Speedo reads double in Gt4 with 328 engine fitted?

Hi,
I’ve bought a 308 gt4 with a 328 engine and box fitted. The Speedo reads double the actual speed.
Ie. phone gps reads 50mph and Speedo reads 100mph!

Am I right in thinking it’s to do with the speed sensor on the gearbox as they’re listed differently between 308 & 328(Mondial)?

Also the mileometre doesn’t work? Not sure if it’s connected to the Speedo in some way?

Has anyone done this conversation? or come across this problem?

many help would be much appreciated.

justin

 

It absolutely is, the odometer problem.

There's "early" and "late" speedo sensors, first of all, so spend some time in the Part Numbers.
But I have no idea if an early 308 can be somehow modified to accept the 328 sender signal, or vice versa.

maybe a call to PaloAlto Speedometer would shed light??

 

..and Welcome!!

That sounds like SOME example of a GT4!!!

Post up some pics and the VIN info..

It's hard to imagine a salvage yard where they said:
"Hey man!! Get the engine out of that red/tan car, and bring it around to stuff in the Series 2 Sunroof GT4!!"

Hard to imagine but obviously it happened!!

 

Saving you some recon, the speedo sensor creates a square sine wave, that is then translated in an IC chip board (now obsolete) in the Speedo, that makes the needle go around!!!

Wheeee!

And the odometer of course is the cumulative measure of these gearbox rotations.
You can almost see Fred Flintstone feet under the car!!

 

Thinking it thru further, the simplest fix might be an age appropriate 328 Speedometer.

Palo Alto will know,
TRutlands might be able to help too..

 

Thanks BigTex for your reply.
Definitely a lot to think about.
So, the early one sends out a different signal than the later ones. From what I can see the two types are physically different?
So, is there an earlier type which is physically the same as the later type but sends out the early compatible signal? Or is there just the two earlier/later to choose from?

Not sure how who the two people mentioned are?

 

Palo Alto (CA) Speedometer: http://www.paspeedo.com/
TRutlands - Ferrari Parts (FL): https://trutlands.com/

 

Big tex said

 

Thanks for the links. I’ll send them a message.

I haven’t owned the car long. Most of the work was carried out before my ownership. If anyone’s interested I can put photos and the info I know about the car on the forum. Not sure where though?
It’s a work in progress running project.

 

Post them here. You have to subscribe though. $15 is cheap for a whole new level of information

 

Congrats, sounds like a fun car. Is it the white GT4 from a Los Angeles collection?

 

GT4 uses a worm gear assy, shaft etc to turn the speedo sensor. QV and later is a reluctor wheel with magnetic sensor. No interchange possible at the gearbox end.

 

No, it’s not white. My one is red, based in the Uk and is a ex-formula classic race car. Nothing fancy, except the 3.2 qv engine came from Marenello UK as a crate engine a few years back and has still only done 1000 miles!!

 

I remember your car when I still had instagram, was following it along. Very cool machine

 

Do a search on "speedometer" posted by Member "alhbln" -- there will be a lot of information about this issue for you in those threads. Adrian (alhbln) is truly the demonstrated expert on speedometer, odometer, speed sensor issues.

 

alhbin has also reverse engineered the replacement IC boards within the gauge.

Perhaps "knowing the target" he could build your gauge into the later style of signal interface.
Good luck!!

 

That’s great thanks. I really appreciate all your help. I’ll do a speedometer and alhbin search. Hopefully I can get it fixed.

Vonbarran, yes that’s me on Instagram.
I started the page on Instagram to document the cars journey and to make friends with similar cars to mine.
If anyone wants to follow its: ferrari_308_gt4_qv

 

And where are them pics!???


Sent from my iPhone using FerrariChat.com mobile app

 

Ask Adrian if he can make you a simple circuit with a flip flop to halve the pulses. I may also need one when I switch to the single coil MSD programmable ignition.

 

Just add MSD 8920 for the tach signal.

 

which/whose if I may ask

 

Hi, I’m still trying to find out as much history on the car as possible. Any help of results, owners etc. would be much appreciated. What I do know I bought it from Atchill Thorpe who bought it of Ben or Alan Cosby.

 

I may end up going 355 throttle bodies and independent ECU so I can loose the EFi so won’t be going the MSD route.

 

I haven’t chased anything or looked up Adrian will do soon. The joys of having a you a family.
Thanks for the advice, much appreciated. I’ll be on it soon.

 

I mentioned my Instagram post on the car. I’ll try and put a few photos up soon. Don’t expect too much.