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New Engine start up
I’m going to start up the new motor next week. I’ve taken one of the webers apart to see what’s in it. I will list the existing parts and what I think they should be changed to. I would appreciate any and all comments. I’ve gone over the Weber Jetting Survey and based my assumptions from there. Too bad there were no 427’s.
427 W hydraulic roller 230/289 @ .050 110 separation total lift .523/549 existing proposed choke 37 40 emulsion tubes f7 f7 main jets 135 150 air correctors 120 120 pump jet 50 50 idle jet 70 65 idle holder 120 120 by pass ? I understand the by pass is under the float. I took it out and there is no number on it. I can blow air through it towards the pump but can’t suck air back. Seems like a check valve. And it could be a 000. (No back flow). On another note I noticed the one carb I have taken apart has 3 transition ports just above the throttle plate. They are at 12/3/6 o’clock and 12/2/6 o’clock. I have been following the tread Webber Transition Ports and see that mine are not symmetrical. These are new out of the box so it seems the factory is not worried about being precise. Also the float is plastic. Thanks for the help. |
On my 48 IDA's, 2 lbs of fuel pressure, phenolic adapters. 38 degrees full advance on the timing. sync the carbs first then adjust the a/f mixture.
very important... fire suppression system. I use a 5 lb Safecraft halon bottle It seems like alot of weber guys have issues with boiling gas, maybe newer gas boils at a lower temp, I turn the fuel pump off a minute or so before turning off the engine. That seems to help. I run mine without air filters. but have to be aware of low flying birds and small deer lolol. I'm getting about 7 mpg. nothing sounds as good as a big block with webers when its winding out. Have fun. |
I've been driving for 2 days now. What fun!!! I want to wait a couple of hundred miles before I start the real tuning. So far it all feels real good. The only issue is cruzing at 2000 rpm. Lopy or miss fire. Not real bad, just minor.
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Tom,
Yes, you're correct with the bypass, no numbers and no holes in the side is a 0.00. You need a wideband O2 data logger to trap the A/F ratio you have at 2000, but by the sounds of it, you have the dreaded Weber gremlin. Progression hole inaccuracies do not help. How have you gone with carb balancing, mixture screws (turns out from seated etc)? |
Lemans24,
Well I have the dreaded boiling gasoline. I started to do the tune with a hot engine that was turned off. I leaned over the engine to get a tool and heard the boiling. Looked down the venturies and saw the squirters squirting and drips coming out of the auxiliary venturies. Pools of gas on the butterflies. I’m going to check the needle valves for construction debris first. Then I’ll make some spacers from 1/2 inch Lexan to curb the heat flow hopefully. Gary, I do have an O2 logger setup. Been waiting for 200 miles of break-in which I got Monday. Balancing is close but not final. I think mixture screws are 1 1/4 out. I'll start moving them towards 3/4. Timing is 36-38. I saw the progression holes in only one carb so I will now check all of them. Thank you guys for the input. |
be aware of cylinder wash. If your dip stick smells like gas, change your oil. I will turn the engine over a few times without starting to clear out gas that is sitting on top of the butterflys. A Porsche guy told me they sometimes put a switch to turn off the "spark" so the carbs can clear out
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some explanation on boiling gas http://www.eps-hane.com/techtips5.html
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Lemans24,
You are right. The oil smells like gas. Got the spacers done. Will put them on tomorrow. http://www.clubcobra.com/photopost/d...insulators.jpg While the carbs. are off I started adjusting the floats. Made my own gauges and got the first one done at 5.5/24. Then noticed a number on the float, 25.5. To me that could mean two things. One, replace the 24 with 25.5. Two, replace the 24 with 25 and replace the 5.5 with 5. I measured the next carb. And it is 5.5/25. What do you guys think? http://www.clubcobra.com/photopost/data/500/Float.jpg |
25.5 refers to the float weight.
25.5 grams. |
Thanks carmine,
The one float was off 1 1/2 mm. I'll adjust the other 3. |
Well so far the plastic spacers are working. No boiling gas!! The carbs. are cool enough to touch with my hand. Before they were too hot to touch. Got a good synchronization on them now. I did the Carburetor set up and lean best adjustment. Got 1/4 turn out on the speed screw and 1 turn out on the mixture screw. I’m thinking the speed screw is not right. I’ve been setting the speed screw to 2000 rpm and turning the mixture screw in and out to indicate rich/lean for the idle circuit. Not real obvious. Seems like I’m to lean with 65 jets. I think tomorrow I’ll start over then use the LM2.
