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3 inch stroke motor project, rod ratio, and mpg

32K views 184 replies 21 participants last post by  4 Jaw Chuck 
#1 ·
my name is Austin, and this is my first real post on here. I hope it doesn't make you guys think I am nuts or have a screw loose. Any ways I have a couple of questions that you guys can help with. I have acquired for a song 2 283 motors, a 327 small journal motor and a 307 from craigslist. These things go super cheap here in Louisville and I know why. It's because everybody wants big cubes to get the power way down low in the rpm range. Anyways, I have been reading about how all the people on here are very much against using these motors in a full size car, and I dont mean in drag racing, but even just a daily driver. I don't mind that I wont win any land speed records thats not what Im looking to do. I just want to get better fuel economy, I cant afford the gas. So here are my questions: #1 If I get 6 inch rods and mate them to stock 350 chevy pistons in that 327 block and hook them to the 283 crank, would that work? #2 Compression height calculator shows about .040 higher in the bore with them, but dropping from a 3.48 stroke of a 350 to a 3 inch stroke is gonna lose alot of compression so is +040 closer to the heads too much? #3 In my mind, rod ratio increases dwell time at tdc so I can run less ignition advance and still burn all the fuel and the same with compression ratio up to a point correct? I would like 11:1 static compression, I think if I watch how much ignition timing I am running it will get better gas mileage especially since I have a huge radiator to keep the heads cool. #4 If nobody thinks a 3 inch stroke is good enough to be in a heavy car then why did gm put them in the 1957 chevy and lots of other heavy vehicles like trucks studebakers and checker taxi cabs until 1968? #5 According to wiki the 327 was the most powerful small block combo ever made until the LS6 in 2001. Even the paltry 307 managed 200 hp (149 kW) SAE gross at 4600 rpm and 300 lb�ft (407 N�m) of torque at 2400 rpm. http://en.wikipedia.org/wiki/Chevrolet_small-block_engine The question is, with the short deck height of the small block, is any more stroke than 3.25" really helping peak power at all, and is more stroke actually hurting fuel economy do to rod ratio? The main question is will 350 pistons work in my 327 with 6 inch rods and 283 crank. Thank you for reading, Austin
 
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#152 ·
I love talking this stuff you guys and I really appreciate all your input! I just had a theory about ten years ago, eventually gathered enough wrong info or whatever to form a hypothesis, and figured out a way to test my theory: Try putting a 283 in a 14,000 van pulling a 2200 lb trailer and see what happens! It won't work very well according to you guys, but I still want to try it. I predict it will get some better gas mileage at least around town or on a flat road at the expense of peppiness. But if it is total fail, then I can stick the 454 back in here and no big deal. I will surely write in here and show you all the youtube vids of my epic failed attempt at running a small high revving motor in a motorhome so you guys can say "I told ya so!" and stuff, don't worry. ;)
 
#156 ·
Hey dirty biker, just do it...
You've gotten some really good advise by some of the best people in here,even if I personally disagree with one of them as far as rod ratio goes.
Along with cobalt and many others that have commented on your post he really knows his stuff.
In my personal opinion the only choice for you is a Diesel.....
6bt Cummins,Dt 466 are 2 great choices.
I really dont think you have any idea of just how much money you are going to pee away building this 302.
I just got through building a 355, cost for parts+ machine work n exclude my labor $4,500.
And its a street engine!
I bet you can find a Cummins out of a school bus complete with trans for less than that.
But you sure are a good debater.............I know what ur up to.........
 
#158 ·
turbolover said:
If you are in this just to get better milage why not do one of the proven things that have been suggested, like a gear swap, OD trans, FI, etc?
turbolover I like your name btw, I wish I had thought of it. It is cool even though I have never owned own, and only driven a Subaru once with single turbo. Makes you sound like you might be a real ladies man...

Warning: Editorial comment follows, viewer discretion advised... The views of Dirtybiker do not necessarily reflect those of this website. Or anyone really.


