timing answer, for better 1/4mil times!! - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #16 (permalink)  
Old 11-08-2010, 10:54 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,182
Wiki Edits: 0

Thanks: 2
Thanked 292 Times in 289 Posts
Quote:
Originally Posted by sickboy84
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???????????
The little drag radial tires will hook at the track. They work a lot lot better than it appears.
They are really gummy. About 14psi hot.
The drag bags make a huge difference on these cars. Extra air in the right bag evens up the axle, chassis reaction.
The short tires give you the net effective gear ratio you need with 3.73's to et good.
Then run a taller conventional radial street tire for cruising and commuting duty.
This gives you the street/strip flexabilty.
A friend used these P225-50-15 BFG drag radials tires on a 350SBC Regal with 3.73's and drag bags and a 10" 3500 stall.
They hooked solid even with nitrous. Yanked the front left wheel at launch.
12's N/A 11's on nitrous.
They work...
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #17 (permalink)  
Old 11-08-2010, 11:47 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,182
Wiki Edits: 0

Thanks: 2
Thanked 292 Times in 289 Posts
Edit: the optimum rear tire pressure with BFG drag radials at the track will be 14 to 22psi hot. The ET slip will show you what works best.
Don't go below 14psi or you risk spinning the tire on the rim.
Install clean and dry on a clean dry rim. (no soap/grease)
Reply With Quote Quick reply to this message
  #18 (permalink)  
Old 11-09-2010, 10:59 AM
sickboy84's Avatar
Registered User
 
Join Date: May 2010
Location: north of mexico!
Posts: 23
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
A lot of work here, thank you very much guys!!!!!!!!
Reply With Quote Quick reply to this message
  #19 (permalink)  
Old 11-09-2010, 11:22 AM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 6,437
Wiki Edits: 0

Thanks: 3
Thanked 331 Times in 288 Posts
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
Reply With Quote Quick reply to this message
  #20 (permalink)  
Old 11-09-2010, 12:05 PM
sickboy84's Avatar
Registered User
 
Join Date: May 2010
Location: north of mexico!
Posts: 23
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
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
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Vacuum advance hooked up directly to manifold....is this bad????? Steve-0321 Engine 69 03-10-2014 05:10 PM
Port or Full time vacuum cool rockin daddy Engine 129 10-05-2010 03:00 PM
ignition timing bad502 Engine 21 02-20-2006 06:57 PM
vacuum advance help batman09 Engine 14 09-09-2004 09:42 PM
Timing Advance concerns Irnguy Engine 6 07-20-2004 10:16 PM


All times are GMT -6. The time now is 01:28 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.