cubic inches vs. head flow vs. rpm

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valid points.
There is a formula for needed cross section as well as cylinder head flow, valve sizes etc for a given C.I.D. Any of the parameters are bendable of another is flexible enough that cover the others short coming. brought out well in David Vizard's book...how to make hp?
gentleman on an AMC website talked about the "smaller" vs. "larger" production cylinder head and that the smaller one would be better for the 401 in certain applications. so much for bigger is better. I like the three categories; my thought is stock modified head for this one. although the Eddy would make it easier to obtain. to really muddy the waters, look at NHRA "stock" and "super stock" before aftermarket heads were introduced. or modified production classes. engine masters and Steve Dulcich(sp?) articles are great! seems he beat to his own drum and did not "build" with parts that the sponsors wanted. all goodness to ponder.
 
abodyjim said:
Here's how I see it, there is basically 3 different categories.
First would be what I call basic. Production block, production heads and I'd even throw eddys in there or any head where the ports resemble a stock port. I beam rods, factory cranks and 4" cranks are the norm it seams. The combinations seem to top out around the 500hp mark.
Next would be moderate. W2's and other aftermarket heads come in to play here. Usually still production blocks with the addition of H beam rods and stroker 4" cranks are used. These builds seem to target a 600 hp mark.
Last would be aggressive. After market blocks, high end cylinder heads, H beam or aluminum rods, 4+" cranks and even some exotic parts. I would consider this category a max effort with a 600+ hp goal.
Now the disclaimer, this is a very basic break down of how I look at it. I'm sure someone on here has or knows of someone that made 1000hp with a stock block, crank and heads. There is overlap from one category to the next with any combination of parts used.
Also, I've been told camshaft lift and compression is your friend for making power so I would look at maximizing those to the combination of parts you chose.
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S

START WITH FULLY CNC`D ALUMINUM CYL. HEADS, and match components from there, wallet allowing, with how far u want to go. Don't forget to pull the heads down and check them, u may want to change a few parts !
 
Mopar has a very limited head selection, you'd have a hard time over doing it heads wise.
 
I’m sure glad I can check air speed on heads I port as this math crap is way over my head. If the speed appoches 380-400 FPS I do more grinding in that area to calm it down some making better flow numbers and more horsepower
 
pittsburghracer said:
I’m sure glad I can check air speed on heads I port as this math crap is way over my head. If the speed appoches 380-400 FPS I do more grinding in that area to calm it down some making better flow numbers and more horsepower
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I’m curious why 380-400 feet per second? I know nothing of hands on porting. What occurs at that speed? Something with the boundary layer? It’s not even remotely near the speed of sound. I think that is around 900 fps.
 
furrystump said:
I’m curious why 380-400 feet per second? I know nothing of hands on porting. What occurs at that speed? Something with the boundary layer? It’s not even remotely near the speed of sound. I think that is around 900 fps.
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That's where trouble starts. I like to keep the speed down a bit more but everyone has their own way of getting it done.

The thing that needs to be remembered is a big port isn't always bad, and a small port isn't always good.

Look at NASCAR. They use cylinder heads today that 30-40 years ago would out flow and are bigger than a square port BBC head. And they make power.

The chances of getting "too much head" especially when you are dealing with Chrysler's.
 
furrystump said:
I’m curious why 380-400 feet per second? I know nothing of hands on porting. What occurs at that speed? Something with the boundary layer? It’s not even remotely near the speed of sound. I think that is around 900 fps.
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As yellow rose said trouble starts and at that speed it has a hard time making the short turn and instead it shoots the turn and crashes into good air going across the top of the port. Kinda sounds like a garbage disposal only different. I attended a two day theory class given by Darren Morgan and he said if you see that speed go after it and reap the rewards. On the exhaust side he couldn’t care less about flow numbers but told us to reach for 325 fps air speed and the port will work great.
 
The bigger then engine, the more RPM you turn, the more head flow you need.

There.
 
I never ever worried about any of this crap before we made 1.745 hp/ci on 91 octane. We just went with the best cylinder heads we could afford.
 
IQ52 said:
I never ever worried about any of this crap before we made 1.745 hp/ci on 91 octane. We just went with the best cylinder heads we could afford.
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Learn to do it yourself and you can really take pride in what you can do. Anyone can buy horsepower
 
Oh yeah......the best we could afford then were Edelbrock RPM 440 cylinder heads that we reworked.
 
I build street and street/strip engines. My customer base is for the most apart middle class. What those details mean is the primary limiting factor is money. So intent, expectation, and budget are the trifecta for me. Once that's all established in a mix that allows to achieve the result, meet expectations, and stay within the budget - the parts choosing comes into play. It's (very) roughly 2cfm per hp when talking about an efficient engine within a certain rpm range. That is regardless of compression ratio, displacement, or fuel. The heads have to move that much within the restrictions of the lobe profile(s) to reach that goal. It's pretty simple at that point as far as engine parts. Rpm range will influence parts choices, as will the intended use of the vehicle. So you either match the engine to the car, or match the car to the engine, depending on the situation.
 
moper said:
Yeah - but solid majority can only buy the parts - not assemble the whole package to USE it.
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But that’s the easy way to go about it. I could have never raced for over 44 years if I had to pay to have things done for me.
 