Oh, ye lover of turbos, and whoever else, I might maybe be biased because of all the years (wasted energy in some peoples opinion I am sure) thinking about the gains of long rods due to piston acceleration and side loading, coupled with gas company conspiracy theories. Yes, you read right. The man trying to keep us down again. Sorry if I disapoint you here but I did say I was a hippy, and as you probably know, us hippies like our conspiracy theories. This time it is the money hungry gas companies putting pressure on the big three to build motors that burn more gas. Hence the (~yawn) 350 chevy and a slew of new big blocks. Why didn't the 265 have 3.48 inch stroke? Hmm maybe they thought 3 inches was good enough I dunno. They could have just made the first one have a 3.75 inch stroke even! Why? Maybe they didn't think it was better or else they would have is why! Then, the gas companies chime in and somehow exhert there influence on the car companies: "So build motors that burn more gas, reduce the rod ratio, increase the stroke, do whatever you gotta do but don't let on what you are up to or else!" ok this is just one mans thoughts here, take with some salt or whatever.. then even "Decrease compression ratios because high compression enables you to get more power from the fuel! Just make the motor bigger instead!" Now sure they give us the guise of getting power in the lowest rpm range possible, because they want you to think thats what the most important thing is. Not manifold vacuum, cylinder filling, intake velocity, none of that nonsense. By using ever higher rear end gears and even overdrive transmissions(that too could be argued as to waste energy by being non-direct drive) We can lug the motor at the lowest rpm it will still get the car down the road and tell them they are getting better fuel economy, let them even pay extra for that od tranny and long stroke high cube motor. And even tho the vacuum gauge would read much higher at +1000 rpm higher cruising down the road, most people will never know or even think to check because they have sheepishly been doing what everybody told them. You thank them for all of this, and give them your money and the banks there interest for financing it for you and so on. Then comes emmisions control. (control? what? hippies hate that!) Do you think it's to save the environment? Heck no. They could care less. It is to burn more gas and sell more cars and stimulate the economy by giving more jobs to skilled laborers like mechanics who get to charge alot to fix your egr valve or air pump. Without emissions control, we might get better gas mileage than with them but with malfunctioning emmisions controls we get even less mileage. So poor people that can't afford to buy a new car with a big motor at least get taxed in gas mileage because they can't afford a mechanic. I bet a lot of mechanics came from the wrong side of the tracks because of that fact. Either way the gas company wins, there plan is working great. The economy is booming because we all go to our jobs and keep making that payment all the while the media keeps telling you to buy a new car! It works. People buy them. Then comes, Heck this last new car sure didn't last as long as grand dads old car did it? I guess they just don't build 'em like they used to... Oh well no biggie as long as I keep buying a new one it won't matter anyway.

Hey I got an idea! Lets just huff some paint, and not think about any of that stuff!!

Ok so I am not saying that any of this is what really happened at all, because it could be completely off in the sense that no bad stuff from the want for money and power ever happened. Like everything has been just fine, like on "Leave it to beaver" or something. Or, I could be off because it was really MUCH worse than any way I could imagine it. I have a very vivid imagination btw.

End of my editorial.
 
#159 ·
turbolover said:
If you are in this just to get better milage why not do one of the proven things that have been suggested, like a gear swap, OD trans, FI, etc?

lol sry i forgot to answer your post TurboLover, I guess it is because I am too poor and dumb from not taking peoples advice early on, and getting into school and being a lawyer or doctor and such. I am poor. That stuff(fuel injection and gears swaps and od trannies) costs more money than a hair brianed theory and a craigslist 283 motor.

"Them that don't know him won't like him, and them that do sometimes won't know how to take him, he ain't wrong he's just different, but his pride won't let him do things to make you think that he's right."

Mommas, don't let your babies grow up to be dirty bikers...
 
#160 ·
An od trans is much less than an engine build. So is a junk yard sourced fi system or a gear swap.

If you want to do something that's fine, but don't bs reasons. Just say, "I don,t understand the way rods work and I want to experiment with a long rod and a short stroke." Curiosity is the only real reason you have but that's perfectly okay.
 
#161 ·
Well I never got better gas mileage with the ford 300 six eecIV system I had, in fact my old 73 van with 240 six actually got better mileage with a single barrell carb and 4.10 gears and no overdrive. There is an astro van I could maybe get cheap tho that has throttlebody on it, but I know it isn't big enough for the 454 since it is v6 but i was thinking about it for the 283. I don't really know how much the rear end gears are to change or how involved it is either. I do have a 350 chevy motor that runs good tho, would that not get better mileage than my 454 and still have enough power because of my 5.13 gears? how hard is it to change gears on my rear end? I think it is a dana 80 but not sure
 
#162 ·
Wow, this thread is getting really long! How bout this: build the 283, go to a junk yard and get a tbi system for cheap and change your rear gears. You said you have a complete 283 so there's nothing more to spend there, the tbi system cant be much more than $150, and you could even get some rear gears from the scrap yard too. For a total of 200 bucks you get better fuel economy and you will make back the money in fuel savings.
 
