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Discussion Starter #1
Im building sheet metal intake for a injected(alky) Hemi using BAE heads. Ive done good amount research on runner sizes,length and cross section. Theres no clear cut way to decide except lots past experiance. I know this is benifit of someone like Wilsons or other specailest in intakes being first choice. Unfortunately there noway to come with cash for that approach.
I would like to get some input from guys running simular sized engine as to what the runner sizes and plenum sizes are roughly on their cars.

I can build a quite a few for cost of new one and right now I have the time,more so than the money. Only cost will be argon,welding rod and some aluminum. I have one already done so please no advice on more to it than I think,maybe more to getting it perfect first shot. Besides provides LOTS of aluminum weldind fun plus few extras oh shit thats hot scars.
 

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Discussion Starter #2
oh Yea few engine specs might help . 4.310 bore 4.500 crank 7.100 rod 13:1 compressions an cam is 284/288 .770 lift injected alky (maybe 30 to 50 % load if wild ahir in ass grows to much) 4.10 gear with 32 tall tire in roughly 1700 lb FED with 1.69 low glide. But that makes it easier to figure what your comparing against.
 

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The link above is a true NHRA "A-Fuel" set-up (90ish% Nitro = Low RPM...maybe 7500). Methanol could spin MUCH faster, thus needing a much shorter runner. Look at Scott Park's small-block version of a similar fuel/car/trans/induction combo...and this is an old picture...the stacks are much shorter now.


Photo by Dawn Mazi-Hovsepian

Stack injection is a common solution, but a good tunnel ram with an Enderle hat on top is hard to beat...simple, easy to tune, good anti-reversion arrangement, lots of "shelf" parts.
 

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FYI I talked to Paul a few weeks ago and he told me he was going in the hospital for what was some major surgery. Told me he was going to be layed up for a good while recovering.
 

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Discussion Starter #7
Not looking for exact same combo something in ball park. Understand not going to be many running hemi head,especaily the BAE stuff. But figurer a 510 to 540 inch combo with simular bore stroke would be good starting point. I have one built and 3 sets flanges already cut out. If my first choice is way off what a few are running w/simular combos then maybe I'll get idea which way to head with next setup. If gure to build cpl and do some testing witht them,but if all are out in left feild all I will learn is hey this don't work. Right now my runners are what I would call a mid range in length and cross section. So if 5 guys chime in and say mine are 2" shorter and 3/4 the cross section then I now what I'll build for second setup. Yea LOTS work but got to learn somehow whats works best.
 

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Discussion Starter #9
Ok what I have is port size 2.125x2.350 top of runner is 2.280x 2.500x6.00 long and almost dead straight shot to valve which is 2.375.

Yea could care less how a carb works on anything I run. If god ahd wanted man to run carbs he would have given man the idea for injection A good trashcan desreves better than a carb(Alan Starr ,Starrliner topfuel owner and tuner Quote) and i agree 10,000%
 

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Discussion Starter #10
I think you still need velocitty to proved cylindr filling as much as possible. Maybe some who disagree but physics might win out here.
 

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I think you still need velocitty to proved cylindr filling as much as possible. Maybe some who disagree but physics might win out here.
I look "down the throat" of Park's little engine might change your thinking. BTW, that particular dragster pictured above went undefeated in its first two full seasons in Jr. Fuel in the Hot Rod Reunion series. For the last few years, he runs NHRA Comp in A/ND and regularly qualifies in the top 5. I think he's running a new chassis this year.
 

