Lotus Elan

Experience with SAS head?

PostPost by: 7skypilot » Fri Jul 24, 2015 4:50 pm

I'm afraid I'm a little late, but here's my experience with a new QED Twin Cam head.

I ordered a 'large port' variant, and fitted 1.625 & 1.375(?) valves. Paul Exon did the machining - excellent. I run Q420 cams.

The engine is very docile, produces around 155BHP in what is essentially a street car. It is reasonably swift on track ("a lovely car let down only but its driver!") and pretty tractable. The only minor problems I have is when driving at altitude in the (European) Alps when it can be a little reluctant to rev when when exiting very tight hairpins in second (perhaps I should use first!). That's a minor price to pay for the delightful performance of the engine.

Compared with original heads the new castings are just superb, and can easily run cams without bearings. I have a very old BDA head, a BDR head and a BDT head - the difference in the two later castings is stunning - no 'flash' or pinholes and an excellent finish, even before machining.

One suggestion; if you use a Cometic head gasket (I wouldn't use anything else on my engines) be sure the finish on the head mating face is very, very good. Cometic give a 'smoothness' figure which is worth achieving. When installed correctly the gasket is immortal!

Enjoy the engine!
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PostPost by: CBUEB1771 » Fri Jul 24, 2015 4:58 pm

7skypilot wrote:I ordered a 'large port' variant, and fitted 1.625 & 1.375(?) valves. Paul Exon did the machining - excellent. I run Q420 cams.


What is your swept volume? Crossflow stroke?
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PostPost by: 1owner69Elan » Fri Jul 24, 2015 6:34 pm

Good to hear of your positive experience with the QED head.

Bodes well for the modern head from SAS that I ordered.

Interested in your choice of large ports for a road engine, but sounds like all is good. I chose small ports as recommended to me for road, but looks like I have same or similar valve sizes (1.625, 1.40) to you.

Be interested in any other mods in your recipe. Exhaust system, carbs, lighter flywheel, stroking, ...
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PostPost by: 7skypilot » Fri Jul 24, 2015 9:24 pm

I have a standard crank, so standard stroke. I don't have access to my data at the moment, but IIRC the pistons are one oversize. Rods are standard, unlike the BD on the Seven which runs a steel crank, longer steel rods (5.23") and slipper pistons (and produces around 200BHp on 45's). If I was building a new Twink from scratch I'd go the steel route if I had the dosh.

Carbs are 40DCOE with appropriate jetting (again, no access to data). I've a Facet silver top fuel pump with no regulator (I've never found the need for one on the Elan) and electonic ignition.

Exhaust is Matty stainless, modified for better flow on the collector and tucked up so close to the chassis backbone that I've used Zircotec heat shield to protect the chassis. The silencer is also tucked up as close as possible to the body to improve clearance on Continental roads whilst rallying. The silencer rubber bobbin support is modified to put the bobbin in compression. I've used Zircotec to shield both the clutch slave and the clutch fork gaiter from the intense heat of the primaries (headers). This prevents the clutch fluid from boiling on slow ascents on long passes like the Stelvio. If I had my time again I'd use Zircotec to coat the primaries - it really does reduce the heat in the engine bay. But there over here in Aldermaston, Oxfordshire... I'm sure you have alternatives.

How's the cooling? A TT 26R rad/header tanks and Cliveyboy fan works a treat and is 'period'. I'm sure there are excellen alternatives from both Cliveyboy and CoolExperts. Silicone hoses are reliable, especially fitted with Mikalor/Norma stainless clamps. Worked OK on the Stelvio a couple of years ago in an Italian heat-wave!

I'm in the Seven at present, but in excellent company - an immaculate E-type and a lovely Sprint - and we're enjoying low 30's (high 80's) on traffic free, dry and generally well surfaced mountain roads here in the European Alps. Hairpin after lovely hairpin - long may it continue!

I was interested with your comments on US bureaucracy - and glad to hear that it's not only this side of the 'pond' that suffers from over zealous jobsworths!

Half the joy of upgrading/modifying is in the planning... have fun!
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PostPost by: 1owner69Elan » Fri Jul 24, 2015 10:50 pm

Thanks for the info on your configuration.

It triggered a question about the alternative concentric slave cylinder inside the bell housing thus avoiding the hot location of the normal setup. Wondering if members have experience with the alternative.

I'm jealous of you tooling around the European alps in your car and with good company.

After I picked up my Elan at the factory in 1969 the car and I traveled throughout Europe. I scared myself a couple of times in the alps.

For the hordes of young students and hippies traveling that summer, mostly hitch-hiking, I was truly privileged. No one in the youth hostels believed I was really driving a Lotus. Not until I showed it to them and actually started it up did they believe it was mine. Then everyone wanted to be my riding companion.
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PostPost by: CBUEB1771 » Sat Jul 25, 2015 4:05 am

1owner69Elan wrote:The alloy used on the SAS heads by all accounts is very hard and is not vulnerable to wear problems


I was going to post some details regarding the LM25 alloy earlier in the week but got tied up with business travel. LM25 is very common in blocks and cylinder heads now. Rohan is correct in that LM25 is chemically similar to the earlier LM8 except that LM25 has lower silicon and and high magnesium content. The SAS website says that their heads are LM25-TF, TF indicating fully heat treated and this is where the hardness comes from. TF heat treatment raises the hardness to about 100 on the Brinell scale compared to about 60 in the as-cast state. Fatigue resistance is lessened, not surprisingly, with the increase in hardness.
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PostPost by: holywood3645 » Tue Jul 28, 2015 9:15 pm

I also live in S California. I based the engine build in my S4 to the QED 420S SS spec, I kept the orginal and built a completey new motor using; decked 711M block 1600 crank and rods ~1700cc, 83.5 bore. Standard Sprint valve size and ports opened and cleaned to match to the twin 40dco151 that are jetted to the QED spec. , I did not skim the head and adjusted CR with the Cosmic (sp?) head gasket. The pistons sit level witht he block at TDC. Then Lucas Constant Energy ignition.

The car runs v strong with good torque about 1700 rpm using 91 plus pump gas. According to QED 145 to 150 bhp,

I think I have a little more cc, but a little less CR than the UK QED 420 SS spec engine. It feels about perfect for a road going elan in California. I'm now looking into upgrading the suspension to complement the additional performance.

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