Inputs on a home built 318 for red light to red light fun
- Thread starter Branden Finkenbinder
- Start date
-
This is not a route to take. It’s also wrong since there is a lack of math to use against what your starting with. Only what he thinks you end up with. It’s an open statement and dumb to make. Very misleading.
Totally inaccurate. Outright wrong.
What you can do is use the tire diameter and gear ratio to mathematically figure out the finish line rpm. That should end up being at max hp/rpm or slightly higher, which would be better.
@Branden Finkenbinder The problem you face is lack of transmission gears and traction on the street. The brand C & F guys have 6 or 8 speed transmissions and you only have 3 for an auto and 4 for the manual.
Multiply your first gear ratio with your rear end gear ratio and adjust it for 10.
Example, transmissions first gear is 2.66 X rear gear or 4.10 = 10.906. This is a good combo for first gear starting line acceleration.
Again -
2.66 D 4.10 = 10.906
2.45 X 4.10 = 10.045
2.45 X 4.88 = 11.956 (rounded up to 12, not to good, to much.)
2.45 X 3.91 = 9.579 (9.6) to low.
Engine wise your behind them in every aspect with the exception of maybe cubic inches.
Multiply your first gear ratio with your rear end gear ratio and adjust it for 10.
Example, transmissions first gear is 2.66 X rear gear or 4.10 = 10.906. This is a good combo for first gear starting line acceleration.
Again -
2.66 D 4.10 = 10.906
2.45 X 4.10 = 10.045
2.45 X 4.88 = 11.956 (rounded up to 12, not to good, to much.)
2.45 X 3.91 = 9.579 (9.6) to low.
Engine wise your behind them in every aspect with the exception of maybe cubic inches.
I don’t know what the brand C & F guys are bringing to the table. If there was a distance and ET on it, that target and faster can be worked out.
The go to intake would be a RPM-AG, which is good for power down to the 11’s in the 1/4. Quicker than, a single plane 4bbl intake would take the car faster but probably suck down low if the car is t well worked out.
I’d definitely go with a tunnel ram. But not on a 318.
The go to intake would be a RPM-AG, which is good for power down to the 11’s in the 1/4. Quicker than, a single plane 4bbl intake would take the car faster but probably suck down low if the car is t well worked out.
I’d definitely go with a tunnel ram. But not on a 318.
C130 Chief
Mechanical Genius
318-3 truck crank. Well at least you've picked the heaviest crank out there for a high rpm engine.
LOL, I wasn't going to mention anything, but now that it's been brought up...
Consider a light weight crank, or get the one you have worked like below.
Dan the man
Well-Known Member
I see a lot of over kill for what you are wanting to do. You need to build it for throttle response and low to midrange torque. Most here are going to disagree with me, but from what your goal is that 750 is to big. You don't need that compression ratio either. Sounds like you are building a race car instead of a fun street car.
IMO, that’s just what he is after. A track car driven on the street. Also a 750 is not to big and even more so on the targeted effort he wants to do.
Branden Finkenbinder
Member
As of right now I need to be 7.99 1/8 Mile or better
You should look up some of Jim Laroy's (IQ52) low compression engine builds. He's proven time and again low compression can make power. And I mean like 7.35:1. you don't have to go that low, but you don't need race gas either. From one compression to another is only like a 3% increase all things equal, so it's not all in compression by a long shot.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
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Rumble said;
For this type of hi-rpm engine and lightweight application I think I would gravitate to a loc-up A518, big rear gears, and a modest stall to prevent runaway tirespin with the smallish rear tires.
the A518 has ratios of 2.45-1.45-1.00-.69od
The loc-up has a ratio of near 1.8 @ zero mph.
With a .69od, and a loc-up, you can run pretty much any rear gear you want.
My thoughts;
>With just 255s and what will probably become a somewhat high ride-height at the back, traction will be a big issue.
>With race gears, it will be only too easy to burn thru first gear..... which is where most street races are won; ie, a 2.4second 60ft is not gonna cut it.
> realizing these things, points to a low-torque bottom end, and a modest stall will help with that. Why an automatic? Because the TC acts as an automatically shifting deep-low gear, eliminating the need for race-gears.
