part of my problem is due to the water pump rattling at high revs. It does sound like a vibration going on inside the top end of the engine when you rev the engine up by hand under the bonnet.

My oil pressure starts off at 80psi, and after the engine warms up drops to about 40psi. Then after its properly hot, it drops to about 20psi. There is no vibration or noise when under load...only when at high revs.

Its a bit niggling.....im even wondering if I have a broken ring. I did have the sump off a while back because of a sump gasket leak ( still not cured )...and shone a torch light up to the undeside of the cylinders. One did look lightly scored. I wonder if a broken ring might cause the vibration / grinding noise ??

Will get the video camera out tomorrow and youtube it for all to hear...

Cheers, Charles.

[bmcecosse]

I hope the oil pressure you report is when idling...... it's the hot running pressure that MATTERS! And no - a ring wouldn't make a 'grinding' noise - which sounds a bit worrying.....

[MarkyB]

When you say high revs, how high?
If you don't have a rev counter, what speeds are you doing in each gear?

[swithland]

When you say high revs, how high?
If you don't have a rev counter, what speeds are you doing in each gear?

Ive made a youtube video to show the problem...but whilst filming, worked out what the problem was and fixed it at the same time....turns out it was the water pump....

http://www.youtube.com/watch?v=v68GcLUWJic

[MarkyB]

Great video, love the plot and the sound track!

Have a look in your book of words and see if ordinary grease is what should go in the pump though.
I know my dad had a can of water pump grease for the 1930's vehicles he used to run.
Later cars don't even have the option to put a grease nipple in, they are "sealed for life"

[swithland]

Great video, love the plot and the sound track!

Have a look in your book of words and see if ordinary grease is what should go in the pump though.
I know my dad had a can of water pump grease for the 1930's vehicles he used to run.
Later cars don't even have the option to put a grease nipple in, they are "sealed for life"

Interesting you say that later cars dont even have a grease nipple because when I put the engine back together during the restoration, I had a choice of two new pumps knocking around the barn and one of them didnt have a hole for a grease nipple. I decided to go with the one with the hole, thinking at the time that you have to some how fill the hole with grease, not thinking for a second that you need to screw a nipple in !! I now wish I had installed the other one !! I suppose if its the wrong grease, I will soon know about it....

[rayofleamington]

I've never had a 1098 hat didn't growl at high revs with load.
The 948 is a lovely smooth engine by comparison.

[MarkyB]

It looks like water pump grease is still available;
A heavy calcium based moderate duty grease for auto water pumps in older vehicles.
I seem to recall it's something to do with how they react with water, the proper stuff wont emulsify when it come into contact with water like ordinary grease will.
As it's a new pump that shouldn't be an issue for ages so I wouldn't worry about it.

[swithland]

I've never had a 1098 hat didn't growl at high revs with load.
The 948 is a lovely smooth engine by comparison.

i would agree with that. A friend has a 948cc Sprite and the engine revs lovely. The 1098cc engine seems a bit rougher.

[bmcecosse]

But it's much better when fitted with the crankshaft damper that BMC were too miserable to fit to the inline 1098 engines (not sure about Spridget engines - maybe ??) - but did fit to the frontwheel drive engines........and indeed to all the A+ 998 engines, and all 1275 engines. These can't be bought new now - so covet any secondhand ones you can find!

[rayofleamington]

the crankshaft damper that BMC were too miserable to fit to the inline 1098 engines (not sure about Spridget engines - maybe ??)

As fitted to many of the 1275 RWD engines? They are basically a very heavy pulley with some rubber between the pulley and the extra mass.

[bmcecosse]

Pretty sure ALL 1275 engines had them.