Hey, on my '81 I have a little play when the steering wheel is in the central position, like you gotta crank it maybe a 1/4" in either direction before the car moves that way. I check the rag joint, and all the tie rods, drag link, idler arm, ball joints, they are all nice and tight. Any help on where I can get a service manual to check the gear box?

 

Hi Texas Jim,

yesterday my mechanic put in place the new spark plugs. The old sparks were OK , the problem was : 2-3 were slightly loose ( those that are more difficult to reach ). Infact I supposed that something was wrong with sparks.

Oh my god , what a difference with new sparks! Above all at low-mid rpm. now my engine runs so smooth...It desn't smoke anymore and I'm sure that the gas consumption will be improved ( good). less noise too. Instead I don't see a great difference at high RPM : but I must probably go for a larger air cleaner ( now mine is 10"), to have more air flow when the carb demands .

before replacing the last spark plug , my mech measured the compression ratio. He had some difficulties in keeping firmly the meter in the spark's hole ( due to high pressure) so we supposed that the actual compression ratio is slightly more than the value measured : we have measured 9:1 . But we think it should be about 9,2:1 . Does this value tell something to you about my engine HP?

power steering . I hear a hissing noise in the play position ( with engine OFF) coming from the control valve. No noise if I go over the play position.
I have checked the gear box watching it through the engine bay( from above): I see the shafts and levers moving without any play there

Set all the 4 tires at high pressure too

thanks
Aldo

 

Curious as to how you can measure compression ratio with a gauge?

 

Me too....
The compression ratio is the TDC cylinder volume vs the BDC cylinder volume. I can't see how a gauge is goin' to measure that. [&:]
The gauge only measures the psi per cylinder, whichgives no indication of the cylinder volume.If your mech knows something I don't, please fillme in on his method.

 

Plus if he's really just measuring compression, then he should have all of the plugs out and carb at WOT.

 

73 shark,
yes you are right. Also my mech told me that to make a correct measure we should remove all the spark plugs...but no time for this now.
So we have made the measure on 1 cylinder only , with all the spark plugs in place, distributor off , carb at full power ( open ).Running the engine with starter only for about 10 sec until we got the measure
I think that at the end the measure has been substantially correct...

The gauge used is a quite usual tool here ( it seems to me), but can't tell you more... If I go to the shop soon , I'll take a pic of this gauge

Aldo

 

That would be nice to see a picture. Can always use a new tool/gauge.

 

One method I heard of for measuring the ratio and CID,..... is to fill the cyl with liquid at BDC, turn the engine over by hand to TDC, and measure the differance in the volume of fluid removed to the volume of fluid used to fill the cyl at BDC. This method is generally done with the engine out of the car and on a stand. It can be done while the engine is still in the car though. I've never used this method, but they used to do it at the race track to verify CID, when there was dispute over an engine's displacement. Some classes limited the CID.( it was done on the compression stroke so that the valves were closed ) This was done with a hose and fitting that would screw into the spark plug hole.

Yes, yes, I know....there is a point where there is a lap over of a valve still remaining patially open during the comp stroke. Especially in a soupedup engine. I don't fully understand how they would get an accurate measurement since it seems to me that there would be a fluid loss out the open valve, but that's what they did at the track. Maybe they would measure the fluid remaining in the cyl by sucking it out and measuring it's volume.

 

That sounds possible but pretty sloppy and fraught with error. You could eliminate the valve overlap problem by backing off the rockers on that cylinder.

I know when youare checking CRout of the car, you need a piece of plexiglass to put over the combustion chamber and sealed with grease and then fill it with a measured amount of liquid to get the cc volume and do the same thing with the piston @ TDC. You also need to know the pop-up volume and valve reliefs. You can calculate the swept volume from stroke and bore dia. Lot of math. [:'(]

 

Well, like I said, I heard of them doin' that, but never saw it done.
The only thing I've ever done is to mic the cyliders before installing the heads. Bore X stroke.