• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

74 Midget At Altitude

Share this page

F

Flatlander

Senior Member
Country flag
Offline
I am looking at purchasing a 74 Midget. It is located at 9000 feet in the Rockies. It drives well, idles great and is a good solid car. The problem is that in accelerating it reaches about 2500-2800 rpm then flatlines and cannot accelerate any higher. Car does not miss or exhibit any sputtering. The owner in trying to solve the problem installed a Petronix ignition system thinking it was an ignition problem but with no solution. If I purchase I will be driving out of the mountains and will have to go up several steep grades. My questions are:

1. Any ideas as to cause?
2. Will problem go away the lower in altitude I get?
3. Would this be a symptom of a larger problem?

Thanks
 
Hi There Flatlander,

I was just driving thru & I`m not a Mechanic but "What does the "OIL PRESSURE" read @ "Start" & then @ "2500rpm"?

If it were "Feul Starvation"; The engine would just quit on you. It certainly does`nt sound like anything electrical & The "Elevation Changes" don`t seem like that would make a difference one way or another.

I`d check "OIL PRESSURE & COMPRESSION".

Best Wishes,

Russ

PS: I`m sure "Hap" will be chiming in soon & He`s a "Pro"!
 
I'm no expert, but it almost sounds like the throttle plate isn't opening all the way. Sort of like a fuel starvation, but more like "throttle starvation". I'd start with just checking over all the linkages. I'd also check the spark plugs to see if it's been running rich or lean.

I've heard that SU's compensate for altitude, and I would think that 9k feet shouldn't phase them.
 
The current owner says that there is good compression and all cylinders are around 90 psi. We will recheck tomorrow (wet and dry) but the 90 psi sounds low to me. From what I can determine it should be 150 psi. Would the low pressure result in a smooth running motor at 1-2800 rpm then flattening and lose of power above? Would a worn engine have uniform cylinder pressure? Would even low pressure be indicative of bad rings, pistons, valves or generally worn engine?

Thanks for everyones good advice.
 
Back
Top