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MG MGA - 1500 Rebuild max effort

Well sports fans, I've finally found metal on the magnetic oil drain plug.
I've had the car since new, I've rebuilt it twice in 80,000 miles, it's .030 over bored, crank is .020 all through. It was balanced, crank polished and nitrided, dished Hepolites, stock cam for street because that is what I had available. The head was ported and falves relieves per the Siebring Sprites in the early '60s, with a modified 3 main exhaust manifold and stock SUs with B needles. The head is cracked at the usual 3-4 exhaust seat area.
After finding where the metal (enough fine granular iron bits to coat the magnetic pin) I would like to replace the crank and rods and do a top notch rebuild.
This will be a street motor, not to rev over 5500 although I do have to go to sustainied 4500 on the freeway driving to work. It will be balanced and "blueprinted" again by Fortech in Auburn, CA. (Seven Enterprises, specializing in Minis, Group 5 champion engines) Where do I find a new crank? I've looked at Carillo and Pauter rods, is there an alternative? What cam is recommended for a later power peak for 4000 Rpm hilly country? Fortech will build a fine MGB head (the block is pocketed for a high lift cam of years ago).
The car is very origonal, 1800V is not an option.
I would really appreciate all of your recommendations on the best modern 1500 rebuild, including research links. Thank you!
Russ



Russ Carnes

Russ,
Check your cam & lifters. Newer oils don't have enough high pressure additives for flat solid cams & lifters. This is further compromised by questionable after market lifter metalurgy. We need oils having an "SG" rating. The only one I've found so far is Mobil 1 20w 50 V-twin Motorcycle oil. I think Moss is selling new cranks & uprated lifters. I'd consider dropping in an early MGB 3.9 pumpkin to lower the freeway revs a bit.
Doug
D Sjostrom

I understand Valvoline racing oil is ok also
gary starr

Thanks guys, the oil technology is new info for me, it will be an important issue after the rebuild. That would be a great new link to share that information.
Moss does offer a new Crankshaft made to their specifications in India. Does anyone have input about this?
Uprated cam and lifters are on the list, if I have to replace the cam and lifters I may as well finish the job with a complete rebuild.
When I rebuilt it the last time I had to do it in a hurry to move the car from a remote location. The #4 bearing wear in indicated that rod was bent so I replaced it with another #4 without balancing it. The rest of the rods have wandered off over the years. That knowlede has been in my mind every time I drive the car (rarely) for years, I can feel it, imaginary or not, it's time to fix it. I'm no spring chicken, I want to enjoy my A while I can still drive it, maintain it, and buy gas for it.
Does anyone have input on replacing the front crank pulley with a damper pully?
Russ
Russ Carnes

Russ,
Get the smaller early damper with the front cover which has a real oil seal. Keep the crank bolt however. I had to do a crank-start at the Stowe event in the middle of a quagmire when my starter died.
Here's the website for the best oil writeup I've seen so far
http://www.lnengineering.com/oil.html
D Sjostrom

I am still puzzled by these comments on older cars having flat valve lifters.
Are there modern cars with curved lifter surfaces? How would you set the valve clearance if they are not hydraulic lifters? I work on both old and new cars and they all have flat lifters.
The comments in many articles about the lack of various additives making the modern oils unsuitable for older engine designs seems to relate to valve gear weight.
Most modern engines have four valves per cylinder and no pushrods. This large reduction in valve gear weight is the likely reason why modern oils no longer need some additives. Many modern engines only have one light spring per valve.
In contrast the mga twin cam, even without pushrods, has double springs for each valve with a spring pressure of 210 lbs.

Mick
Mick Anderson

Mick,

As it was explained to me, the zinc and phosphate additives created a protective layer between the cam and the tappets, and created a bit of drag which rotated the tappet to distribute the wear. Modern engines apparently have more surface area on both the cam and lifters, reducing the need for the additives which have been removed from modern oils to protect the catalytic converters. Crane Cams makes a break-in additive which can be added to modern oils for regular use in our "antiques," and Castrol is marketing "Black Label Line" for classic cars.

Ken
k v morton

I'm wondering if it might be because roller tappets are becoming more prevalent in modern cars?
Del Rawlins

This thread was discussed between 06/10/2007 and 10/10/2007

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