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Post by polarapirate on Jan 14, 2020 23:26:40 GMT
Damon, you were talking about intakes. What is your opinion of Offenhauser 2X4 hi rise ( if you could actually call them that, guess they are compared to their low profile version) intake manifolds, like for a Pontiac, how well do they flow ? I notice a lot of designs in their outdated catalog. They are kind of pricey, too. Anybody else ever tried Offenhauser intakes ?
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Post by Fugly on Jan 15, 2020 2:04:08 GMT
Depends on how big the engine is/ how fast you are trying to go. Ports are not really big enough (cant be ground enough) for a big engine, and there is no where near enough plenum ( could be solved with a spacer)
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Post by oldracer on Jan 15, 2020 2:49:45 GMT
Depends on how big the engine is/ how fast you are trying to go. Ports are not really big enough (cant be ground enough) for a big engine, and there is no where near enough plenum ( could be solved with a spacer) reason #453 why I was mentioning other intakes, by your own words not big enough for a big motor. so what does a guy with an off brand do if he wants to run with the mopars in the faster classes. don't you think the big box indy intake is a gloryified tunnel ram in a box?what about the mod man, just a big open box with some runners, who ever said it was legal? just cause Indy made them and pushed them to us. cross rams are just tunnel rams laying down so they fit under the hood . I'm only stating this cause the intakes in question are not true tunnel rams (even if they're call that) as far as the rules state fit under the hood and oversized scoops.
an no I don't like to stir the pot just bringing up stuff I've heard from other people that probably are afraid to bring it up.
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Post by Fugly on Jan 15, 2020 4:02:30 GMT
I said THAT intake had those attributes...the alternative , period version that will work? ...STR 15 for the low deck, STR 14 for raised. Mine is a 15, Dave Ardoin has one, as well as Mike Kurz to name a couple I know of. The Modman , from a technical perspective is more a combined plenum single plane than tunnel but I won’t argue that it may be in a gray area of the rules. The Indy box was developed by Dave Duell in the early NMCA ( not current org)/NSCA days and approved at that time. The factory crossram will support low 10’s/ high nines with Arlens mods. There are similar intakes for Chevys,( I just supplied on to a Chevy NSS racer who I hope will be coming to a VNSS race this year) Pontiacs and the Fords have the tunnel port ,etc. None are cheap or laying around at Sears, but they can be had and do work.I said before , and will repeat, I did not make the rules and in some cases don’t necessarily agree with them. That said, this class was formed with a specific intent. The older rules started with the phrase “full size cars....” . I think people don’t realize or miss this part- that is why Mustangs , Camaro etc. aren’t included. This is NOSTALGIA super stock , not “1960-!969 revisited” , only a part of it. I realize Cuda’s and AMX are in and the stories for how that happened are known. Was it the right decision at the time? I don’t know..w.hat I do know is once you change one rule, along will com another and another. There are people out there who can definitely verify this. I and others spent a lot of money to create cars that were legal when this started and I suppose that’s part of the reason I have the opinion it should be left alone. The class has survived 3 decades properly and Victory has the highest consistent car count I have ever seen in NSS-there must be a reason? Is it perfect, probably not...however, every suggestion on this thread has been repeated over the years ad nauseoum and has been tried by some, generally without good results. I don’t say that to discourage or argue, its just a plain historical fact and repeating it likely wont have any different results than seen before IMO.As far as the tunnel ram goes, two of the intakes that were disallowed were quite definitely tunnel rams by manufacturer description and visually,they did not exist in that era to speak of and were used in Pro stock , not SS, just a fact. Of course they are the easier , cheaper route to more speed, but ( and I am being a smarta.. ) so is nitrous.... Take this as a well intended discussion, no offense meant....