>but the lo-stall is a total hindrance at the shifts... so to overcome that, you need two things; a close ratio transmission, and a cam that covers the rpm-drop. The A904/A727/A518 are the closest-ratio automatics that Mopar gave us to fit our cars.
> how does it work?
> check out the 5.2M power-curve below. This is a beer-keg EFI engine so you won't be able to get this shape of torque-curve, but I can use it to illustrate my point.
Part-1
lets assume for this exercise, that you have a Standard A833(2.66low), 4.10s, and 27" tires. Let's say that you soft-launch at 3000rpm, trying desperately not to spin the tires too badly. At 3000rpm, this 5.2M is making say 298ftlbs. Working thru the trans and gears, this comes to; 298 x 2.66 x 4.10 =3250 ftlbs at WOT, into the axles. Your 255s will light right up at WOT, and your race is history.
On your next try, you launch at 2400/285 ftlbs and into the axles this comes to 3108 ftlbs and again, at WOT, the tires light right up.
On your next try, you launch at 2000/276ftlbs at into the axles this maths to 3010 and yur still getting tirespin at WOT.
The bottom line is that, using this dyno-chart, 4.10s are just too much on the start-line, on the street, for WOT. But you sorta need the 4.10s to compress the run into three gears between stoplights, to maximize the application of your power. For instance, top of third gear with 27s is;
76@5500/83@6000/90@6500/ 97@7000
so already, 4.10s are sorta looking like the wrong gear on the big end.....
Part-2
lets assume for this exercise, that you have a Standard Ratio automatic, 3.73s, 27s, and a 2200stall that manages a 1.6ratio with your low-torque engine. At 2200 this 5.2M is making 280ftlbs. thru the powertrain, this comes to
280 x 1.6 x 2.45 x 3.73 = 4100ftlbs at zero mph. Immediately, the tires start to spin. Just as quickly the TC drops ratio, so, a few feet out, the ratio may have dropped to say 1.3. This automatically reduces the axle torque to 3330ftlbs at WOT. Compare this to 3250 with the Manual trans/4.10s, and Hyup your 255s are still spinning. This is no accident, I chose all the parameters to level the playing field.
Part-3
Now that we have the starting line evened out, lets see what happens when we go thru the gears; first the 4-speed. The ratios are 2.66-1.92-1.40-1.00, and 4.10s.. To the road this is; 10.91-7.87-5.74-4.10.. that 5.74 Third gear will get you 83mph@6000
Now the Auto; say a Standard A904. The ratios are 2.45-1.45-1.00, and 3.73s make the road gears to be 9.14-5.41-3.73.. However, the TC affects all these numbers and differently in each gear, because the TC multiplier is always changing with the input of engine torque versus the roadspeed. You have already seen what 1.6 can do on the starting line, now lets see what happens at speed. 9.14 becomes 14.62 at zero mph, reducing to an estimated 11.88 at shift rpm, so lets record it as 14.62/11.88. That 5.41 may become 6.49 at speed, and 3.73 might be 4.10 at speed. So then, the new estimated ratios are;
14.62/11.88-6.49-4.10. That's a 4-gear automatic isn't it...... and 6.49 will get you 74mph@6000
Part-4
The 4.10 manual-trans will cruise at 65=3350 with the 27s
The 3.73s will cruise at 65=3050 at zero-slip (locked up), perhaps as high as 3170 @4% slip. With a .69 overdrive, this becomes 2100@ zero-slip.
