Air does not like anything too close. I may lob a bit of but if the wall is right by the bottom of the carb base it often bothers jetting. If you work with any of the old Mopar Crossrams or SS 6 pack manifold you learn that had they made even a 1 inch more space under the carb base hrizontally from the short corners in the plenumn, jetting could probably have been square instead of the fudged way it has to be . Air flow in the open (IE as in a relatively large space like a plenum) is different than air flow along or near a wall. That is my thinking and is based on previous experience. I might be all wet but I want to be sure I dont introduce any unusual problems to the design. Since the plenum is not oversize I have some wiggle room without making it lazy. I would like all four, barrels to feel the same and I think extending the plenum makes that happen as well. I played around with a flow bench for several years. If i learned one thing it was air doesnt always think like we do. I also did some smoke tests to see what happens and even placed dust particles in manifolds and ports to see where the dead spots were. (In a 440 for instance the bottom of the port at the intake surface will not disturb dust even so it is ZZZZZZZZZZ and irrelevant to the rest of the port.) After I saw that I stopped grinding down there. Just for fun I think I have a pic of my old bench. A flow bench will teach you what to do , that is true, but it will often teach you what not to do and sometimes while heart breaking that is more significant. Sorry i got carried away. I just find this stuff so interesting. Don
I laid out a pair of reinforcing plates in1/4 inch alum and cut them out on my trick aluminum saw ;>) The plates will be what the plenumn side intake runners are welded to and then the plate and runner assemblies will be welded to the plenumn. This makes construction much easier and also gives some additional bracing. I cut the inside of the plates out by drilling a series of close small holes and then cutting through the between section with a spin saw bit in a dremel. A few minutes with a file cleaned it up. here is one side as it progressed and mocked up as it wll be. Race night this weekend at Shannonville. I will try my Holley 4 bbl set up then for the first time. I imagine it will be winter before I complete this manifold. Don
Keep us posted, Don! I've still got my .100 over 12.5:1 balacnced, blueprinted, ported, /6 sittin in the garage, with a 4bbl Offy and a Clifford weber intake. Still kinda like to do something different.
It will be interesting for me to try it compared to the offy with a DP. I will have no excuses if it doesnt work well. Don
That's along the lines of what we are using on our HA/GR...a pair of 1 3/4 SUs on a long log. Hasn't run yet so we'll have to wait and see how well it works.
Yes I saw your project. Most impressive. No Baloney just stepped up and built it. It looks right. I bet it works great. I was a Austin MG JAG Triumph Mech when I first moved to Belleville. We also sold AMC (Main line) SUs are good carbs. Don
I finished the milling on the manifold flange plate as well I used my BIG SPIN saw for that. Kearny Trecker 2H Vertical mill. I also finished the final fit on both of the reinforcing plates i was working on yesterday. Bit by bit it is coming together. I had to stop for the day and clean the dragtser and load it for tomorrow 's T&T at Shannonville. While my mind is into this tunnel ram I want to see also how much difference I get between the old Eddy AFB and the Holley DP that is on it now. Don
I found I needed a tall carb spacer to Ram it to my slant six. You're using a lot more science than I did. Have fun at test and tune.
I did NOT read this thread word for word so may be missing something? Personally, I would make a single "PORT" runner design, but with runners connected to a common plenum intake so that I could install the needed 6-banger port 3x2 carb configuration "side-draft" carb's like that was on the old "Blue Flame" '53/'54 'Vette 6-banger engines. Or install the the more common 2G's/2GC's or all of the later Holley 2-barrel carbs vertically straight up like stock if the hood-line is tall enough to allow mounting them. pdq67
Well you are certainly free to do it that way. I believe this design will work very well. Not all will agree I understand but here is the bottom line. It will have to give a definate improvement over the Offy with Holley which I hope already is a definate improvement over the AFB with Offy which ran the same as the six carb set up. I have explained quite a bit of the theory or how and why already in the early posts on this thread. Anyway I am commmited to this design. I believe I will be rewarded for my efforts with a reduced ET and a bunch more HPs. BUT as an experimenter I am also well aware that the best laid plans of mice and men go astray. I am ok with that too. Airflow is a different kettle of fish. Our natural ideas about how it works and the real way it works are often quite different. The ET slip will be the final judge. I dont want to get into a discussion of how I should build it if that is OK. Been at this perfomance thing a long time and it is also what I made a significant part of my living at so it aint my first kick at the cat. If this spurs someone on to build what they think is a better design. That is fine too. If you have one under construction as well show us. And for Bobw, put that pipe back on your wood stove!;>))) Don BTW Here is what I made for it before. You would be happier with this design i guess. I am betting this tunnel ram is faster. if I didnt think so I wouldn't be building it.
