1967 Retrogauge mini tach and TFI/Microsquirt

[lukep6470]

Hi,

After two years of running without the tach hooked up I decided to wire it up today. I have a Microsquirt running a TFI dizzy.

I hooked the tach up to the green wire of the coil (In theory the -ve terminal of the coil) and went for a blat.

The tach seems to be reading incorrectly. Over reading but about 200rpm at idle and wavering all over the place when driving. It always reads too high.

Has anyone run one of these with TFI? Do I need a tach adapter?

[hybrid]

Have you seen the threads on the Megasquirt forums?
They talk about making a circuit using a relay coil to generate the signal needed to drive an old tacho.
http://www.msextra.com/forums/viewtopic ... 8378f127dc

[lukep6470]

Hmm, looks suspiciously like a tach adapter.

Dammit I disconnected the MSD one when I hooked up the TFI.

Oh well time to pull the dash out again!

[boofhead]

Good one. I have not had to try and make an analog gauge work. I like the way the OP in the thread embedded the transistor and resistor inside the relay case. Rather cool.

[lukep6470]

OK so I've had a busy weekend. I now have a 25K resistor in series with the tach and am using the coil from a relay connected between the resistor and the tach going to ground. This appears to be working properly.

The needle on the tach is steady and compared to Tunerstudio the tach is over reading by about 30rpm throughout the rev range (I'll chalk that up to calibration).

[hybrid]

[boofhead]

Good work.

So Dart block project?

[lukep6470]

The brakes look good so the 347/363 is back on the project schedule

[boofhead]

Ok - good to know. Get back to me if you want to catch about possible cam choices.

[lukep6470]

BTW A co-worker in Texas has an evil twin to my 67 coupe. In Red and White as opposed to my blue and white:

Sky Sports

We were joking around that a "Fedora" plate is available in Australia. The start of a company fleet maybe.

[lukep6470]

Ok - good to know. Get back to me if you want to catch about possible cam choices.

An XE274HR has shown up for sale in that other Mustang forum but looking at it I think the lobe at the bottom of the picture doesn't look that great.

So I'm looking at either an XE274HR or a Lunati 20350711, AFAIK either one are good for mid 400HP without a silly idle.

[Shaunp]

363 go XE282, and get it ground on 110 centres

[boofhead]

I really like CompCam camshafts in general and the XE lobes really work well.
I have used many CompCams and many XE lobes (as well as others). The issue for you is that the XE lobe is a fast lobe (faster than the Voodoo) and I do not think your Springs are good enough - the XE/XFI lobes need 150lbs at the seat - 130 is not enough as you will loose valve control around 6000 RPM and power will drop off quickly. I know the documentation from Comp would say 130 is fine but they do that because of the SADI core - they do not want the heavier load on a non billet core. So of the two the Voodoo would be the better choice unless your prepared to do a Spring upgrade. In which case the world would open up. As far as HP goes, the 363 with the Voodoo it should have between 420 and 440 at 6000 RPM. Note: This is an educated guess and it could well be up to 30 HP more if it is efficient engine.

[Shaunp]

Rod's 408 has a 282 Voodoo and its a pussy cat very streetable I reckon that cam would be great in a 363 as well it a big enough engine to take it in its stride. The 282 voodoo is about 580 lift from memory, I go straight to that if you dont want a custom ground XE type cam. A 363 needs 235 at 50, if you have good heads you could 235/235 but really want 600 thou of lift, you could run 1.7 rockers which is what I'm doing on my 347 to get 600

[Shaunp]

Ive got a set of those Trickflow springs here which would be ok for an XE lobe as well, they are about 145 I think and they are really a PAC spring, if Lukes caps are the right size quick to swap them out.