MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - midget 1500 power loss on reaching operating temp

Dear All,

as i am reaching the great time of year where i have gathered a pile of spares and am manfully putting them on to my car in prep from a great summers use..fat chance i stay in glasgow, but i am also reviewing things that disapointed me in the previous season on one of those is a lack of power once the car comes up toward normal operating temp, that said it is not as if i have a failure the car will happly run for hundreds of miles and stop and start okay but it lacks the satisfaction and zip of when i first start to drive it at the beginning of a journey can anyone give me guidance on improving or is this something we are all encountering.

regards

Douglas
df mccabe

gie it some welly :)
rachmacb

May guess your valve clearances are to tight... definatly a bad thing.

if your pure stock the spec is .010 -.012 inches

if your modified .012-.015

if you have a roller tip hi lift rockers .015-.018

Prop
Prop

Douglas,
Sounds like it could be weak fuel mixture - I would take the plugs out and check the colour.

And if you are in a fettling mood I suggest that you check / set the tappets. They may have closed up which would reduce the power as the engine warms up

Guy
Guy Weller

Sorry Prop, seems that you type faster than I. Must go and re-tune my fingers!

Guy
Guy Weller

DOH...SORRY, vary SORRY!!!

Scratch those specs...those are for a 1275 engine NOT the 1500

I dont know the specs for a 1500, BUT I still think your valve clearance is to close

Prop...I really need to learn to read and comprehind
Prop

LOL.

Yeah but I screwed up with bad info spec. good call on the week fuel mixture.

as in wild west shootouts...better to be accurate, then fast on the draw.

Prop
Prop

hi thanks for the feed back I changed the carbs last year and got no difference so will probably start with the valve cleances and report back, am i corect in thinking that these should be done with the engine warm?

regards
Doug
df mccabe

No, Doug... adjust them cold.

Cheers,

-:G:-
Gryf Ketcherside

And another blood bath debate begins....LOL

Sorry doug, thats one of those pensoil vs castrol debates...no real solid consensous...

Personally My newest approch is to do them cold, then run the engine up to temp and re-chack and adjust them hot...Im more in the Hot camp therory myself after someone mentioned in the last round of debates you only drive the car cold for a few minutes the rest of the time its hot so you want your valves to be set at the temp your driving...Wack or Fact, I thought it was a good point.

Prop
Prop

Prop,
You are right about the car running at hot most of the time. But the point is how the clearances are specified in the first place.
If the design engineers have calculated a dimension to set at cold, they have allowed in their calculations for the differential expansion of all of the components as it heats up so that the operating clearances end up correct at normal running temperatures. Generally, setting at cold is easier to be consistent rather than hot which really needs one to know how hot, and to maintain the engine at that temperature whilst adjusting all of the valves.

40 years ago I worked a lot with a whole series of Triumph Heralds, and with Minis (which I rallied). Then the valve clearances I used were for cold setting on the Minis, whilst on the Triumph engines I adjusted them hot, with the engine running whilst doing the adjustment. That is quite fun to do with everything jumping around and splashing oil about as you set them. It also plays havoc with the feeler gauges!

Guy
Guy Weller

and burns your skin

Guy you forgot to mention that

HOT OIL HURTS

You had to set the tappets hot and running on the old Vauxhall Viva engines too, luckily just a socket in the bucket rocker arms
bill sdgpm

Trust me Im no expert in this field...I just play one on the internet...LOl

Perhaps the cold vs hot debate is a simplier one...maybe it comes down to the engine and its designers...having worked on my work truck this weekend the manual is spcific that they need adjusting when hot (Toyota 22re)

but I sure can see both sides of the coin

Prop...Now im on the cold team, sorry hot guys, but Im sure Ill rejoin you tomarrow..LOL


PS... Yeah im thinking that sounded a little gay also
Prop

Right, the clearances as specified allow for heat expansion. Adjusting them hot; that is, with everything already expanded; will leave them loose.

I once had to set the valve clearances in a Mazda 626, and the book said to do it hot. Easy, thinks I - just warm it up, pop the cover, and go to it. So once it was all up to temp, I found that you had to remove all kinds of hardware that was bolted to the rocker cover, like steel PCV pipes, air filter brackets, yadda yadda. Just about the time I'd finally dug my way down to the valve train, all the time hoping that things were still hot enough, the Mrs. called from the house and said that supper was ready. That makes the only time in over 26 years that I haven't answered the dinner bell. I apologetically let her know that it was going to be a while...

Anyway, just another fun thing about adjusting valves hot.

-:G:-
Gryf Ketcherside

I have only logged in a couple of times over the last yearand in asked questions i was only expecting to benifit from the knowledge and debate that is clearly contained within the knowledge of the forum but have to say that i find the bantter and debate a real hoot, better than a night in the pub.

without opening the manual doe anyone know the valve clearance hot or cold?

PS I think rather than try the ajustment with the engine running I will try grabing potato chips from boiling oil firsh seems like just as much fun and spares the feeler gauges

regards

Doug
df mccabe

.010" cold for the stock cam. For anything else, follow the cam manufacturer's recommendations.
Tim Michnay

This thread was discussed between 18/04/2010 and 21/04/2010

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.