gkull

I drove around for nearly 20 years with a 700R4 and 4.11 gears. Until I got smart and went to a manual tranny. The TKO 600 was a very good investment. I still used the 4.11 for the first three years and just a couple of months ago swapped it out for 3.55

LiveandLetDrive

Wrong. There is indeed a reason they arrive at the line at those temperatures, try looking at the temps at the end of the 1/4mi! That is simply a matter of getting a head start on a very transient condition. Do you think F1 or Le Mans cars run 120-140* temps?

Yes, you do have to be sure you aren't getting detonation, and for practical purposes a car without a knock sensor should probably play on the safe side. But that does not mean colder is better. Cold cylinder walls suck the temperature out of the combustion and make less power, not more. Where exactly the "safe side" is is a matter for debate I suppose.

You also want the oil as hot as it can chemically handle for its expected lifetime, and of course the engine must be designed to have the correct tolerances within the temperature range it will experience.



gkull, how do you like the 5th gear cruising with the 3.55's? I just inherited a TKo-600 w/ 4.11's setup and as the rear isn't built for the power the car puts out I intend to build up another with a numerically lower gear as the 4.11's are just useless trying to take off in 1st.

gkull

I've got a big solid roller cam that idles at 1100 and runs the best over 2000 rpm. My motor pulls hard right to my 7000 rpm rev limiter. So it made the first 4 wonderful for around town and 5th as road gear that put it in when going over 60 - 65. I also live where the freeways are posted at 75 mph So I generally drive under 100 mph where ever I go.

http://www.secondstrike.com/technical/GearCalc.asp


Gear 1st 2nd 3rd 4th 5th 6th
Trans Ratio 2.87 1.89 1.28 1.00 0.64
Overall Ratio 10.19 6.71 4.54 3.55 2.27

1500 11 17 25 32 50
2000 15 23 33 43 67
2500 19 28 42 53 83
3000 22 34 50 64 100
3500 26 40 58 75 117
4000 30 45 67 85 134
4500 33 51 75 96 150
5000 37 57 83 107 167
5500 41 62 92 118 184
6000 45 68 100 128 200
6500 48 73 108 139 217
7000 52 79 117 150 234

DRIVESHAFT

Below is an interesting quote from Darin Morgan, who was employed by Reher and Morrison at the time.

All naturally aspirated gasoline burning engines drop 2.5 horsepower for every ten degrees of temperature increase and 4 per 10 after 165F. You can flip it around ( hot heads, cold low viscosity oil or cold heads and hot high viscosity oil) but the mean average drop in power is still 3.25:10. 3.25 horsepower per 10 degrees. A Pro stock engine is launched as cold as we can get them. If I could launch that &%%$# at 65 degrees I would do it in a heart beat! Heat Kills power. I know I have some people who will disagree with me on this but I have proven it over and over and over again. A cold engine with ultra low viscosity oil will fly on the race track. In most forms of racing a cold engine is an impossibility so tuning factors must be instrumented to overcome the heat. Cold engines are only practical in Drag racing so it as mute point in any other form of racing to even consider running the engine cold. If you run an engine at 180F then you tune the combination to run the best at that temp. If you take the same engine and TUNE it to run at a colder temp,,,, Its an easy 15 to 20 horsepower.

chevymans 77

how did it work for you?

buddy has two 4l60's sitting in his shop, just did not want to install one due to first gear.

Neal

chevymans 77

Interesting

Neal

gkull

I used an $1100 3500 stall 9.5 inch lockup TC with a 5000 rpm auto shift govenor. So for racing you put it in second gear position let off the brake while flooring it. My tranny would do a 1-2 at 5000 rpm and then I would click the shifter into 3 and 4th at 7500 rpm.

That was with my old 383 and it would bight pretty good with 10X26 goodyear slicks. It was a very consistant 11.70s car back then.

like your motor you might want to buy a 3500 -4000 rpm gov for wide open throttle shifts.

