Hey, i've got the 5.5 power valve i put in mine since i'm pull 14lbs of vacum at idle so divide by 2 is 7 then minus 1.5= 5.5 power valve. I took the 51 jets mout put some 54's in made popping go away for awhile but not it's look like i may need to step the jets up to 55 or 56 maybe weather change or something making it run a tad leaner then before? oh and i have a 31 size pump shooter if i remeber correctly it used to be 25 then i changed it to a 28 now i'm seeing if the 31 is working for me. It feels faster with the 31 shooter on it but i still have a ppunch it to the floor hesitation i'm thinking my next course is changing the pump cams. i've been fidling with vacuum secondary springs also. We'll have to swap idea about the carb so i can fix my problems and help you fix yours maybe.

Kev

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Thanks for the info Kev. My 390 has 59 jets, 8.5 power valve and a plain vac sec spring in it. I don't know what size shooter it's got, can't see any numbers on it
I think the guys that rebuilt this carb did it to suit my engine, but I think I'll be changing jets and PV. I kinda get the feeling that they just put in what they had handy. 59's seem a little big, but I am running 63's in my 350 Holley now, so we'll see how it runs when I finally get it on the car, hopefully this weekend.

Cheers, Jon.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

I have an update for ya. I set aside some time for tinkering tonight since it dawned on me since you got the juices flowing about carbs. After worked i did a 1st gear pull didn't come alive till maybe 4000rpm which i thought was weird. That got me think eh maybe i can't fix the hesitation at this moment but i can fix this so i pulled the stock silver spring out of the secondary put in the purple (lighter spring) 75% hesiatation instantly gone and it pulled harder all through the gear so i put the lightest spring i could put in and some more hesitation gone so now the car pulls harder. I think i'll go to the track next wed. i have renewed zeal and ideas to get this tuning done i've been so busy lately i'm making some time now. JUst wanted to let ya know. Ya 59 jet sounds a bit big i mean i'm not saying my motor is some kind of beast but it runs good and a 59 would be too rich i would think.

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390 Holley is on and running, not tuned 100% yet but not far off. I went to a carby place on Monday after playing with the mixture settings on Sunday night. I was able to get some A/F readings done, unfortunatley I don't know exactly what they were, but the carby guru there just told me that at idle it's a little bit lean, which is fine. Then we checked it at 3000rpm just to see if the primary jets(59's) are too big and it's not running rich at all. It's all good.
I couldn't help myself so I took the car down to the track on Monday night, just to see how it would go with the carby as is. A little dissappointing really. Previous fastest with the 350 Holley 15.582@87.45, with the 390 15.501@88.83. Track conditions were pretty much the same both times temp wise but the earlier run with the 350 was in 49% humidity and Monday night it was 71% humidity. I'm hoping that played a big part in not going much quicker. Any drag racing experts want to comment on this?
I checked the plugs after each run and they were clean as a whistle.
So now I've got a starting point, with room for improvement.
Since Monday I've now found out a few things that definitely contributed to not such a big improvement. I've worked out that the secondary barrels are only opening 2/3 of the way (quick change vac sec spring kit is on it's way) I'll play around with some lighter springs, that should improve things a bit.
I've also changed the position of the screw on the pump cam from #2 to #1 and that has made a good "off the line" difference. Next might be an increase in shooter size, but at this stage it feels OK............but could a bigger one be better??? I might try the 31 shooter out of the 350, no harm in trying these things. Luckily I don't have any hesitations or any problems right now, I'm just looking to improve things. Any more ideas are welcome.
So that's where it's at. Even without the secondarys coming in ie just driving it as a 2BBL carb it's so much better than the 350. Stomping it from idle with the 350 it would take off, stomping it from idle with the 390 the car loses traction for a bit then takes off.

Also forgot to add that I swapped out the 85 PV for a 65, I'm only pulling 9 inHg of Vac at idle in gear (14 in Neutral)

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

Just adding to an old thread here in hope that I might get some ideas and help from you guys.

Since my last time at the track I've gone from the locked 3.7 gears back to my open centre 2.92 gears, I know, not good for drag racing but the owner of the 3.7 diff wanted it back. Anyway, the best I ran with the 2.92's 18 months ago was a 16.37@84mph. Since then I've replaced the 350 Holley with a 390 and added a Crane Hi-6 ignition, i didn't think it was too much to hope to run at best a 15.99 but the best I could get was a 16.22@85mph. I'm wondering why the addition of the 4BBL carb hasn't really improved things performance wise???
While I was at the track I played around with secondary springs and the short yellow spring produced the quickest times so I think that side of things is fine.
As I said in my previous post I only went 0.08 sec quicker with the 390 and 3.7's, I guess at least this time I went 0.15 sec quicker. Am I being too optimistic or is this small amount of improvement to be expected???
Oh and the addition of the 390 has not really improved the 60' times, but on the street is feels quicker off the line??
Any thoughts on all this are greatly appreciated.
Cheers, Jon.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

That all makes sense. For a torque motor, changing axle gears doesn't make a big difference. You would have to have better head and cam to use 3.7 gears more effectively. Also, the Holley 2bbls (350 and 500) work VERY well on Slants. I would expect only a small gain from the 390 swap.

I swapped from 3.00 to 3.55 gears in my Valiant a few years back and the ET was almost identical. 60 ft and MPH was a bit better, but ET was only 0.05 better.

I'd say get a better flowing head, a bit higher comp, and a bit bigger cam. Head will be the main thing - spend money on big valves and porting. Cam Tilley in Sydney could either do the head or know where to have it done right.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks for the reply Lou.
I kind of feel like the 390 was a waste of time really. I just thought, and was told, that the 390 would liven things up. The head on this engine has had some work, port 'n pollish etc. with Ford SB Windsor valves. Maybe that's not enough. I am still running pretty low comp. too.
The 3.7's did make a big difference, went from a 16.37sec ET to 15.58sec with just the gear swap.
I think the 350 might find it's way back into active service soon.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

Well I almost got into the 15's with my 2.92 gears. I was racing at the Nostalgia Drags last weekend and my quickest pass for the day was 16.18@84mph. Unfortunately I was eliminated in the third round, I broke out, ran a 16.292 on a 16.300 dial in......damn it!!!!
I'm sticking with the 390 Holley, mainly because I sold my 350, but also because I'm having a higher comp head put together to try and get more out of the 4BBL carb.
I find it interesting that my 60' times are only about 0.15sec slower with the 2.92 gears when compared to the 3.7 gears. Hardly seems worth the annoyance of high revs on the freeway.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

Just giving you guys an update here. I finally ran a 15 sec 1/4 mile with 2.92 gears......yay!!!
I got to run my car down the track last night, first time with the new higher comp head. As you have read my goal was to run 15's with my 2.92 open centre diff. I'm trying to get a good balance between cruisey and quick.
Previous best with old head and 2.92 was 16.18 @ 84mph. First run last night 16.04 @ 86mph , then I remembered I had the purple spring in the carb secondary barrels I use that spring on the street to keep the fuel consumption down. Swapped that spring for the short yellow one to bring the secondaries in earlier and bingo 15.79 @ 87mph. then another run 15.73 @ 88mph. I'm happy. Compression is my new best friend.

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62 Valiant, 225cid Slant 6/PB 904 with lots of good bits

http://www.moparmarket.com/readersrides ... user=SV162

Nice work! I have done this on my '68 Dart (15.90s back in 1999 or so) with 2.94 gears and it made for a nice street combo. Hoping to get my Slantkota truck into this range with 2.76 gears...

Cheers!

Lou

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Home of Slant6-powered fun machines since 1988