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 Post subject: Rpm At The End
 Post Posted: Thu Apr 20, 2006 8:11 am 
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Location: Albertville,MN
I was wondering does it mater when you shift rpm wise from let say 6000 or 6700 does it change your rpm at the finish line? Just curious because I'm not comfortable coming through the traps at 7250 BBC Stock steel crank 2 bolt block. I have 4.88 gears and run a turbo 400. I have a throttle stop and last year I had 3.50 seconds in it and ran 11.12 at 131.99
I need to get to sst numbers 10.90 but am worried about Rpm.I also picked up 4tenths of a second in the 1/8 mile this year. Anyone ever use the stop at the end? I know change gears but dont have money or time yet.


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 Post Posted: Thu Apr 20, 2006 8:28 am 
 
wow that's hauling booty

I run a BBC myself in a 66' Chevelle weighs 3645lbs with me in it and I go through the traps at about 6,200 to 6,300 with a 4.11 gear at about 118mph with an ET at about 11.35 with 28" M/T on the back

I also run a two bolt block with a Eagle cast crank but stroked

Really, I don't know, me personally, I would like to keep it below 7,000 rpm's if it was my car.

What type of cam do you have?

I wonder myself what dictates how much you can spin an engine before it could be detremental to it.

Guys here in the know will post and let us know for sure \:D/ \:D/

Mitch

Oh by the way I would not think where you shift would effect what rpm it went through the traps at I assume that is all driven by your final gear ratio, of course if you never got it into third it would LOL LOL


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 Post Posted: Thu Apr 20, 2006 8:34 am 
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Location: Albertville,MN
The cam is a solid roller cam. A little one @.050 288 squared with 750 lift squared 110 seperation. Valve springs are 280 closed. eagle h-beams rods.


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 Post Posted: Thu Apr 20, 2006 8:41 am 
 
Alot bigger than my cam, solid roller .665 Advertised and 285 duration

You've got some nice rods in it for sure.

You know what your HP is I've heard that you should not make more than 600 to 700 HP on a cast crank I think I read that someplace, don't know if its accurate though.

I'd be carefull though, Just my oppinion and it don't mean diddly \:D/

Mitch

Oh how about a taller tire that would do it would'nt it, if you got room


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 Post Posted: Thu Apr 20, 2006 8:44 am 
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Location: Albertville,MN
Well I dont know the HP but run 6.0 in the 1/8 with a 3000 pound car.


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 Post Posted: Thu Apr 20, 2006 9:47 am 
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Location: Mason City, Iowa
i was gonna say gears off the start, but i see you already mentioned that you know thats what should be done, so i guess you answered it for me

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R/T: .194
60': 2.322
330: 6.379
1/8: 9.803
MPH: 71.37
1000: 12.781
1/4: 15.314
MPH: 88.79


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 Post Posted: Thu Apr 20, 2006 10:36 am 
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Hummm, 6.0s in the eight mile = mid 9s in the quarter mile. I think the split is something like 6.35=9.90 That being said, ya got a lot left in that thing even at 10.90! From what I've seen with "STOP" racing the MPH is usually still there even when you limit low gear. I was looking at a Dodge Omni last year that ran the 10.90 index and he was running 145 on the other end with it using the "STOP". That car had a 4:30 rear gear.

As far as using the stop in high gear goes, I've never heard of anyone ever doing that but that's not saying it can't be done. A timer is a timer but personally, if I was racing that class I'd prefer running the guy down rather than having him run me down, which is what will happen if you do stop it in high gear.

I guess all in all the only way to really do what you are trying to do is change the gear, which you say you don't want to do.

Decisions, Decisions?

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Last edited by Ken0069 on Thu Apr 20, 2006 10:39 am, edited 1 time in total.

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 Post subject: Re: Rpm At The End
 Post Posted: Thu Apr 20, 2006 10:37 am 
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Superpro wrote:
I was wondering does it mater when you shift rpm wise from let say 6000 or 6700 does it change your rpm at the finish line? Just curious because I'm not comfortable coming through the traps at 7250 BBC Stock steel crank 2 bolt block. I have 4.88 gears and run a turbo 400. I have a throttle stop and last year I had 3.50 seconds in it and ran 11.12 at 131.99
I need to get to sst numbers 10.90 but am worried about Rpm.I also picked up 4tenths of a second in the 1/8 mile this year. Anyone ever use the stop at the end? I know change gears but dont have money or time yet.



I dont think a change of 700 RPM for the shift is going to change RPM in the lights. But that will depend on how far down track you are making the shift and how much HP you have to play with.

If I recall correctly ... down track throttle stops arent allowed anymore. I could be wrong on that .. but I know there was a change made along those lines.


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 Post Posted: Thu Apr 20, 2006 12:18 pm 
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Finish line rpm is a function of finish line speed so shift rpm doesn't affect the finish line rpm unless it changes the finish line mph like the others have said.

T-stopping at the finish line will cause bigger inconsistency than early T-stop. Not something to do whether it's legal or not.

Going from 11.12 to 10.90 by changing the T-stop timer won't affect the mph at all. Like ken said, it runs pretty close to the same mph when stopping off the line vs no stop, so changing the timer a little won't change the mph and therefore the rpm won't change either.

Weather will have a bigger effect on mph than your T-stop.

Rick


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 Post Posted: Thu Apr 20, 2006 12:36 pm 
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Allright I will order 4.30 gears today dam it. Just hope I can still run super gas with these gears


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 Post Posted: Thu Apr 20, 2006 12:58 pm 
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Superpro wrote:
Allright I will order 4.30 gears today dam it. Just hope I can still run super gas with these gears


If that thing is running 6.0s in the eight mile without the stop then there's no reason it won't run mid 9s without it, which puts you on the stop to run 9.90

As far as the gear goes, Rick can give you some computer generated numbers for that ratio if you want. Just ask and it shall be done!

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 Post Posted: Thu Apr 20, 2006 1:06 pm 
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Ok Rick I'm asking. 32 inch tire I run 6.01 @116.73 1/8 mile car 3000lbs turbo 400 4.88 gears now. hp around 700 would like to see 6800 rpms at end of 1/4 mile.


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 Post Posted: Thu Apr 20, 2006 8:25 pm 
 
So Rick is the man for ratio's and rear ends that's cool to know =P~ =P~ I'll have some Q, soon

Mitch


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 Post Posted: Thu Apr 20, 2006 8:34 pm 
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as far as your crank goes, launching off the line is where you will break it before spinning it up at high rpm at end of track. that rpm with factory steel crank is fine.

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 Post Posted: Thu Apr 20, 2006 8:44 pm 
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Superpro wrote:
Ok Rick I'm asking. 32 inch tire I run 6.01 @116.73 1/8 mile car 3000lbs turbo 400 4.88 gears now. hp around 700 would like to see 6800 rpms at end of 1/4 mile.


I'm guessing it will run 9.45 @ 145mph. If your converter has 5% slippage (hard to say for sure but 5-6% is common) and if your slicks have 102" rollout then a 4.30 gear, that would put you at 6800 rpm at 145mph. Changing to a 4.30 gear may slow it down a little (ET not speed).

Rick


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