Stall converter
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Stall converter
I´m running a car (3000 lbs aprox )with this config engine :
400 cid
compression 8.7:1
holley 800cfm carb (vacum secundaries)
Y 2" headers with 4 collectors of 2.5" and 4 exhaust pipes
crane cam HIT-282-2-NC, it says;
Intake@cam 306 @valve531 Rocker Arm ratio
exaust@cam 323 @valve 560 1.73
Cam timting opens closes Duration
@.0029 Intake 28 74 282 degrees
exhaust 80 30 290 degrees
rpm starts and ends : 2500 - 6000
recomended 2500 stall converter
what would happen if I use this engine on this car with a c6 and standard converter with standar stall ( i think 500-800 rpm)?
wont it run at all ?
400 cid
compression 8.7:1
holley 800cfm carb (vacum secundaries)
Y 2" headers with 4 collectors of 2.5" and 4 exhaust pipes
crane cam HIT-282-2-NC, it says;
Intake@cam 306 @valve531 Rocker Arm ratio
exaust@cam 323 @valve 560 1.73
Cam timting opens closes Duration
@.0029 Intake 28 74 282 degrees
exhaust 80 30 290 degrees
rpm starts and ends : 2500 - 6000
recomended 2500 stall converter
what would happen if I use this engine on this car with a c6 and standard converter with standar stall ( i think 500-800 rpm)?
wont it run at all ?
Postmaster
Joined: Aug 2001
Posts: 4,270
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From: Delaware
Fortunatly it's a light car, but you will have very little torque below 2000 RPM.
I wouldn't use a cam like that in a motor with only 8.7:1 CR. The intake valve closes at 74 degrees ABDC, and the piston is 1.2" up in the cylinder at that time. The dynamic compression ratio is a meager 6.5:1. You should have a dynamic CR around 8:1 or higher.
I wouldn't use a cam like that in a motor with only 8.7:1 CR. The intake valve closes at 74 degrees ABDC, and the piston is 1.2" up in the cylinder at that time. The dynamic compression ratio is a meager 6.5:1. You should have a dynamic CR around 8:1 or higher.
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thanx, yeah Im planning on getting 9.5 to 1 flat top pistons but would it be really that bad to use the engine with that compression for a couple of months ? too much gas cunsumption ? or wouyld it bring my horses really down ?
Postmaster
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From: Delaware
It will run like a 289 with bad valves. I don't think that you will hurt anything. How rough it is will depend on the overlap. I'll try to figure the overlap later. Chances are the vacuum at idle will be very low. Do you have power brakes?
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From: Delaware
OK, I checked the overlap. The lobes are on 114 degrees Lobe Separation Angle. The overlap is only 58 degrees. That should idle OK and produce plenty of vacuum at idle for power brake operation. It is only the torque at low RPM that will be low. You could pick up some torque by installing it 4 degrees advanced, until you get the new pistons.
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From: western montana
Originally Posted by danlee
You should have a dynamic CR around 8:1 or higher.
from what i've ascertained the optimum dynamic compression for 87 pump would be approx 7.4-7.8; 92 pump would be 8:1-8.3:1....engines typically run best between 7.5 and 8.5 but need good quench to run closer to 8.5...
Or, am I screwed up on that? wouldn't be the first time i reckon...is the 8:1 dynamic needed due to the cam?
stock stall converter should be about 13-1500 rpm??? Thats a huge cam and needs mucho compression..
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Thanx, yes you are right, so mean while getting the new pistons I will advance the timing chain of the cam 4 degrees , this will give me more torque, Is it safe ? at high rpm wont it break ? Can you pst the results of the test you made ? thank you very much
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Postmaster
Joined: Aug 2001
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From: Delaware
By advancing the cam, by 4 degrees the DCR goes up to 6.7:1. That will improve the torque at low RPM.
You will need a timing set with multiple keyways. Many good aftermarket timing sets have multiple keyways. I suggest a good double roller timing set, like a Cloyes or Edelbrock. The multiple keyways are usually +4 degrees, 0 degrees or 'straight-up', or -4 degrees. You should use a Degree wheel to check your Intake Lobe Center to be sure that you have installed it correctly.
You will need a timing set with multiple keyways. Many good aftermarket timing sets have multiple keyways. I suggest a good double roller timing set, like a Cloyes or Edelbrock. The multiple keyways are usually +4 degrees, 0 degrees or 'straight-up', or -4 degrees. You should use a Degree wheel to check your Intake Lobe Center to be sure that you have installed it correctly.
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From: Delaware
Horsepower = Torque X RPM/5250.
Torque = Horsepower, when the RPM is 5250.
If you advance the cam, you move the torque curve down the RPM scale. So you will get less Horsepower and lower peak torque, but you will improve your low RPM torque. If you retard the cam, you will move the torque curve up the RPM scale. Now your peak torque will be higher at high RPM, and the horsepower will be higher, but you lose low RPM torque.
I like a motor that doesn't have so much cam that the low RPM suffers badly, but has great intake and exhaust flow, so the torque curve is flat. Big cams need very high compression ratios to provide any low RPM power.
A drag car will have very high compression and a big cam, but need a stall converter to get moving.
Torque = Horsepower, when the RPM is 5250.
If you advance the cam, you move the torque curve down the RPM scale. So you will get less Horsepower and lower peak torque, but you will improve your low RPM torque. If you retard the cam, you will move the torque curve up the RPM scale. Now your peak torque will be higher at high RPM, and the horsepower will be higher, but you lose low RPM torque.
I like a motor that doesn't have so much cam that the low RPM suffers badly, but has great intake and exhaust flow, so the torque curve is flat. Big cams need very high compression ratios to provide any low RPM power.
A drag car will have very high compression and a big cam, but need a stall converter to get moving.
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so even if i get a good set of pistons, i will need a torque converter to move my car ?,( I checked the weight of my car and with out a passenger is 2200 lbs only !, made a lot of fiber glas mods ) so I should change the cam ?
