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 Need Tuning help-Pro Systems-Big Block 
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Joined: Fri Jan 10, 2014 11:59 pm
Posts: 19
I've had quite a time tuning a new Pro Systems carb that I purchased. I've called Patrick and he does answer emails quickly, however what he has prescribed has not quite gotten me where I think I should be, with a custom carb.

After several modifications Patrick has recommended, I have a part throttle "gurgle" that seems to come in around 1800-2600 rpm, right where it's a pain during part throttle cruise. Also on the top end I have a little cutting out as well. My setup is fairly straight forward:

454 2 bolt main block-ARP main studs, ARP head studs, bored .030, torque plate honed, align honed, BHJ decked, cleaned, magged, etc.

Scat 4340 4.25 stroke crank, Scat H beam 6.385 rods and SRP -18.0 forged pistons, floating with Mahle file fit rings, Clevite H series bearings. 10.7 comp with NGK FR5 plugs.

Straub hydraulic roller 247/250 @.050 .631/.603 on 107, Morel 6403, AFR 290's, Air gap port matched intake.

Right now the carb is set with 83 primary jets, 95 Secondary. He had me enlarge the power valve feed on primary side to .070, upper emulsions were drilled to .035 on primary block (from .028) idle air bleeds .092 (is this too high) and high air bleeds .032

I've got a pretty rich smell at idle, more than what I would like. I've done a few test runs and plugs appear to be pretty decent, however I believe I'm going to get a wideband installed so I can better tune...

What do you all suggest? Thanks ! Jason


Fri Mar 11, 2016 12:36 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
Have you tried larger primary metering rods? :roll:


Fri Mar 11, 2016 2:53 pm
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Joined: Fri Jan 10, 2014 11:59 pm
Posts: 19
Uh oh...I did put in some old Carter rods I had laying around..Is that bad? lol....

Unfortunately this is quite new territory for me with some of the stuff he suggested....I was thinking this carb would have minimal work needed... :\'(


Fri Mar 11, 2016 2:58 pm
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Joined: Fri Feb 08, 2013 2:37 pm
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Carter rods? In a Mikuni? I heard that is the new trick of the week, but I haven't tried it.

What venturi and throttle bore sizes does your carb have? Is it really a Mikuni? Mikuni carbs are all perfect right out of the box, so I don't think that is what it might be. I thought Carter rods fit a Hitachi.


Fri Mar 11, 2016 3:19 pm
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Joined: Fri Feb 08, 2013 2:37 pm
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Your leg is being pulled because you didn't mention what size of carb you have. 4150, 4500, 750, 850, 950, 1000, 1050, 1150, 1250, etc. etc. Your ID is "Blownchevelle68" but you haven't said if your carb is for blow-through or draw through, or if it actually is supercharged or not. You will get the advice you seek, you just need to add a few more details.

:thumbl:


Fri Mar 11, 2016 3:44 pm
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Joined: Fri Jan 10, 2014 11:59 pm
Posts: 19
Oh wow...One of those days, forgot the most important piece...lol. Sorry I will get the build sheet and post soon. Thanks a million for the help (and ribbing) ;)


Fri Mar 11, 2016 4:06 pm
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Joined: Fri Jan 10, 2014 11:59 pm
Posts: 19
Hopefully this shows up


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Fri Mar 11, 2016 5:57 pm
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Joined: Fri Feb 08, 2013 5:50 pm
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What ignition, plugs, timing specs...


Fri Mar 11, 2016 11:43 pm
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Joined: Fri Jan 10, 2014 11:59 pm
Posts: 19
Timing is locked at 34 on Msd pro billet dist, 6A box and blaster coil.


Sat Mar 12, 2016 12:29 am
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Plugs? My first suggestion would be to lower the idle feed, link below. If you are not up to thread all holes find a machinist friend to help, last case I can do it for a small fee. Start at .035

viewtopic.php?f=25&t=18


Sat Mar 12, 2016 10:41 am
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