ERA #783 - with questions

[Mooch]

I ran a quick spreadsheet of MPH vs RPM for the different TKO-600 setups, with the rear ratio in the top left corner and the gear ratios down the left. What do you think of the 3.31 rear with the 0.82OD? My motor should be in the high 500s for hp at the crank, with torque to match. I'll have to figure out my cruising RPM in the next few days.



EDIT - By the way, this is calculated with 26.5 inch diameter tires.

[xracerbob]

Congrats on your new ERA. I was faced with all the same questions and came up with some alternative solutions-

On the rear gear and trans- I went with the 3:54 and a G-Force T-5 with the optional .75 fifth gear. This seems to work really well. I rarely use fifth anyway, but its nice to know you have it when just cruising. I also have a Pond 482.

Sound deadening- I put Dynamat on all the surfaces in the cockpit that get carpeted. My footboxes get warm, but not hot like I have heard so many other people speak of.

Ceramic coating of the pipes- I spent a lot of time checking into this and there is one that is really different- Swain Technologies. http://www.swaintech.com/store.asp?pid=10296 Too lengthy to explain here, but one of the best things I did. I did the sidepipes as well. They do not get nearly as hot as many others I have checked. Yes, you can still burn yourself, but it will be 2nd degree instead of 3rd degree.

A couple other suggestions- get the Quicktime bellhousing- does not need to be trimmed like the Lakewood and saves a bunch of weight. Use an aluminum flywheel for faster acceleration and a more responsive motor.

Good luck with the build and have fun!

[patrickt]

Alright, it was mid 70's today so I took her for a nice drive and paid particular attention to what you've asked because once you've driven your car for a while you don't notice stuff like this unless you really pay attention. Here is what I believe to be true:

1) With pusher fans, big radiator fan, extra venting & heat shielding, and ceramic coated pipes, in mid 70's weather you don't notice the engine heat at all. Zero heat comes through the firewall or trans area.

2) For pleasant cruising at highway speeds, with your wife, with whom you presumably want to chat with from time to time, anything above 2700rpm is going to be unacceptable because of engine noise (and I have specially crafted "quieter pipes" too).

3) If your car's engine is civilized enough to run without hiccupping at 2000rpm or just over, I would use that as your benchmark for the highway cruising speed that you expect to drive at, and then back in to your gears from there. If you plan on racing your car at speeds over 120 or so, forget about the .64 overdrive altogether.

4) Don't forget that you will also be going slow, so don't make your gear combinatioin too steep in first gear.


EDIT -- BTW, I bet you only need like 50 ft/lbs of torque to cruise at 70mph. It's how your engine runs at that RPM and whether you can lightly accelerate from that speed, at a given rpm, without it burping...

[RodKnock]

I think your goal should be to be around 2,200 RPM at 70mph. I have the 0.82 5th and a 482, but with the Kirkham 3.42 rear end. Cruising on the freeways (65mph speed limit) around that rpm seems optimal for me.

The 3.54's with the 0.82 5th just doesn't look good for freeway cruising.

[Excaliber]

Hmmm, I was thinking a .8 would work well with my existing 3:31. Sounds like my rpm drop might be to much though. I might reconsider the whole issue...

WHAT? You mean you gotta loose the glove box when installing a heater in an ERA? Well that sucks, I LIKE my glove box. But moving to the mainland I wanted to install a heater. I'll pass on the heated seats, that big 427 keeps me warm enough, with the heater, it should be plenty.

[patrickt]

RodKnock's choice is a nice one. BUT, if you are honestly going to casually cruise at 80MPH then you will be turning 2800RPM with this setup. That's pretty loud. If you're going to cruise in the mid to upper 60s, then his setup is very nice. The absolutely number one rule when spec'ing out your Cobra, or talking to your engine builder, is To Thine Own Self Be True.

[RodKnock]

Originally Posted by patrickt

RodKnock's choice is a nice one. BUT, if you are honestly going to casually cruise at 80MPH then you will be turning 2800RPM with this setup. That's pretty loud. If you're going to cruise in the mid to upper 60s, then his setup is very nice. The absolutely number one rule when spec'ing out your Cobra, or talking to your engine builder, is To Thine Own Self Be True.

You can't casually cruise at 80 mph in Northern California with "Ponch and Jon" on the freeways waiting to give you a ticket.

