My head choice dilema... - Page 2

jimberg · 06-14-2001, 01:47 PM

Just so you know what kind of time spans we're talking about here. At 1000 rpms, it takes the crank .06 secs to make a revolution. If advance is at 10 degrees it's about 0.0017 seconds of explosion time we're talking about. At 6000 rpms, it would take 62 degrees of advance to allow that much time, but with the speed and heat being generate, total advance can only be little more than half of that.

------------------
351W 89 Mustang GT Convertible

[This message has been edited by jimberg (edited 06-14-2001).]

TJR · 06-14-2001, 02:54 PM

jimberg....That's a lot of info, I had to read it twice to catch everything I missed the first time

.

------------------
1989 lx notch
89,000 miles
bolt-ons,stock heads/cam
60'- 2.07, 8.90@78, 13.93@99

jimberg · 06-14-2001, 03:24 PM

I just hope it's useful info.

------------------
351W 89 Mustang GT Convertible

MiracleMax · 06-15-2001, 12:03 AM

Quote:

Originally posted by jimberg:
Just so you know what kind of time spans we're talking about here. At 1000 rpms, it takes the crank .06 secs to make a revolution. If advance is at 10 degrees it's about 0.0017 seconds of explosion time we're talking about. At 6000 rpms, it would take 62 degrees of advance to allow that much time, but with the speed and heat being generate, total advance can only be little more than half of that.

don't forget though, combustion chamber shape and volume, rod/stroke ratio, spark plug location, piston shape, ect. effects the total timing needed

I had a shop teacher adamantly maintain that no engine could be revved past 6,000 rpm or so (yeah rite!) since his calculations were based on a steady state burn (gasoline),
unfortunately he didn't any other variables in account when he did the math!

For a high RPM engine, a small chamber with a good R/S ratio is desirable, along with a port/chamber design which promotes good fuel atomization/homogezination.

a. a small chamber reduces the time it takes to burn the A/F mixture across the chamber
b. a high r/s ratio creates more piston dwell time at TDC
c. highly atomized and homoginized fuel tends to burn more rapidly.

jimberg · 06-15-2001, 09:54 PM

Right, the timing isn't linear for another very obvious reason. By compressing the gases faster at higher RPM you generate more heat which will cause detonation earlier and earlier.

------------------
351W 89 Mustang GT Convertible

Mach 1 · 06-16-2001, 09:47 AM

jimberg - how is the timing being non-linear (advances with rpm) going to discourage detonation?

jimberg · 06-16-2001, 12:27 PM

Sorry. That was unclear. Advance in degrees can be linear in relation to rpms, but advance in an actual time interval would not be. e.g. The 0.0017 seconds in above example.

The faster you compress a gas, the more heat will be generated since there is less time to dissipate the heat. This extra heat will add to the potential for detonation.

------------------
351W 89 Mustang GT Convertible

Unit 5302 · 06-16-2001, 03:53 PM

I think jimberg's been readin a lotta physics lately.

Mach 1 TFS added me to the payroll 3 months ago, they keep telling me the check's in the mail, but for some reason, it always get's lost?

Mach 1 · 06-16-2001, 10:48 PM

Yeah, the old "check is in the mail story"...heard it a hundred times myself...lol.

I think Jimberg is confusing himself......

------------------
1993 GT/AOD
'93 Mustang GT

RobertD · 06-17-2001, 09:52 PM

Trick Flows it is....

Thanks!

------------------
Robert
91GT; 88 ASC McLaren #709

Zack87GT · 01-13-2005, 03:32 PM

Have you thought about AFR heads? Edelbrock is an excellent choice as well!!

andy669 · 01-13-2005, 04:46 PM

This thread is 3 1/2 years old. Whatever he decided, I'm sure its a done deal my now. :lol:

Andy

Rev · 01-15-2005, 03:30 PM

I use TFTW heads and couldn't be happier. I have enough low end torque to smoke the tires with a C-4/3.25. I don't know what I would do with anymore low end torque. One other good thing about the TFTW, is that they have a raised valve cover rim that allows using roller rockers with poly-locks and still be able to use stock height valve covers.

On the other hand, I've heard that the AFR 165 heads are "kick ass" in the torque and power department. I think I would have been just as happy with those too.

