Rejetting question
Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
Likes: 0
From: Inver Grove Minnesota
Rejetting question
I pulled my plugs and noticed that they have black carbon build up on them. It is a holley 750 dual inlet on a modified 350. Also, I'm getting my old 2 1/4 inch system with crappy mufflers replaced so far I have some pypes violators of the 2 1/2 inch variety. Should I wait until I get my new muchg better flowing exhaust on before I rejet? When I do change them out, how far down in size should I start with? It has 70's in it now.
Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
Likes: 0
From: Inver Grove Minnesota
I am still in the process of getting all of the kinks worked out after changing from a gm crate motor with 76 cc heads and a tiny cam. Getting the jet size right is the last think I have to do.
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
After I modified my motor, I jetted my Q-Jet up to .074, which I think is as big as they get. I did notice that with the cam it needs more fuel, probably because it's getting more air. However, my gas mileage has stayed the same as before the mods. Go figure......
So, if you have sooty plugs you might want to check all components of the intake - compression - power - exhaust cycle for the cause.
So, if you have sooty plugs you might want to check all components of the intake - compression - power - exhaust cycle for the cause.
Le Mans Master
Joined: Apr 2006
Posts: 5,403
Likes: 95
Justin I saw one of your threads awhile back about backfire into
your exhaust system did not say anything. My old 302 came
from the factory with a 254 at .050 solid cam the same holley
vacuum carb you have, it had 3.73 gears 2.20. M21 trans. I use to
run it up in low gear past what the cam would really make power
to 8000 on the tach to see it make 60 MPH. I would back off with
no backfire in the exhaust. But when I pulled the plugs they were not
black in color. The car just had the original points dist the coil
probably put out about 20,000 volts. I had a problem with point
bounce so I bought two sets of points cut the spring on one of them
put it behind the other that got rid of the point bounce problem, wore
the block on the points a little faster but points were cheap in cost.
I remember driving a 63 impala with a 283 superduper mild cam two
barrle carb, run it up in rpm a little shut the key off pump the gas a little
turn the switch back on Ka-bam out the exhaust.
your exhaust system did not say anything. My old 302 came
from the factory with a 254 at .050 solid cam the same holley
vacuum carb you have, it had 3.73 gears 2.20. M21 trans. I use to
run it up in low gear past what the cam would really make power
to 8000 on the tach to see it make 60 MPH. I would back off with
no backfire in the exhaust. But when I pulled the plugs they were not
black in color. The car just had the original points dist the coil
probably put out about 20,000 volts. I had a problem with point
bounce so I bought two sets of points cut the spring on one of them
put it behind the other that got rid of the point bounce problem, wore
the block on the points a little faster but points were cheap in cost.
I remember driving a 63 impala with a 283 superduper mild cam two
barrle carb, run it up in rpm a little shut the key off pump the gas a little
turn the switch back on Ka-bam out the exhaust.
Last edited by Little Mouse; Jul 2, 2007 at 03:53 AM.
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Thread Starter
Safety Car
Joined: Jun 2005
Posts: 3,841
Likes: 0
From: Inver Grove Minnesota
Justin I saw one of your threads awhile back about backfire into
your exhaust system did not say anything. My old 302 came
from the factory with a 254 at .050 solid cam the same holley
vacuum carb you have, it had 3.73 gears 2.20. M21 trans. I use to
run it up in low gear past what the cam would really make power
to 8000 on the tach to see it make 60 MPH. I would back off with
no backfire in the exhaust. But when I pulled the plugs they were not
black in color. The car just had the original points dist the coil
probably put out about 20,000 volts. I had a problem with point
bounce so I bought two sets of points cut the spring on one of them
put it behind the other that got rid of the point bounce problem, wore
the block on the points a little faster but points were cheap in cost.
I remember driving a 63 impala with a 283 superduper mild cam two
barrle carb, run it up in rpm a little shut the key off pump the gas a little
turn the switch back on Ka-bam out the exhaust.
your exhaust system did not say anything. My old 302 came
from the factory with a 254 at .050 solid cam the same holley
vacuum carb you have, it had 3.73 gears 2.20. M21 trans. I use to
run it up in low gear past what the cam would really make power
to 8000 on the tach to see it make 60 MPH. I would back off with
no backfire in the exhaust. But when I pulled the plugs they were not
black in color. The car just had the original points dist the coil
probably put out about 20,000 volts. I had a problem with point
bounce so I bought two sets of points cut the spring on one of them
put it behind the other that got rid of the point bounce problem, wore
the block on the points a little faster but points were cheap in cost.
I remember driving a 63 impala with a 283 superduper mild cam two
barrle carb, run it up in rpm a little shut the key off pump the gas a little
turn the switch back on Ka-bam out the exhaust.
I haven't had that problem since I changed to the msd e-curve. That seem to make it run alot smoother.
Could you elaborate on this some.