Part-5
Now lets talk powerband;
>First, the manual trans and shifting at 6000; the rpm drops average around .72, so from 6000, that drops to .72 x 6000 =4320. so a powerband of 6000 less 4320 =1680. Your cam has to cover most of that. Say your peak power occurs at 5700, then drops slowly, you could then recalculate to a powerband of 1380rpm. This is pretty tight, and you could run a pretty big cam on a very tight LSA and get away with it, expecting not much torque on the bottom. The 4.10s will help you there. Or
>Second, with the automatic, the rpm drops are staggered; .59 on the 1-2, and .69 on the 2-3. So again, shifting at 6000, the rpms drop to 3540 and 4140 for powerbands of 2460 and 1860. With a power-peak again around 5700, the requirements are 2160 and 1560. This requires a DIFFERENT cam than the 4-speed does. You cannot run the same tight LSA cam, and expect good results. That means the power of a same duration cam will be less, but powerband is broader. This type of cam also loses cylinder pressure so eats bottom end, requiring more cubes or more cylinder pressure to cover. Or more gearing.... Since we are only at 3.73, this is easy to accomplish, but it will sacrifice cruise-rpm. However, with the very low .69 ratio of the Mopar overdrive, 3.73s is too low anyway. There is no way to give your big-cammed 318 enough ignition timing to satisfy 65=2100. By 2400 is is becoming possible. For 65=2400 in loc-up, your gearing needs to be 4.30s.
Your new road gears with 4.30s are; 16.85/13.70-7.48-4.73-3.26-2.97; wait what? I count 6 gears... That's right; the box has 4 gears, the TC is infinitely variable between about 1.8 and 1.1 which is a full gear ratio, and the loc-up is equivalent to about a half a gear. That totals 5.5 gears! However, that 7.48 will only get you 64mph @6000, while 4.73 will get you 102, so we have a problem here. You will need a bigger cam to stretch 7.48 out to a higher mph, or a smaller cam and shift earlier to bring 4.73 down; else 84mph will come in at 4500ish(in 4.73roadgear); which as already stated by Rumble and others; "makes no sense".
Part-6
Ok so, as previously established with the manual trans and 4.10s, 5.74 roadgear(Third) gave us 6000@84mph, which IMO is a good target. To get a ~5.74 roadgear with an auto would take ~5.38s for third gear, or 3.23s in second. With the 3.23s I get
14.24/10.29-5.62-3.55-3.23 in LU; and 5.62 delivers 6000=86. The 5.38s would get you
23.73/17.08-9.36-5.92-5.38 in LU, and 5.92@6000=81.5 mph
Lets put the ratios side by side so you can see what's going on; First the Manual, then auto;
10.91-7.87-5.74-4.10 and 5.74@6000=84mph
14.24/10.29-5.62-3.55-3.23 in LU; and 5.62@6000=86mph
>As you can see, the 4-speed puts a gear between 10.91 and 5.74, that is missing between 10.29 and 5.62 of the auto, whereas the auto gives a gear under 10.29 that is missing with the 4-speed. But, the auto gives you one to 1.5 more gears at the top
But again, to pull that wide 1-2 split, you need a wider LSA cam.
Part-7
And the wildcard is the A518 with 5.38s; the Roadgears are;
23.73/17.08-9.36-5.92-4.08-3.71in LU, and 5.92@6000=still 81.5 mph but 65 is now 3000.. First gear is gonna be pretty tricky, and you can easily start in second for most of the time, giving you a closer ratio between second and third. Because of all the torque multiplication going on, you could probably use the 4-speed cam, with the tighter LSA. With this combo, you also don't need a hi-stall.
Part-8
For those that want to know; For this exercise I used the following TC multipliers; 1.8 diminishing to 1.3 in first, 1.2 in Second and 1.1 in Third. Thus the A904 gears look like;
4.41/3.18-1.74-1.10 and 1.0 in LU. The A518 adds .76/.69LU, and may drop the 1.0
^My thoughts as well^
For this type of hi-rpm engine and lightweight application I think I would gravitate to a loc-up A518, big rear gears, and a modest stall to prevent runaway tirespin with the smallish rear tires.
the A518 has ratios of 2.45-1.45-1.00-.69od
The loc-up has a ratio of near 1.8 @ zero mph.
With a .69od, and a loc-up, you can run pretty much any rear gear you want.
My thoughts;
>With just 255s and what will probably become a somewhat high ride-height at the back, traction will be a big issue.
>With race gears, it will be only too easy to burn thru first gear..... which is where most street races are won; ie, a 2.4second 60ft is not gonna cut it.