And anyway, turning 2,800 rpm is really no big deal for an extended time with these 482's. Maybe with one of those puny 447's it might be a lot work, but no worries for a 482. (calm down Patrick, I'm just joshing around).

[ZOERA-SC7XX]

Originally Posted by Excaliber

Hmmm, I was thinking a .8 would work well with my existing 3:31. Sounds like my rpm drop might be to much though. I might reconsider the whole issue...

WHAT? You mean you gotta loose the glove box when installing a heater in an ERA? Well that sucks, I LIKE my glove box. But moving to the mainland I wanted to install a heater. I'll pass on the heated seats, that big 427 keeps me warm enough, with the heater, it should be plenty.

Don't know who you spoke with, but I have the heater and the glove box. It was never an issue, as the heater box is centered under the dash.

[patrickt]

Originally Posted by ZOERA-SC7XX

Don't know who you spoke with, but I have the heater and the glove box. It was never an issue, as the heater box is centered under the dash.

Me too, they don't even get close to one another.

[Rickd]

If I were ordering again, with the TKO 600, I would definitely have gone with the .82 OD and I would have ordered a 3:31 rear rather than the 3:54. I really don't like the .64 with the 3:54 rear. If you are driving a lot in the 60 - 70 mph range, it is a real pain - you want to shift - but that huge drop sucks big time. My old cobra had a T5 with a .75 OD and I had a 3:31 rear - which was a nice combo.

[patrickt]

Originally Posted by Rickd

If you are driving a lot in the 60 - 70 mph range, it is a real pain - you want to shift - but that huge drop sucks big time.

Rick is right on the money with this and he's put his finger on the .64's weakness. But Mooch, don't go with anything just because someone else went with it -- you've got to choose this one all by yourself and gear it to your engine and driving speed. Whatever you do, *don't* go with a 3.54/.64 combination just because I did.

[elmariachi]

Originally Posted by patrickt

Rick is right on the money with this and he's put his finger on the .64's weakness. But Mooch, don't go with anything just because someone else went with it -- you've got to choose this one all by yourself and gear it to your engine and driving speed. Whatever you do, *don't* go with a 3.54/.64 combination just because I did.

This discussion highlights the fact that you need to talk to your engine builder about how he builds your stroker. By design, if built and cammed right it should be plenty torquey...enough to pull you out of the 2k/70mph hole if you go with 3.50/.64. But as you say, you gotta pick your cruising band and plan your setup from there. Don't listen to me either, I didn't plan diddly squat where this is concerned>>>>During my build I found a brand new still-in-the-box .64 TKO 600 on Craigslist for $1000 and made what my wife commonly characterizes as an "impulse spend."

[Mooch]

Again, another calculation with TKO-600 gear ratios through the cruising band with 26.5 inch tires. I figure there a lot of people who have been doing this calculation on their own. Hopefully they can just refer to this. I had to put it in a code box for the formatting.

RPMs         3.54w0.64od      3.31w0.82od     3.54w0.82od
 
1500              52              44              41
1550              54              45              42
1600              56              46              43
1650              57              48              45
1700              59              49              46
1750              61              51              48
1800              63              52              49
1850              64              54              50
1900              66              55              52
1950              68              57              53
2000              70              58              54
2050              71              60              56
2100              73              61              57
2150              75              62              58
2200              77              64              60
2250              78              65              61
2300              80              67              62
2350              82              68              64
2400              84              70              65
2450              85              71              67
2500              87              73              68
2550              89              74              69
2600              90              75              71
2650              92              77              72
2700              94              78              73
2750              96              80              75
2800              97              81              76
2850              99              83              77
2900             101              84              79
2950             103              86              80
3000             104              87              81

This is the equation:

MPH = (RPM*pi*d)/(12*88*g*od)

Here are the variables:
MPH = MPH
RPM = RPM
pi = 3.14159
d = Tire true diameter (inches)
g = rear end gear ratio
od = final gear reduction for overdrive


Once I talk with my engine builder, hopefully tomorrow, I'll let you know where I'm going with the gearing decision. I think I'm going to have the trunk lid finished, and I am still mulling over the seat heater and interior insulation options.

[Excaliber]

Good post Mooch! So, 70 to 75 is around 2400-2600 for a .8 with a 3.31. That's just about perfect for my setup, cam profile, etc. I need to stay just a hair over 2000 to be comfortable, a little more is better. So 60 mph and up would work for me.

