I would like to know what gear everyone is running on there inline 6? I had problems with car 30 yrs. ago with 300 six shearing flywheel bolts at 5,000 rpm (harmonics) was told common on 6cly. I could go above but 5to 5,5 would happen every time if held there . I am running a 223 ford (62) I was just wondering where everyone was running on the top end. The 223 is basicly stock (for now), just don't like the idea of the clutch and flywheel joining me!! IT A'NT COOL IF IT A"INT LOUVERED. THANK'S wreck of o'l 97
Well maybe I'm off base, But I'm going to run 4.10 gears with G78x15 tires. The rear end is out of a S10 blazer...
Do what you can to keep the revs below 4500. If you drop the oil pan and take a look at the main bearings or lack there of you will understand what I am talking about. I have a 223 inliner in my 59 custoom 300 and it has around 3.00 to 1 gears in it. It turns 3000 at 60 and trust me, its definitely wanting another gear.
Haven't heard of that one, Is it a Ford thing? Not slamming Fords, I'm just not familiar with'em. I've run 235 series Chevs and slants for 40+ years (and I don't baby'em) with no problems. That said, inline 6s have always been a good tractor engine. Under square and long stroke, they do their best work at low and mid range. So going past 5000 doesn't give you much on a stocker anyway. And let's face it, you won't be spending much time at that tach level either, it's only a quarter mile. We're running 3.23s turning 30" hides for now (out of necessity) and have at least half a gear left over at the end. We have an 8" Ford rear we're building with 4.10s that'll likely wind up turning 28 inchers.
Play with the following formula to determine the rpm you'll be turning: RPM= MPH x Ratio X 336 Tire diameter Example: 110mph x 4.10 ratio X 336 = 5412 RPM 28inch tire Higher ratio = less RPM Taller tire= less RPM I hope this helps. Ron
Thanks for info I was at apoint on where i need to decide what rear to use I have 9",8" and 8.8. The 8.8 has a 3.73 locker moser axles and disc brakes and is the lightest. the 9" I have many pigs from 2.83 to 6.50 with spools left over from circle track racing but problem these are heavy. The 8" I have 3.25 3.5 and4.11 pigs. I know 6 power is all in the low end and mid range,and falls off at the top end, is everyone starting in 2nd and only shifting once. I have a 4sp od I could use but shifting could be a problem. I know traction with L-78 15 tires is a problem. Just thinking these things out before I start mounting motor and trans. Tight space ,too many doughnuts for 285lb. 6,1 56 yr old kid. Boy i'am depressed guess i'll have another doughnut. thanks for help, remember (it a'int cool if it a'int louvered) well i have rambled enought for now got to punch some louvers on a 27 track roadster. WRECK OF OL' 97
Hi Louvered48! By using the website listed above, you can make your own chart on gear ratio's in a few minutes. The thing about traction problems most likely will not be a factor unless you have over 400 horse power. With the modern tracks and the glue that they put on the track, they do hook up. You can look on You Tube at 2b's record run and see him pop up the left front. with that chart : 6000 RPM with 28 in tire and 3.55gears = 140 MPH
thanks JOE cool site been playing numbers , easier than doing math (lazy) . 9" too heavy 8" easy gear change , and my 8.8 lightest got 3.73 locker and extra 4.10 gears
welcome back Godzilla! do you still have Rodan? And if so are going to bring it to Tulsa? If so we will see you then Ron. Remember in Tulsa everyone runs every round. Joe
Dont get me wrong, I dont baby the 223, but I do realize that there is a serious lack of main bearings in these things. That being said, I have had mine right to the floor several times on the interstate way late at night. My tach goes to 6000 and I was really close to that. It held together and didnt make any unnatural noises, but lets just say, I was trying not to flinch. The other big problem with these engines is the funky angle at which the timing chain runs. If one is on the gas and then lets up quick, the chain, if its a little old and stretched, will jump rather easily. Been there and done that olnly once, but from the old timers that I know, they have said, it is/was a common problem. The best feature of my current 223 is 25 mpg at a steady 60 mph. I can smoke the tires in first and reverse and run 100 mph into the wind. If I didnt have 2 other 59 Fords with FE power under the hood, I would say, who needs to feed 8 cylinders?
The shortage of main bearings and the long, heavy crank in the 302 GMC was the primary reason I made so many changes in the rotating ***embly. I didn't want to build an engine with all those heavy parts and have it blow up when I tried to turn it 5500 rpm. I reduced the piston weight 400 grams, the piston pins 84 grams and the rods almost 100 grams. That reduced the total piston/pin/rod weight more than 1 1/4 pounds each. Building these old engines are like trying to make a silk purse out of a sow's ear. Ron
Ron, If you take weight off the rods and pistons, do you have to also take it off the counterweights on the crank?
Desert, Good question. I wondered about the same thing but couldn't find an answer. However, when we (and other engine builders I talked to) build an engine with different rods/pins/pistons, even the stroke, the engine is balanced normally. But, I know to make a serious BB Chevy live at rpm the crank needs center counter weights. To answer your question; I feel the counterweights should be reduced....I just can't find out how much. I'm sure at the HP and RPM this engine will be seeing it shouldn't be a problem. (fingers crossed here). I did buy a new Fluidampr to help damped the harmonics. I've talked to some of the guys running at Bonneville and they said the GMC has a dangerous harmonic right at 6000 RPM and you need to stay below, or above that RPM or you'll have crank/bearing problems. I'm going to keep my engine below 6000 unless I get beat. Ron
Ron, is that Fluidamper a stock part number or custom? If it's stock, how many grooves does it have (I like Fluidampers, thinkin' about one for the truck, not 'necessary' I know)?
A better (BIGGER) harmonic balancer is always a good investment on an older 4 main 6 cyl. It helps keeps the bearings looking good by taking some of the whip out of the crank. What else could a HB be good for ...? A 6's crank is usually balanced w/o bob weights. Soo.. Have any of you " over or under " balanced an inline crank? Think about it. What is the Red Line you set for your engine? Why did you pick that rpm? Picking your brain. I'm off to work, I'll give you some time to think about these things.
Fluidamper for a SBC also fits a GMC. You don't have to do any modifications. The GMC has a 5/8" bolt to hold it on with also. You have to make a timing marker and it sure makes timing a lot easier to accomplish. I was running a stock 270 GMC block and I saw 6000+ and with the Fluidamper I felt no viberation. With new light weight rotating ***embly it will be interesting to see what rpms feel comfortable. I am running 380 gears in the rearend. I used clay today to check valve clearance and I have .290 so I could have gone a lot bigger cam. I'm puttting the new engine in the car tomorrow the 4th. I hope to run the cam and bearings in monday. I plan on doing a little test drive before going to Tulsa on friday. Sorry for the ramble.Roy
ne**ussian, 6 1/4", PN 620101 for SBC as 348 & Godzilla said. No mods required on my GMC. CrkInsp, Bigger balancer is best. Balanced 348chevy & my crank w/o weights I want a "useful" rpm range of 3-6000 rpm. I don't like to rpm any higher than needed to get the job done. Hopefully, I won't have to spin it above 5500. These old engines have terrible intake & exhaust ports. They usually were rated about 32-3600 rpm so they didn't need to flow any air. I've got my intake to flow above 260 cfm so it could be turned tighter and make more power with a bigger cam. From my calculations if I shift at 5500 rpm it will drop to about 3000 rpm. Thats why I want it to grunt in the mid range. Most of the time during the 1/4 mile is spent in high gear and mid rpm's. Ron
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