> realizing these things, points to a low-torque bottom end, and a modest stall will help with that. Why an automatic? Because the TC acts as an automatically shifting deep-low gear, eliminating the need for race-gears.
>but the lo-stall is a total hindrance at the shifts... so to overcome that, you need two things; a close ratio transmission, and a cam that covers the rpm-drop. The A904/A727/A518 are the closest-ratio automatics that Mopar gave us to fit our cars.
> how does it work?
> check out the 5.2M power-curve below. This is a beer-keg EFI engine so you won't be able to get this shape of torque-curve, but I can use it to illustrate my point.
Part-1
lets assume for this exercise, that you have a Standard A833(2.66low), 4.10s, and 27" tires. Let's say that you soft-launch at 3000rpm, trying desperately not to spin the tires too badly. At 3000rpm, this 5.2M is making say 298ftlbs. Working thru the trans and gears, this comes to; 298 x 2.66 x 4.10 =3250 ftlbs at WOT, into the axles. Your 255s will light right up at WOT, and your race is history.
On your next try, you launch at 2400/285 ftlbs and into the axles this comes to 3108 ftlbs and again, at WOT, the tires light right up.
On your next try, you launch at 2000/276ftlbs at into the axles this maths to 3010 and yur still getting tirespin at WOT.
The bottom line is that, using this dyno-chart, 4.10s are just too much on the start-line, on the street, for WOT. But you sorta need the 4.10s to compress the run into three gears between stoplights, to maximize the application of your power. For instance, top of third gear with 27s is;
76@5500/83@6000/90@6500/ 97@7000
so already, 4.10s are sorta looking like the wrong gear on the big end.....
Part-2
lets assume for this exercise, that you have a Standard Ratio automatic, 3.73s, 27s, and a 2200stall that manages a 1.6ratio with your low-torque engine. At 2200 this 5.2M is making 280ftlbs. thru the powertrain, this comes to
280 x 1.6 x 2.45 x 3.73 = 4100ftlbs at zero mph. Immediately, the tires start to spin. Just as quickly the TC drops ratio, so, a few feet out, the ratio may have dropped to say 1.3. This automatically reduces the axle torque to 3330ftlbs at WOT. Compare this to 3250 with the Manual trans/4.10s, and Hyup your 255s are still spinning. This is no accident, I chose all the parameters to level the playing field.
Part-3
Now that we have the starting line evened out, lets see what happens when we go thru the gears; first the 4-speed. The ratios are 2.66-1.92-1.40-1.00, and 4.10s.. To the road this is; 10.91-7.87-5.74-4.10.. that 5.74 Third gear will get you 83mph@6000
Now the Auto; say a Standard A904. The ratios are 2.45-1.45-1.00, and 3.73s make the road gears to be 9.14-5.41-3.73.. However, the TC affects all these numbers and differently in each gear, because the TC multiplier is always changing with the input of engine torque versus the roadspeed. You have already seen what 1.6 can do on the starting line, now lets see what happens at speed. 9.14 becomes 14.62 at zero mph, reducing to an estimated 11.88 at shift rpm, so lets record it as 14.62/11.88. That 5.41 may become 6.49 at speed, and 3.73 might be 4.10 at speed. So then, the new estimated ratios are;
14.62/11.88-6.49-4.10. That's a 4-gear automatic isn't it...... and 6.49 will get you 74mph@6000
Part-4
The 4.10 manual-trans will cruise at 65=3350 with the 27s
The 3.73s will cruise at 65=3050 at zero-slip (locked up), perhaps as high as 3170 @4% slip. With a .69 overdrive, this becomes 2100@ zero-slip.
