The engine builders "black art" (AKA Rod ratio)

Discussion in 'Classic Mustang Specific Tech' started by Rusty67, Nov 7, 2007.

  1. brianj5600

    brianj5600 Active Member

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    There are a lot of variables. I like to read and try to understand them, but know that if I want the absolute most out of my engine, I will need help from a professional.
     
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  2. rbohm

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    when it comes to cylinder head ports, long rod engines prefer small ports, where as short rod engine prefer larger ports. this is one reason why a 302 built similarly to a 289 works well at low rpm, but falls flat on it face at higher rpms, compared to a 289 that doesnt get off the line quite as well, but will rev to 6500 with ease compared to a 302. if you build a 302 with much larger ports and valves, it will rev like a 289 does at higher rpms. drop the larger ports on a similar 289, and you have an engine that falls flat on its face at low rpms, compared to a small port head, but will rev to the moon with the breathing potential.
     
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  3. brianj5600

    brianj5600 Active Member

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    What is a big port? And what is a small port? I have seen more talk about port cross section, but not so much runner volume. Runner length can skew comparisons on 2 heads with the same volume.
     
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  4. SoCalCruising

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    blkfrd: Missed your Q about the Webers first time 'round. I got them from Redline. The bellcrank location and linkage left much to be desired - it was hardly possible to have the passenger bank of carbs act in sync with the driver's side bank because the passenger side was slaved. The idle adjustment was also slaved. All that made for banks that wanted to act out of sync. Luckily, I have a Weber expert in the family :). He restores English cars and has worked a lot on Webers - mostly DCOEs (Jags and Aston Martins), but he got the downdrafts working pretty good. Jetting is close, but it still needs to be dyno's for final jetting. I'm working on scheduling that.

    I used to have a ported Stealth intake and HP series 650 DP on it. The carb was reworked by a local pro. It ran pretty strong, but it's picked up both HP and torque all over with the Webers. The throttle response is just wicked. You are correct about tuning, just as you stated it. I have 4" stacks on it now. If I ran the short ones I could fit an air cleaner under my stock hood, but not with the 4"ers. I don't want to give up anything down low. I'm running just screens on them for now, but I have an air cleaner setup ready - just have to decide how I'm going to get the extra hood clearance. Probably, I'll opt for the '67 style hood for '65-'66 cars. That means paint, tho, which opens up another can of worms....

    I am planning to write up a more comprehensive post on the Weber experience as soon as I have the car dyno'd. I know people will want to know how much power it makes. Webers are not for everyone, certainly, and I want to share my experience so that anyone thinking about them will have that to draw from .

    The cam is custom - 230/236 at .050 with about .57x" on the intake and a bit less on the exhaust on a 111" LSA. It's installed at 107* on the intake. It's just big enough to cause off-idle issues with both the Holley and the Webers. We may tune it out, given a little a more time.

    I appreciate your attitude about my posts. I noticed your combo long ago and thought it was pretty creative. Personally, I vacillated between building the 331 with a 5.315" rod and more C-H, vs. the 5.4" rod and shorter piston. I would up with the 5.4" rod because I liked the Mahle PowerPak pistons so well. They are light, have no oil-land support ring, and are coated. Had I not found them, I might well have used the shorter rod. There are a lot of Chevys running around with short rods and they seem to do pretty well.
     
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  5. blkfrd

    blkfrd Member

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    Sounds like I could fit this setup under my hood ('67 shelby style for a '65/'66). I almost pulled the trigger on this when I had to rebuild my engine last year. Instead I opted for a single plane. The single plane is nice, but it's not Webers.

    I believe we both have a common acquaintance...Dana Williams. I went to his place in Colton a few years ago and had him do some work on a vacuum secondary carb I used to have. He sure knows his stuff and I believe he is equally knowledgeable about Webers if I remember correctly.
     
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  6. rbohm

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    small port = stock 289/302 cylinder head

    large port = world products windsor sr head on the same engine

    huge port = boss 302 head on the same engine
     
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  7. SoCalCruising

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    Yeah, I know Dana. He did my Holley. He also does most of the Weber setups in the immediate area. There's also a guy in Fullerton that is supposed to be good. The guys at JMC Motorstport in San Diego have some experience, too. I had originally planned to have Dana dial in my Webers, but my cousin filled me in on all that he's done with them and then volunteered himself. He did a good job with the linkage. Dana will probably see them at some point.

    I didn't notice you are from Corona. Come by Farmer Boys Sunday at 11A and introduce yourself, will ya?
     
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  8. bnickel

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    lot's of info has been posted since i left. you guys are diving into more technical stuff than i can comprehend at the moment, i'll have to go back and re-read everything. i still stand by what i said earlier though that if you have the room in the block run the longest rod possible for the combo without compromising the piston/ring package. in my case that's the 6.58" 400 rod with a KB piston, the pin get's up to right under the ring land but there's enough meat there that the ring is not compromised. so that's what i'm going to build, if i was looking for all out power i would use a stroker crank but i want as much mileage as i can get out of this thing, both fuel mileage and actual driven mileage, i plan on using a high velocity small port head (afr 165 outlaw if the budget allows or e'brock or ford racing x303 if not), smallish hyd. roller cam and hopefully fuel injection of some kind. i also plan to run E-85 in it at some point as well so i need to keep the compression ratio up there and the CR with the long rod setup is right where i want to be as well. so my combo is mostly planned out already.
     
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  9. Hack

    Hack Active Member

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    If you're going to run E85 I would think you really should build for it in the first place. Ethanol has a LOT less energy content than gasoline (about 30% less), so a lot of parts will change when swapping. Plus you'd probably want to take advantage of the 104 octane. :)
     
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  10. bnickel

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    exactly why i'm aiming for around 10-10.5: compression, the cam and everything else i have planned fo it should all work fine with the E-85 and i'm also planning on as many coatings as the budget will allow too mainly to keep the heat in the combustion chamber and for extra lubrication protection IE: piston top and cylinder head coatings as well as intake and exhaust coating and piston skirt and bearing coatings as well. those are the main ones i'm looking at and if the budget will let me i'll do others as well. i'm also planning on stainless lines and possibly a stainless tank too, we'll see how it all plays out once i actually start on it, hopefully next spring or summer.
     
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