60 mph and 4000 rpm

[stefan]

i am newcomer since 2 months ( series 1.5 2+2 4.2 L ) and realizing that my car was made for the us market, what should be done beside choosing a 3.07 diff and 3 SU carbs to make it as European as possible and drive it that way !!
many thanks for the tips and tricks stefan

[daverawle]

i am newcomer since 2 months ( series 1.5 2+2 4.2 L ) and realizing that my car was made for the us market, what should be done beside choosing a 3.07 diff and 3 SU carbs to make it as European as possible and drive it that way !!
many thanks for the tips and tricks stefan

Hi Stefan and welcome, it's nice to hear from a Luxembourg resident; I was 20 years living in Junglinster and Cents - England now.

I don't think you will be turning 4000 rpm at 60 mph even with a US spec diff - either the speedo or the rev-counter or both are incorrect. 3000 rpm at 60 would probably be nearer to what you should get with a 3.54 diff.

I suggest using a GPS in place of the speedo and temporary wire-up an advance timing light (switched to rpm) and fix it to the dash top, then you will know what's happening.

Dave

[Heuer]

Stephan

Welcome to the Forum. You can use this calculator to work out what your rpm/speed should be: http://wahiduddin.net/calc/calc_speed_rpm.htm

As for changes the 3.07 diff was standard in Europe but you may want to consider a 2.88 diff for modern traffic. Really depends on what you intend to use the car for - high speed touring or local driving. e.g. My car has a 2.88 diff and 5 speed gearbox so in 5th 3,000 rpm equates to 100mph.

[Heuer]

Stefan

The twin Stomberg setup was introduced to get the E-Type through tough pollution laws in the US. Unfortunately it had the effect of markedly reducing performance (about 30bhp less than the SU cars). Conversion is a very good upgrade which will improve performance although it will increase fuel consumption a bit. With an ITG filter the induction roar is to die for!

The biggest problem is finding and buying a set of triple SU's and manifold off an E-Type. The carbs from the Jaguar saloons look the same but are not appropriate. Also you will need to ensure you get a set designed for the 4.2 rather than the 3.8. Bear in mind you will also need the correct throttle linkage and coolant hoses (for the manifold). You will also probably need the carbs rebuilt by a specialist rather than a local mechanic. If you have not yet got a set of SU's I can thoroughly recommend David Lonsdale who can supply a fully re-built and polished set with the correct manifold and linkages for about ?1,900 or can restore yours for about ?450. David can be contacted at: Classic Carburettors - (SU carbs sale and restoration) T: 07786 912011 davidnlonsdale@aol.com

As regards your revs/mph issue I think it must be related to a faulty instrument as even the US spec 3.54 diff would give you about 90mph at 4,000rpm. The calculator I pointed you to is very simple to use:

1. Enter your engine speed - 4,000 rpm in your case.
2. Enter you transmission gear ratio - suggest you use 1 (i.e. direct drive) which is fourth gear in an E-Type
3. Enter your diff ratio - probably 3.54 if it is a US car
4. Enter you tyre radius - 13.25" for a 185 tyre, 13" for a 205/70 such as a P4000
5. Click 'calculate' for the speed

You can then try changing the diff ratio to 3.31, 3.07 or 2.88 to see what speed you will get with each in 4th. By keeping the diff ratio constant you can change the transmission ratios (2.68, 1.74 or 1.27) to see what you can expect through the gears. Armed with this information take the car out on the road with a Sat Nav which will give you an accurate speed measure. You should then be able to decide whether it is the rev counter or speedo which is wrong. The speedos are designed to match the diff (list of serial numbers here: http://etypeuk.com/forum/viewtopic.php?t=951 ) so check your car has the correct one; if not it can be recalibrated to match. The S1 and S1.5 rev counters using the camshaft generator are prone to low reading due to weak magnets. Dave Rawle sells an easy to fit electronic board which cures the problem: http://etypeuk.com/forum/viewtopic.php?t=292

[stefan]

hi guys i pick up the conversation we had some weeks ago
my car is in the garage and my mechanic found out that i don t have a 3.54 but a 3.31 differential but more important the rev counter is reading to high !?!? ; with the engine @ 3000 rpm it indicates 4000 rpm and this goes up even more at higher revs. Now i visited the classica in Essen germany which i recommend seriously and i spoke to a guy from the jagshop in London who told me that i could send him the tacho to be calibrated, what about this option ? is this possible knowing only that the ratio is 3.31? or should i go for dave 's electronic board, many thanks for the good help
kind regards stefan

[Heuer]

Stefan

If you have the tach generator mounted on the right rear camshaft cover then Dave Rawle's conversion is your best bet. If you have the later S2 electronic tach it will not work. Which do you have?

[daverawle]

hi guys i pick up the conversation we had some weeks ago
my car is in the garage and my mechanic found out that i don t have a 3.54 but a 3.31 differential but more important the rev counter is reading to high !?!? ; with the engine @ 3000 rpm it indicates 4000 rpm and this goes up even more at higher revs. Now i visited the classica in Essen germany which i recommend seriously and i spoke to a guy from the jagshop in London who told me that i could send him the tacho to be calibrated, what about this option ? is this possible knowing only that the ratio is 3.31? or should i go for dave 's electronic board, many thanks for the good help
kind regards stefan

Hi Stefan,

I note you have a SI 1/2, do you have the ac generator on the inlet camshaft? If you do, and it's reading high, I can only think that the gauge and/or the generator have been replaced at some stage. They were fitted as a matched pair and always read low due to aging. If you have the later (SII) type tacho, where the ignition coil is fed via the gauge then the reading can be x2 due to old electrolytic capacitors in the gauge itself.

Dave

[frogeater]

Hello,
Thank you for this very well documented post (once again!) :D

[stefan]

hi again ,things are progressing rapidly : i have the later electronic tach so i can forget dave's invention ! BUT WHAT NOW ??? at "the gauge.com " i found however something interesting , price is ok , do the uk members have any experience with these products ??
secondly , instead of bringing down my diff from 3.31 to 3.07 my mechanic suggests me to build in an overdrive because it should be less expensive .
what are the pros and contras ??
feel free to comment , regards stefan

[1954Etype]

hi again ,things are progressing rapidly : i have the later electronic tach so i can forget dave's invention ! BUT WHAT NOW ??? at "the gauge.com " i found however something interesting , price is ok , do the uk members have any experience with these products ??
secondly , instead of bringing down my diff from 3.31 to 3.07 my mechanic suggests me to build in an overdrive because it should be less expensive .
what are the pros and contras ??
feel free to comment , regards stefan

Stefan, if you have a long wheelbase car, you can fit an overdrive unit - but it will involve an engine out procedure. If your car is SWB, you can't fit one. Swapping the diff is the most cost effective way to bring the revs down. Also, removing the back axle cage is a lot easier than removing the engine and gearbox.

[stefan]

hello guys
just to inform the people who were so kind to give me advice
.i changed the diff to 3.07 and built in a new rev. counter . this was the best solution keeping the original gearbox.
the ride was never so smooth and quiet. i can only recommend this option
best regards
stefan luxembourg