When considering MY trans gearing I ALSO want to keep a close eye on 1st gear, not to low. The wide ratio top loader is just about right with the ratio's on the bottom three. I think the T600 mimics those ratio's fairly closely, making it a wise choice.

[patrickt]

Have you given any thought to a solid flat tappet cam?

[ERA Chas]

Originally Posted by patrickt

Have you given any thought to a solid flat tappet cam?

BAAAAAAAAAAAAAAAHAHA!

Cool one Pat. The guy<s in a trunk-sound-deadner and seat-heater-or-not quandry and you want him to adjust valves??
He's getting a 482 with juice roller so the noise won't offend his wife. Also nothing north of 5800.

Take your medicine and give the flat tappet song a rest Pat.

[patrickt]

Originally Posted by ERA Chas

BAAAAAAAAAAAAAAAHAHA!

Cool one Pat. The guy<s in a trunk-sound-deadner and seat-heater-or-not quandry and you want him to adjust valves??
He's getting a 482 with juice roller so the noise won't offend his wife. Also nothing north of 5800.

Take your medicine and give the flat tappet song a rest Pat.

Well, my Redskins did manage to stumble in to a win, so maybe I should just quit while I'm ahead and go to bed now.

[Mooch]

Originally Posted by ERA Chas

BAAAAAAAAAAAAAAAHAHA!

Cool one Pat. The guy<s in a trunk-sound-deadner and seat-heater-or-not quandry and you want him to adjust valves??
He's getting a 482 with juice roller so the noise won't offend his wife. Also nothing north of 5800.

Take your medicine and give the flat tappet song a rest Pat.

I'm not sure how to take that. You seem to imply that because I'm asking about sound deadening and seat heaters that I can't turn a wrench, almost offendingly so. Thanks for the welcome. If I'm reading too much into this, then I'm sorry, but easy on the newb.

I actually was going to do an original 427 marine conversion with flat tappets, but after examining the block I turned to the aftermarket blocks and it seems that the Pond blocks run better with hydraulic rollers.

[patrickt]

Originally Posted by Mooch

I'm not sure how to take that. You seem to imply that because I'm asking about sound deadening and seat heaters that I can't turn a wrench, almost offendingly so. Thanks for the welcome.

I agree with you Mooch, ERAChas was clearly out of line. You should just ignore him. He can be kind of a jerk from time to time.

[ERA Chas]

Originally Posted by Mooch

I'm not sure how to take that. You seem to imply that because I'm asking about sound deadening and seat heaters that I can't turn a wrench, almost offendingly so. Thanks for the welcome. If I'm reading too much into this, then I'm sorry, but easy on the newb.

Mooch,
With all due respect to your wrenching and sensibilities and your newness here:

I attempted to illustrate that you may be at cross purposes with your needs and wants for this type car. You can spend for all the ginger bread you want but virtually none of it will make a Cobra replica a cozy, comfy quiet touring car. It's items you'll spend money on now that you'll wonder why a year from now provided you put more than 500 miles on it. Pat said earlier that some things are just not as much fun as you think they'll be.

It's like missing the point of Cobras-a C6 or 350SL would fill those bills much better than a Cobra. You're buying 600 LB Ft of torque- totally opposite what a comfort-seeking passenger would want. A warm sweater, parka or skiers underwear would be a better investment than heater, seat crap, top, side curtains, radio or ashtray. Vettes even come with a draft blocker.

Ironically the one thing you would find helpful-you've deleted! Get the glove box dash! It's not big but it's a good place for the MSD, cell phone, spare fuses, pen and pad and -amazingly-gloves!

The point of giving you the link to the other thread was so you might realize that driving in weather colder than 50 is more than a little uncomfortable-it's harmful to the motor for oil temp-but what the he!!, it's your $18K. Thin weight synthetic oils are not the answer either. Yes they flow fine but they don't get hot enough to burn off the condensation in the oil. Slow death for motors.

So I'm not just a shoot-from-hip wise a$$. Learned a lot of lessons from building and driving the same car for a long time and I'm dumb enough to think passing on what I learned might help a guy or save him money or disappointment. Big lesson is; spec you car to please YOU- not any prospective passengers. And don't try to make it something it can't ever be. Choose a different weapon for others needs.

There's one really dumb option you did not check on the ERA list-
At least your car won't look like this:


Oh and don't mind Pat- we must all remember He knows everything!