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MG Midget and Sprite Technical - Novel Camshaft Virus (CAMVID-71)

I have been driving the midget and the B as much as possible but with the lockdown, they are sitting more than usual.

I took the Midget out on the highway last night and noted a definite lack of power, especially on hills. Terrible fuel economy also. The last time the car became less than spritely, I rebuilt the engine and found the camshaft and most of the lifters to be badly scuffed. This was about 75,000 miles after the first rebuild (which was at 172,000 miles) and the car has gone another 45,000 miles or so since rebuild N°2. I am suspecting that with less frequent driving that the camshaft has again developed wear with dry start ups. I have been using engine oil blended with extra ZDDP and have used STP with ZDDP and a ZDDP additive. Like last time, the change was fairly sudden, waking up one day to find the car grossly underpowered.

Is short camshaft life something we must live with now? I have owned the Midget since new in 1971 and have always done lots of highway driving. It certainly is a pain to remove the engine just to change the camshaft although I imagine that it could be done by removing the radiator, timing chain and sprocket. I am not sure how the lifter replacement would be managed in situ with the 1275 since there are no tappet chest covers.

Any suggestions for changing the camshaft with the engine in the car would be appreciated as well as avoidance of the Novel Camshaft Virus into the future.
Glenn Mallory

For longevity use a cross drilled billet camshaft where the oil is pumped out of a hole at the base of each lobe.
Alan
Alan Anstead

Yes a cross drilled billet camshaft is best. Not sure what is available over the pond. Another thing to check is the cam followers which have to be ground correctly so they rotate. I went through a set in less than 5000 miles as they were incorrectly ground. Kent cams in the uk supply cam kits including the corretly ground followers.
Bob Beaumont

I will plan to use a Kent camshaft and follower set and appreciate the recommendation. I am assuming that these require a slotted oil pump drive?

In looking at these cams, are there any recommendations as to the degree of tune? Driving is city and sustained highway. Would the mild Road option be best? High torque touring? I am not up for a terribly lumpy idle.
Glenn Mallory

Glenn
If you change the camshaft profile you may need a dizzy with a different curve or your Cr may not suit &c
If you look up A.C.Dodd, on facebook, and PM him, he would probably make a recommendation to suit the state of tune of your engine and your perceived need be it uprated or stock. If the camshaft fitted has suited you over the years then why not continue. A.C.Dodd designs his own camshafts but also has his own stock camshafts made, by Newman Camshafts here in Kent, to ensure the correct tolerances.
I know several people that have used his camshafts as I have fitted them and timed them in. He can probably supply a stock cross drilled billet camshaft to suit your needs.
I have one of his camshafts 'under the bed' , for one of my own cars, but haven't got around to fitting it yet.
Alan
Alan Anstead

Yes the cams have a slotted drive and you will need to change the oilpump if its the old star drive. I have a Kent 246 (I am sure Newmans have n equivalent) which is mild but has more low down torque It has a bit more 'bite' than the standard cam. I use pistons with a 6cc dish which gives a CR, with the fast road head, of 10.5:1. The distributor has a matched curve which was done by Aldon Automotive. I use a pair of 1.5 HS4 carbs. It s a very nice engine which is fine for London driving as well as touring in Europe.
Bob Beaumont

Bob
You are now adding to the cost.
Modified head, bigger carbs, uprated dizzy.

If using an A.C.Dodd 'road torque' cam 9.5 : 1 CR is recommended. I have been involved in two engines where we 'de-tuned' them that is to say reduced CR's by using cometic gaskets. In one case we disposed of the modified head and reverted to stock. Both owners are now happier with the results. Of course had they started from scratch less add-ons wouls have been required and less cost.

I have organised two 'Audiences' with A.C.Dodd for Kent Midget & Sprite Club members at my home. He has had quite an impact with his ethos to tuning and maintaining. His FB is well worth a visit.
He is much better known in Mini circles. The picture is getting dated.
Alan






Alan Anstead

A selection of A.C.Dodd camshafts. It is worthwhile discussing your project first for a recommendation based on your aspirations.
Alan


Alan Anstead

This thread was discussed between 14/08/2020 and 16/08/2020

MG Midget and Sprite Technical index

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