I've heard and read from some of the slant guys that the 390 appears to be an excellent choice 4 barrel for a mildly hopped up 225. After our rebuild we went with the 390 and the motor has never sounded better. Now during our couple test drives down the street and back the car has a low end flutter under light acceleration. I was just curious as to how some of you guys have your 390's jetted? Accelerator pumps information?? etc... Once we open up the 4 barrel under heavier acceleration, it's time to hang on to the wheel. haha

Thanks guys in advance!

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Linder Tech.com
Bubba's Trailer Park

The Holley website should have a chart of the profiles and shot size for the acc pump cams...I think stock yours has an orange 466 cam in it... you can always "up" the cam by removing the cam screw out of the throttle arm and putting it in the #2 position for more shot (if you get a big puff of black out the back the shot is too big), if that covers the "hole" then things are ok (but check plug for color when doing carb changes).
The holley should work fine with 51's in the primary (some heavier builds are closer to 53's for primary jetting)...spending the money on a secondary metering block allows you to tune the secondaries sooner...also if you get the secondary quick change pod and spring kit, you can adjust how "soon" the secondaries kick in...so far I use the black spring to lock out the secondaries for tuning the primaries, purple spring for daily driving, and tall yellow when gas mileage doesn't matter but speed/power is needed for "short .25 mile road tests"...

Getting a Holley carb book will help a bit, mostly because they have all the charts in one place, as well as some nice pictures to help you see what's going on...


If the flutter is really low down like in the transition circuit, you can try to unscrew the idle screws out another 1/4 to 1/2 a turn to see if that cures it, if not, you may have to modify the transition slot in the base of the carb (widen with emery cloth slightly), or play with the restrictions in the primary metering block...

good luck,

-D.Idiot

Does the flutter happen at the same manifold vacuum reading each time it happens?
What size power valve is in the carb.?
Drive the car around with a good vacuum gauge attached, that will tell you a lot.
DD

Terrific info, thanks for the tips.

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Linder Tech.com
Bubba's Trailer Park

We do have a vacuum gauge on the car, but I can't remember what the reading was. The carb is probably stock off the shelf, but we haven't opened it up yet to see what we're currently using for the power valve or jets.

Driving wise though the flutter is in the same 0 to "x" percentage of throttle. We'll know more specifics after we look into it. It's next on our little list of tuning improvements. I appreciate all you guys input and suggestions to help our little slant run and perform good.

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Linder Tech.com
Bubba's Trailer Park

is to see what is in the carb so you can take some notes and have a base line...also if it's an older Holley (pre-1992) it will require a backfire valve installation so you don't blow the power valve during a carb backfire (7 dollar insurance...post 92 carbs already have one installed)...checking the vacc. reading at that level will also tell you a few things, especially if the vacc. drops off and opens the power valve for enrichment and floods things out at that time (that carb stock should be a 6.5" valve...most guys swap to something lower like an 8-10 depending on build and vacc. reading at idle and in the power band/cruise).

Another good "buy" is getting the master rebuild kit they offer at $70...it has enough cams/springs/gaskets/etc... to rebuild/retune the carb quite a few times and make lots of changes (considering I used to go through a few $20 rebuild kits for gaskets and things, that wasn't such a bad deal and I have some spare gaskets for the Holley 2300 2 barrel guys when they stop by to visit...)


-D.Idiot

Where could I find a Four Barrel Carburetor for my 225? I can't find a four barrel intake manifold either?

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John C. Venturino Jr.

turbo, you can post in the parts wanted, look on ebay (there a four barrel manifold on there now), JC whitney has Offy, depends on which one you want.

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Excuse me, does this smell like chloroform to you?

Awesome. We'll take notes upon pulling it apart and I'll update with our findings.

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Linder Tech.com
Bubba's Trailer Park

Thanks for the help again. We got the car out last night and did a couple of those .25 mile test's down the road and back. We got the easy change spring kit and found we were happiest with the yellow spring. Car ran really good, a very small amount of black smoke dumping the throttle wide open and all the low end flutter that we noticed is gone. Growing up pop's always believed in running them just a tad on the rich side as opposed to too lean. We'll sacrifice that extra couple miles per gallon and probably leave the yellow in for now and get some road time on the car and break the motor in.

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Linder Tech.com
Bubba's Trailer Park