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post #1 of 15 (permalink) Old 07-15-2018, 08:23 PM Thread Starter
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BP 306 Runs Rich

I have a Blueprint Engines 306 in my 65 Merc Cyclone. (car came with this engine installed) It had 77 miles when I bought it. It has 250 miles now.



The previous owner installed the factory 289 cast iron exhaust manifolds on the engine due to clearance issues.



The engine has run rich since I've owned it, especially when cold before the choke activates. The fuel economy is very poor. It's not as bad when the engine has warmed up but is still rich. I back the car into the garage and the smell goes into the house. (attached garage). The engine has a 180 thermostat and runs at 170 degrees.



I've been working on other issues so I hadn't addressed this one yet.



Could the cast iron exhaust manifolds be causing this problem (lack of exhaust flow)?



Should I install smaller main jets (2 sizes) to correct this?
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post #2 of 15 (permalink) Old 07-16-2018, 07:27 AM
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Re: BP 306 Runs Rich

if it is rich at idle, the jets wont affect it. first thing to do is check float level
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post #3 of 15 (permalink) Old 07-16-2018, 03:36 PM
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Re: BP 306 Runs Rich

And the carburetor is a ......?

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post #4 of 15 (permalink) Old 07-16-2018, 04:31 PM
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Re: BP 306 Runs Rich

Sounds to me like you need to dial in the carburetor- it was probably never done. Get the manual for it and make all the proper adjustments.

1964 Thunderbird 390 V8, AOD, F.A.S.T. EZ EFI 1.0, Victor intake, MSD Ignition.
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post #5 of 15 (permalink) Old 07-16-2018, 07:19 PM Thread Starter
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Re: BP 306 Runs Rich

I forgot to mention I turned the idle screws in 1/8 turn. I didn't have a vacuum gauge attached (not sure which port to use for that) .
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post #6 of 15 (permalink) Old 07-16-2018, 07:28 PM Thread Starter
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Re: BP 306 Runs Rich

Quote:
Originally Posted by Iowan View Post
And the carburetor is a ......?


Ha Ha. Yeah, I think the carb is kind of important. I think it's a vacuum secondary Holley 4160. Thanks for the reminder

Last edited by 65merccyclone; 07-16-2018 at 07:31 PM.
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post #7 of 15 (permalink) Old 07-16-2018, 07:40 PM Thread Starter
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Re: BP 306 Runs Rich

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Originally Posted by extech View Post
if it is rich at idle, the jets wont affect it. first thing to do is check float level

I'll take a look at that. Thanks
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post #8 of 15 (permalink) Old 07-17-2018, 09:26 AM
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Re: BP 306 Runs Rich

Blueprint sets their engines up conservatively since they will be run under different conditions around the country. That means that the as delivered jetting tends to be on the rich side.

I have their 347 with the same carb, etc as yours. It also ran rich. Here's what I did.

1. Set the choke two notches lean from the "zero" position.

2. Jetted down 2 jet sizes

3. Idle screws set a 1-1/2 turns out from zero.

4. Installed spark plugs that are one heat range hotter. This means Champion C61YC or equal.

You also may find that you can advance the timing 2 to 4 degrees depending on the quality of the gas in your area.

1966 Falcon, 347 stroker and C-4
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post #9 of 15 (permalink) Old 07-17-2018, 12:59 PM Thread Starter
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Re: BP 306 Runs Rich

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Originally Posted by falconfred View Post
Blueprint sets their engines up conservatively since they will be run under different conditions around the country. That means that the as delivered jetting tends to be on the rich side.

I have their 347 with the same carb, etc as yours. It also ran rich. Here's what I did.

1. Set the choke two notches lean from the "zero" position.

2. Jetted down 2 jet sizes

3. Idle screws set a 1-1/2 turns out from zero.

4. Installed spark plugs that are one heat range hotter. This means Champion C61YC or equal.

You also may find that you can advance the timing 2 to 4 degrees depending on the quality of the gas in your area.

Falconfred,



Excellent. That is really good advice and will provide a great starting point. Thank you very much.
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post #10 of 15 (permalink) Old 07-17-2018, 05:21 PM
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Re: BP 306 Runs Rich

Check the float levels as well. The fuel bowls may be overflowing into the venturis.

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post #11 of 15 (permalink) Old 07-17-2018, 09:33 PM Thread Starter
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Re: BP 306 Runs Rich

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Check the float levels as well. The fuel bowls may be overflowing into the venturis.

Will do. Thanks for the tip.
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post #12 of 15 (permalink) Old 07-24-2018, 07:13 PM Thread Starter
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Re: BP 306 Runs Rich

Quote:
Originally Posted by falconfred View Post
Blueprint sets their engines up conservatively since they will be run under different conditions around the country. That means that the as delivered jetting tends to be on the rich side.

