Bryan

Quick break today..waiting for it to get warmer so I can crawl underneath. Used the time to make sure shocks and solenoid I bought actually fit (before I wait 6 months to find they don't). Measuring heater hose, wires etc.

Oh, I understand that, and after other's posts I see why a combined manifold works well. It was more just wondering if anyone had tried 3 separate side draft carbs on straight pipes or normal carbs on elbows. It would be very cheap to do..maybe not as great as a $400 - 500 manifold but better than a single carb stock intake. Length of pipes probably critical with engine's RPM range.

Well, do you think there's room for improvement in what you're seeing? Maybe I worded it kind of harsh, but the intake should not be like that for optimum flow.

Anything has to be better than the stock intake manifolds...

Ah ha..an individual pipe separate from others would have a pull, stop, pull, stop pulse. Multiple ports pulling on a carb would have a continuous pull if it was designed correctly..

That was a long read, but see what you mean. The common manifold has to be designed properly to work correctly... -> quotes "Volume is a rather imprecise terms when analyzing a plenum. As interior space increases (vs. cylinder volume) the buffer or anti-reversion effect increases, but this isn’t linear and probably decays to a minimum value with some multiple of cylinder size." ......."Ideally, each runner entry should also have unoccupied floor radially with OD about 2.5 × runner ID. This insures separation of the wave signals, and allows maximum wave energy recovery since the runner wave sees this as “open”. "

Yep, had an older motorcycle..getting all the slides to lift at the same time is a chore when there are independent cables. A one cable pulling an adjustable bar system would be the best. I don't know what a balance tube is, but it seems like the intake ports pulling the flow in different directions might be an issue. Single pipes would be pulled in a pulse, but not experience any side flow.

On some motorcycles, yes. But 2 or 3 carbs on a common (open internally) log manifold, wouldn't you have a flow from the sides (or center) as each piston (or 2) pulled down? And it changing direction depending on which piston is intaking? Am I misunderstanding the process?

I saw the old Webers and other older carbs but Webers seemed pretty complicated. The Mikunis are relatively cheap, have idle & main jets, a mixture needle that can be adjusted, etc. They come in sizes from below 20 mm up to 48 mm..

Even if they were regular carbs, I wonder why it's always a joined system when 3 upturned elbows would have equal lengths and directly feed the ports without any side currents from carbs on each end.

Ok, just a crazy thought, I won't be doing this. Given the outer original intakes are longer than the center, and 3 straight pipes could be adapted to any size of simple flat slide Mikuni carbs, wonder why nobody has attempted this? I was looking at calculations that suggest a 230 ci motor at 4000 rpm and 100% (I know it's not) volumetric efficiency would be about 260 CFM. CFM Calculator (summitracing.com) Flatheads are probably at 70% VE so say a guess is 186 CFM. 186/3 is 62 CFM.. Was looking at Mikuni carbs (a lot of looking since they don't give CFM on their specs, you have to check on forums for people that have measured flow) and it seems like 22 -24 mm models would be about the right size. Even if someone bashes me and says you could have 6000 rpm, okay, you just recalculate for larger carbs. I think you could get a solid tube linkage to pull up on 3 cables. Maybe rig something to pull/push the chokes in. Plus if you have vacuum advance & modified PCV you'd have to tap in somewhere. Then it's a matter of the right pipe lengths, inside diameter would be the same as the block hole. Only other problem, does the rear pipe/carb have clearance to the firewall?

Haven't seen a lot of metal clips offered..had the same question about wire holders, and have something like that holding the rocker chrome under the door. Might have to measure, find where it's holding the part and substitute a modern one.

Thanks but I just ordered a set of duals from Stovebolt a few hours ago. Really appreciate the offer though.

