200ci i6 Compression Test

cgstarry · September 15th, 2007, 12:09 AM

Hi All,

We did a compression test on our '66 inline 6 and have a few questions about the results.

We got 140psi on all cylinders and no change after squirting in some SAE 30 oil so we concluded the rings were OK.

I also suspect the valves and head gasket are ok since all the cylinders are the same.

One thing is bugging me: The specifications for the engine state the compression should be 155-190psi at sea level. Did I only get 140psi because in Minneapolis we are about 850feet above sea level?

I rechecked the procedure outlined in the shop manual. The one thing I missed was propping open the throttle plate. Could this accoiunt for the difference in compression? I turned the engine over 5 cycles on each cylinder.

Thanks for any info / guidance.

John

460brevill · September 15th, 2007, 08:01 AM

sea level and throttle plate make a diff.if you got 140 all the way i would leave it alone.

cgstarry · September 17th, 2007, 11:17 PM

Sounds good to me - thanks!

John

67ATX · February 15th, 2011, 02:49 AM

never hurts to conduct a leak down test, though Snap On gauges are the only ones I've found to be accurate.

RagHead · February 16th, 2011, 05:46 PM

Sounds good to me also

. If it aint broke don't fix it. If it runs good and strong leave it alone.

September 15th, 2007, 12:09 AM	#1
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	200ci i6 Compression Test Hi All, We did a compression test on our '66 inline 6 and have a few questions about the results. We got 140psi on all cylinders and no change after squirting in some SAE 30 oil so we concluded the rings were OK. I also suspect the valves and head gasket are ok since all the cylinders are the same. One thing is bugging me: The specifications for the engine state the compression should be 155-190psi at sea level. Did I only get 140psi because in Minneapolis we are about 850feet above sea level? I rechecked the procedure outlined in the shop manual. The one thing I missed was propping open the throttle plate. Could this accoiunt for the difference in compression? I turned the engine over 5 cycles on each cylinder. Thanks for any info / guidance. John __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

September 15th, 2007, 08:01 AM	#2
460brevill Hardcore Enthusiast Join Date: Apr 2007 Location: Farmville VA Posts: 1,327 iTrader: 0 reviews	sea level and throttle plate make a diff.if you got 140 all the way i would leave it alone. __________________ i sixing 200 six with 300 hp.

September 17th, 2007, 11:17 PM	#3
cgstarry Regular 2007 Mustang GT, 66 Coupe Join Date: May 2007 Location: Minneapolis, MN Posts: 125 iTrader: 0 reviews	Sounds good to me - thanks! John __________________ Vista Blue 2007 Mustang GT Premium Coupe 5 Speed FRPP GTA Axelbacks, AMSOIL XL 5W-20 Steeda CAI w/ High Flow Elbow, SCT xCalibrator 2

February 16th, 2011, 05:46 PM	#5
RagHead Newbie 1966 Mustang Convertible Join Date: Sep 2008 Location: Louisiana Posts: 24 iTrader: 0 reviews	Sounds good to me also . If it aint broke don't fix it. If it runs good and strong leave it alone. __________________ Dare to Differ: *STAY INLINE* 1966 Mustang convertible, candyapple red, black power top, black interior, auto trans, autolite 1100 carb, Pertronix Ignitor, Scarebird 4 lug disc brake conversion, duel master cylinder. 1976 Cobra II

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February 15th, 2011, 02:49 AM	#4
67ATX Regular 1967 Mustang Coupe 302 4V Join Date: Feb 2011 Location: Austin Texas Posts: 184 iTrader: 0 reviews	never hurts to conduct a leak down test, though Snap On gauges are the only ones I've found to be accurate.

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