I and a friend both need an improvement in manifolds for our /6 engines. He asked me what I would want and so i sat down and designed one tuned for 6000RPM average. Today i fabbed up a wooden model to make sure all works out before I spend the $ for the Aluminum square tubing which this manifold is designed to use. i designed it for 2 500 Holley Two barrels. (Which are really only about 700 CFM together when rated in four barrel rating pressure drop instead of the artifical two barrel ratng system. )A pair of two barrel injection throttle bodies were used for mockup (cause I dont have any holley two barrels , yet.) I will get the flange water jet cut but will do the rest in house. This has my attention as it is SO doable and inexpensive. I will work it in around otherstuff but if you are interested keep an eye out for future updates. Why wood first? Better to mess up $4 of wood than $50 of aluminum Don
Just a thought. I raced a 292 chevy in the early 90's. I made the the intake and plenum.The runners I think about 12inches long.I made them from electric conduit. You can buy all kinds of u bends now steel,ss steel aluminum. Pm If you would like to talk
Yes I have explored that route before. Many of the bends can be used. This one however really doesnt need any. Tuned length is 15 inches including the port. Entry angle is less that 7 degrees and can be coaxed a little by uising the 1/8 th wall square tubing. The slant six ports are already square. I made a steel one before for 6 carbs and ran it for a couple of years. I still got a photo here I think. (Still have the manifold too. ) To my shame i hadnt seriously thought about making a new manifold till Paul Amado, a friend of mine was talking to me about it. I did a quick drawing using paint on my computer. Measured a spare head in the shop and did the math. I realized right then what a straight forward design it would be . Now I was interested. The current manifold is untuned or probably more correctly has some cylinders not bad and some way too short. The new design has less than 1 inch variation in tuned length. The two longest cylinders in the current manifold, have the best plug colour which may or may not mean a whole lot but it gets me thinking. I mocked it up today in wood and was surpised how well everything fit. Part of it comes from the runner length which helps make the approach angle of the manifold acceptable. That was not a factor in designing it . Just a lucky break. I am going racing this weekend so i am focused on that but probably next week this will happen since it does not require a great deal of time or expense. The biggest problem will be finding the two rebuildable 500 2 bbls. Thanks for the tips . Do you have any pics of your unit. I would find them interesting. Don
Don check with the local oval track guys a lot were restrict two a two brl before the use of the 602 crate engine
YEs We have a bunch of stock car racers here with two barrel rules. You know the big problem? Stock car guys and drag race guys here dont really get along. Oh so maybe if I suck it up for a day or so i can find a deal. I will do my best. My wife says though "Don , you dont have a diplomatic bone in your body" But seriously you are right. Maybe in your area there are guys who used to run the 2bbl holley before the rule thing. My brother lives at Kempville area and his two boys are into cars. I will email them tonight and see what they can find. I am embarrased at how straight forward this manifold will be. Embarrased that i didnt do this a long long time ago. It just never crossed my mind i guess. Thanks for the idea on the carbs source. There are some strange things going on in your garage i see. Very interesting! Don
nothing strange just par for the course, I'm just too busy to work on my stuff a lot isn't hamb friendly,having a hard time getting parts in a timely fashion, still waiting for the block to come back from the machine shop so I can assemble JMP's motor so he can get at least one race in against Dennis Black's Panic Attack at Sanair and go to Shannonville this year, may see you there.
Ill look forward to that. Actually i am loaded up waiting to go this afternoon. hope to make a few passes and see if we gained or lost with our mods. Here are some more wooden manifold pics. Spent about 1 hour today sorting out tubing sizes that will work and making minor changes. Hope to get the aluminum Monday morning.
Hey just another thought you need to look at this guys stuff John Marcella He builds sheetmetal intakes. You see what i mean The turn from the carbs is to sharp That what I was telling you about elbows and stuff. kind of like a 3into 1 twice header
Curious question, did you put a 1/2" radious on the runners as they come out of the plenum, made my own tunnel ram for a 351C and did not do this, lots of trouble until the redesign thanks to Hogans.
I know you said the throttle bodies are for mockup, that you're gonna use carbs, but I just want to say that I really dig those Ford pickup throttle bodies. Which engine size are those 2 off of? I keep thinking about trying to put one off of a 460 on top of a 3-71 blower, with a plate underneath to hold the injectors.
Just posing a question to you. On a tunnel ram, or sheet metal intake with either 2 carbs or split 4 barrels, there is a throat from each carb feeding each runner. Do you think you might have distribution problems such as the middle runner between the 2 carbs being lean ? I'm also wondering if the floor of the plenum shouldn't be slanted towards the runners. I see the flat floor as a area where the fuel could puddle.
