I found an awesome car with very low miles. The condition is awesome except that the motor tested 85PSI on all 6 faces.

Would you buy a car with that low of a compression? Or is that even low at all?

Should I be saving up for a new engine within the year or two?

Thanks for those who rebuild engines...

 

That question hangs heavy on the car of the car.

i might buy my friends 91 FC with 235,000 original miles. but its 5 dollars.

 

it also depends how the person did the compression test. if its a steal of a deal the compression numbers should be irregardless anyways.

 

So you guys don't think 85PSI is too low?

 

From the sticky:
28) What should the compression be?

Compression test results are reported as six numbers: 3 per rotor. (This is not the same as the compression ratio). Higher, more equal numbers are best. The original Mazda specs dictate 8.5+ kg/cm² as new (121+ psi), with 6.0 kg/cm² (85 psi, 690kpa) being minimum acceptable. Maximum difference should be 1.5 kg/cm² (21 psi, 150kPa) from the highest to lowest value. It is important this test is carried out using proper equipment and under the correct conditions for rpm and engine temperature. Mazda dealers are generally reliable for performing this test, so long as they follow the procedures precisely.

 

That's pretty low, but if the car is a nice, low mileage example, it might be a good bargaining chip.

Does it have a boost gauge? What's it pulling for vacuum?

 

What type of gauge did they use for compression? If both front and rear are reading the same and consistent on all faces then I wouldnt worry to much about it. I would worry if one is reading a lot higher than the other.

 

Ground Zero Motorsports did the compression test. It was consistent on both the front and rear. 85PSI seemed low to me but this car has 29,000 miles and the owner mainly used it for taking pictures and what not.

He babied the thing and I couldn't see why it would have such low compression numbers but then again, I haven't "really" seen the car in person.

I guess it's time to take a trip to see it...

Thanks Jason.

If you have any other tips for me, let me know.

 

85psi is quite low, IF the test was done properly...fuel disabled, one plug out of each chamber, 250 cranking rpm, throttle open, etc. Anywhere below 95psi you start to have hot start/flooding issues, slightly rougher idle, etc. Turbo rotaries have a way of turning 90psi into 0 really fast.

If the deal is good enough, then buy it with the intent of rebuilding. Really, there are very FEW circumstances that one can buy an FD withOUT the intent of rebuilding. IF you buy an original engine car, at this stage in it's life regardless of mileage, you can figure it needs freshening up. If you buy a car with an older rebuild with say 40-50k miles, well that engine is starting to decline as well. IF you buy a car with a newer rebuild, half the time it wasn't done properly and needs to be gone back through.

 

Thanks Kevin. You know who I'm going to if I decide to rebuild (hint: it's you).

Mike