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Tom,
Sounds like you know what you're doing. Spacers made of Lexan, wow, can you see through them on the engine? If your oil has smelt like fuel, I'd be changing it, and pulling the spark plugs out for inspection, maybe start with a fresh set now you're closer on your tune. |
Tom:
You need to adjust for best lean idle condition with the idle speed as low as possible - 750 rpm or so. 2000 is way too high. |
Gary,
I did not polish the edges of the Lexan so you can’t see in the engine. But when the engine backfires up the carbs,the Lexan lights up like a light bulb. Scared me at first, I thought it was flame. I changed the oil and filter. I forgot about the sparkplugs, thank you. Zimmy, You're right. I tried both rpms and the lower did work better. The 2000 rpm is to be sure you are in the idle circuit for tuning that. But that didn’t work for me. The 700 rpm is the lean best tune. I was trying two different things. I ran the LM2 and got 2000/11.7 2500/11.4 3000/11.6 3500/12.3 Looks rich to me. I did not have a smaller idle jet. So I changed the choke to a 37 from a 40. Made it richer, lots of popping cruising at 2000 rpm . Today I’m changing the idle jet to 60 from a 65. |
Quote:
I can see you're checking for mixture strength and the effect the mixture screw has as a "trimmer" while at the mid point of the transition circuit. Not many do this, but a very good test to prove which way to go. Throw in your 60 idle, and your 40 chokes, or 42s if you can get them. I run 38s in a 308. I'd bet that 427 with a 230@.050 roller and quad IDAs is real torquey combo. |
On your linkage, make sure you push the gas pedal all the way down to the floor with out having it connected to the carbs (holding it to the floor), then work out the length of the linkage to the bell crank etc. so as to not pull the linkage too far when flooring it.You probably already thought of that, but I would hate to see your carbs get stuck wide open.
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Gary,
I put in the 60 idle and the 40 chokes and A/F went to 18/21. I really thought I was going the right direction. Not. I could hear detonation. I now have everything back to first startup. Major popping at cruise speed 2000/2500 rpm. Maybe air leak? I’ll check around spacers and header gaskets. Then keep adjusting mixture screws 1/4 turn at a time and drive. I punch it in 3rd and it feels like it's trying to leap off the road and fly. I think the rear tires are braking loose. Lemans24 I’m glad you brought that up. On my list but forgotten. I’ve got a place I can put in a throttle stop |
Tom,
Leave the 40 chokes in and put the 65 idles back in? Maybe your 37 chokes with an F7 on a large motor creates an early main system and hence a rich overlap at 2000 - 3000 rpm. |
Found the air leak. All 4 left side spark plugs not tight. All 8 plugs not gaped to 40. Stupid. Stupid. Stupid. I’ve seen it in print on this site. “It’s not the webers it’s something else.” I drove around and 1/4 turned the mixture screw. I am now at 1 1/2 turns out. No more popping. It’s running good. Not great but good. I have not checked A/F. I hope it’s rich, it feels like it.
I have to fly out of town tomorrow for 3 weeks. When I get back I’ll jump in and continue. Will post my progress. Thanks for the help! |
Hi Tom.
Hope you have it running good. No, it's not the Webers, it's the condition & tune.... I wonder. You say AF was 18- 21. Was this when idling? On Idle, the mixture can be quite lean without any danger or problem. The AF on light, cruise/part and full throttle is what you should check. On the popping/ not running well issue: In my experience, it is VERY easy to have a too fat idle (idle screws too far out or too big a jet). This will cause the plugs to foul, and the plug won't fire at throttle and hence a stumbling and weak engine. I's not always easy too see this problem by analyzing the plugs. The only way I found to work is to "measure" the temperature of header primary tubes (either by hand (ouch!...) or spit/water, or by an IR- meter). All should be equally HOT! when idling. On a hot engine very little gas have to enter the throats on idle. (I moved down from 65, as some said to be correct, to 50 in idle jet and finally got the engine to run right.) RS |
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