Part-5
Now lets talk powerband;
>First, the manual trans and shifting at 6000; the rpm drops average around .72, so from 6000, that drops to .72 x 6000 =4320. so a powerband of 6000 less 4320 =1680. Your cam has to cover most of that. Say your peak power occurs at 5700, then drops slowly, you could then recalculate to a powerband of 1380rpm. This is pretty tight, and you could run a pretty big cam on a very tight LSA and get away with it, expecting not much torque on the bottom. The 4.10s will help you there. Or
>Second, with the automatic, the rpm drops are staggered; .59 on the 1-2, and .69 on the 2-3. So again, shifting at 6000, the rpms drop to 3540 and 4140 for powerbands of 2460 and 1860. With a power-peak again around 5700, the requirements are 2160 and 1560. This requires a DIFFERENT cam than the 4-speed does. You cannot run the same tight LSA cam, and expect good results. That means the power of a same duration cam will be less, but powerband is broader. This type of cam also loses cylinder pressure so eats bottom end, requiring more cubes or more cylinder pressure to cover. Or more gearing.... Since we are only at 3.73, this is easy to accomplish, but it will sacrifice cruise-rpm. However, with the very low .69 ratio of the Mopar overdrive, 3.73s is too low anyway. There is no way to give your big-cammed 318 enough ignition timing to satisfy 65=2100. By 2400 is is becoming possible. For 65=2400 in loc-up, your gearing needs to be 4.30s.
Your new road gears with 4.30s are; 16.85/13.70-7.48-4.73-3.26-2.97; wait what? I count 6 gears... That's right; the box has 4 gears, the TC is infinitely variable between about 1.8 and 1.1 which is a full gear ratio, and the loc-up is equivalent to about a half a gear. That totals 5.5 gears! However, that 7.48 will only get you 64mph @6000, while 4.73 will get you 102, so we have a problem here. You will need a bigger cam to stretch 7.48 out to a higher mph, or a smaller cam and shift earlier to bring 4.73 down; else 84mph will come in at 4500ish(in 4.73roadgear); which as already stated by Rumble and others; "makes no sense".
Part-6
Ok so, as previously established with the manual trans and 4.10s, 5.74 roadgear(Third) gave us 6000@84mph, which IMO is a good target. To get a ~5.74 roadgear with an auto would take ~5.38s for third gear, or 3.23s in second. With the 3.23s I get
14.24/10.29-5.62-3.55-3.23 in LU; and 5.62 delivers 6000=86. The 5.38s would get you
23.73/17.08-9.36-5.92-5.38 in LU, and 5.92@6000=81.5 mph
Lets put the ratios side by side so you can see what's going on; First the Manual, then auto;
10.91-7.87-5.74-4.10 and 5.74@6000=84mph
14.24/10.29-5.62-3.55-3.23 in LU; and 5.62@6000=86mph
>As you can see, the 4-speed puts a gear between 10.91 and 5.74, that is missing between 10.29 and 5.62 of the auto, whereas the auto gives a gear under 10.29 that is missing with the 4-speed. But, the auto gives you one to 1.5 more gears at the top
But again, to pull that wide 1-2 split, you need a wider LSA cam.
Part-7
And the wildcard is the A518 with 5.38s; the Roadgears are;
23.73/17.08-9.36-5.92-4.08-3.71in LU, and 5.92@6000=still 81.5 mph but 65 is now 3000.. First gear is gonna be pretty tricky, and you can easily start in second for most of the time, giving you a closer ratio between second and third. Because of all the torque multiplication going on, you could probably use the 4-speed cam, with the tighter LSA. With this combo, you also don't need a hi-stall.
Part-8
For those that want to know; For this exercise I used the following TC multipliers; 1.8 diminishing to 1.3 in first, 1.2 in Second and 1.1 in Third. Thus the A904 gears look like;
4.41/3.18-1.74-1.10 and 1.0 in LU. The A518 adds .76/.69LU, and may drop the 1.0
Dan the man
Well-Known Member
I see a mismatch combination, big carburetor, unknown intake manifold, small port small valve heads, compression ratio that probably won't match either the cam or rear gear's.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
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My 367HO 68 Barracuda went 7.92@93mph @ 3457pounds raceweight and 930 ft. My 60ft was 2.2/2.4
Your Early-A may come in at 400pounds less raceweight. The Wallace says that @3250 and 7.99, that will take 315 Flywheel hp. But I'm pretty sure that calculator is based on SS suspension, so with street suspension, you will lose about a half second in the 60ft. To compensate for that, you might need another 75 hp, to total 390.
With a 318, that is doable, but yur asking a lot from iron heads and 10.5 Scr.