Here's two more sense, I received a lot of criticism for my design but kept on anyway. The 1st carb was from a De Soto hemi which we replaced with a current Edelbrock version. It's hard to test something like this unless you can go to a track or dino. I graded a track in my backyard but it made so much dust I couldn't tell if the neighbors were complaining and had to quit. Then I went to a dead end street nearby and it reaches 4000 in 2nd so fast I ran out of room. However during the testing we removed the carb numbers of times and did not find pools of fuel in the floor of the plenum. Hopefully we can get some track time in yet this year. Don't give up, Pat
Got the trans fixed today and all back together. Worked on a couple of other minor things too. Give up? There is absolutley no chance of me giving up. I aint made that way. Love your ride by the way. Fun level looks very high. Don
Worked on it today again. Cut holes in the plenum for the runner plates on the big vertical mill. Trimmed the runner a bit closer. Little by little we are getting there. Don
Here is what it looks like inside. It will be radiused and neater when welded but I am liking it already. Don
I used a small CFM Q-jet on a clifford intake for my 292 chevy in a 68 chevy stepside. Started with a 3 speed O.D. and went to a 700R-4 with lock up converter. It ran really strong with a 3 into 1 header set..loved it but your setup looks much wilder...hope it goes OK for ya.
Interested to see how it works. Who knows, the state of manifold design now might be about where camshaft design was in the '40s.
what name is on that intake , there was a couple of versions of that intake . I made a copy out of steel. Thanks Bob
Today I temporarily fastened the carb plates to the plenum with screws (where it would hurt anything) and bored the carb throttle bores. I bored them purposly small because it is a lot easier to remove metal than to add. it. During the early construction phase one wants to be careful and leave some wiggle room.
Here's one I built for a 300 Ford bracket car. It's not on the track yet. The car has gone over 100 in the 13's with a 4 barrel.
Hi guys the HAMBstirrer here in OZ, this is a definite no way to do a manifold. looks wild runs like shit. Runners just too long.
Is this in an early Chevy,62-64 maybe? Giz'QUOTE=292belair;5685476]here's mine I got from the dirt track boys down east, works good at high rpm! [/QUOTE]
Well since you asked and since I used to teach engines in college, sit down and I will explain. . First this is a slant six. It has a stroke of 4.12" so it isnt going to survive 7000 RPM nor does it need it. 6000 RPM is my max desired and if the manifold is tuned to 5700 or 5800 I will still be a happy camper. The RULE of thumb for tuned length is the RPM in thousands (IE 6000 in Thousands is 6 (6 thousands) divided into 90. The tuned length is the distance from the back of the intake valve to open air. In the case of a tunnel ram to the plenum (where the runners end and meet an open chamber) so 90/6=15 inches The runner length is arrived at using this and subtracting the length already in the head to from the flange to the back of the intake valve. Many many manifolds are too short and get their power because they are adding carb rather than actually tuned. Now I know some of you think that one should not use science and math to figure out hot rodding stuff. You would tell me "I am a hands on kinda of guy and dont believe in all that theory." I love guys like you. Especially when they are in the other lane at the drags. The truth doesnt care whether one believes it or not. It is the truth regardless. Then there are the folks who say "If was that simple someone wold already done that." Slap yourself in the mouth! Never say that. Thomas Edison one of the greatest inventors whoever lived, concieved in Canada and born in Milan Ohio once said, "Inventions are made by people too stupid to know they wont work." If my shop wall had a motto I would put that there in big high letters. After 41 years of fooling around with race cars and motors I have learned to forge ahead regardless of popular opinion if it seems right to me. Sometimes I fail but always i learn. This week I have been learning to cast parts in aluminum.(See Motorcycle Wheels to Handi Van Axle thread for video). At 60+ years old it is exciting to learn and try new things. Manifolds I have made before and have had success with them. The Max wedge mopar crossram has 14 1/2 inch runners. A typical BB mopar RB engine flat tappet peaks around 6150 RPM . 90/6.150 = 14.63 inches.There seems to be a pattern forming here! Don
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