Ok First beacuse a tunnel ram uses a box the air /fuel has no trouble making the turn. If it was a restricted path it would be impossible but because of the plenum it works wonderful .In fact if you study fluid dynamics (and I have an enginnering manual on it my pro. eng. father gave me when he moved into a "home" )there is a whole section making fluids turn without severe flow loss by using a plenum or chamber for the turn instead of makng the turn in pipe or tubing. The flow loss IS THE Least with this method. In fact very minor so the turn thing is not mportant. I will pay attention to the entry raduis . Thanks for the hint. You will see a split four sitting on the manifold now. One I made a few years ago fom a Holley Dp spread bore.. The ford throttle bodies are from a 351. The 302 ones are slightly smaller. They would work fine for anything. Mechanical or electronc injection. Cheap decent looking too. This manifold though will have twin Holley 500s just because. Now to todays work. I bought the aluminum. I rough cut it in my household table saw with the normal wood saw blade. It saws better than some woods. I learned this trick from a friend in Hanau Germany. I have to decide right now which way to build it . Straight out ,all together or with mild spacing. I'm thinking! Give me a moment to decide. Each method has some advantage. because of the plenum by the way and the height over the runner area while one would not want to get stupid it is not as critical as one might think. Volumes and runner lengths are what is critical. I will have to taper the runners where they meet the head. This should not be too hard. I have a plan. The taper will also spread the tuned range slightly although not a whole lot. Now I know the $64 question is have you ever built one before? A tunnel ram ?Well yes. sort of. I made this 2 x4 conversion top about 15 years ago . Did it perfom? Why yes it WORKS wonderfully If you race in Kitamat BC you have seen it on Paul's car right now. Enuf for today. Quit and think for a bit is always a good policy. Don
Ur right about a wicked scoop! I once a showed a young lad how to make a scoop out of fiberglass using blue foam pieces to make the shape and them melting out the stuck foam with laquer thinner. I might do that. Trouble is his turned out so good even i could hardly believe he did it. The top for the ram manifld in the pic is wood but I did get it cast and on my website I think in one of the projects pages you can find a pic of the finished project. And it did/does work very very well. The original wooden model is in my basement and yes we ran that way in wood for a whole year. Why? because it added some MPH and dropped some ET. I then transferred it to aluminum over the winter. Don
I'll be watching this one. I built a 6x2 manifold for big chevy and it was definitely harder than I thought. Have you thought about large base rochester 2g's? I bought the circle track ones rated at 500 cfm for 210.00 a piece.
about 12 years or so ago , i had a 3x2 inline intake for a gm 250 style 6....had 3 rochester big base carbs , no common plenum , but did have a small connecting tube between the runners. seems like the runners were around 10" long or so.....and for some strange reason , i want to say it was a man-a-fre......but thats been a few years back. it was off a dirt car.
Yes I have thought about the rochesters and in fact have used them before. Since i am a carb guy I did my own. They are harder to find used now. We used to get them off 455 Olds two barrel engines back in the day.You would need a search party to come up with them now. I cannot afford to buy new stuff anyway. My race budget is $100 per month, period. If we cant find it cheap or make it we simply dont have it. Quite frankly the lack of extra cash is an inspiration. Anyway I want a pair of 500 holleys . I live in a stock car area so i am sure there are some old beat up corroded stuff lying around a few shops in this area and I can spend time a plenty if that is what it takes instead of cash. I figure free or $25 bucks each if I am lucky. I have a few carbs i can trade as well including a 9510 Holley which is not a bad piece. Don
I was just thinking (always a highly dangerous proposition, in my case!) .....but have you thought about maybe running a pair of 'List 0-80507' 390 CFM Holley 4-bbls, instead of the two 500 cfm 2-bbls? The '0-80507' is the 'NASCAR' 4150-style, 'double-pumper' 390, not the more common, 4160-style 'vacuum secondary' 'small-engine' universal street 390. The 0-80507''s are pretty spendy new (like 700 bucks-plus each!!! ), but lot's of non-NASCAR dirt and pavement tracks also mandate this carb as their 'spec carb', so there are lots around, available used, for a fraction of their new price. The way Holley flow-rates their 2-bbls compared to their 4-bbls, I imagine the 390 4-bbl would flow about the same as the 500 2-bbl. I think the advantage though, would be, that having 4 smaller venturis per carb, as opposed to two relatively large ones, would provide better mixture quality over a wider rpm range and particulary and lower and medion engine speeds . Also having four jets compared to just two to play with, would allow for finer tuning.capabilities. Mart3406 ==========================
