just for fun...
Thread Starter
|
Junior User
Joined: Mar 2005
Posts: 96
Likes: 0
From: up north
just for fun...
I was out in the guys room today,changing oil. Since I have never checked the compression on the motor that was built with your help , I desided to do it.
Well here are the results.
390 .030 over
-20 cc pistions kb's
crane cam 941
stock heads cced @72
.040 head gasket
.000 deck height
167to 172 lbs throttle closed
192 to 198 throttle open
then I started it ran to 3000
and recheked 1 cylinder wile running 218
just for fun
mike
Well here are the results.
390 .030 over
-20 cc pistions kb's
crane cam 941
stock heads cced @72
.040 head gasket
.000 deck height
167to 172 lbs throttle closed
192 to 198 throttle open
then I started it ran to 3000
and recheked 1 cylinder wile running 218
just for fun
mike
Posting Guru
Joined: Aug 2005
Posts: 1,036
Likes: 1
From: NE Ga
What kind of vacuum are you getting with that setup. Thats the same setup I have except I have silovlite 1131 pistons...not sure of the difference though, not a piston expert. Oh and I don't remember my deck height either. I'm only getting 14-15" of vaccum unless I crank my initial timing up to about 16. Then I can get 16" of vacuum.
Thread Starter
|
Junior User
Joined: Mar 2005
Posts: 96
Likes: 0
From: up north
vacume is 13 to 14 @ 750rpm
17 inital advance
stock dizy is curved @ 20 total starting @1500 and in mall the way @ 3500
adjustable vacume advance 10 total @ 18 inches of vacume
must burn 92 or ping ping
17 inital advance
stock dizy is curved @ 20 total starting @1500 and in mall the way @ 3500
adjustable vacume advance 10 total @ 18 inches of vacume
must burn 92 or ping ping
Posting Guru
Joined: Aug 2005
Posts: 1,036
Likes: 1
From: NE Ga
Ok good, I was wondering if I had something wrong to only be gettin that little of vacuum. I'm still workin on curving mine. With 17 initial yours doesn't buck at hot startup? Mine bucks at only 15-16 initial. Seems like I can't win for loosing on this motor for some reason. I don't mind learning but I hate going in circles.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
This is where Bear would step in and remind me of my evil ways, but I'm gonna say it anyway... 
73F100*8Mile, you might need to go to an inverted vacuum advance like I did. My setup was such that I was lucky to get 11 inches of vacuum at 900RPMs. And that was with a huge initial already.
Like you, it would not want to start when hot - too much advance. I had to hook the vacuum advance to manifold vacuum, adjust it just right, and got 18 degrees of advance at idle to get the vacuum up to 15 inches or so.
The good part is, with the vacuum advance hooked up this way, you have NO advance when starting because it's not making any vacuum yet. So it would fire right up very easily.
And, when leaning on the gas, the timing would RETARD so that it wouldn't ping so easily.
Of course, the cam, it's timing, and other factors should be "fixed" instead of using a vacuum advance band-aid like I just described. But sometimes it's more fun to turn things around
73F100*8Mile, you might need to go to an inverted vacuum advance like I did. My setup was such that I was lucky to get 11 inches of vacuum at 900RPMs. And that was with a huge initial already.
Like you, it would not want to start when hot - too much advance. I had to hook the vacuum advance to manifold vacuum, adjust it just right, and got 18 degrees of advance at idle to get the vacuum up to 15 inches or so.
The good part is, with the vacuum advance hooked up this way, you have NO advance when starting because it's not making any vacuum yet. So it would fire right up very easily.
And, when leaning on the gas, the timing would RETARD so that it wouldn't ping so easily.
Of course, the cam, it's timing, and other factors should be "fixed" instead of using a vacuum advance band-aid like I just described. But sometimes it's more fun to turn things around
Posting Guru
Joined: Aug 2005
Posts: 1,036
Likes: 1
From: NE Ga
Well see thats the thing, I don't knnow much about cam timing when it comes to advancing or retarding it. I don't know what the results are so I'm not gonna spend all that time going in there to do something I know nothing about. What are my options with cam timing? Is that where I should be looking? Ignition timing isn't doing hardly anything for me and like I said, I'm just going in circles with it. I will probably do the reverse vac advance like you did as a bandaid for now though.
Senior User
Joined: Sep 2006
Posts: 162
Likes: 0
From: Newbury Park Ca.
Trending Topics
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
Originally Posted by aMoneypit
218 is 14.8:1 at sea level!!!!!!! What are you using for fuel?.......
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
Originally Posted by 73F100*8Mile
Hey how do you figure compression anyhow? I think I checked mine and it was around 190psi. Whats that good for ratio wise?
Posting Guru
Joined: Aug 2005
Posts: 1,036
Likes: 1
From: NE Ga
Krewat, can you take a stab at my post above about cam timing. I'm not experienced at all with changing my cam timing. What does advancing/retarding do for your motor? Is that something I should seriously consider since I'm having troubles with pinging?
Thread Starter
|
Junior User
Joined: Mar 2005
Posts: 96
Likes: 0
From: up north
What dizy are you useing? Did you check your mechanical advance ? From my little time playing arround with your set up, I think @ 2000 you want it to start and @ 4500 end. but think this is with a truck with a auto and 3.01 gears. The heaver the car the slower the curve. A stock dizy with 2 light stock springs will get you very close. May need to bent the tabbs out to slow stuff down a bit.
The vacume advance should have a good stout spring in it. G et a few of the shelf and push the arm in you should feel the differnce. Just my 2 cents.
The vacume advance should have a good stout spring in it. G et a few of the shelf and push the arm in you should feel the differnce. Just my 2 cents.
Senior User
Joined: Sep 2006
Posts: 162
Likes: 0
From: Newbury Park Ca.
Ratios
Originally Posted by 73F100*8Mile
Hey how do you figure compression anyhow? I think I checked mine and it was around 190psi. Whats that good for ratio wise?
Thread Starter
|
Junior User
Joined: Mar 2005
Posts: 96
Likes: 0
From: up north
Originally Posted by aMoneypit
Volumetric air pressure at sea level is 14.7 Lbs per sq inch.......A naturally asperated engine pumping 147 psi would then be 10 to 1. Dividing the compression gauge reading by 14.7 will get you in the ballpark. However, as mentioned, cam timing, and especially overlap will drop the actual results. The fact that the 218 PSI was obtained with the engine running, (not sure how) doesn't change what the air/fuel charge is seeing in the cylinder.....IMO his compression gauge may need a little calibration......You can also do the math. Convert cylinder volume to CCs, and divide that number by the combustion chamber CCs......Yes, there are varibles, valve reliefs, domes, etc etc, but you can figure it to a knats *** using the numbers instead of gauges....aMP
Thread
Thread Starter
Forum
Replies
Last Post
DanielT28
1994.5 - 1997 7.3L Power Stroke Diesel
81
Jun 17, 2015 11:02 PM
ssg1957
1948 - 1956 F1, F100 & Larger F-Series Trucks
8
Jan 17, 2015 08:43 AM
jmadsen
1957 - 1960 F100 & Larger F-Series Trucks
34
Jun 20, 2014 01:17 AM