All Small Six Winter Project: Better breathing with a large log

[DON]

Hey, I'm wondering what plate I should get to do the 2V mod on the large log head.

I was considering the tri-power Offy adapter as well but I wonder if there is any benefit of the 3 - 1 barrel carbs over a Weber 38/38. I figure if I were going to do something with multiple carbs I'd go all in and do what Jann did on his Falcon with the Volvo transmission and the 3 2-barrel carbs with direct fuelling to each cylinder. That's beyond where I'm at at the moment.

Does this one work with a Weber? https://www.vintageinlines.com/product-page/autolite-holley-2v-conversion-adaptor

Is there any benefit to the spacers? 500 CFM, 350 CFM?

Thanks,
Andrew

I can see much benefit running 3 carbs thru the original one barrel intake. Cutting the log off and feeding two cylinders per carb is a whole other story. That is an improvement over the log, but a lot of engineering.
I couldn’t see the link, but it says it’s Holley. Holley and Webber are different bolt patterns. That’s part of the advantage of using a narrow 4 bolt pattern on the intake. Then you can make an adapter from that to any pattern you want and then change it to another pattern
Spacers are a benefit- smooth the air flow out. A lot of science involved, but basically, the more the better. Mine is going to end of between two and 3 inches. Just make sure you clear the hood

 

[aussie7mains]

Just as a talking point, many years ago i helped a guy with an early 200 log head, he cut 3 holes in the side of the log and bronze welded in suitable stub pipes with a flange for Su side draft carbs. It seemed to work quite well. The English used to do a lot of inline sixes with two SU carbs and this works well also. IMO two SU 1.75 carbs world work. The best location would be between cylinders2&3, and 4&5. Su run at an angle so could be semi downdraft which helps. The single hole would be plated closed and the log could be used as a pressure balance. I did try 2 1.75 SUs on a manifold I made for a 250-2v engine I was fiddling with years ago, but it was never fully developed. I dont know what the USA availability is, they are fairly cheap here, many pomme cars used them, Jags, rover V8s, MGBs, try there, I dont think new ones are available.

 

[Kritas]

Just as a talking point, many years ago i helped a guy with an early 200 log head, he cut 3 holes in the side of the log and bronze welded in suitable stub pipes with a flange for Su side draft carbs. It seemed to work quite well. The English used to do a lot of inline sixes with two SU carbs and this works well also. IMO two SU 1.75 carbs world work. The best location would be between cylinders2&3, and 4&5. Su run at an angle so could be semi downdraft which helps. The single hole would be plated closed and the log could be used as a pressure balance. I did try 2 1.75 SUs on a manifold I made for a 250-2v engine I was fiddling with years ago, but it was never fully developed. I dont know what the USA availability is, they are fairly cheap here, many pomme cars used them, Jags, rover V8s, MGBs, try there, I dont think new ones are available.

There are many available on Ebay in various states of repair. I just bought a nice set for my TR6. I paid $299 for the pair with a fresh rebuild. I've been considering putting a pair of side drafts on my 250 head. A spare manifold came with the carbs that I could cut up and use to modify the head.

 

[Frank]

Hey, I'm wondering what plate I should get to do the 2V mod on the large log head.

I was considering the tri-power Offy adapter as well but I wonder if there is any benefit of the 3 - 1 barrel carbs over a Weber 38/38. I figure if I were going to do something with multiple carbs I'd go all in and do what Jann did on his Falcon with the Volvo transmission and the 3 2-barrel carbs with direct fuelling to each cylinder. That's beyond where I'm at at the moment.

Does this one work with a Weber? https://www.vintageinlines.com/product-page/autolite-holley-2v-conversion-adaptor

Is there any benefit to the spacers? 500 CFM, 350 CFM?

Thanks,
Andrew

Holley/Ford 2V bolt pattern is larger than Weber.

 

[drag-200stang]

Two guys here have been low 14,s in the 1/4 with 3 carter YF,s that is as fast as a stock Boss 302.
Down draft is the way to go, why put the runners and carb over the header heat, room, and the log ports are at about a 45 degree angle, why bend down and not up and let gravity work for you. It can be made at home with hand tools , I did when I was 16. and my high school daily driver. Strut brace may need mods and hood clearance may need some clearancing. There is a nice fiber-glass cowl hood out there. There is more power in a homemade tri-power because the production made one, make the opening to small to work well because they make it easy to for everyone and they center it between the ports. If you move it closer to 2 and 5 you can get a larger hole and seal better. People will say but,but, it is not centered, but I say that it is more important to have a stronger suck signal to the venturi, plus ports 2 and 5 are made to pull from the center not back the other way. Oh and the look you get when you pop the hood especially if you use the long cobra air cleaner fabled to fit. I used gasket material and aviation Permatex and never any leaks to seal the home made adapters. The linkage was pretty hack, today you can buy some nice stuff to make it work and not resort to welding rod and erector-set parts.