Re the fat floor puddle thingy. The runner will be inset and a slight lip will automatically occur Also My engine runs little more straight up than stock so the runners will have a slight down ward slant although not much thirdly at 118 MPH and 6000 RPM I am hoping the puddles wont have time to form. Hopefully staging will not be a problem. I have done quie a bit of playing around with manifolds, runnners and stuff over the last 40 years or so and really most of the hand made stuff I made did work well. Well enuf someone gave me money for them. I have one severely reworked Team G for a 440 that no one has jumped on. It did work very well though adding a couple of MPH to a 4150 car. Maybe after i am gone my wife can get a few bucks for it at "the sale" ;>) Don
Yes the 390s would work but I am committed to the Holley 500s for now. It s German blood thing. You might call it stubborn but we call it determined. I think i have more chance of finding the 500s but you know if two 390 four barrels showed up i would be on them like ugly is on a moose. And you are also right. Two four barrels on a six tunnel ram would look very cool. There is another private reason why I am going with the 500s for now. Don
Worked on the taper for the runners for the last two days. I have it pretty well where I want it but it will need a bit of massaging yet before final welding. Also made a firm deal for one 500 two barrel today and perhaps a second will be available. He is thinking. I wasnt intending to be going at it this hard but it seems to be pushing itself along. Don
I know I said i thought I would get this waterjet cut but I have the pattern and I have the mill so it just didnt make sense not to do it here. I wanted to send this in to the thread "biggest baddest mills on the HAMB" but they were the wrong type of mills . I know this isnt the biggest or baddest but it is still quite stout for a home shop. It is a Kearney Trecker 2H circa 1939. Don
Don - I noticed by your last pic that the 2 center runners are shorter than the outer ones - will that effect flow at all ? - just curios as I am designing a manifold for a 4 cyl to replace the throt bod on the 2.5 in my Dak - I need something that works well and looks cool with the HEMI style valve cover I am making to fit over the stock one - going to look like HALF A HEMI - also are you setting your 2 carbs so that the butterflies are opening into your runners or are they kicking the mix to the rear of the plentum as Ive heard that the mix will "favor the back 2 or 3 cyls if the butterflies kick to the back - dont know myself but that is what I herd - Jaxx
They are shorter by 1/2 inch. Very minor difference . Very few manifolds would be that close even. Comparatively speaking the manifold I have now has over 6 inches in difference and only the outside two are even close to tuned length. I could run them all straight i which would make them all the same but i like distribution I get from grouping them in threes under the carbs. The offest from the carb barrels is equal for all three. This may be a personal quirk but I am going to try it this way. If you want a good expample of a tunnel ram with uneven length that works check out a BB chevy ones for stock pattern intake ports. All of the sudden the 1/2 inch becomes insignficant. 1/2 inch is about 400 RPM in tuning but because the angled ones are longer and shorter both they share a very similar average tuned length. What will be the real test is what the car runs or doesnt run when I install it. I have already had one 4412 carb donated to the project. One to go. In the meantime I am switching carbs on the current manifold from Eddy to Holley (600DP)just to see what happens. Leave no stone unturned is how we go at it. Don
A plenum of sufficient size distributes air fuel very well. The more distance you have or space between the runner entry and the carb entry the better the distribution however if you get too much space the manifold can be lazy or lack a crisp response. I choose the 3x3 and was tempted to go to 4x4 but I am sticking with the 3x3 for now because with a tiny engine I need the respnse as much almost as i need the hp. It is always easier to gain Et at low end or the start of the race then at the end. Et gains at the top end are the most expensive$$$$$$$$, While it does take a fair amount of hp to gain MPH it takes a lot of HP at the end of the track to make a significant change in ET. At the begining every change you make mutilpies because you are now going faster at every stage of the run. A combination of both works best for me. Good Hp but instantaneous response is what I like. Don
This is an exceptionally informative thread, keep up the good work. I look forward to seeing the end results.
I was back at it this afternoon. I made reinforcing plates to weld the inner runners to before welding that to the plenum. Makes the welding and attachment easier and stronger. I also made 2 carb plates and did a trial fit with the one carb I have. Still need another one but it will come. FLange is still in the mill. I do a couple of openings when I have time. Little by little it is coming together. Don
I am looking at my own picture thinking if I use a rear bowl from a four barrel on the next carb they will come out together. I believe I have one too. It will look cool I think doing it that way and will be easier to plumb. Don
Cool! One question though, why is there space past the intake runners on each side of the plenum? Is it just for a larger plenum?
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