And, for you, the 60ft is a big deal. To try and get those skinny 255s to hook, you may have to spend a lot of money to make up that 1/2 second.
More gears and or more closely-spaced gears will help to keep your average hp up, which will also help to reduce your ET.
God help us.
Indeed!!!!!!
Dan the man
Well-Known Member
If I read the OP correctly, he's wanting to build his car for stop light to stop light fun. His combination is off. He wants a cam that will let him spin the 318 to 7,500 rpm's, the cylinder heads just won't support that rpm, neither will those 273 rocker arms. He has a heavy crankshaft, rocker arms. No mention of a intake manifold either but he will need a single plane. If he was to build it with the parts that he listed I think that the car would be a dog off the line. A 3.91 or even those 4.30 gears are going to make that 318 scream at cruising speeds. I knew a guy that had a 383 with a 1050 Holley denominator and it was a dog off the line, carb was to big. He put a 850 on it and it ran great. I may not have the years experience that most on here have but I do know that he's combination is as mismatched as it can be.
Dan the man
Well-Known Member
Are you talking about dynamic or static compression ratio?
Dan the man
Well-Known Member
If that's the static compression ratio, wouldn't that bring the dynamic compression ratio to 6.0 or lower? Isn't a dynamic compression ratio of at least 7.0:1 needed to make decent power?
No. Search low compression 440 by IQ52.
I skimmed through this, the OP wants a 7500-8000 rpm 318 with 1.88 360 heads ?
At best with stock heads will squeak out 350-375 hp which ain't bad but you'll only need to turn 5400-5800 rpm to hit those numbers. Cam heads plus intake/exhaust etc... Has to be capable together and match with the rest of the combo to hit those rpm and make power, just a cam that's says 4000-8000 rpm on the box isn't gonna do it.
Build a solid combo and turns what turns and makes what it makes people get to caught up in numbers. 5400-5800 is a decent amount of rpm and can make good power there especially with large displacements.
At best with stock heads will squeak out 350-375 hp which ain't bad but you'll only need to turn 5400-5800 rpm to hit those numbers. Cam heads plus intake/exhaust etc... Has to be capable together and match with the rest of the combo to hit those rpm and make power, just a cam that's says 4000-8000 rpm on the box isn't gonna do it.
Build a solid combo and turns what turns and makes what it makes people get to caught up in numbers. 5400-5800 is a decent amount of rpm and can make good power there especially with large displacements.
Cledus
Well-Known Member
What the OP is doing looks very similar to my latest build.
318 std bore zero decked line bored
cast crank balanced
kb 399's
scat I beams
used racer brown Stx-19 got sick of waiting on a cam this spring found this local
ported 308 casting heads added 2.02s and a good valve job
Edelbrock Torker II its not the best intake i know but its what i could find
edelbrock 1405 carb until i rebuild one my 750 holley
Still shaking it down but it pulls good to 7k even with the babie carb had a demon 850 on it but throttle response was a little lacking i think a 750dp will be about right
I have to change the rear gear its got 2.93s and with the A-833 od trans i have not put it into 4th gear yet. It burries the speedo past 85mph in the 82 D-150 test chassis which is way faster than that truck with manual brakes should be going.
Is it a ideal street engine no way but I enjoy driving like I just slammed my hand in the door.
318 std bore zero decked line bored
cast crank balanced
kb 399's
scat I beams
used racer brown Stx-19 got sick of waiting on a cam this spring found this local
ported 308 casting heads added 2.02s and a good valve job
Edelbrock Torker II its not the best intake i know but its what i could find
edelbrock 1405 carb until i rebuild one my 750 holley
Still shaking it down but it pulls good to 7k even with the babie carb had a demon 850 on it but throttle response was a little lacking i think a 750dp will be about right
I have to change the rear gear its got 2.93s and with the A-833 od trans i have not put it into 4th gear yet. It burries the speedo past 85mph in the 82 D-150 test chassis which is way faster than that truck with manual brakes should be going.
Is it a ideal street engine no way but I enjoy driving like I just slammed my hand in the door.
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