I can only give real world street examples. Take the smallest LA, the 273. Nice package, makes decent power. Next step was 72 340 J heads, 1.88 intake valves, 71 340 intake and TQ. This added 1,000 usable rpm and added quite the WOW factor. But it was a bit crazy on the street, luckily it was a 4 speed car so I could just keep it in a lower gear. Both sets of heads were pocket ported, gasket matched top and sides, milled to NHRA minimum cc chambers, and a good 3 angle valve job. The only engine I heard of that the heads were too big for the street was the Ford Boss 302. 351 4 barrel Cleveland heads on 302 cubic inches pushed the usable rpm past the streetable comfort range.
 
66fs said:
I can only give real world street examples. Take the smallest LA, the 273. Nice package, makes decent power. Next step was 72 340 J heads, 1.88 intake valves, 71 340 intake and TQ. This added 1,000 usable rpm and added quite the WOW factor. But it was a bit crazy on the street, luckily it was a 4 speed car so I could just keep it in a lower gear. Both sets of heads were pocket ported, gasket matched top and sides, milled to NHRA minimum cc chambers, and a good 3 angle valve job. The only engine I heard of that the heads were too big for the street was the Ford Boss 302. 351 4 barrel Cleveland heads on 302 cubic inches pushed the usable rpm past the streetable comfort range.
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add 426 Hemi's to the list to. Dogs on the street and even the track till LOTS of work is performed on them. Salt flat cars. LOL
 
pittsburghracer said:
But that’s the easy way to go about it. I could have never raced for over 44 years if I had to pay to have things done for me.
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Understood - and no disrespect meant. I'm one of those that does for those who can't because I can't afford to do for myself...lol. Life's funny that way sometimes.
But in regard to the OP - He's not your type of racer from what I gather, and your type is getting more and more rare.
 
pittsburghracer said:
But that’s the easy way to go about it. I could have never raced for over 44 years if I had to pay to have things done for me.
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I agree with Moper on that one. For many, experimenting on assembling an engine for the first time is a scary thing to possibly screw it up and destroy it. Then to watch all the hard earned money go down the tubes in minutes flat.... ugh! It does take a certain amount of guts to gamble on what you may not believe you have inside yourself. The cost factor for a simple rebuild is high enough for many only to do it once. And that gambling factor isn’t in them. I don’t blame a anybody for having an experienced hand do it for them.

I would not make a bet on something I know nothing about when the bet cost is high and the probability of failure is good due to my inexperienced past with the cost being whatever it maybe. In the case of a full engine, tht cost could be a months pay? 2 months pay.

I did a lot of teeth cutting when I was single and at home with the parents. (Over 30 years ago) Then, it would have been disappointing to fail, not catastrophic. Now, even though I’m making 10 times the money, it has to be used for much more important things than toys. I may not be as brave as when I was a kid to potentially throw away money on a failure.

To that end, I was happy to pay the man. When the man came over, to install my pool, the electrician to run wires, to install my kitchen, to put the roof on my house, I was happy to pay him to do it right, do it once, do it quick, make life easy for me.

When I was in the biz with the garage, I was doing what I considered an easy thing. Anything from the easy brake job to helping a local hit rodder/street racer tune his car, swap a cam, change exhaust, etc... For many of us, this is EZ crap to pull off. For others, it’s a monster dirty greasy puzzle that has huge dangerous consequences.

I personally love screwing together an engine. I love to tinker with them. For others, it’s a big scary thing.
 
I lucked out on my very first build. A local Mopar expert took 13 months to build an engine for me. He even went as far as to build a dirt track engine for a customer I sent him before mine. I made a promise to him that day that I would never wait again, and haven’t. All I had were books to learn by. I sure wish I had the Internet and forums like this around back then. 62 years old now and still have most of my old S&K sockets I bought when I was 16.
 
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pittsburghracer said:
I lucked out on my very first build. A local Mopar expert took 13 months to build an engine for me. He even went as far as to build a dirt track engine for a customer I sent him before mine. I made a promise to him that day that I would never wait again, and haven’t. All I had were books to learn by. I sure wish I had the Internet and forums like this around back then. 62 years old now and stuff lol have most of my old S&K sockets I bought when I was 16.
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you are exactly right !!!
But look at what you have now... An A body with 2 feet of daylight under the front tires.
None of which came overnight..
May I state the obvious? When a enormously generic question is asked about 'how much HP can I make' comes, there is never (almost) a simple answer. At least I haven't been able to condense decades worth of experience into a single sentence...
 
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