What kind of camshafts are these?

[collins_dan]

I just tested my timing, and at idle it is advanced 15 degrees. This seemed like a lot to me, so I sent an email to the PO. He said that the cams need to be that advanced and look for the handwritten note in the owners manual. Well, I found it, but don't know what it means.

L2
In open 42 close 82
Ex open 82 close 42
Dur In 304 Ex 304
Lift In 35 Ex 35
Valve set In .006 Ex .008

With the help of fellow elan.net member Don Butler, I've been trying figure out why the car runs hot at idle and why its stumbles on the highway. The stumbling looks to be due to gas frothing as the strombergs did not have thackery washers, a number of gaskets were missing and the o-rings were completely crushed. The running hot could be due to this very advanced timing. The funny thing is that the car idled and ran very smoothly, and is very fast.

I appreciate anything anyone can tell me about these cams and how I need to set the engine up to run properly with them.

Thanks, Dan

[lotocone]

Dan,

I can't tell you much except that there is a Cosworth L2 cam. Try doing a search. There is previous info listed for Cosworth L2.

Bob

[collins_dan]

I actually already tried that and from the descriptions, they sound more like L1's given the duration of 305. But, whether they are L1's or L2's, I'm not knowledgeable enough to understand what the implications are of the differences. Thanks. Dan

[leifanten]

For what it is worth, I had a similar problem with my stromberg twincam. I had to run ignition very advanced and it overheated and ran poorly on the freeway.

It turned out that the common denominator was too lean mixture (in my case due to a mysterious little plastic washer put in around the needle by the rebuilder - see my thread on this)

Lean mixture will require a more advanced ignition setting and will make the car overheat at speed. I would check my mixture before playing with the cams.

[collins_dan]

Thanks. We came to a similar conclusion and are now trying to source B1BT needles. I currently have B1Y needles, which are too lean. I may try to recess them about 1/32nds to see if that helps. Any suggestions of where to find B1BT's?

Dan

[oldelanman]

Dan,
You can get all the Stromberg needles from Burlen in the UK but they don't list B1BT -are you sure you have the number right? They do list a B1DT needle.
http://www.sucarb.co.uk/ProductSearchResults.aspx?SearchTerm=needle

Scroll through to page 18

Regards,

[collins_dan]

Thanks Roger, you could be right, it could be B1DT.

Dan

[leifanten]

I run B1Y needles, and keep a set of B1G in back-up. The B1G is slightly richer. However, the mounting height of the needle and the jet plays a huge difference in mixture. So I would go ahead and check that before changing out the needles. Also I set my jets 2mm below the deck and the needles with the shoulders flush with the air valve piston and it runs great! When the needle was 1.5mm recessed into the air valve piston it ran too rich.

[collins_dan]

Thanks. I'll try it. How do I measure how far in I have mounted them? Someone suggested trying 1/32nds to start with.

Dan

[oldelanman]

Hi Dan,
Just found this needle data in the archive and it does list the B1BT needle you are looking for but not the B1DT which Burlen list ! Might be worth getting in touch with Burlen to clarify what is available.

http://www.lotuselan.net/uploads/stromberg_needle.xls

Apologies for hijacking this thread.

Regards,

[69S4]

I run B1Y needles, and keep a set of B1G in back-up. The B1G is slightly richer. However, the mounting height of the needle and the jet plays a huge difference in mixture. So I would go ahead and check that before changing out the needles. Also I set my jets 2mm below the deck and the needles with the shoulders flush with the air valve piston and it runs great! When the needle was 1.5mm recessed into the air valve piston it ran too rich.

I'm in the middle of rebuilding my Strombergs at the moment so I've been trying to find as much info as I can on stuff like this. Leif's jets are recessed 2mm but mine (original jets) were down just under 3mm. When this subject came up before Oldelanman posted some info that said 2.5mm for single carbs and 2.3mm for twin carb setups. I'm not quite sure why these figures should be different so a couple of days ago I asked Burlen what figure they used when they're rebuilding carbs. They're getting back to me ...

On the face of it I would have thought that differences here would have had a substantial effect on the flow characteristics but then again the older Strombergs held the needle still and moved the jet up and down, so maybe it's not quite so important. Either way, I've gone for a figure in the middle and set the jets at 2.5mm. Moving them wasn't as difficult as I thought it would be. A bit of heat in the casting plus my version of tool 83 92 789 ( the factory tool for hammering them in and out) and it was done in a couple of minutes. My version of the factory tool was a suitably sized 1/4" deep socket.

