OK, looking for some advice from Nailhead guys. I've got a 1962 401 which has been completely rebuilt with new internals. It has a 60 over rebore and now has an Eelco dual-quad manifold with 2x Edelbrock 1405 600cfm carbs. Its running Geardrive torque tube style lakes headers with mild baffles. So it looks from the plugs as if its running lean. It goes well, but the plugs are consistently very pale cream in colour. I want to put bigger jets in, and maybe change the metering rods, but what size should I aim for? I don't have access to a dyno before that is suggested. Ball park is what I'm looking for. And with all due respect, please don't reply with comparisons to small block 350 Chevys - it's advice from Buick guys I'm looking for. Thanks Gus
I know railheads like lots of carb, but I find it hard to believe that a 401 would need more than 2x600 could deliver. The usual scenario is to step two jet sizes. I think that would be the most economical thing for you to try. Leave the metering rods as is.
If your plugs are cream colored... You are real close to perfect! I would go one step richer on the metering rods .... 2 jet sizes is a big jump on those. If it runs good and it doesn't surge at a steady cruise.. why change it? Sent from my Moto G Play using The H.A.M.B. mobile app
^^^^^ Agreed!! First get two Edelbrock carb tuning kits(one for each carb) with all the jets and springs and rods, go one step richer with the metering rods. drive it, see how it feels and check the plugs. Once you feel like you have a good mix, you can play with the metering rod springs to change the rate and timing of the enrichment from the metering rods. Don't forget you can change the rate of the accelerator pumps on the edelbrocks too. Play with metering rods and springs, your jets are close now and you can get real crisp throttle and even decent mileage if you take you time and fine tune it. Some people hate the Edelbrock carbs, I really like them and for me they are really easy to tune, but then again I hate any Holley that is not a 94....
I think you will find that reading plugs while using E10 (or more) gasoline is considerably different than with no-ethanol gas. I have been in your area, but do nor know how your fuel is mixed, most likely different than U.S. fuel. I use a wide band exhaust gas ****yzer to determine A/F correct mixtures.......my '65 Nailhead is happy with a single 1405 carb and box-stock jetting using E10. I am not too far off sea-level....if I remember correctly, you are in the midlands......higher al***ude mixture. Remember that you need to check the A/F mixture at higher RPM, not while in the idle circuit. My experience with Nailheads is they tend to run rich with stock carbs, factory jetting....never saw one run lean.
I'll ignore the insult to the proud Scottish nation (LOL - the Midlands always refers to a part of England) but I always use premium fuel rated at 98 or above that uses very little ethanol. Checking the A/F ratio is exactly the problem, as I don't have that facility on my car. See pic for reason 1930 Model A by EvilGus posted Apr 4, 2018 at 8:29 AM
cant help much with your issue. but I like the look of your ride and your engine. Grats on the Eelco intake. best out there for Nailneads. What cam are you running in that?
Things changed when lead came out so plug reading isn’t the same ,take it to a dyno and get the mixtures and timing done for the fuel your using.
Sorry about the midlands reference.......my friends there are actually displaced Brits.... (of the House of Stuart...isn't everyone?).....oh well..... I stick the probe in the end of the pipe when there is no bung for the sensor. Looks like you could do that for each bank....left and right collector tubes......maybe someone there has one you could borrow? BTW......great looking Model A!!
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