Rev

Hozer 88GTConv · 01-16-2005, 12:23 PM

Another vote for TW's...
Man, do I love them! Especially w/ 3.73's, but my neighbors for some reason don't appreciate them nearly as much.

01-13-2005, 03:32 PM	#31
Zack87GT Registered Member Join Date: Jan 2005 Posts: 33	Re: My head choice dilema... Have you thought about AFR heads? Edelbrock is an excellent choice as well!!

01-13-2005, 04:46 PM	#32
andy669 Registered Member Join Date: Jan 2001 Location: Moline Il Posts: 901	Re: My head choice dilema... This thread is 3 1/2 years old. Whatever he decided, I'm sure its a done deal my now. :lol: Andy __________________ 88 coupe 91 LX NMRA Pure Street 5120

01-15-2005, 03:30 PM	#33
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Re: My head choice dilema... I use TFTW heads and couldn't be happier. I have enough low end torque to smoke the tires with a C-4/3.25. I don't know what I would do with anymore low end torque. One other good thing about the TFTW, is that they have a raised valve cover rim that allows using roller rockers with poly-locks and still be able to use stock height valve covers. On the other hand, I've heard that the AFR 165 heads are "kick ass" in the torque and power department. I think I would have been just as happy with those too. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

01-16-2005, 12:23 PM	#34
Hozer 88GTConv Registered Member Join Date: Feb 2002 Location: Jacksonville, FL Posts: 706	Re: My head choice dilema... Another vote for TW's... Man, do I love them! Especially w/ 3.73's, but my neighbors for some reason don't appreciate them nearly as much. __________________ 1988 GT Convertible 331 10:1 TW heads, GT-40 intake, MSD, TRW flattops, B Cam w/ 1.7's, MAC exhaust, 24's, 70 TB, 76 MAF, 3.73's, Pro 5.0, Koni's, Anderson PMS, Wideband 02, yatta, yatta... One week with new motor, two speeding tickets...joy

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06-14-2001, 01:47 PM	#21
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Just so you know what kind of time spans we're talking about here. At 1000 rpms, it takes the crank .06 secs to make a revolution. If advance is at 10 degrees it's about 0.0017 seconds of explosion time we're talking about. At 6000 rpms, it would take 62 degrees of advance to allow that much time, but with the speed and heat being generate, total advance can only be little more than half of that. ------------------ 351W 89 Mustang GT Convertible [This message has been edited by jimberg (edited 06-14-2001).]

06-14-2001, 02:54 PM	#22
TJR Registered Member Join Date: Apr 2001 Location: Bowling Green, OH Posts: 270	jimberg....That's a lot of info, I had to read it twice to catch everything I missed the first time . ------------------ 1989 lx notch 89,000 miles bolt-ons,stock heads/cam 60'- 2.07, 8.90@78, 13.93@99

06-14-2001, 03:24 PM	#23
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	I just hope it's useful info. ------------------ 351W 89 Mustang GT Convertible

06-15-2001, 09:54 PM	#25
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Right, the timing isn't linear for another very obvious reason. By compressing the gases faster at higher RPM you generate more heat which will cause detonation earlier and earlier. ------------------ 351W 89 Mustang GT Convertible

06-16-2001, 09:47 AM	#26
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	jimberg - how is the timing being non-linear (advances with rpm) going to discourage detonation?

06-16-2001, 12:27 PM	#27
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Sorry. That was unclear. Advance in degrees can be linear in relation to rpms, but advance in an actual time interval would not be. e.g. The 0.0017 seconds in above example. The faster you compress a gas, the more heat will be generated since there is less time to dissipate the heat. This extra heat will add to the potential for detonation. ------------------ 351W 89 Mustang GT Convertible

06-16-2001, 03:53 PM	#28
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	I think jimberg's been readin a lotta physics lately. Mach 1 TFS added me to the payroll 3 months ago, they keep telling me the check's in the mail, but for some reason, it always get's lost?

06-16-2001, 10:48 PM	#29
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	Yeah, the old "check is in the mail story"...heard it a hundred times myself...lol. I think Jimberg is confusing himself...... ------------------ 1993 GT/AOD '93 Mustang GT

06-17-2001, 09:52 PM	#30
RobertD Registered Member Join Date: Jun 1999 Location: El Paso, Texas, USA Posts: 170	Trick Flows it is.... Thanks! ------------------ Robert 91GT; 88 ASC McLaren #709