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Old 11-08-2010, 07:35 PM
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timing answer, for better 1/4mil times!!

Hi again, hotrodders, hello, well i was in the track the last weekend and i didnt like it the time of 14.95, 2.4 60ft the car loose power up to 4000 in the 3d shift, the run was like this, second shift in 5500 rpm, 3rd shift in 5500rpm, and after that in the 4000rpm range loose a little the power, here the mods of the car....

my mods are, lunati voodoo .504,.492 lift 268/276, dish pistons, street dominator intake dual plane, street avenger 770 cfm carb, the rear axle is 3.73 and the diameter of my (very very old tires) is 27x10 inches, and the tranny its rebuild but stock, (original converter), the car is my daily drive got A/AC here is the video, http://www.youtube.com/watch?v=MJ-s2V8v1BE

the tires are full street tires very old, the car its all complete.

THE QUESTION IS, the timing is in 12, how much you think would be nice for dont loose the power in high rpm?? wich racetires diameter you think would be good??

if you need more info, or i didnt explain, dont hesitate, i know my english its not the best, please if need something let me know...

and a lot of thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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Old 11-08-2010, 08:14 PM
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What type of cylinder heads? what exactly are the piston type and dish volume, you will need a healthy compression ratio for that cam, the stock converter is not helping.

What type of distributor? you could use more base timing more like 18 or 20, then you will need to limit your mechanical advance, depending on the type of heads you want about 34-36 total advance at 3000 rpm without vacuum advance.

There could be a thousand reasons you are running low ET's, is the car hooking up at all or are you smoking the tires off?
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Old 11-08-2010, 08:33 PM
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i know im not helping but the heads are stock with the necessary springs for the cam, a very very little ported, i wish i could give you numbers but here in this city its impossible, the pistons are morosa dish stock (but new)in .040 with 4 valve relief you can see it in the video, aint got the compression exactly but i know this cam at least needs 9.00 and i dont have it, i think i got 8 or 8.5, i know it works up to 2200rpm but for now i dont wanna use a converter for the $$, my distributor its the original with a msd 6a, the tires jump in the start and jump and drift in the second shift, when they loose the grip the first time my times where in the 15.30 and the 15.00...

the distributor works with vaccum, so if want to put the base in 18 or 20 i need to block the advance in high rpm?? the weights of the distributor are the stocks

i know the balance in my car its not the best for know, maybe with converter and compression i could reach the 13s here in the sea level, but for now i dont care run in 14, but i wish i could make the 14.70 more easy...

with the same tires but original cam and original springs and stock manifold and a stock quadrajet the car raced the 15.10 so... im a little pissed off... jejejeje
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Old 11-08-2010, 08:44 PM
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drag racing takes $$$$ to go fast!
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Old 11-08-2010, 08:51 PM
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Originally Posted by BigRoy1978
drag racing takes $$$$ to go fast!
i know, go big or go home!!, but everyone makes what is in his range, this last months i spend a lot of money in the engine tranny and diff, thats why the converter needs to wait a littlee
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Old 11-08-2010, 09:26 PM
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why? its not gonna run like it should without the right converter, or good tires.

drag racing and dirt circle racing share a couple things....gotta have everything that works with everything else, and you HAVE to have a good set or tires...its the only part of your car that contacts the ground....think about it lol
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Old 11-08-2010, 09:41 PM
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The adjustments to the distributor may help you out some but it is not going to get you into the 13's, bigroy is correct.

but since you asked maybe you can find out some more about setting your timing

Make the adjustments to the base timing and the mechanical advance first, then add some vacuum advance after. The vacuum advance will not be in effect at WOT while making a pass anyhow

Make sure that you have verified TDC and that your timing pointer is accurate at TDC, get a timing tape on the damper that goes up to 60 deg BTDC

Test the amount the mechanical advance is adding,,,parking brake on, kids clear dude

Rev the motor to 3500+ or till it stops advancing the timing, and adjust the distributor till you read 36 BTDC, then without distributor moving let the thing idle at 700 rpm and take a base timing reading. Check it out and post what you find, imo chances are that you will need to limit the mechancial advance to run the correct base timing for that cam.
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Old 11-08-2010, 09:43 PM
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Quote:
Originally Posted by BigRoy1978
why? its not gonna run like it should without the right converter, or good tires.

drag racing and dirt circle racing share a couple things....gotta have everything that works with everything else, and you HAVE to have a good set or tires...its the only part of your car that contacts the ground....think about it lol
i know that, thats why im asking which diameter tires would be better, maybe with a 26 x10 run better without converter than a 28xXX without converter, i know its not the best cause the cam needs a converter and compression, but as i said, everyone fights in his range....
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Old 11-08-2010, 10:17 PM
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Quote:
Originally Posted by Custom10
The adjustments to the distributor may help you out some but it is not going to get you into the 13's, bigroy is correct.

but since you asked maybe you can find out some more about setting your timing

Make the adjustments to the base timing and the mechanical advance first, then add some vacuum advance after. The vacuum advance will not be in effect at WOT while making a pass anyhow

Make sure that you have verified TDC and that your timing pointer is accurate at TDC, get a timing tape on the damper that goes up to 60 deg BTDC

Test the amount the mechanical advance is adding,,,parking brake on, kids clear dude

