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SOUTHWIND377
01-22-2002, 08:21 PM
I want to see if anyone is running a similar combination and what they are baselining ther tune-up on. I have a 454 with a compression ratio of 7.25 to 1 with a mild cam around .580 lift, cast-iron rectangular port heads with 2.25/1.88 valves and some pocket works. Littfield 6-71 with two 850 double pumpers top it off, I am running 12-13 psi on boost and about 38 degree timing. The problem is I am super rich at and idle but it has power valves in the primarys and the secondaries are blocked off. The jetting is at 78 on primaries 90 on secondaries. BDS and Littlefield said block of the power valves and square it off to 76 on both. I just don't know if I want to make a drastic change because it runs good on the top end but it could be a little fat not sure. Does anyone have a similar set up any info will help. Thanks

Craig
01-23-2002, 04:29 AM
I run a B&M 420 on a 509 with 2 Holley 750's. Jets are 78 all around. We came to that jetting on the dyno. Runs good and doesn't load up.
Craig

SOUTHWIND377
01-23-2002, 07:13 AM
Craig what kind of boost, and fuel are you running? I am just wondering if I should square them off @ 78 or go mabey with 80's squared off and then work from there since I have a little bigger carb's.

Infomaniac
01-23-2002, 07:15 AM
SOUTHWIND377 If you are too rich at idle, do not look anywhere else but the idle circuit. You need to see where the throttle valves are in relation to the transfer slots. If there is more than a few thousandths of transfer slot showing, you need to open up the hole in the butterfly valves.
Also the basics, float level adjustment and idle mixture screws cannot be overlooked.
If the powervalves are leaking (blown due to backfire)it will cause this condition also. I choose to not run powervalves in blower applications.

SOUTHWIND377
01-23-2002, 07:30 AM
Infomaniac, thanks for the advice the float levels and idel mix. I have checked, I wasn't aware until Sunday afternoon that what ever shop setup the carbs for me left the power valves in the primarys. I no that the motor has sneezed a time or two so I am assuming that they are probably blown. My main problem is that everyone I talk to has there carbs squared off, when I got mine back they had 78/90. I think that is to much difference between primaries and secondaries. I have thought about going 80's or 81's squared of after blocking out the power valves. What do ya think? I appreciate the advice guys!

sgdiv7
01-23-2002, 07:33 AM
I did mine a little different, I jetted my primarys to run the best at cruse. My engine runs at 10 in. vacuume at cruse then I used the secondary jets to tune the fuel mixture for WOT. I have manifold ref powervalves. mech pump w/ 7 1/2 lbs fuel psi. I run just a little on the rich side and I use a knock sensor for insurance.
Bill

Infomaniac
01-23-2002, 07:43 AM
SOUTHWIND377 Sorry I thought your problem you asked help with was rich idle.
As far as jetting goes. If it runs good, so what about everyone elses jetting.
I do think yours is jetted way rich.
If you are actually needing that much jet (tuning the engine has led to these jets) I would say you are having problems getting enough fuel to the carbs.
If this is just the jets it came with. I would say take out the powervalves and leave the jets alone until you get some tuning time.
I choose to stagger the jets for fuel economy. You drive around with the primaries so I jet them down. Just make up for it with the secondary jetting.
To keep your tuning nightmares to a minimum. Do what I recommend with the powervlaves and tune for wide open with the secondaries. You will probably end up with about an 82 in the secondaries.
Just my opinion
Oh Yea: That is quite a bit of timing. Hope you have race gas. If not you better back it off if you start leaning down the mixture.
[This message has been edited by Infomaniac (edited January 23, 2002).]

Craig
01-23-2002, 04:17 PM
Originally posted by SOUTHWIND377:
Craig what kind of boost, and fuel are you running? I am just wondering if I should square them off @ 78 or go mabey with 80's squared off and then work from there since I have a little bigger carb's.
Boost is about 8 pounds, fuel is av-gas all the time, only because I have flat top pistons(9.3 CR) as opposed to the dished my engine builder prefers. I also run 34 degrees advance locked in, hence the av-gas.
I think the whole key is the dyno. This is the second motor I've had set upon the dyno and both were turn key from day one. The 509 only has that blower surge that takes some getting used to when shifting. $500 well spent in the grand scheme of things http://free.***boat.net/ubb/biggrin.gif
Later,
Craig

RumRunner
01-23-2002, 04:19 PM
Are your power valves boost referenced ?
Do you have vacuum at idle ?
Hve you checked your intial butterfly settings ?