 

[Kritas]

Two guys here have been low 14,s in the 1/4 with 3 carter YF,s that is as fast as a stock Boss 302.
Down draft is the way to go, why put the runners and carb over the header heat, room, and the log ports are at about a 45 degree angle, why bend down and not up and let gravity work for you. It can be made at home with hand tools , I did when I was 16. and my high school daily driver. Strut brace may need mods and hood clearance may need some clearancing. There is a nice fiber-glass cowl hood out there. There is more power in a homemade tri-power because the production made one, make the opening to small to work well because they make it easy to for everyone and they center it between the ports. If you move it closer to 2 and 5 you can get a larger hole and seal better. People will say but,but, it is not centered, but I say that it is more important to have a stronger suck signal to the venturi, plus ports 2 and 5 are made to pull from the center not back the other way. Oh and the look you get when you pop the hood especially if you use the cobra tri-power air cleaner fabled to fit. I used gasket material and aviation Permatex and never any leaks to seal the home made adapters. The linkage was pretty hack, today you can buy some nice stuff to make it work and not resort to welding rod and erector-set parts.

Good point about mounting carbs over the headers.

 

[DON]

Just some photos of the mod. The four holes he made are not semetrical, you can’t flip the adapter end for end- the holes won’t line up. Not a big deal but a pain when making adapter and bothers my brain!!.
Other than that, I think he did a good job. Bolt /screw sizes are all 5/16 x 18. He made the throttle bore holes 1.635 on the inlet side and 1.70 on the outlet side.
Let me know if you have any other questions
The adapter:

 

[DON]

And the intake mod:

 

[Frank]

That's a nice intake Don! Did you do that work? (Need to send you a big6 log intake for the same treatment!)

 

[awasson]

Yep, that is a super nice job on the intake log modification @DON. That is exactly how I'll be doing mine

I've seen a lot of mods and adapters where the adapter takes a separate barrel carb base and dump it into an oval. Is there a benefit to maintaining the separate barrels as long as possible like yours or is it fine to just dump it into the log via an oval? I'm looking to get the best bang for the buck.

I haven't read the report but I thought I read that Vintage Inlines did dyno tests and found that they got 6% increase RWH from the funnel adapter and they got 24% from direct mod 2V on the log. That would be an astounding increase in power.

 

[awasson]

Just as a talking point, many years ago i helped a guy with an early 200 log head, he cut 3 holes in the side of the log and bronze welded in suitable stub pipes with a flange for Su side draft carbs. It seemed to work quite well. The English used to do a lot of inline sixes with two SU carbs and this works well also. IMO two SU 1.75 carbs world work. The best location would be between cylinders2&3, and 4&5. Su run at an angle so could be semi downdraft which helps. The single hole would be plated closed and the log could be used as a pressure balance. I did try 2 1.75 SUs on a manifold I made for a 250-2v engine I was fiddling with years ago, but it was never fully developed. I dont know what the USA availability is, they are fairly cheap here, many pomme cars used them, Jags, rover V8s, MGBs, try there, I dont think new ones are available.

SU's would be interesting to try out. My (late) Dad was an MG guy. He was a Chrysler guy too but he got this weird MGB bug when I was about 11 years old and it stayed with him all his life. We had loads of SU carb bits and pieces here and there and he had a really good understanding of how those carbs worked. That was all gone by the time he passed on but he would have gotten a kick out of 3 SU's hanging off the side of an L6 head. I was a Mikuni side draft and Weber down draft guy when I got into BMW 2002 money pits.

 

[awasson]

Two guys here have been low 14,s in the 1/4 with 3 carter YF,s that is as fast as a stock Boss 302.
Down draft is the way to go, why put the runners and carb over the header heat, room, and the log ports are at about a 45 degree angle, why bend down and not up and let gravity work for you. It can be made at home with hand tools , I did when I was 16. and my high school daily driver. Strut brace may need mods and hood clearance may need some clearancing. There is a nice fiber-glass cowl hood out there. There is more power in a homemade tri-power because the production made one, make the opening to small to work well because they make it easy to for everyone and they center it between the ports. If you move it closer to 2 and 5 you can get a larger hole and seal better. People will say but,but, it is not centered, but I say that it is more important to have a stronger suck signal to the venturi, plus ports 2 and 5 are made to pull from the center not back the other way. Oh and the look you get when you pop the hood especially if you use the long cobra air cleaner fabled to fit. I used gasket material and aviation Permatex and never any leaks to seal the home made adapters. The linkage was pretty hack, today you can buy some nice stuff to make it work and not resort to welding rod and erector-set parts.

I had the same thoughts about making a tailor made tri-power setup and getting the carbs out there to service the front and rear cylinders.

In terms of CFM, I ran the numbers and it seems if I’m being pretty optimistic with my efficiency and RPM’s I really don't need more than 300 - 320 CFM. I tried to look up the flow on the Weber 38/38 and the internet seems to think it flows 275 - 330 CFM. That seems a broad range bit it’s probably an ideal carb for the plans I have for the head, valves, compression and camshaft. Then again if I were to switch gears and go with a tri-power setup (now or in the future), what carbs would you recommend looking at? Since it’ll be tailor made, I can really choose whatever carbs I want and get something that’s not unobtanium.