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Post by Fugly on Jan 15, 2020 4:46:27 GMT
Here’s an idea- instead of arguing points over and over- here are some pointers... The STR I use also has too small ports ( not as bad as the offy) but it does work. Most people think the engine sucks the air in-this is not true and its an important concept. Air has weight and basically falls in the evacuated space in a cylinder -why is this important? Because you only have so much time to fill the cylinder(s) and less the faster you turn an engine. To make an older intake work there are a few things to look at. The plenum is basically a “storage area” - most of our engines are firing 2 cylinders or more consecutively in the firing order (5 and 7on Chrysler) and what happens with no plenum is you get lean cylinders or semi filled cylinders, both hurt power. So the smaller intakes with no plenum can be helped with spacers. A couple races have used this theory one was protested but won- why? The rules say “ Manifold top may be modified for carb placement”-while it may be “constructive reading” of the rule, its legal- “ I want my carbs closer to the hood”....Too large a plenum will slow velocity which will kill the mid-top end. Runners should not be just hogged out-they should have an included angle between 3-8 degrees ( angle between top of runner and bottom if you drew a line between the port size art each end. This is because of friction/ turbulence within the intake-making the exit side smaller than the entrance is similar to putting you finger over the end of a garden hose- increases velocity and resuspends mixture, making up for friction losses (this is oversimplified and if you want to learn it, there is an SAE “paper”-600+ pages callled short pipe dynamics.) so to use the old intakes make the ports bigger, try to maintain some taper top to bottom, and size the plenum for the engine size/speed ( generally in our case make it bigger)...hope this helps
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Post by rebelrouser on Jan 16, 2020 2:01:58 GMT
My car has a single four barrel Edelbrock victor Jr. max wedge port intake with basically a box welded on top of it and the tops of the runners cut off, so both carbs will be exposed to the engine. As Damon said, the rules say factory cast manifold with modifications to the top are allowed. My manifold fits under an almost stock mopar hood scoop, not the big oversize ones like most of the guys run. I have a total investment of $400.00 and some time with a spool gun. I have a homemade flow bench, I used to determine where to cut the runners at. The manifold is 3 tenths quicker than a factory mopar cross ram. My car has run a best of 9.64 @ 140 mph, at 512 cubic inches, and two AFB's I am not a rocket scientist and do not have the resources that a lot of the faster cars in our class have. As Damon mentioned a little reading and understanding the physics involved is why it works. It really needs longer runners but it works pretty good as is. It's not that big of a deal to get something to work if you want to go fast and stay in the rules. I never ran the Indy manifolds, cross ram or modman, simply because they cost too much, and Russ told me one time basically if you don't buy my parts your car will never run 9's, well it runs 9's and does not have a single Indy part on it. Not saying Indy does not make good stuff they do. I have a set of pro comp Edelbrock copy head castings I bought for $600.00 and did the porting work myself. Again I would have liked to have had a set of Indy heads, I am sure it would go faster, but I could not afford them. My carbs were bought at a swap meet for $50.00 each, with some simple modifications they run very well. Drag racing is a sport that you can spend as much money as you want. As I said in another post, one of the things I enjoy is building something and making it work.
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Post by c5farmer on Jan 16, 2020 21:35:11 GMT
I just want to know why this intake is legal......
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Post by c5farmer on Jan 16, 2020 21:37:19 GMT
And this intake is not legal.....except one is on a Mopar and one is on a Chevy??
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Post by sportf on Jan 16, 2020 23:16:29 GMT
Maybe it is, but it looks like an "elevated plenum" with runners going down at a steeper angle than the Mopar intake (which may look elevated in the picture, but is about the same height as a stock plenum.
I think the intake rules between Victory and NMCA is the same, unless they changed that rule also once you are in the 9's?
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Post by polarapirate on Jan 17, 2020 0:48:23 GMT
Jerry, the Mod Man Mopar intake you have a picture of above is advertised in the Indy Cyl Head catalog on page 30, with bold type "Think Short Tunnel Ram !". So does that mean Indy is selling it as a tunnel ram or just wants you to imagine it as a tunnel ram. Guess the intake rules need to be clarified. Last I saw NMCA was allowing 4 bbl intakes, new rule change.
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Post by sportf on Jan 17, 2020 1:15:38 GMT
NMCA has allowed single 4 manifolds for a long time now. But I am pretty sure there is no tunnel rams.
You can define a tunnel ram in a lot of ways. Mine is, plenum elevated, to allow straighten runners downward to intake port. But I think you also have to look at engine style. That is, you can put your hand under a stock intake manifold on a BB mopar, but you can't put a finger under a stock Chevy manifold.
So, when you see space under some intakes, it may or may not be elevated.
If you are building a car to run within the rules, just check with someone before you drop some money on a part that won't work within the rules.
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Post by Fugly on Jan 17, 2020 4:59:41 GMT
Ok....I don’t know if the question on the Modman is serious or not, but for fun I will answer it. Number one , the rules specifically state no tunnel rams and the title for the other intake on mfg ad is Holley Pro Dominator Tunnel Ram-the Modman advertising does not call it a tunnel whether they meant to imply it was as good as one or not. I know that is not enough explanation, so here goes the technical explanation. In order of power production by intake design lowest to highest-dual plane , single plane, cross ram, tunnel ram , tunnel ram with divorced carbs.... A true tunnel ram is designed with long ( relatively) runners and a fairly straight shot at the ports. The straight shot I think is obvious, runner length maybe not-this is the condensed , simplified reason: intakes behave just like a tuned exhaust header. The intake pulse is not a single pulse, but rather a two part multiple pulse event. The initial pulse is strong, fast and short followed by several others of varying strength and length. These are referred to as orders of magnitude. Typically , we deal with 5 orders in manifold design and tune to the third, because it arrives at an optimum time and length to take the most advantage of. A short runner like the Modman or most single planes is not long enough to tune to and , while it will help some if tuned right, its not nearly as good as a long runner tunnel not to mention the curves to be navigated. The pictures presented are a little misleading on height unless you pay close attention.The Modman is basically a common plenum single plane. As far as crossrams(including the ones available for the Chevys and Pontiacs- they are in fact a layed down tunnel ram,but called a cross ram. They are period correct ,used on super stock in the day, etc, but not as good as a tunnel because of distribution issues and the curve they must follow like a single plane. Maybe that helps?
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