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MG MGA - Valve Springs / Spring Caps Source

I just keep adding the work!

Since the new camshaft is going in, as well as a new clutch and flywheel, and new walve seals, I am contemplating adding single valve springs and alloy caps to lighten things up. I have found myself driving my A increasingly harder as the newness of a full restoration wears away. I am having much more fun as well.

I am having a bit of difficulty locating single springs and the alloy caps themselves specifically noted for a 1500. I know the heads from other B-series engines will fit the A, but I don't want to assume anything else is compatible. I plan to add an MGB head one day, but for now I will use the stock head.

Any suggestions?

Thank you, Tom


I wouldn't use the alu caps as the retainers have been known to pull through over time. Really the weight isn't that big of a deal and the standard springs are ok unless you are worried about valve float at high rpm - over 5500rpm.

In my race engine I am using Moss's heavy duty springs (double) w/OE steel caps, and tubular pushrods from a B. This engine gets rev'd to 6500 every shift and I have had no problems with floating the valves.

In my experience, always looking for more hp, money is best spent on a good cam and a well breathing head, intake and exhaust.

have fun!

It depends on the type of cam, and the tappets. MGA and early MGB tappets are tall and heavy, needing dual springs to rev to 6000+. Later MGB (18V engines) tappets are short and light (with longer pushrods), and can rev to 6000 using single springs.

When I installed a Crane fast street cam into my MGA 1500 (with early "18" head and dual springs) it would go into valve float promptly at 6000 rpm, which was somewhat disheartening just when the new cam wanted to go faster. Heavy duty dual valve springs took care of that problem, and it revs happily to 7000. I couldn't say if a change to alloy spring caps would have done it without HD dual springs (but maybe not).

Then I built a 1600 with the Crane fast street cam, 18 head with HD dual springs, also the lighter 18V style tappets and long pushrods AND alloy spring caps. I have no idea where valve float might come in with this setup, but I can say for certain that it does not happen at 7500 rpm (and it runs out of torque by then anyway).

A couple of the alloy spring caps failed due to poor manufacture (thin edges). I replaced the broken ones temporarily with standard steel spring caps. It still revs freely to at least 7000+ with the standard caps (HD dual springs and light tappets).

I then found a better source for the alloy spring caps, more consistent in manufacture (NC lathe parts), and no more problems with the alloy parts since May 2004 (more than 20,000 additional miles). I bought those from Wishbone Classics, thanks to Kai Raddicki for the heads up on the source. There has been no indication of any pull through of the retainers.

I am pretty sure the Crane fast street cam (with increased valve lift) will reduce the threshold for valve float in the 18V engine with standard single springs, same as it did with the earlier engine with tall tappets and dual springs. I do not know if the alloy spring caps alone would be sufficient to make up the deficit. I would certainly like to hear a user report.

In any case, if you are doing any type of cam upgrade on the 18V engine I would sincerely recommend installing dual valve springs and double row timing chain and sprockets. You would not be happy with a fast cam that goes into valve float at 6000 rpm (even if it wasn't intentional).
Barney Gaylord

I will be using the Crane fast street cam, 18V tappets and pushrods. Stock 1500 and head.

I know the head has been shaved and I will add eybrows per your reccomendation and you excellent e-mail on how to properly measure to cut (thanks). Just being safe.

I have so much fun driving through the mountains, and now that I know the limts of the car I am certain I can easily hit 6000 rpm + from time to time, especialy in those tight twisties.

I think 7000 would be enough, but am debating if I want to build a 7500 rpm capable car that may rarely see those speeds.

With this in mind, a set of heavy duty valve springs may be just what I need, and when I am ready for the new head, go for the springs and caps. However, if the stock 1500/ head combination won't handle it then I can just wait.
Tom Baker

The "18" head has larger valves and better porting, almost identical to the "16" head used on the 1622 engine, a noticeable advantage over the "15" head, especially with a warm cam.
Barney Gaylord

This thread was discussed between 05/06/2007 and 07/06/2007

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