Valve spring choice

[Hsquad12]

I am replacing the cracked head on my 91 e30 with a 94head of an e36 and wanted to ask if I should use the dual valve springs for the e30 or the single spring set up from the e36?
Both have the 7mm valves and I'd like to go for the most reliable set up, hence I am leaning towards the original dual springs.
Does anyone have a compelling reason to go one way or another aside from creating a high revving hand grenade?


Oh, and I managed to pull the valves using a G-clamp and a wrench for removing oxygen sensors plus a telescoping magnet on and old antenna. Worked a charm and far quicker than other methods I've used in the past. Happy days

[Darky]

Hi

The original e30 valve springs are the best oem BMW set up for the m42, however if you use them then are stuck with the 7 mm valve stem due to the retainer. Late m42 came with behive spring and 6 mm stem which is a lot better.

I've even seen a m52 with oem m42 dual springs but he had to get the retainer made for the 6 mm valve stem though.

Hope this helps Rohan

[Hsquad12]

Thanks Rohan.
I'm not sure I understand what your saying- dual spring or single beehive?
From what I've read online Bmw reduced weight of the valvegear and also their fixed costs when the replaced the dual spring set up with a single spring. This cost saving helped the engine rev higher, reduce weight and profit margin. A fine solution for b,w but is this the best one for an owner?
 The new head I bought do $100 is it the shop and I only had it in my possession for about 15minutes between the time I bought it and dropped it offer for a pressure test, guides, valve seats etc....
I was going to drop my dual springs and valves to the machine shop this week and ask the, to use the best of the 7mm valves and whichever springs I decide on between now and then......
Thoughts?

[Darky]

Hi
Yes beehive is the single spring.
You are right BMW went from dual to single to save money. Also made them weigh less, however the dual setup has better tension. So if you are going with more aggressive cams that would be the way to go.

Also the single has one advantage of being able to allow greater valve opening but from memory that only came into affect at over 12.5 mm. Ie massive

Somebody did a comparison of a lot of the BMW oem valve springs. M42 e30 won. There was 4 compared.
E30 m42, e36 m50/m42, can't remember the others. It was on a different forum.

You sure the 94 head has 7 mm stems that was around the time they went to 6 mm.
If I was you I'd try to get 6 mm valves in. Plus polishing and porting your there may as well.

Cheers Rohan

[Hsquad12]

Thanks Rohan.
The Bentley manual shows that from 93 onward the M42 was fitter with 6mm valves so unless i source new top retainers for the smaller valve guides i think i have to go with the single beehive spring set up on the newer head.
the other option would be to fit new valve guides for the 7mm valves but unless the existing guides are worn that seems like a lot of work for nothing
what a bummer 

will cross my fingers that my new head is a 92 and and will check on the retainer options during the week should i need plan -B

[Hsquad12]

Does anyone know of an off the shelf upper valve plate that can be used with a 6mm valve stem and the dual springs from an e30 m42 for my mongrel build?

[Darky]

Hi

I believe your best bet is a new retainer for the dual spring and 6 mm valve.

Kms racing industries do retainers in titanium or steel. They do Mainly honda bits though.

Cheers