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Re: holley jet size 35? [Re: viperblue72] #1697537
11/18/14 10:36 AM
11/18/14 10:36 AM
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Pretty sure a #53 or a #56 jet is too fat. My 72 225 ran a #50 stock.


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Re: holley jet size 35? [Re: Supercuda] #1697538
11/18/14 02:04 PM
11/18/14 02:04 PM
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Just from looking at the picture I can tell you your old jet was at least a 72.

You may be able to go smaller one or two jet sizes from stock, maybe more depending on your altitude. I'd start reducing jet size until you get lean surging at cruise, then go up one number. Holley says you have to make a two number switch to have a noticeable change, but on such a small carb I'd go one step increments.

I have bought jets on the 'bay but I have found a local place that'll sell me a pair of jets for $4.00. Some are new, some used...but unless some donkey messed with the holes, they work.

Another area where one can make the engine work better is ignition advance curve. Unless you have a problem with detonation, bringing it in faster will add some snap to the engine's performance.

R.

Re: holley jet size 35? [Re: viperblue72] #1697539
11/18/14 02:56 PM
11/18/14 02:56 PM
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Quote:

I can't update mpg yet. But with these changes my top speed went from 78mph to 85mph. I'll update mpg soon.
I also installed a #56 jet. It appears smaller than what was in it.




Out of curiosity what what is the actual carb number ?

Re: holley jet size 35? [Re: 62maxwgn] #1697540
11/18/14 04:30 PM
11/18/14 04:30 PM
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Quote:

Quote:

I can't update mpg yet. But with these changes my top speed went from 78mph to 85mph. I'll update mpg soon.
I also installed a #56 jet. It appears smaller than what was in it.




Out of curiosity what what is the actual carb number ?




I don't have the carb number now, but I did look the numbers up and it was out of a '68 dodge pickup.
I have not been able to find anywhere stock jet sizes were listed. I got the #56 from a guy on the net, so it's not necessarily right.

Re: holley jet size 35? [Re: dogdays] #1697541
11/18/14 04:32 PM
11/18/14 04:32 PM
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Quote:

Just from looking at the picture I can tell you your old jet was at least a 72.

You may be able to go smaller one or two jet sizes from stock, maybe more depending on your altitude. I'd start reducing jet size until you get lean surging at cruise, then go up one number. Holley says you have to make a two number switch to have a noticeable change, but on such a small carb I'd go one step increments.

I have bought jets on the 'bay but I have found a local place that'll sell me a pair of jets for $4.00. Some are new, some used...but unless some donkey messed with the holes, they work.

Another area where one can make the engine work better is ignition advance curve. Unless you have a problem with detonation, bringing it in faster will add some snap to the engine's performance.

R.





With the new distributor, I did have to back the timing off just a bit due to detonation. Now that the vacuum advance is working.

Re: holley jet size 35? [Re: viperblue72] #1697542
11/18/14 04:35 PM
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Any info on what jet sizes to use would be appreciated. This #56 is a large improvement, but one person says #56, another #53, another #50, etc.
I would love to tune this thing to run just a tad lean would be optimal for best performance, mpg, and longevity.

Re: holley jet size 35? [Re: viperblue72] #1697543
11/18/14 05:01 PM
11/18/14 05:01 PM
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My suggested #50 jet was based on the 72 Dodge FSM's listing for a 72 Swinger with a 225, which is what I had. That carb had a #56 in it and got horrible mileage.


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They say there is always the exception that proves the rule.
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Re: holley jet size 35? [Re: Supercuda] #1697544
11/18/14 05:13 PM
11/18/14 05:13 PM
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Quote:

My suggested #50 jet was based on the 72 Dodge FSM's listing for a 72 Swinger with a 225, which is what I had. That carb had a #56 in it and got horrible mileage.



Thank you for the info! I appreciate your info And I will try and work my way down once I confirm it's rich.

Last edited by viperblue72; 11/18/14 05:17 PM.
Re: holley jet size 35? [Re: viperblue72] #1697545
11/18/14 06:56 PM
11/18/14 06:56 PM
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After going through the master parts manual the 53 jet is listed for eight 225 truck applications in 1968 except for one and that is a 56.