Rev the motor to 3500+ or till it stops advancing the timing, and adjust the distributor till you read 36 BTDC, then without distributor moving let the thing idle at 700 rpm and take a base timing reading. Check it out and post what you find, imo chances are that you will need to limit the mechancial advance to run the correct base timing for that cam.
Thanks!! this is very usefull, i will came the next time with a 26x10 slicks and a 28x10 slicks time to let you know how help and with the timing in better shape, i can get the tires just to try, thank you very much guys, really apreacciate.
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Old 11-08-2010, 11:25 PM
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A lot of info here! and everything make sense, no doubt very usefull, i really apreacciate, thanks for all the things, F-bird, custom10, with this info i can reformulate a few things on my plans, now i have a north for my heads and with a few things more, i will check the timing as you said come with news in a few weeks after the next drag event!
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Old 11-08-2010, 11:35 PM
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i dont have the 1/8 mile, the track its starting after two years problems, and the speed its and estimate of 98mphr 100mphr cause im in 5000rpm at the end of the track, the ''teory'' says im in that speed for the ratio gears and tires, but i dont know how exactly its that, and the 4.56 sounds very very scary, this is my daily driver, really, i use my car 6 days for week, 4.56.... holy****!!!!!!!!!!!!!!!!!!!!!! with a th350 jejeje!! damn it!
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Old 11-08-2010, 11:40 PM
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the tire you said for a 3.73 rear axle its 24 inches for 8, i've got a doubt, that size in the track would be a problem for the traction i think, 26x10 sounds better... =S what you think???????????
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Old 11-09-2010, 11:59 AM
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A lot of work here, thank you very much guys!!!!!!!!
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Old 11-09-2010, 12:22 PM
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Quote:
Originally Posted by sickboy84
Hi again, hotrodders, hello, well i was in the track the last weekend and i didnt like it the time of 14.95, 2.4 60ft the car loose power up to 4000 in the 3d shift, the run was like this, second shift in 5500 rpm, 3rd shift in 5500rpm, and after that in the 4000rpm range loose a little the power, here the mods of the car....

my mods are, lunati voodoo .504,.492 lift 268/276, dish pistons, street dominator intake dual plane, street avenger 770 cfm carb, the rear axle is 3.73 and the diameter of my (very very old tires) is 27x10 inches, and the tranny its rebuild but stock, (original converter), the car is my daily drive got A/AC here is the video, http://www.youtube.com/watch?v=MJ-s2V8v1BE

the tires are full street tires very old, the car its all complete.

THE QUESTION IS, the timing is in 12, how much you think would be nice for dont loose the power in high rpm?? wich racetires diameter you think would be good??

if you need more info, or i didnt explain, dont hesitate, i know my english its not the best, please if need something let me know...

and a lot of thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
If the engine will pull red line in first and second but not in 3rd, this is a clear indication that the total gearing is not low enough. The engine looses leverage as the gears move up with each shift. The engine is either not capable of pulling red line in top gear, which is common for the vast majority of vehicles, or doesn't have time to rev that high in a quarter mile.

One solution is to go back thru the engine for more power, the other is to lower the final gear ratio such that the engine is hitting red line as it gets into the 100 foot trap at the end.

Total gearing is a combination of actual gears and tire size. A smaller diameter tire requires more revolutions to go a distance, this is the same as actually changing gears. In your current situation unless the car is spinning the tires thru the traps, going to a stickier or wider tire would slow the car since the engine already doesn't have enough leverage to keep on revving in high gear.

Your 3.73s need to be 3.89, or 4.11. Traction will become a problem with lower gears as the engine is gaining mechanical leverage on the tire. A high stall converter allows the engine to be revved higher in it's RPM range where there is more power, it will also create traction problems in the lower gears. But in and of itself will not improve the engine's inability to get to red line in high gear other than a harder launch may get you into the traps before the 2-3 shift. there's nothing inherently wrong with running thru the traps in second gear. There are many ways of getting the vehicle thru the traps with the lowest ET and highest speed, you have to experiment to find the combination that works best the answer isn't always found in more power.

You mentioned dished pistons. The cam you're using has a very aggressive rate of lift. Fast lifting at the valve whether coming from the cam with 1.5 stock ratio rockers or being arrived at with 1.6 ratio rockers or a combination of both makes the engine behave as if it has more duration. Where this gets to be a problem is that more Dynamic Compression Ratio is being sacrificed than one would calculate with typical DCR equations. This means your Static Compression Ratio is not as effective as it would appear with straight forward measurements. Which is a complicated way of saying this engine most likely needs more compression. Dished pistons if the type that have a circular dish lack sufficient squish/quench area opposite the valve pocket. This has the result of the flame front moving slower while having a greater tendency to detonation than using pistons that are flat topped or use a D shaped dish. A circular dish piston needs more spark advance to get power but the additional advance either in the rate it comes in or the amount makes the engine more ping prone. If you're running large chamber heads you should use a flat top piston. If these are tight chamber heads use a D dish piston. In both cases with this cam try to get the static compression up around 9.2 to 9.5 with a cast iron head and about a ratio more if the heads are aluminum. In both cases you also want to keep the piston crown clearance to the head's squish/quench deck around .040 inch. That's going to be a total space of the clearance from the top of the piston to the block's head deck which for an OEM small block Chevy is .025 inch, plus the gasket. With the OEM deck clearance of .025, that leaves only space for a .015 shim style gasket. If the block has been zero decked than you can use a.040 inch thick gasket. A piston with a circular dish has too much area too far away from the squish/quench to be effective. This increases the octane requirement from the fuel or forces compromises with ignition timing to stay under the detonation limit all of which costs power.

But in the short term, this combination needs stiffer final gears to go faster, that is the shortest and least expensive route to faster times.

Bogie
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Old 11-09-2010, 01:05 PM
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im agree oldboogie, the fastest way to get better times its modifying the diameter tire or the final gear, as firebird said tooo, i know im not going to 13s or 14 flats, and as i said a few post ago, i know my combo its not the best, but at this time i just wanna race the 14's just easier, i dont care run the 14.90 but i wanna make it always, im gonna use a sticky tire low diameter in two more weeks i will the results
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