question about compression
Thread Starter
Joined: Sep 2006
Posts: 42
From:
question about compression
on a fresh rebuilt motor(302 now 306), does it have more compression before or after break in ?
I have been playing with my timing and at one point had it way over 14 deg with no pinging, ran great just did not want to cruise very well, so how did I get away with that unless my compression is low do to engine only has like 30 miles on it ?
I have been playing with my timing and at one point had it way over 14 deg with no pinging, ran great just did not want to cruise very well, so how did I get away with that unless my compression is low do to engine only has like 30 miles on it ?
Thread Starter
Joined: Sep 2006
Posts: 42
From:
RE: question about compression
long story but I will make it short..just had it rebuilt...changed pistons (did not have to) but did it on recommendation of machinist / engine builder. says it should end up around 10:1
now I do have a hot battery in it and a new starter but it does sling it over very fast. even play with the timing I know when you get it to high most of the time the motor does not want to turn over. I have not had this problem.
now I do have a hot battery in it and a new starter but it does sling it over very fast. even play with the timing I know when you get it to high most of the time the motor does not want to turn over. I have not had this problem.
5th Gear Member
Joined: Feb 2006
Posts: 3,768
From:
RE: question about compression
ORIGINAL: chadjones99
long story but I will make it short..just had it rebuilt...changed pistons (did not have to) but did it on recommendation of machinist / engine builder. says it should end up around 10:1
now I do have a hot battery in it and a new starter but it does sling it over very fast. even play with the timing I know when you get it to high most of the time the motor does not want to turn over. I have not had this problem.
long story but I will make it short..just had it rebuilt...changed pistons (did not have to) but did it on recommendation of machinist / engine builder. says it should end up around 10:1
now I do have a hot battery in it and a new starter but it does sling it over very fast. even play with the timing I know when you get it to high most of the time the motor does not want to turn over. I have not had this problem.
Thread Starter
Joined: Sep 2006
Posts: 42
From:
RE: question about compression
well at first for what ever reason the computer was not adjusting the timing. the yellow wire the goes to the spout was dead. I traced it back to the computer and it was good. I think it was loose some were? so I had set the timing were the car would run good under power. I am going to guess I think it was 25-30 ,but like I said the computer was not advancing it.
so it would run good under power but did not want to run cursing. like 40-50 mph it had a mis going on, and a small surge.
I also am having fuel pressure problems I think that the screen is clogged because when I set the fuel pressure at 38 vac line off, I put it back on and its around 31 but when you rev it up it drops to 25. so I got the computer advancing the timing now and have set the base timing to 13 ish.. it runs good but feels like it is lacking some power. I don't know if this is due to the fuel pressure ( most liky )
or due to the engine being tight I only have about 25-30 miles on the motor.
my mods are this...
edlbrock performer heads
edlbrock performer intake with 65 MM throttle body and 24 lb injectors , roller rockers
E303 cam, MAF converted , aluminum radiator with electric fan
A/C delete , SMOG delete , 373 gears , flowmaster muffler with CAT delete
short shifter and upgraded T-5 , aluminum drive shaft , reend traction bar
I think that is it ... I had the same set up on the old motor , but was playing with 19 lb injectors turned up to 42lb and I think I had a better bottom end take off I also have a 70 mm throttle body but don't have it on till I figure out the problems I having now.
so it would run good under power but did not want to run cursing. like 40-50 mph it had a mis going on, and a small surge.
I also am having fuel pressure problems I think that the screen is clogged because when I set the fuel pressure at 38 vac line off, I put it back on and its around 31 but when you rev it up it drops to 25. so I got the computer advancing the timing now and have set the base timing to 13 ish.. it runs good but feels like it is lacking some power. I don't know if this is due to the fuel pressure ( most liky )
or due to the engine being tight I only have about 25-30 miles on the motor.
my mods are this...
edlbrock performer heads
edlbrock performer intake with 65 MM throttle body and 24 lb injectors , roller rockers
E303 cam, MAF converted , aluminum radiator with electric fan
A/C delete , SMOG delete , 373 gears , flowmaster muffler with CAT delete
short shifter and upgraded T-5 , aluminum drive shaft , reend traction bar
I think that is it ... I had the same set up on the old motor , but was playing with 19 lb injectors turned up to 42lb and I think I had a better bottom end take off I also have a 70 mm throttle body but don't have it on till I figure out the problems I having now.
Thread Starter
Joined: Sep 2006
Posts: 42
From:
RE: question about compression
here some pics of.. cant beleave it 20 years old now ?
i feel old this was the same type car i drove when i was a teen
[IMG]local://upfiles/48155/CEF1B7D5B3494C308D2E87DCDC9EAFFA.jpg[/IMG]
[IMG]local://upfiles/48155/72447FF399A84E0BAB71AB2509ACDFF4.jpg[/IMG]
[IMG]local://upfiles/48155/8584ADDE2CB14F809990A129FC0F4D56.jpg[/IMG]
i feel old this was the same type car i drove when i was a teen
[IMG]local://upfiles/48155/CEF1B7D5B3494C308D2E87DCDC9EAFFA.jpg[/IMG]
[IMG]local://upfiles/48155/72447FF399A84E0BAB71AB2509ACDFF4.jpg[/IMG]
[IMG]local://upfiles/48155/8584ADDE2CB14F809990A129FC0F4D56.jpg[/IMG]
5th Gear Member
Joined: Feb 2006
Posts: 3,768
From:
RE: question about compression
ORIGINAL: chadjones99
well at first for what ever reason the computer was not adjusting the timing. the yellow wire the goes to the spout was dead. I traced it back to the computer and it was good. I think it was loose some were? so I had set the timing were the car would run good under power. I am going to guess I think it was 25-30 ,but like I said the computer was not advancing it.
so it would run good under power but did not want to run cursing. like 40-50 mph it had a mis going on, and a small surge.