Just don't know...I'm about to pull the engine and trans out of my 1948 Dodge sedan. First time

That's fantastic work but just something I didn't want to do. Too many modern failures on engines the last few years (brother, nephew, step-mother). Always the sensors or computer. Would be nice if with vacuum, mixture, intake temp, exhaust gas sensors a person could have a dash control to fine tune mixture..know it wouldn't be instantaneous but something that wouldn't fart out and leave you stranded. Or maybe computer controlled but a standard fail default, when sensors and everything else fails it would still run and just give a warning.

Today was either depressed or tired. Was stiff and aching yesterday. I cleaned up where I had been working, cleaned and sorted my tools and stuff. Everything was on the floor. No work besides cleaning. Notice I have 2 bolts that were broke. The left one possibly some time in the past. End of bolt was rusty. Anyway, think I'll leave it to a machine shop. Why break off a hardened easy out in the bolts. Looked at the ports..exhaust valve ports are nasty with crud. Intakes are clean, but noticed the head bolts extend down to the edge of the intake ports. See pics. On the intake manifolds I looked at the ports. They could have done better, two outer ones have a large step between the tube and edge.

Do you have an engine hoist now? If you were worried about the weight taking it out that has not changed putting it back in. Hard to answer.

An O2 sensor?

The guy at Stovebolt selling me the dual headers suggested I get an electric fuel pump or put a mechanical 1957 one on. Says the line routing is different. Might go electric but dang..was trying to stay original. Still don't like the idea of mechanical diaphragms being open to the engine if they leak. That bothers me.

Maybe 2 1/2" max . It would be good insurance if I started upgrading the engine and intake. Going to mostly putt around town. The reason going with duals is all the old original manifolds on Ebay are more expensive, and I don't want to risk getting a stressed or cracked one.

That's what I'm afraid of. Back in the 70's when I was a lot younger, broke an easy out off in an intake bolt on a 71 Camaro. Other drill bits just bounced off of it. Had to take to a machine shop. Might heat up red hot and try to back out instead.. The other matching bolt on the rear hardly had discernable threads. Any opinion on Langdon headers and the dual to one Y? Using existing intake with the new exhaust? 3 of the 4 bolts on bottom were already broke off before I got it.

Worked all days yesterday (10-5 pm). Basically one bolt would not come out. I thought by drilling/grinding the head off I could pull the manifold off of the shank. The bolt shank was also fused to the manifold. I ended up breaking the bolt off about a 1/2' from the block. Need to remove that one. Wonder if I should remove all the remaining studs or just replace the one? The threads look pretty good on the others.

Well, taking off the exhaust and intake manifold didn't go well. One bolt stuck and wouldn't come out. Had a small existing crack in front exhaust tube but managed to crack the manifold in half by "gently" prying on it. And it was gently. Well, going for a set of Langdon stovebolt dual headers since the price isn't much more than the outrageous existing manifolds on Ebay. I have another Dodge in the woods but think I'm going to go thru that process AGAIN to get the manifold? Don't laugh but I'll probably get a Y-pipe and join the 2 pipes off the header. No 2 mufflers, no trying to run 2 pipes past the fuel tank (very tight). And I'll still use my existing single carb intake. Does anyone see a problem doing this?

One thing I was careful about while stuff was going downhill, made sure I didn't pry against my valve covers. Also didn't wedge anything against the block surface where the gaskets are. Think I might go for dual headers..wish there were single collector headers with the collector in the rear.

Turned into a **** show today..taking the manifolds off...and all the bolts came off except that LAST ONE. Never does. So, I finally go my drill out to drill the head off, so the manifold could be pulled off. With the bolt head off...NOOOO, we ain't gonna come off. Well, I found that you cannot pry even lightly on cast iron..it popped right at the intake heater. Anyway, I found it was already cracked on the front tube. Last insult, the bolt was still stuck in the last remaining header fragment. Tapping, turning, etc...still broke off with about a 1/2 " sticking out. Crap. Well on the bright side maybe I'll put dual headers on it. Plus with the intake, there was only one bolt holding the exhaust manifold to the intake. The rest were already broke off