Needle selection looks like a real minefield. I had B1Ys in my carbs and have replaced them with the same. All the listings I can find say B1Y for UK spec Elans except Miles Wilkins who says B1Y fixed (ie not biased) or 2BAR floating. The 2BAR is substantially richer from half throttle onwards. I'm not sure what a not biased B1Y is, or even if it exists. B1Y is listed in my Stromberg book as a biased needle - that's what the B indicates. Talking of needle bias, the old needles that came out were biased towards the butterfly, the new ones, the other way (as the books say it should be). You can't put the needle in the wrong way round. The old needle had left a wear groove in the jet so it's just as well to be replacing both of them together.

There doesn't seem to be as deep a pool of knowledge about these carbs as there is about the Webers and I suspect it's only going to get worse as time progresses. Not being able to find fundamental info like jet heights and needle selection (never mind stuff like temperature compensator settings) means that the carbs are only ever going to be "near enough". Much of the info we have here is spread out over multiple posts, many of which are nothing to do with carburation. Anyone want to become the Keith Franck of Strombergs?

[rgh0]

The specification is an L2 spec, the 300 plus a little duration of the L1 cam but the standard lift. I have never liked the L2 cam as the duration is to long for the lift with a resultant good top end power but a real torque hole in the mid range. It was really a cheap hot up option cam that was easy to do as was a bolt in change and did not require head dismantling for changes to valves and springs but a real performance compromise is made because of that.

The overheating and high idle advance is almost certainly in part at least due to a excessively lean mixture and I would work on that first before working other potential causes. The cam itself is very unlikely to be a contributor if timed right.

cheers
Rohan

[collins_dan]

Thanks for the advice all. This is all very helpful. When I first got the car, it ran incredibly rich at idle, so rich that it really couldn't be driven around town in traffic as it would just bog down. I changed plugs, which helped a bit, then rebuilt the engine as it was going through oil like crazy and had low compression. Now the car runs great, not too rich anymore, but the plugs don't look like they are too lean either. Nice dry light brown. It still gets hot in traffic and had some issues breaking up on highway as mentioned earlier, which I hope has now been addressed. I'm coming to realize that the PPO did a lot of these short cut methods to improve performance (see my post about how my rear suspension adjusts).

So, what must have happened, is he dropped in the new camshafts, but kept the original needles. In order to take full advantage of the camshafts, the timing was advanced to 15 and the mixture was enriched, creating all the challenges driving around town, but was probably great on the track, which was how the PPO used it. So I will look for some new needles that will enrich the mixture at the top, and adjust the advance to 12 as a starting point. It is 8 right now and doesn't feel as quick. Don has used the B1BT needles with success to this end. If I can't find those, I'll try to find something similar that fits my pistons. Mine are the kind that are only adjustable from the set screw, so the base is narrower than the fully adjustable ones. I'm reluctant to recess the current B1G needles as I think that will get me back to where I started, too rich at idle. This spreadsheet has been great for determining what to try.

If my approach is flawed, please let me know. I'm not an engineer by training, as many of you are, so don't fully understand the basic principles at work here. I have not been playing with cars my whole life, this is a fairly new thing for me, so I am still learning, but greatly enjoying. This group has been incredibly helpful. I don't think I could be doing as much on my own as I am were it not for the support of the group. Please let me know if my approach is the right one, as it sounds like my next step will be to contact Burlen to see what's available.

Thanks. Dan

[msd1107]

Re: Stromberg needles.

It has been almost 40 years now, so memories are fuzzy. But B1G, B1Y, and B2G ring a bell. One is stock, the other I switched to (G to Y or Y to G).

I was looking for a leaner mixture at low throttle openings, with stock mixture at WOT. I had adjustable needles, so moved the needles down until I was satisfied. When done, the car was extremely cold blooded at startup (always needed choke) and until thoroughly warmed up, but otherwise fine and with much improved gas mileage.

After the 36,000 mile maintenance (when I had the rev limiter adjusted up to 7,000 from the 6,200 it was stuck at) I took the car out to a newly opened stretch of freeway with no traffic and got to just under 7,000 rpm on a 3.55 differential and 165-13 tires. So the WOT top end mixture was good.

Around town, gas mileage was around 35 us mpg. On several trips, we got over 42 mpg with a best of 45.2 (LA to SF on just over half a tank). The car was a FHC, 165-13 tires running at 28/33 psi. Two people, luggage and picnic basket.

David
1968 36/7988 (Now, was a '69 36/9xxx back then)

[collins_dan]

Due to a slight coolant leak at the back of the engine, the head will be coming off this winter for a new gasket. Other issues to be addressed at the same time; number 3 cam follower appears to have been nicked by a cam lobe and one of the intake valves is not shimmed correctly. (Don't ask, used a twin cam expert for engine rebuild 5 years ago that wasn't so expert.) Also thinking about switching L2 cams for Sprint spec cams. I use the car mostly for the road. I think it runs great with the L2s, but that's all I know. Never driven another elan. Opinions here seem to be that L2s are not good road cams and that the Sprint cams are, plus sounds like it would be a bolt in change. Thoughts? Thanks, Dan