Then I put in a 427 sbc of around 600 hp and the car because very traction limited even with my big 315X17 rear tires. I could leave 100 yard twin black stripes in second gear. Auto trannies start to really suck as power exceeds 600. The torque converter is a TQ multiplier and the big stall put me right into the start of the power band


So I started looking at higher powered manual trannies

LiveandLetDrive

gkull,

My cam is also a solid roller, .577"/.583", 248/254@.050, 112LSA. Short of stomping on it in 5th gear at <2000 I've yet to find anywhere it isn't terrifyingly powerful. 3.55's sound like a pretty good option. It gets over 18mpg highway astonishingly enough but I'll take all I can get! It is to be a fairly frequent daily driver.



Hmm, that is interesting. I'd like to hear the theory of why that's supposed to work beyond just "I've seen this work." (Not that that's to be discounted by any means, I'm just curious what other factors are at play.) Cold intake charge to pack the mix into the cylinder, sure, but once the valve closes and you're ready to start expanding some gasses you want atoms bouncing around like crazy (aka heat) so they're at the right place at the right time for combustion to progress. Is that out of a book?

DRIVESHAFT

Its not from a book. Darin will post on the SpeedTalk forum on occasion.
He wrote it there, and has made similar comments on more than one occasion.

ja1724

Based on what I've heard from many Top Fuel and Funny car drivers I would have to disagree. Nowadays, when they light up the tires before a run it is still to get them tacky but more so to get the engine up to operating temp which is anywhere from 180 on the low side to 220.

DRIVESHAFT

You really cant compare cars that are so different. For starters the fuel cars run nitromethane, not gasoline.
They dont even have cooling systems (solid block), and they can shove as much air as they want to into the cylinders via a large blower.
Talk to a Pro Stock or Comp Eliminator guy and see what they tell you.

LiveandLetDrive

They run solid blocks because they want it to run hotter (both gas and nitro have a cooling effect, the nitro's is just much stronger). Would still be interested to know the "why" behind the "what."

chevymans 77

Well its official,

I now have total control of my temps and its 96* outside

On to installing the AC

Thanks for all the help from everyone

The oil cooler took care of my heating issue

Neal

chevymans 77

Ealier in this thread Matt G. had suggested that I could measure air flow changes through the radiator by measuring voltage from the fan motor while not energized. Back then I was so caught up with fixing my heating issue that I let this one fall to the back of the list.

I recently had to re-rout my data logging cables so I decided to try Matt’s idea. I ran a wire from one of my 11” SPAL fans into the cabin and connected a DVM and sure enough I can get a good voltage reading from the fan motor. I’m seeing around 1.5 volts at 50 mph, 2.4 volts at 60 mph and around 3.2 volts at 70 mph. I was able to run 3 tests and the voltage was pretty close to these readings each run. I was able to see when my seal ( a piece of pipe insulation) between the top of the radiator and the core support partially blew out allowing air to bypass the radiator during one of my carburetor tuning test runs.

It’s a little hard to keep an eye on the DVM and the road when doing carb tuning test runs so I’ve connected the fan motor leads to my data logger so I can log the voltage while driving. This will also allow me to compare RPM’s with air flow to see if any changes I make to the cars front end effect air flow. My plan is to add a splitter and an air dam under the front of the car as BeeJay has done to see if it’ll increase air flow through the radiator.

The voltage readings are form memory so they may be off a little but they’re close, I was busy watching AFR, RPM and the road. This is why I’m wiring it through the logger, I’ll be able to down load it to my laptop and study the voltage compared to RPM’s.

Of the three tests I’ve done the ambiant temps were in the mid 70’s for one mid 60’s for one and in the low 50’s for one. The fans are on a 195* on 175* off switch mounted in the radiator just below the inlet hose. I make about a 10 mile round trip, the same rout each time, and the fans have never come on during this run until I get to my driveway. My house is about 3/4 of a mile form the highway and once off the highway I average around 15 to 20 mph. The fans usually come on just before I get to my house. I cruise at 40, 50 and 60 MPH and a WOT pull form 3000 to 5000 rpm each run with the same results from the fan.

Neal

68/70Vette

FYI: The L88's were certainly high performance, high horsepower (550HP) engines, but the stock L88 radiators were not that big. The L88 aluminum radiator is the same radiator used in the 1968 327 350 HP engine. (This my recollection.) The L88's were intended for racing, and on a racetrack these "small" radiators were sufficient.