 

[Frank]

In terms of CFM, I ran the numbers and it seems if I’m being pretty optimistic with my efficiency and RPM’s I really don't need more than 300 - 320 CFM.

 

[DON]

That's a nice intake Don! Did you do that work? (Need to send you a big6 log intake for the same treatment!)

No, I didn’t do it, I bought it that way. A guy out of California did it and as old them on auction. The machine work was a little rough but I had that touched up and new springs for the cam

 

[awasson]

Well 4 of the 6 intake valves I ordered from Rock Auto are the 1.75" intakes for a Ford inline 6 and 2 were for a Saturn SC Coupe 1991-98

They're totally useless to me and I just checked the price, they're valued at double the price of the valves I ordered.

I just put in another order for the valves and shipping is 4x the price of the valves. I ordered them originally with some other things so as to offset the shipping costs... Argh...

Anyway, I compared them briefly with the smaller intakes that the head came with and there is noticeably more meat on the back of the valve than the OEM valves have so I'm glad that it's been suggested to back cut them.




I still need to find a shop to do the work now. I'll talk to the guys who I have machine the block. Fancy head work on old ford inline 6's isn't their bread and butter but you never know. I was very impressed with the work they did on the cleanup, bore and hone and grind and polish of the block and crank so I'd be more than confident if they're up for it. They turned it around fast too.

More to come.

 

[drag-200stang]

I had the same thoughts about making a tailor made tri-power setup and getting the carbs out there to service the front and rear cylinders.

In terms of CFM, I ran the numbers and it seems if I’m being pretty optimistic with my efficiency and RPM’s I really don't need more than 300 - 320 CFM. I tried to look up the flow on the Weber 38/38 and the internet seems to think it flows 275 - 330 CFM. That seems a broad range bit it’s probably an ideal carb for the plans I have for the head, valves, compression and camshaft. Then again if I were to switch gears and go with a tri-power setup (now or in the future), what carbs would you recommend looking at? Since it’ll be tailor made, I can really choose whatever carbs I want and get something that’s not unobtanium.

I am not a carb expert, I used what AK Miller said to use and that was the the YF from the 240 for the main carb and the 144 engine square bowl Holleys on the out board spots. The Holley were susceptible to float needle flooding and any little thing/debris would leak on the headers What helped was screwing the filter directly to the carb. I liked the linkage set up one to one and all three carbs the same size, It worked best for me, your driving style my be different. I got sick of the small Holley's and went with 3 240 engine YF,s, keep in mind that they are one of the tallest one barrels. .That cut 1/4 mile times .30 seconds but needed a smart foot, no smashing it to the floor fast at low rpm,s.
Use smaller carbs for easy driving and good response and larger carbs for more top end power.

 

[awasson]

I am not a carb expert, I used what AK Miller said to use and that was the the YF from the 240 for the main carb and the 144 engine square bowl Holleys on the out board spots. The Holley were susceptible to float needle flooding and any little thing/debris would leak on the headers What helped was screwing the filter directly to the carb. I liked the linkage set up one to one and all three carbs the same size, It worked best for me, your driving style my be different. I got sick of the small Holley's and went with 3 240 engine YF,s, keep in mind that they are one of the tallest one barrels. .That cut 1/4 mile times .30 seconds but needed a smart foot, no smashing it to the floor fast at low rpm,s.
Use smaller carbs for easy driving and good response and larger carbs for more top end power.

What you say about the 1 to 1 linkage and all three being the same size makes sense to me too. All of my motorcycles have had cable controlled, slide carburetors (even my first dirt bike) so I’m pretty aware of low speed throttle control.

I hear that the synchronous setups are nicer for drivability but it seems to me that the engine will be happier with all ports getting a similar volume of air and fuel. Lots to consider on that front for sure.

 

[drag-200stang]

The beauty of the Offy style linkage, even better if you use bell cranks with a lot of holes is that you can do one to one or any thing in between. Just play with it to find what you and your engine likes.

 

[DON]

Closer to the carb pivot point—quicker throttle movement

 

[bmbm40]

I had the same thoughts about making a tailor made tri-power setup and getting the carbs out there to service the front and rear cylinders.

In terms of CFM, I ran the numbers and it seems if I’m being pretty optimistic with my efficiency and RPM’s I really don't need more than 300 - 320 CFM. I tried to look up the flow on the Weber 38/38 and the internet seems to think it flows 275 - 330 CFM. That seems a broad range bit it’s probably an ideal carb for the plans I have for the head, valves, compression and camshaft. Then again if I were to switch gears and go with a tri-power setup (now or in the future), what carbs would you recommend looking at? Since it’ll be tailor made, I can really choose whatever carbs I want and get something that’s not unobtanium.

Tri-power is a big switch! Three carbs are cool to look at, definitely says high performance. I doubt that I could keep them tuned properly. Has anyone ever direct mounted two Weber 32/36? Probably enough cfm on the primaries for a good everyday driving experience but a decent snap when you floor it.