Tricarbs are sweet. Makes for eye candy at the car shows. I entered 3 judging shows and came home with 3 trophies. I think it was the tripower set up that did it. The joys of multiple carbs are that you have endless time making adjustments. I use Webers ICT/ICH combo. The beauty of Webers are that there’s a lot of adjustments. The downside is that there’s a lot of adjustments. A wideband 02 made tuning much more accurate.
All Small Six Winter Project: Better breathing with a large log
- Thread starter awasson
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- large log head
This relates to all small sixes
Oh no… it’s happening. Scope creep. I’m starting to seriously consider multiple carbs. Maybe I ought to have the log machined for 3 openings and bolt covers on the outside ones so I can go with the Weber to begin with and then expand to multiple carbs later. I really want to have the head done for next spring.
In terms of running multiple carbs, I figure/hope it’s dialing them in that’s the work. If the linkage is good, they should remain in tune. My hot rod BMW had twin Mikuni 44mm side drafts. I put them on, dialed them in and drove the car for many years without needing to do anything aside from plugs, points and oil changes. My motorbikes are all multi-carb’d as well and I’ve never had carb balancing issues. I would think cab balancing would be less of a critical issue on a log than if each carb was a closed circuit on each cylinder too.
In terms of running multiple carbs, I figure/hope it’s dialing them in that’s the work. If the linkage is good, they should remain in tune. My hot rod BMW had twin Mikuni 44mm side drafts. I put them on, dialed them in and drove the car for many years without needing to do anything aside from plugs, points and oil changes. My motorbikes are all multi-carb’d as well and I’ve never had carb balancing issues. I would think cab balancing would be less of a critical issue on a log than if each carb was a closed circuit on each cylinder too.
3 is just more than 1. Cool, but more of everything, adjusting, 3 to keep clean, three to keep functional, the kits to rebuild, 3 fuel lines, three linkages. I had to adjust mine about once a yr. Sometimes 2x. Since most i6 headers don’t split the cylinders front and back, I would think the only way to adjust the mixture would to be do them all the same turns out on the screw. But carbs adjustment just isn’t like that, they will be close to the same, but they are just a little different
3 is just more than 1. Cool, but more of everything, adjusting, 3 to keep clean, three to keep functional, the kits to rebuild, 3 fuel lines, three linkages. I had to adjust mine about once a yr. Sometimes 2x. Since most i6 headers don’t split the cylinders front and back, I would think the only way to adjust the mixture would to be do them all the same turns out on the screw. But carbs adjustment just isn’t like that, they will be close to the same, but they are just a little different
“3 to keep clean”. That definitely something to consider
I had to laugh at that when I read it… It’s absolutely true.Well, I’m still pretty keen to do a tri-power setup at some point but for now, maybe I’ll stick with the single Weber. I might machine the openings at each end in preparation for tri-power but it’ll be easier to bolt on the new head with the single carb if I just do the single 2v for now and according to sensible numbers, rooted in reality, the 38/38 flows the right amount of CFM.
Next up, I should have all of my valves this Tuesday or Wednesday. We had our Thanksgiving in October but we’re celebrating US Thanksgiving with some friends next weekend, so I’ll be putting this on the back burner until a little later. It’ll be December in a little over a week too, how did that even happen?
The carbs are not necessarily going to tune the same. (Idle mixture). Using a digital tach on a timing light and careful tweaking of each will get the job done. On this Aussispeed intake the two mixture screws on a single 2 barrel aren't the same. Outboard barrel is slightly richer. . . Anyway tri-power is cool regardless. vssman's pic above makes me want to run out and start drilling holes in my intake!3 is just more than 1. Cool, but more of everything, adjusting, 3 to keep clean, three to keep functional, the kits to rebuild, 3 fuel lines, three linkages. I had to adjust mine about once a yr. Sometimes 2x. Since most i6 headers don’t split the cylinders front and back, I would think the only way to adjust the mixture would to be do them all the same turns out on the screw. But carbs adjustment just isn’t like that, they will be close to the same, but they are just a little different
I've found that to be the case with the 38/38 as well. If you dial it in for best lean idle, the front barrel is slightly different than the rear. The rear is happier just a little leaner than the front. Not a massive difference but slightly.The carbs are not necessarily going to tune the same. (Idle mixture). Using a digital tach on a timing light and careful tweaking of each will get the job done. On this Aussispeed intake the two mixture screws on a single 2 barrel aren't the same. Outboard barrel is slightly richer. . . Anyway tri-power is cool regardless. vssman's pic above makes me want to run out and start drilling holes in my intake!
I’ve got all the valves now, including the 144 intakes 1-15/32” that I’ll use for the exhausts.
In terms of back cutting the valves, I just ran into an Uncle Tony video about back facing the valves. It’s the same idea as far as I can tell and he does it with a file and a drill press (drill in a vise in his video).
He does the intakes to remove the hump on the backside of the valve and he does a little on the exhaust valves just to smoothen it. He doesn’t do much on the exhausts because he mentions that the direction of flow doesn’t make the shape of the back side of the valve as critical as it is with the intake.
In terms of back cutting the valves, I just ran into an Uncle Tony video about back facing the valves. It’s the same idea as far as I can tell and he does it with a file and a drill press (drill in a vise in his video).
He does the intakes to remove the hump on the backside of the valve and he does a little on the exhaust valves just to smoothen it. He doesn’t do much on the exhausts because he mentions that the direction of flow doesn’t make the shape of the back side of the valve as critical as it is with the intake.
I've had two very bad experiences with guys who are well known for their work with Ford sixes. For me, it's not a matter of cost. It's a trust issue. There are way too many stories of parts/engines/cars being held hostage by shops, long delays before work is done, etc. etc. That's why I do almost everything myself even if I have to learn how or buy new tools.
Best video I’ve seen yet
I watched a bunch of that guys videos last night. He’s got a bunch of them that talk about porting and cleaning things up around the combustion chambers. He’s working with much more performance oriented stuff than a 1969 log head but the theory is the same. Get rid of sharp edges and consider the direction of the flow. I also watch David Visard videos on porting and he also recommends not messing with the shape of anything; just get rid of casting imperfections and remove obstructions from the flow.
That guy (Eric Weingartner) says you can’t back cut your valves at home. My drill press and bastard file say I can and I’d really love to give it a shot but maybe I should just ask the shop to back cut the valves at 30 degrees from the seat surface.
Engine Fan
Well-known member
So what is the optimal back cutting angle for the 200’s? Or does it matter which head and valve size?
I see a project for my lathe
I don't know what the recommendation is. I've got the Falcon book so I'll do some reading and see if they came up with a specific angle. The seat angle is 45° and I have read and viewed video where they discuss 30° and 32°.
EDIT: I would suggest using a stone or a file rather than a cutting tool on the lathe to prevent it from chattering.
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