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Tach reading off on Vintage Speedster - adjustment?

D dougbok

The tach on my Vintage Speedster if off significantly - probably by at least a third. The engine, runs out of steam (fairly screaming) at about 3000 rpm, and appears to be equally off at lower rpm, even at idle. I am the third owner and just bought it and the two previously owners were apparently not too technically oriented so it may have been off since new. I have owned a slew of real 356's and a Spyder replica and a VW powered Puma so I have a feel for aircooled engines.

It is almost like the tach is in a 6 cylinder mode - is this possible? Is there an adjustment? The car has the original green 356 style gauges and was a turn key car. I just installed a Mallory Unilite distributor and Mallory coil but I am pretty sure it was the same before I did that. In any case I don't think that should matter. Maybe I'm wrong.

There was an old post with a similar problem but no real solution was offered so I am hoping someone might have a like experience and a cure.

 

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WOLFGANGWOLFGANG'89 CMC FWB, FL Supporting Member

I have an old hand held Sears dwell meter with tach built into the gauge.  A garage hook quickly hookup their gauges and tell if its off. Since you are familiar with VW air cooled you know 3k rpms could be only 55 MPH or so.  "Out of steam" could be valve adjustment, carb adjustment  or timing. I put a Delta CD ignition in 914 years ago and remember tach issue after install - think it was erratic needle jumping due to higher signal voltage though.  Fix was an inline resistor - can't remember ohms.   Google problem on the Mallory site.

 

Old Chinese replica gauges are troublesome - fix is new guts.

Last edited by WOLFGANG
D dougbok
Originally Posted by ALB:

I know some aftermarket tachs have a switch on the back that you can adjust to the # of cylinders (4, 6, 8) but I've never heard of the 356 replica gauges being that way. According to the tach, what does it idle at? Al

It idles at around 600rpm and I know it is turning over higher than that. The engine pulls just like it should and it will pull right up to highway speeds, just that the tach seems to read too low. Maybe just a crappy gauge. The gas gauge and temp gauge aren't working either. I think I will try to pick up some 914 gauges and see if I can have 356 style faces and chrome bezels installed if I can't fix these.

Thanks for your reply

D dougbok
Originally Posted by WOLFGANG - '13 CMC FWB, FL:

I have an old hand held Sears dwell meter with tach built into the gauge.  A garage hook quickly hookup their gauges and tell if its off. Since you are familiar with VW air cooled you know 3k rpms could be only 55 MPH or so.  "Out of steam" could be valve adjustment, carb adjustment  or timing. I put a Delta CD ignition in 914 years ago and remember tach issue after install - think it was erratic needle jumping due to higher signal voltage though.  Fix was an inline resistor - can't remember ohms.   Google problem on the Mallory site.

 

Old Chinese replica gauges are troublesome - fix is new guts.

The fix may be new guts, you are right. I may try that. Thanks for your reply/

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