I have their 347 with the same carb, etc as yours. It also ran rich. Here's what I did.

1. Set the choke two notches lean from the "zero" position.

2. Jetted down 2 jet sizes

3. Idle screws set a 1-1/2 turns out from zero.

4. Installed spark plugs that are one heat range hotter. This means Champion C61YC or equal.

You also may find that you can advance the timing 2 to 4 degrees depending on the quality of the gas in your area.

I thought I would provide an update


1. I already had the choke set to where yours is set.



2. The documentation I found on the net indicated the 4160 carb comes with #64 main jets so I ordered 62's.They arrived today and I started replacing the jets. I soon found there were #66's in this carb so I had jets that are 4 sizes smaller.



Since I had it taken apart, I installed the #62's and went for a test drive. It stumbles when I accelerate so it looks like the #64's are what I need. I'll order those tonight.



3. I turned my idle screws in until the engine started to die, then backed them out 1/8 turn. They are now set to 1 full turn.



4. I'll be replacing the spark plugs tomorrow. I also pulled a plug and the outer rings is fouled but the tip is white. It looks like it had a .40 gap on it.


I checked the timing. With the vacuum advance plugged, it's at 12 degree BTDC. With vacuum, it looked to be 36 degrees. At idle, it makes 15 lbs of vacuum.
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post #13 of 15 (permalink) Old 07-26-2018, 07:11 AM
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Re: BP 306 Runs Rich

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Originally Posted by 65merccyclone View Post
It stumbles when I accelerate so it looks like the #64's are what I need. I'll order those tonight.
It could actually like the #62's and just need more power valve. Holleys are highly adjustable and Webers even more.
You're actually contouring the fuel delivery curve through your rpm range with load compensation. When you get it perfect on Saturday night might be off the following Saturday. It's temperature, pressure, and humidity dependent. That's why serious drag guys record those number and the setup they were running. When the same conditions arise, they go to the combo that worked well, before. Now for your daily driving, you don't have to be that detailed. They're calibrated fuel leakers. Get it as close as you can and you'll probably be happy with it.

Learning and tuning your carb is a fun and satisfying project. Here are a couple vids from Holley.

https://www.holley.com/blog/post/car...b_tuning_tips/

https://www.holley.com/blog/post/hol..._valve_tuning/

Good luck,
Steve
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post #14 of 15 (permalink) Old 07-27-2018, 10:19 AM Thread Starter
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Re: BP 306 Runs Rich

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Originally Posted by kapnk View Post
It could actually like the #62's and just need more power valve. Holleys are highly adjustable and Webers even more.
You're actually contouring the fuel delivery curve through your rpm range with load compensation. When you get it perfect on Saturday night might be off the following Saturday. It's temperature, pressure, and humidity dependent. That's why serious drag guys record those number and the setup they were running. When the same conditions arise, they go to the combo that worked well, before. Now for your daily driving, you don't have to be that detailed. They're calibrated fuel leakers. Get it as close as you can and you'll probably be happy with it.

Learning and tuning your carb is a fun and satisfying project. Here are a couple vids from Holley.

https://www.holley.com/blog/post/car...b_tuning_tips/

https://www.holley.com/blog/post/hol..._valve_tuning/

Good luck,
Steve

Interesting commentary Steve, especially 'calibrated fuel leakers'.



This isn't even a daily driver, just a fun project car. I want it to run good and make the right power. I know running rich is wrong all around, so I'm trying to correct it. I'd like to take it to the drag strip but probably won't do that.



Regarding the power valve, it came with a 6.5. I've watched several videos and it seems power valve tuning is vacuum based. The timing on the engine, as I got it, is set to 12 degrees BTDC with the vacuum plugged. With the vacuum connected it makes a little over 15 lbs at 900 rpm. According to the videos, I should be able to install a 7.5 in it. Do you think this would be a good combo with the #62 jets?


Thanks for the comments. I used to have souped up VW's with webers. I spent some time getting those dialed in. I loved the sound those carbs make.
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post #15 of 15 (permalink) Old 07-30-2018, 04:11 PM Thread Starter
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Re: BP 306 Runs Rich

Quote:
Originally Posted by AdrianS View Post
Check the float levels as well. The fuel bowls may be overflowing into the venturis.

This turned out to be the biggest problem even though the level was only slightly off (high).



The plug gaps on the original plugs were between 35 and 45 (varying by plug). I installed new C59YC plugs that were properly set to .045 gap.



I also changed the wire connection to the HEI distributor after confirming it was a 14 gauge wire. I'm not sure if this helped or not but the HEI distributors have a specific requirement for the wire size.



the engine runs much better now. Just the slightest hint of odor at idle. I'll fill the tank and do a gas mileage check.



Thanks everyone for the advice.
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