hi!
my trucks been sitting here beside its organ donor for a while and ive been busy....
one of my cousins made me a deal, he would do the engine work (he does ford fe rebuilds for fun....) and give me a new aluminum 4 bbl intake and an in need of a rebuild 4 bbl carb for my 65's engine, in trade he takes whats left of the donor.... he has enough bits and parts to put together a whole truck so he is excited. I get all my work done for free by someone I know who can do the job right and I'm happy.

now for the question... I just read where when you do a compression test you take all plugs out and do it warm, with the throttle open.

when I tested the donor engine I did it different, first off the engine was cold because we had no gas to do it warm, and I didnt take out all the plugs, just one at a time with the throttle closed.

now I know better, but I have this nagging question...

how will doing it my bass ackwards way effect the reading? I got 135+/- 2 or 3 lbs on every cylinder, I took the reading twice before moving to the next cyl.

my 65's test gave me different readings on all, some 160 some 130ish and the one 30lb one (the reason for replacing the heads) .

I dont wanna swap these donor heads to mine if the way I tested em would effect it for the worse. I will retest when we move it and its been warmed up but I dunno when that will be.

would the method I used give me a false reading and if so why? what does taking the plugs out and opening the throttle do anyway?

I was going to put in a new valve, but I think the donors heads with all even compression readings is better than mine with each having a different reading... (or am I wrong there too?)

also from the casting#'s and the handy books I got (via your recomendation) I found the heads are not as I was told but are 73 heads on a 73 engine... most likely the originals.
the 76 heads are better suited to unledded gas right?
that and I wager they have less miles on em (98K on the donors clock).

I never knew my cousin was so into FE series trucks... he has a graveyard of parts and more toys and tools than I have.
plus he actually enjoys working on em.... He said he will remove and clean the whole engine, flush it and clean every nook and port and hole.... and whatever else he sees that needs cleaned replaced or fixed.
not a bad swap for a 200 buck truck...
I checked out his rebuild efforts on his other trucks, no leaks and clean as a whistle engines, so it seems he is maticulus about it. His trucks run beautiful.

ANYWHO... whats the scoop on my bass ackwards testing method and how off does it throw the reading?

 

theres nothing wrong with what you did!

 

then why does the standard instruction always say remove the plugs and wire the throttle open?
whats that do?

 

Its gives a more accurate psi. It will be higher when you do this!
Its not so much, how much comp you have as long as its a 100+ and with in 75% of each other

Just wondering do you torque your lugnuts to proper torque spec?
Do you use dielectric grease on new plug wires?

Well, sometimes, some people do, who cares! Samething compression testing.

 

ah cool, then the reading would be a bit higher.. thats great! then those heads are really reading 135+ on all 8.

the engine vac was at idle 15hg and thats at a rough idle.

ok, now the 73 vs 76 unleaded gas compatability Q.... 76ers beter than the 73's?

I cant find exactly when they started using unleaded and imporved the seats (or whatever they did for the unleaded gas..)

 

both have headened seats and are equal. Both are probaly d2te heads.

 

The best reason for doing it warm is if it has worn rings and you like getting burned taking out spark plugs on a hot engine. I would do a FE warm because it is easy to get at the plugs, I would never do a Chevy 350 warm because I hate burning myself on the stupid manifold over spark plug design. I really do not think it matters much either way.

That main reason for removing all the spark plugs is to make it easier to crank the engine over so you do not nuke the starter and battery.

The idea about the throttle open is so it can suck in the max. amount of air on each cyl. Otherwise the ones nearest the carb. might read slightly higher in a carb. engine.

From reading this board after a couple of years I gather 100 psi and more is good for a FE, so I would not worry about an engine that was doing 135+ cold.