Re: holley jet size 35? [Re: 62maxwgn] #1697546
11/18/14 07:26 PM
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Bill,
Thank you for looking that up for me. I will probably downsize my jetting to stock, and go down a size or two from there if possible.
Fwiw it was listed as a '68 automatic pickup.
Is there anywhere I can find this kind of information on the internet?

Last edited by viperblue72; 11/18/14 07:28 PM.
Re: holley jet size 35? [Re: 62maxwgn] #1697547
11/18/14 07:29 PM
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There you go, better data.


They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
Re: holley jet size 35? [Re: Supercuda] #1697548
11/18/14 08:11 PM
11/18/14 08:11 PM
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Steve,
I know these didn't all come with the same size jet. I'm sure you gave me correct information for 72.
I know there were very slight variances of the volley 1920. But I have no idea why there are so much variance in jet size.
I am comfortable putting the original jet size back in for some reason. I know all slant sixes were almost unchanged through the years for the 225 other then slight here and there. My 81 never came with this carburetor but I love the simplicity and how it is running. I hope I didn't sound as if I was brushing anyone's advice. I will be glad to use a 50 jet if my engine is happy. Being some of you are curious about my mileage improvement as I am too. I will fill her up tonight and calculate it and report back. Check my plugs and likely order some more jets.
Sorry for the long winded post.

Re: holley jet size 35? [Re: viperblue72] #1697549
11/18/14 08:50 PM
11/18/14 08:50 PM
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Hey, no sweat, I didn't know the specs for a 68 truck and I couldn't find anything on the net, so I gave you the specs I had as a starting point. As long as it works out in the end that's all that matters. My Swinger was a CA emissions car so who knows how that might affect it.


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They say there is always the exception that proves the rule.
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Re: holley jet size 35? [Re: Supercuda] #1697550
11/18/14 10:31 PM
11/18/14 10:31 PM
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Viper that ain't a long winded post! I went & checked my Holley jet box & was surprised that they start at 64 from the numbers in this thread that are way lower


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Re: holley jet size 35? [Re: RapidRobert] #1697551
11/18/14 11:14 PM
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Quote:

Viper that ain't a long winded post! I went & checked my Holley jet box & was surprised that they start at 64 from the numbers in this thread that are way lower




That's because that box is the performance jetting,not applicable to one and two barrel carbs.You'll find those jets all have the number stamped on the side.

Re: holley jet size 35? [Re: 62maxwgn] #1697552
11/19/14 12:09 AM
11/19/14 12:09 AM
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Quote:

That's because that box is the performance jetting,not applicable to one and two barrel carbs.


Oh Ok that makes sense


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Re: holley jet size 35? [Re: RapidRobert] #1697553
11/19/14 12:37 AM
11/19/14 12:37 AM
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Quote:

Quote:

That's because that box is the performance jetting,not applicable to one and two barrel carbs.


Oh Ok that makes sense





Yeah, but thanks for sharing, as I was just looking at prices for those assortment kits earlier and considering one.
I have to order jets online as the local parts stores aren't carrying holley jets like they used to.

Re: holley jet size 35? [Re: viperblue72] #1697554
11/19/14 01:49 AM
11/19/14 01:49 AM
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Just filled up after driving only 65 miles. That was with a top speed jaunt for about 5 miles and letting the truck warm up the last few mornings for 15 minutes each. Still 11mpg.
Time to hit up jegs.

Re: holley jet size 35? [Re: viperblue72] #1697555
11/19/14 02:20 PM
11/19/14 02:20 PM
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My 570 Street Avenger is running 54s in front. But the lowest altitude I see is 4300 ft. Some of the 650 spreadbores went as low as 50s on the primary side, IIRC.

R.

Re: holley jet size 35? [Re: dogdays] #1697556
11/19/14 03:15 PM
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My 11 second duster with 4.11s and 408 stroker got better mileage than this.

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