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I'm in the same boat as you are as I have the time, patience and know how to build one but the money is scarce as well. As i don't share the same engine combo as you have I still am building mine as an injected Alky setup and have been doing all sorts of studying on port size, taper, length, volume as well as plenum science. There really is not much out there for info for the injected guys because the world of carburation as been dominating. However from what I have found is basically that the injection induction is much more forgiving than a carburation intake. You can be off a little on your sizes. For my buildup I found some info from the carb side of it and went from there. My motor is a 722ci so mine is quite bigger than what you have but building the intake still falls in the same plane. I used a 30 % increased taper and volume from my port size of my heads and that is what gave me my final dimension at the end of the port. I'll have to find the calculation I used but i ended up with 9 13/16" port length and that is the total port length from the back of the valve. Plenum volume i used for my application was 2 to1 of the cubic inch size of the motor (1444ci). Then i figured out the actual size of the volume from there which also included the adapter for the injector. It seems to be in line with most of what I have seen for a carburated version of this kind of manifold. Mine is also a convertor/automatic so it makes a difference in plenum and runner as well. Your probably running a clutch where I think its not as forgiving as my combo would be.
I could dig up a bunch of my notes and formulas if you need.
 

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Discussion Starter #14
I agree Parks car hauls ass. Cpl thing first its small block spinning its ass off with 3.75 crank.Mines spinning 8000 MAX with 4.5 crank. If I tried so spin it at same rpm probly north 10 grand Id have more of this,
. Anyone want to guess at what rpm that happened 9500 to 10,000 on alky motor with 44 lbs boost.If you have have never driven a car with real blower , they never quit pulling reguardless rpm

With injected 526 i figure turning it 8000 is about all I want to do,unless I get some better valvetrain. So a huge runner might not work as well with rpm differance. Plus there are a few who think the larger and larger ports are part of reason some bigger heads are not as consistant,seems intake runner size would effect also. While I would a no hold barred car again right now i have to reprogram myself to think consistant more than anything,if winning is goal. If it isn't then stay home has always been my thought.

I guess since 2.875 bore is max for Jr.Fuel area of 6.5 sq inches(- shaft and butterfly edge area) and my first manifold has cross section of 5.7 sq.inches I could build another with shorter and fatter(more tapper) and compare the two. maybe setup for 2.400 wide and 2.800 tall for 6.72 area a18% increase.

Might help tune car to run on questionable tracks with more top end and less bottom end torque.
 

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Regarding plenum volume on injected engines - I worked with Mark Kinser from Iowa on some dyno tuning. He does quite a bit of injected applications, including tuning EFI systems on his dyno. I asked him how the plenum volume affects performance on an injected engine, and this was his response:

"The less plenum volume an injected engine has, the more "zippy" the throttle response. At one end of the spectrum is stack injection with NO plenum...VERY throttle responsive. The other end of the spectum is a large tunnel ram arrangement. This yields a "softer" throttle response, which can be desireable in truck or tractor pulling where you roll into the throttle to prevent blowing-off the tires. Wide open max power will probably not be very different."
 

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Paul, I didn't realize Mark was still into the racing stuff. Used to see him all the time when he ran a TAD. I'll have to hunt him down and say hi!
 

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Discussion Starter #17
Thats helpful since I have two types injectors one sits on top of tunnel ram base and adds no volume the other is simular to enderle bug except shorter and wider. According to that the only differance would be in the snap of throttle so I can run either with very little performance differance.
 

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Discussion Starter #18
Also explains why when lil brother ran injection on this motor with nothing more than short adapter sitting on a blower manifold it is was ver respnsive reguardless tuneup.
 

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Regarding plenum volume on injected engines - I worked with Mark Kinser from Iowa on some dyno tuning. He does quite a bit of injected applications, including tuning EFI systems on his dyno. I asked him how the plenum volume affects performance on an injected engine, and this was his response:

"The less plenum volume an injected engine has, the more "zippy" the throttle response. At one end of the spectrum is stack injection with NO plenum...VERY throttle responsive. The other end of the spectum is a large tunnel ram arrangement. This yields a "softer" throttle response, which can be desireable in truck or tractor pulling where you roll into the throttle to prevent blowing-off the tires. Wide open max power will probably not be very different."
This actually gives me a better feeling about the combination that I have been building and designing for myself. Being that this motor I have is being used for mud racing, a "softer" throttle response is actually a great thing considering the lack of traction. However I don't know how my thinking holds true seeing that I am also adding a boat load of nitrous to it as well and most of it is right at the launch.
 
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