Engine running crummy

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boilermaster

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So I have been tweaking carb settings and getting my engine running really well. I was going over the build sheet for my carb and found out that my jets were 12 sizes apart! Was set up with 68’s in the front and 80’s in the rear. I always thought that they should be more like 8 sizes apart with a power valve in the front only. So I replaced the primary jets with 72’s and left the 80’s in the secondaries. Engine responded very well. It had a slight hesitation and now it’s gone. I still need to check the plugs, but I’m very happy with how it ran yesterday.
Jpaz,

You must have a great tune, as you have the same primary and secondary jetting as myself lol.

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So I have been tweaking carb settings and getting my engine running really well. I was going over the build sheet for my carb and found out that my jets were 12 sizes apart! Was set up with 68’s in the front and 80’s in the rear. I always thought that they should be more like 8 sizes apart with a power valve in the front only. So I replaced the primary jets with 72’s and left the 80’s in the secondaries. Engine responded very well. It had a slight hesitation and now it’s gone. I still need to check the plugs, but I’m very happy with how it ran yesterday.
Jpaz,

You must have a great tune, as you have the same primary and secondary jetting as myself lol.

Boilermaster
Ya, it’s really running good and I hope it stays this way! Lol

 
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John, now that you finally have that all dialed in and running good, I would be interested in what mileage you are getting with the QF HR735.

If you can get some numbers for in town and highway as well as highway only, I'd grateful. I currently get an average of around 15-16 mpg US with the 670 Holley and 65 67 jets. 

Great to know you're up and running again, now all we need is some warm dry weather!!

 
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Gas mileage? Lol!! I’ve never really paid attention to that Geoff. I don’t think I will get the numbers you’re getting. I just run around town and if I do go on the freeway it’s only for a few miles. 3k rpms going 70 I don’t think it’s worth keeping track of. My guess is 10-12 in the city and probably not much better on the freeway.

 
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Gas mileage? Lol!! I’ve never really paid attention to that Geoff. I don’t think I will get the numbers you’re getting. I just run around town and if I do go on the freeway it’s only for a few miles. 3k rpms going 70 I don’t think it’s worth keeping track of. My guess is 10-12 in the city and probably not much better on the freeway.
 As 73Pony says, "Smiles per miles" certainly get that and for sure running the Mustang isn't like driving the daily driver on long distance trips. However, we pay close to double what you guys pay for Premium, so cost is a bit more of a concern.

In reality, I use gas consumption as a gauge to the way it's running and in this case a gauge as to the performance of the QF 735 v Holley S/A 670.

It looks like your revs are fairly close to mine with a 3.25:1 diff. @ 2700 at 60. I don't often get to drive on the 401 to get a cruising rpm at 70, but it is around 3200 I think.

If you think about it fine, if not no worries.

 

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