rough idle? is it too lean? Easy test:
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,017
Likes: 79
From: central FL, near the beach.
rough idle? is it too lean? Easy test:
Today i came up with a new test, rare for a guy 55 
So my 61 just came out of 3 yr+ storage 355 Magnum 270H 224/224
Has a choppy idle at 800.
at 550 is shakes badly. Not that i need a 550 idle, but just to test my idea. the mixture screws don't have any effect as i turn them from 2 to 3+ turns out. this indicates a lean IFR hole(it is .028"now). Before i drill it, i want to confirm it will fix it.
So i take an eyedropper with gas and drip it in both barrels; it smooths out, no more shake, but choppy at 550 like it was at 800.
easy test even a novice can do.
So my 61 just came out of 3 yr+ storage 355 Magnum 270H 224/224
Has a choppy idle at 800.
at 550 is shakes badly. Not that i need a 550 idle, but just to test my idea. the mixture screws don't have any effect as i turn them from 2 to 3+ turns out. this indicates a lean IFR hole(it is .028"now). Before i drill it, i want to confirm it will fix it.
So i take an eyedropper with gas and drip it in both barrels; it smooths out, no more shake, but choppy at 550 like it was at 800.
easy test even a novice can do.
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,017
Likes: 79
From: central FL, near the beach.
so here is another easy test available in person in my $1000 a day seminar
Look down the throats and turn up the idle until fuel flows from the 2 front boosters. on my 72 it was 1500.
3000 NOTHING!
3500 RT booster ONLY
4000 still NOTHING from left! And it is shaking.
so there u have it, after 3+ yrs in storage, i'd better fix this before i go for a ride.
Look down the throats and turn up the idle until fuel flows from the 2 front boosters. on my 72 it was 1500.
3000 NOTHING!
3500 RT booster ONLY
4000 still NOTHING from left! And it is shaking.
so there u have it, after 3+ yrs in storage, i'd better fix this before i go for a ride.
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,017
Likes: 79
From: central FL, near the beach.
the re-usable metering block gasket looked fine, but after 14 yrs it lost its' springiness.
so i replaced it
Left booster 2700
Right 2500
Big improvement, but they should be equal!
i stuck my finger in the L venturi at 2500 and flow came right out, and it got real smooth, indicating it was too lean. not a big surprise -how can it run right with no gas from one side? also i have #55 jets no spare fuel!(down from 60 stock.) This problem may explain why the O2 sensor cross jetting indication on my 61 was OPPOSITE my 72. This carb is not pulling equally. anyone see this before? ideas appreciated! EDIT: using drills as a go/no go gauge, i checked the booster holes, 0.111 fit in the right, but only .102 & .106 in the left. casting flash causing the problem?
venturis checked out =
.
(I also sprayed carb cleaner thru the bleeds and block).
so i replaced it
Left booster 2700
Right 2500
Big improvement, but they should be equal!
i stuck my finger in the L venturi at 2500 and flow came right out, and it got real smooth, indicating it was too lean. not a big surprise -how can it run right with no gas from one side? also i have #55 jets no spare fuel!(down from 60 stock.) This problem may explain why the O2 sensor cross jetting indication on my 61 was OPPOSITE my 72. This carb is not pulling equally. anyone see this before? ideas appreciated! EDIT: using drills as a go/no go gauge, i checked the booster holes, 0.111 fit in the right, but only .102 & .106 in the left. casting flash causing the problem?
venturis checked out =
.
(I also sprayed carb cleaner thru the bleeds and block).
Last edited by Matt Gruber; Oct 24, 2007 at 11:08 AM.
Thread Starter
Race Director
Joined: Oct 2000
Posts: 15,017
Likes: 79
From: central FL, near the beach.