I also am having fuel pressure problems I think that the screen is clogged because when I set the fuel pressure at 38 vac line off, I put it back on and its around 31 but when you rev it up it drops to 25. so I got the computer advancing the timing now and have set the base timing to 13 ish.. it runs good but feels like it is lacking some power. I don't know if this is due to the fuel pressure ( most liky )
or due to the engine being tight I only have about 25-30 miles on the motor.
my mods are this...
edlbrock performer heads
edlbrock performer intake with 65 MM throttle body and 24 lb injectors , roller rockers
E303 cam, MAF converted , aluminum radiator with electric fan
A/C delete , SMOG delete , 373 gears , flowmaster muffler with CAT delete
short shifter and upgraded T-5 , aluminum drive shaft , reend traction bar
I think that is it ... I had the same set up on the old motor , but was playing with 19 lb injectors turned up to 42lb and I think I had a better bottom end take off I also have a 70 mm throttle body but don't have it on till I figure out the problems I having now.
well at first for what ever reason the computer was not adjusting the timing. the yellow wire the goes to the spout was dead. I traced it back to the computer and it was good. I think it was loose some were? so I had set the timing were the car would run good under power. I am going to guess I think it was 25-30 ,but like I said the computer was not advancing it.
so it would run good under power but did not want to run cursing. like 40-50 mph it had a mis going on, and a small surge.
I also am having fuel pressure problems I think that the screen is clogged because when I set the fuel pressure at 38 vac line off, I put it back on and its around 31 but when you rev it up it drops to 25. so I got the computer advancing the timing now and have set the base timing to 13 ish.. it runs good but feels like it is lacking some power. I don't know if this is due to the fuel pressure ( most liky )
or due to the engine being tight I only have about 25-30 miles on the motor.
my mods are this...
edlbrock performer heads
edlbrock performer intake with 65 MM throttle body and 24 lb injectors , roller rockers
E303 cam, MAF converted , aluminum radiator with electric fan
A/C delete , SMOG delete , 373 gears , flowmaster muffler with CAT delete
short shifter and upgraded T-5 , aluminum drive shaft , reend traction bar
I think that is it ... I had the same set up on the old motor , but was playing with 19 lb injectors turned up to 42lb and I think I had a better bottom end take off I also have a 70 mm throttle body but don't have it on till I figure out the problems I having now.
Thread Starter
Joined: Sep 2006
Posts: 42
From:
RE: question about compression
yes you are right I was just running on base timing but now I am not. some how it started working. before when I would set the base timing were it should be and put the spout back in it would not advance. so I set it high. but after having the computer out and moving the wires around it is now working so I set it back to 13 deg. it just feels a little week. but it is also have a fuel pressure problem and that may be why it feels week and the motor is not broke in yet also. tomorrow i plan on dropping the gas tank down to clean the screen if its bad I will post pics
you would think if the fuel pressure drops to 25 lbs from 30 when I rev it than when I am driving it and hit the gas it takes off strong but not strong as it should be it is most liky losing fuel pressure and power? well see
like I said I had the same motor in before the rebuild and it was stronger than now. but I did not have a fuel pressure problem and that motor was broke in.I also played with using 24lb injector ( that I have in right now ) and 19 lbser I felt like the car drove stronger on the bottom end with the 19lber in. and turned up high
you would think if the fuel pressure drops to 25 lbs from 30 when I rev it than when I am driving it and hit the gas it takes off strong but not strong as it should be it is most liky losing fuel pressure and power? well see
like I said I had the same motor in before the rebuild and it was stronger than now. but I did not have a fuel pressure problem and that motor was broke in.I also played with using 24lb injector ( that I have in right now ) and 19 lbser I felt like the car drove stronger on the bottom end with the 19lber in. and turned up high
3rd Gear Member
Joined: Sep 2006
Posts: 760
From:
RE: question about compression
fuel pressure concerns me (as should you) more than spark advance. Don't run a new motor lean. That's the worst thing you can do. You definately have a spout issue......I will see what I can do about getting you a wiring diagram.. I believe it goes from the pin at the TFI to pin 36 at your pcm... at least on a '90. Worst case scenario, just overlay (cut it out and make your own circuit) it and be done. Now fuel pressure. I don't have a lot of experience with aftermarket stuff and am typing with no reseach. Likely the bigger injector flows more fuel at the same duty cycle as your old ones - with means your pcm has to compensate somehow and at max flow they may flow more dino juice than your pump can supply. Your pressure regulator works fine but you may have a restrictive supply. DON'T drop the tank until you check the filter. Honestly just replace the damn thing. It likely needs it. It could be that simple. Otherwise the pump is worn, the pickup is clogged, there is resistance in the pump wiring or the lines are now too small for the injectors. In order for me to make an accurate guess, I suppose I need to research what kind of fuel management changes bigger injectors require.