Exactly! Yeah TR6 is a solid choice, but if doing nitrous the BR7 is the way to go

 

Great, yes will do nitrous but be after the new year for sure.. ill swap then, thanks for all the help! will keep updated and get pics of heads posted and with car running.. hopefully won't be too long.

 

 

No problem, sounds good. Keep us posted for sure

 

4 10's don't have top end speed, 4 10's are for drag race.

 

In that race it wouldn't have mattered since the Cobra was pulling more and more as the race went on. With 4.10's this cammed Camaro would accelerate faster in every gear. The only difference is the overall top speed in each gear is less

 

Slogo's point is valid. 1/4 mile gear ratios are completely different from roll racing. It all comes down to average power through the run. And with airplane gears in a roll race you can make some really nice average power. Think about how much harder 1st gear pulls than 2nd, 2nd more than 3rd and so on. This isnt a 1/4 mile so no need to to get 4 gears in. So go back to the stock 342's and now 3rd gear gives you almost the same speed as 410's in 4th. Affectively keeping you in the highest average hp rpm rage for longer, not to mention the wasted time shifting.

 

I see what you are saying, and you are right in a sense, but I still think a big cammed LS1 like this one will perform better overall with the 4.10 gear. If it didn't have such a big *** cam I believe your idea would apply moreso

 

Exactly, Cobra pulled on Camaro because Camaro has 4 10's, Camaro was already
wound up, mechanical advantage runs out quick. Drive shaft has to turn 4 times just to turn
axle once, thats not good for top speed. A car with 4 10's needs to start a race from
low to no speed, not a rolling from 40 mph start.

 

That was added while I was eating/typing.

 

In this particular case I respectfully agree to disagree. To each there own

 

If you prefer top speed to dragstrip performance, then higher axle gears, like 2.76:1 or 3.08:1, may be called for. The higher gears will reduce engine rpm versus road speed. Another way to look at it is that the car will go faster at the engine’s rpm limit than it would with lower gears. Low-speed acceleration will suffer, but that can be cured with one of today’s manual five- or six-speed trannies that provide lower First and Second gears for acceleration and also feature overdrive for even more top speed—or engine-rpm reduction, depending on how you look at it.


Here is complete article. http://www.hotrod.com/articles/how-gear-works/

 

That article makes total sense, but there are more things consider in this particular case as well. So let's take this mentioned cammed LS1 as an example since thats what we are discussing here. The race was about 45-125 mph. If he had stock gears he'd lose that torque multiplication advantage right from the get go, which would allow the Cobra to have even more of a lead early on. Then there's the fall back rpm in the next gear. With the 4.10 he will fall back less rpm wise into the next gear, thus putting him more into the powerband on each successive shift...which is a good thing for a big peaky type cam like the t-rex. I think the real question becomes which gear would be the "best" gear in this circumstance. Maybe it's nether the 4.10 or the stock gear, but I still think the 4.10 has better chance than the stock one in this case all things considered.

I'll give you a great example of my own car vs my buddy's HCI LS1 with a 6-speed and stock 3.42 gear. His HCI is very similar to mine along with bolts and tune. The only major difference is my 4.10 to his 3.42. He wanted a 50 mph roll in 2nd gear, because he said that was his sweet spot, so I gave it to him. I started in 2nd as well. I was at about 5000 rpm (him maybe 4000-4500 if I had to guess) we honk it off and I almost immediately pull a car length on him. Now since I have to shift before him he pulls up on me a little, but when he shifts I pull on him a little. Basically I held a good one car lead to the top of 4th. Consider we both shift twice in this race, but just at different times due to the gearing.

 

With a large cam, a steeper gear is most definately needed, regardless of roll or dig runs. Large cams make power up top. They are dogs downlow. Is a longer gear was used, the car would fall on its face until power band is reached. 4.10's or any steeper than stock gears will allow the racer to stay in their powerband throughout the whole run...

 

Subscribed.
Interested to see numbers on this head combo. Contemplating doing heads/intake this winter.

 

Bigger cams have increased rpm range. More rpm is like having longer gears. If the gears are too long then the engine falls out of its power range on the gear change. You off set this by adding steeper gears and rev it higher. Any cam car with a M6 will most definitely benifit from 4.10 gears and a 26" tire. Go to a gear calculator page and compare speeds with 3.42 gears @ 6000rpm vs 4.10 gears @ 7000rpm. 3.42 gears would be 135mph in 1:1, 4.10's would be 132mph in 1:1.

 

In general this is what I've seen roll racing too. On stock gears generally won't pull as hard with every upshift. And gets worse with every upshift. Even stock LS1 benefit from 4.10.

Say car 1 with stock gears makes 430 torque and car 2 with 4.10 makes 400. When you do the maths, car 2 is actually netting 15% more torque to the pavement. The equalizer is 4th gear on stock ratios and fifth gear on 4.10. First four gears, advantage 4.10.

One caveat to throw in is MOI. Say you build a awesome HCI and then put a LS7 clutch in it. The weight means the engine can't rev as quickly vs a lighter clutch. If you're going to limit the engines ability to rev, you won't want as tall a rear gear, because the motor won't rev as readily.

I can take mine to 7500 with no fear. In stock gears, and tall tires, that's almost 70 mph. 4.10's would put my shift point "back" to 50-55 or so, but the gearing will mean the pavement torque I had at 60 in first I'll have at 80 in second.

In a T56, you'll be drag limited before you run out of gear in sixth

 

Ha Ha where did this go, we all know low gears help an engine get into it's power band quicker, my original comment was 4 10's killed THAT race in post #11.
Listen to it , he downshifts, car is already in it's power band with not much more rpm to go,
as race starts to progress tan colored camaro gets out run because he's already out of
rpm. 4 10's and top speed don't go together.

 

Good point about the clutch too. Most people overlook stuff like that when looking at a scenario like this. I see what the other two guys are saying, and it is valid in certain applications no doubt, but not so much in this one. As I'm sure you know having the initial hit in a race is everything, and it takes a vehicle with a lot more power to make up that ground in a very short period of time like in this particular race. If the Camaro had stock gears on this run he would've been pulled even harder right from the get go (since he would've been in 2nd either way) by the Cobra.

 

You need to rewatch that video...the Camaro was right where it needed to be...it was in 2nd gear for 3 seconds. He simply did not have enough power for the Cobra, had nothing to do with gearing. Fyi the Camaro is Pewter not Tan.