#163 · (Edited)
Well because the whole point of this thread is to make good gas mileage with ancient technology, 5.13 gears and a 283 with a stock cam because a 1.9:1 rod ratio makes for a high rpm motor and can get good gas mileage at 4100 rpms or whatever because thats where it make its highest volumetric efficiency. Lower gears will only hurt mileage they way I see it because I will lose manifold vacuum by not having the revs up. Furthermore, I believe a properly tuned carb, especially one only three moving parts like the fish carb, can deliver every bit as good of gas mileage as throttle body fuel injection. Actually, a carb could get better gas mileage because I can tune it a bit leaner than fuel injection will let me run. It has been shown that by injecting a small spray of water into your manifold while you are cruising you can run a tiny bit leaner and not ping or run too hot. I can still benifit from using the o2 sensor to see just how lean, I have welded a bung on my right bank downpipe, but I can't afford the 30 dollars for the gauge.

The rest of this post you can just skip over, I am venting.

I need to buy gas to go down and see my baby and baby momma and son and sons mamma who I never even met since he has grown up, he is 12 years old now. They all live within 75 miles from each other. I need to pay my verizon wireless internet bill of 100 dollars and I think my mom is going to lose all her rental houses to foreclosure. I have about 125 dollars. The bank takes the house that I stay in the back yard of, the house my dad built my mom when I was a baby, on the 9th. Banks are ruthless let me tell ya. They may take the other houses she owns too soon. Hopefully not. :(
 
#164 · (Edited)
@ Dirty Biker I am a firm believer in long rods
If could stuff a foot long rod in a s.b. i would do it.
Every race engine I ever built had long rods
Every street engine i ever built had long rods
Ive seen the difference in a dyno and a Smokatron
..............It Works.................
By the way the water injection you are referring to was extensively used in aircraft piston radials... big radials as wright 3350 turbo compound, P/W 4360
and some R2800s. It was a water alky mix,alky prevented freezing at flight levels(high altitude)
 
#165 · (Edited)
topwrench said:
@ Dirty Biker I am a firm believer in long rods
If could stuff a foot long rod in a s.b. i would do it.
Every race engine I ever built had long rods
Every street engine i ever built had long rods
Ive seen the difference in a dyno and a Smokatron
..............It Works.................
By the way the water injection you are referring to was extensively used in aircraft piston radials... big radials as wright 3350 turbo compound, P/W 4360
and some R2800s. It was a water alky mix,alky prevented freezing at flight levels(high altitude)
Dude you must be really friggin out there to know that about the water injection. You are sposta use the windshield washer fluid that they sell by the gallon at gas stations. It has denatured alky in it. But regular water works too some say.

anyways,

Thanks Brother, I was hoping there was at least one guy on here who didn't think long rods were pointless when I joined this forum. People do not seem ok with spending alot of money on a long stroke/short rod motor and then being told that the geometry that they settled on is wrong for peak power. I can't blame them.

I think therefore I am. However I did read somewhere tho that a 1.75 is considered “ideal” by some respected engine builders, if the breathing is optimized for the design.

Breathing is what you guys taught me about. Thank you all, btw. A 383 is not limited by rod ratio or side loading, rather it is limited by the tiny heads it has that keep it from breathing well above a certain rpm. It is simply trying to pump faster than the ports will let it. Am I correct? So it just runs out of breath above a certain rpm unless it has really nice heads on it.

My theory is that if I can get enough money to buy 6.25 rods, and pistons for a 350 chevy with 6 inch rods, then I can use these crappy small port heads and still make power when I need to by revving up an octave, yet save money by not having to buy more parts. Sounds reasonable right? I also think a super low rpm torque cam with almost no lobe overlap and plain 1.5 rockers but yet still has .4 lift will still have near peak volumetric efficiency at 4100 rpm because of the long rods. Would somebody desktop dyno this for me?
 
