Crate engine swap advise please?

[73 C10]

What jets ? and what Rods do you have in there now ?

Between this and my previouse post it tried a few things.

I got an adjustable light.
The light said base was 20* BTDC. The tab said 16*.
I set base to 16* with light.
The tab showed 12*. So I learned something there.
So here is what I tried. You'll see I tried to tried one thing most times and incremented timing and mixture.

# - BASE* BTDC - Vac.Adv. - Jet - Rod
1 - 20 - 11 - 98 - 6857 Hammer down spark knock
2 - 20 - 11 - 98 - 7037 This took the power part of the needle from .01" lean from stock to .01" rich from stock. Still knocking.
3 - 16 - 11 - 98 - 6857 Dropped timing. Leaned power. Still knocking.
4 - 16 - 11 - 98 - 7037 Tried richer power. Still knocking. Smells rich.
5 - 14 - 11 - 98 - 7037 Dropped timing. Still knocking. Smells rich.
6 - 12 - 11 - 98 - 7037 Dropped timing. Still knocking. Smells rich.
7 - 12 - 22 - 98 - 7037 Removed Vac. Adv. limiter. Still knocking. Smells rich.
8 - 12 - 22 - 98 - 7037 Changed spring to 5". Still knocking. Smells rich.


Bad gas?

 

[73 C10]

Rich,

He is lean if he is getting spark knock. Pinging is too much timing. Spark knock is too low of an octane rating or too lean of an A/F mix.

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I may not be describing the sound accurately, but I thought it was pre-ignition or detonation.

What i'm calling "knocking", sounds like a rattle that rises with RPM.

 

[350runner]

Try backing down the timing to 8btc

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[MadOgre]

Between this and my previouse post it tried a few things.

I got an adjustable light.
The light said base was 20* BTDC. The tab said 16*.
I set base to 16* with light.
The tab showed 12*. So I learned something there.
So here is what I tried. You'll see I tried to tried one thing most times and incremented timing and mixture.

# - BASE* BTDC - Vac.Adv. - Jet - Rod
1 - 20 - 11 - 98 - 6857 Hammer down spark knock
2 - 20 - 11 - 98 - 7037 This took the power part of the needle from .01" lean from stock to .01" rich from stock. Still knocking.
3 - 16 - 11 - 98 - 6857 Dropped timing. Leaned power. Still knocking.
4 - 16 - 11 - 98 - 7037 Tried richer power. Still knocking. Smells rich.
5 - 14 - 11 - 98 - 7037 Dropped timing. Still knocking. Smells rich.
6 - 12 - 11 - 98 - 7037 Dropped timing. Still knocking. Smells rich.
7 - 12 - 22 - 98 - 7037 Removed Vac. Adv. limiter. Still knocking. Smells rich.
8 - 12 - 22 - 98 - 7037 Changed spring to 5". Still knocking. Smells rich.


Bad gas?

the 070 is to rich for cruise and the 037 on a 098 jet is to lean for power SO... We go up on the jet and work down again SO.... 101 jet with 075 X 047 rod


BUT..... That timing needs to get dialed in correctly First!

 

[MadOgre]

I would go with a total of 32 degrees until the carb is set up correctly then afterwards you can try advancing back up to 36

 

[MadOgre]

the 070 is to rich for cruise and the 037 on a 098 jet is to lean for power SO... We go up on the jet and work down again SO.... 101 jet with 075 X 047 rod


BUT..... That timing needs to get dialed in correctly First!

Forget this for now!

 

[73 C10]

I would go with a total of 32 degrees until the carb is set up correctly then afterwards you can try advancing back up to 36

Wouldn't the total be 52*?

If base is 12*, VA is 20* and mechanical is 20*. All measured in crank degrees.

 

[MadOgre]

I may not be describing the sound accurately, but I thought it was pre-ignition or detonation.

What i'm calling "knocking", sounds like a rattle that rises with RPM.

Ok well that may not be spark knock it could be exhaust rattle or any thing rattling.

How does it smell Rich ??? The exhaust is black and smells like fuel or you can smell fuel from under the hood?

Maybe your set up just fine As that rod and jet puts you at 10-12% Rich which is where I would figure you should be! And so does Rich.

Maybe you have other issues like incorrectly set timing and or something rattling around under the hood and maybe your floats are set to high? I just fixed a fuel smell the other day by setting my floats a tad lower. Do you have a fuel regulator? You do need one!

 

[MadOgre]

Wouldn't the total be 52*?

If base is 12*, VA is 20* and mechanical is 20*. All measured in crank degrees.

I meant with out the vacuum advance. The vacuum advance shouldn't be any more than 16 degrees

 

[350runner]

Wouldn't the total be 52*?

If base is 12*, VA is 20* and mechanical is 20*. All measured in crank degrees.

Dude that's way too high...

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[MadOgre]

And actually the 6857 rod on a 98 jet is not correct. The 70 x 37 on a 98 jet is what I was referring to as 10-12% rich


the 57 is now lean on power and the 68 is rich on cruise from stock. If you were to run 57 on the rod you would have to go with a larger jet otherwise you are leaning it out

 

[73 C10]

Ok well that may not be spark knock it could be exhaust rattle or any thing rattling.

How does it smell Rich ??? The exhaust is black and smells like fuel or you can smell fuel from under the hood?

Maybe your set up just fine As that rod and jet puts you at 10-12% Rich which is where I would figure you should be! And so does Rich.

Maybe you have other issues like incorrectly set timing and or something rattling around under the hood and maybe your floats are set to high? I just fixed a fuel smell the other day by setting my floats a tad lower. Do you have a fuel regulator? You do need one!

The rich smell is all around the truck when tuning and jumping out after a drive. It wasn't bad until I put the 7037. I chose .07" to stay close to riches .068" on cruse because I am having a power related rattle. Sounds like when my Harley gets hot and there isn't enough octane in the gas.

 

[73 C10]

And actually the 6857 rod on a 98 jet is not correct. The 70 x 37 on a 98 jet is what I was referring to as 10-12% rich


the 57 is now lean on power and the 68 is rich on cruise from stock. If you were to run 57 on the rod you would have to go with a larger jet otherwise you are leaning it out

Yeah. You and Rich are having an argument on this, and i'm trying both for you guys. How do you think I feel? Rich doesn't go off the chart, and others said listen to him.

No offence intended. Are you missing that? I went right on the chart too. and I tried stock.

 

[MadOgre]

I think Rich was right in that you need to get your timing settled first. The 20 on the vac can is too much!

As far as the rods and jets go, its simple math. The higher the rod # the leaner it goes with in a given jet size. So a rod size of 057 x 037 is the richest going all the way up to 075 x 057. And the other way for Jets 077 is the smallest leanest and 119 is the largest richest jet


The first #s on the rod are for cruise and the second # for power.

eg:

70 x 57
70 x 52
70 x 47
70 x 42
70 x 37

The cruise remained the same at 70 but the power went from lean down to rich

75 x 37
73 x 37
71 x 37
70 x 37
68 x 37
67 x 37
65 x 37
63 x 37
62 x 37
60 x 37
58 x 37
57 x 37

Here the cruise went down from lean to rich while the power stayed the same @ 37

The jets now go from lean to rich in this order

77
80
83
86
89
92
95
98
101
all the ways up to 119

 

[73 C10]

And actually the 6857 rod on a 98 jet is not correct. The 70 x 37 on a 98 jet is what I was referring to as 10-12% rich


the 57 is now lean on power and the 68 is rich on cruise from stock. If you were to run 57 on the rod you would have to go with a larger jet otherwise you are leaning it out

When we are talking about spark knock on power, aren't we only taking about the tip of the needle. I thought I step on the peddle, the vacuum drops, the needles pop up, and we using the tip. I tried .037" - .057" with no rattle change. Which looks like it goes equally both sides of stock spec of .047". From lean to rich.