#169 ·
Dirty Biker said:
Would somebody desktop dyno this for me?
If you want an accurate estimate, techinspector1 has said the following is needed:

techinspector1 said:
DYNOSIM REQUIRED DATA....
Bore
Stroke
Rod Length
Cylinder head flow, intake and exhaust 0.100" through 0.700" or whatever the mfg gives for range
Intake valve diameter
Exhaust valve diameter
Static compression ratio
CFM, type of induction (2-bbl, 4-bbl, TBI, TPI)
Intake manifold type, mfg (single 4-bbl, two 4-bbl, one 2-bbl, three 2-bbl, individual runner Weber, mechanical fuel injection, low-rise, high-rise, tunnel ram, dual-plane, single-plane, part no. if you have it.
Exhaust system (be specific, primary tube size if long-tube headers)
I have quite a library of CompCams (give me part number, not grind number) in my files, but if you are using another mfg, I'll need type (flat, roller, solid, hyd.), intake valve lift, exhaust valve lift and the following timing info and at what tappet lift the info is valid...(0.006", 0.050") I can calculate from 0.020" if I'm given enough information, but again, that takes my time.
Intake opens ______BTDC
Intake closes ______ABDC
Exhaust opens______BBDC
Exhaust closes______ATDC
 
#170 ·
cobalt327 said:
If you want an accurate estimate, techinspector1 has said the following is needed:

DYNOSIM REQUIRED DATA....
Bore 4"
Stroke 3"
Rod Length 6.25"
Cylinder head flow, intake and exhaust 0.100" through 0.700" or whatever the mfg gives for range I don't Know what this means. Can somebody help? I would use stock single hump chevy heads at first then maybe try 1996 and up vortecs. There is 062 heads for sale now for 150$ on cl
Intake valve diameter 1.94
Exhaust valve diameter 1.5
Static compression ratio 10:1
CFM, type of induction (2-bbl, 4-bbl, TBI, TPI) 400 cfm, I think. I have the two barrel carb and the single barrel fish carb. I think they are both about 400 cfm, maybe a little more. I don't know if the motor would ever breath enough even at high rpm to need a quadrajet.
Intake manifold type: Dual plane stock two barrel manifold, I also have a dual plane four barrel manifold from a 350 and a quadrajet, might try it both ways to see if it makes any difference
Exhaust system: small diameter long tube headers, single exhaust pipe and no muffler say 1.5 inch primaries and 30" length
CompCams 12-300-4 [49] There may be a better cam, I didn't call them.

Thanks Alot!
 
#171 ·
Dirty Biker said:


This is me me having a great day however a piece of metal from the grinder had just got in my eye and I was mad about it a little bit. I later used a big magnet to get it out. Maybe dragging a magnet across my eye was a bad idea, but it sure felt better right away. I tend to over simplify apparently.
I have also used a magnet to get steel out of my eye , but I didn't drag it across my eye . I decided I'd rather use safety glasses than a magnet after that though .
 
#172 ·
The comp can part number for the factory muscle cam that is sposta be the same as the original 302 solid lifter cam is #12-107-3, It would be good to compare it to the rv cam in the desktop dyno if I could.



I learned that eye glasses or sun glasses are not the same thing as safety glasses, stuff still gets in there. I once went to the doctor and he asked me if I do alot of welding and grinding and stuff, I said "Yeah why?" he said "Your contact lenses have metal shavings in them, they may have saved your eyesite." So yeah, wear the dumbest looking safety glasses you can.
 
#173 ·
I found that out the hard way as well. And always wear a breathing mask when you pull out the cartridge rolls, otherwise you'll be blowing out cast iron boogers for about a week- can't be good for your lungs.

BTW you need to think of a cam with much smaller seat duration if your after mpg's and you can't run that high of compression in that engine with that HUGE load. Otherwise it'll sound like a can of rocks- until you blow a piston.
 
#174 ·
Man turbolover I thought that 240h grind was the mildest torque cam they had, Which one do you think might be better? Oh maybe you were thinking the stock chevy 302 cam that I just posted? Yeah I agree that would be the bad for mpg for sure but just to compare the two could be useful.

what about that guy trying to use the saab turboes on his ride? There is a saab turbo car at the u pull it here in Louisville, the turbo was off already even. i was checking it out thinking the same thing when I read that guys post. How do you use only one big turbo on a v8? I know people do it but it kinda makes more sense to use one small one on each bank, maybe on some super shorty block hugger headers or something.
 
#176 ·
Camquest is just a toy program, ok for comparing cams for power trends, but don't put much stock in actual hp figures it gives you. After all, it is a marketing tool for Comp Cams, to get you to buy their cams. I have it but only use it to compare power curves between a group of cams I think will fit the bill for an engine I'm spec'ing out at the time.

It's not even close to a true dedicated dyno program like DynoSim or Performance Trends Engine Analyzer. It is way to simplistic about manifolds, heads, and exhaust...just off the top of my head.
 
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