4:56 or 4:88's Big Chevy ?

impstocker · 05-15-2014, 07:40 AM

Good Morning,
Started to prep my 12 bolt for installation but did not like the way the preload felt, so I will go through it. Now I have a chance to install the 4:56's instead of the 4:88's

I ran the 4:88's in my 68 Impala I/S car with the 396/325 combo. Going through the traps on a good run was 6600 RPM but this was a stick car.

I will be running the same 396/325 in my 65 Impala but with a Turbo 350. I expect to RPM higher now with the converter on the far end, would the 4:56's be better? I know when I come close to 7000 RPM with that motor it loses power. I also run 30" tires. Racing weight will be the same as the 68 Impala - heavy! 4095 lbs in I/SA

Any input would be appreciated!
Will Lamprecht - NED 65 Impala in progress I/SA

njk53 · 05-15-2014, 01:54 PM

Will, this is the same question I have. We run pretty much the same combo as you do but, in K/SA Chevelle Wagon and weigh 4255 w/driver. We run a 402/300 BBC with a 350 trans. We currently have a 4:56 in it but, I am not happy with the 60' foot times. We also have a 30" tall tire. I thought about going to a smaller diameter tire but I don't think it will be enough. I'll be interested to see the comments.

05-15-2014, 02:41 PM

I made the same change last year when I went from a manual to an auto trans. I had a 5.0 gear and went to a 4.56 along with a radial tire, and that gave me the same trap rpm. If your happy with going through at 6600 I'd go with a 56 or a 33. Good luck

Dan Fahey · 05-15-2014, 05:49 PM

Quote:

Originally Posted by impstocker

Good Morning,
Started to prep my 12 bolt for installation but did not like the way the preload felt, so I will go through it. Now I have a chance to install the 4:56's instead of the 4:88's

I ran the 4:88's in my 68 Impala I/S car with the 396/325 combo. Going through the traps on a good run was 6600 RPM but this was a stick car.

I will be running the same 396/325 in my 65 Impala but with a Turbo 350. I expect to RPM higher now with the converter on the far end, would the 4:56's be better? I know when I come close to 7000 RPM with that motor it loses power. I also run 30" tires. Racing weight will be the same as the 68 Impala - heavy! 4095 lbs in I/SA

Any input would be appreciated!
Will Lamprecht - NED 65 Impala in progress I/SA

Did you get the Deeper First Gear in the T350?
Getting that Plus Sized Car off the line with an Auto will need some gear.

Will it go 7000rpm?
You want it all spent before going through the traps.

D

impstocker · 05-15-2014, 09:26 PM

Thanks everybody for the input. The TH 350 does have the 2.75 first gear- No, the motor lays over after 6800 - with the stick I did try a pass shifting at 7000 and the car slowed down 2 tenths!

I seem to get the same idea Todd gave me- use the 4:56's, now i just got to find that set i have!

Wow, that Chevelle station wagon can be that heavy! I had to put 135 lb ballast bar in the back to make the 4095 weight for I/S

Will Lamprecht- 65 Impala in progress-

njk53 · 05-16-2014, 08:12 AM

We also put a ballast bar in the station wagon. That is what the NHRA requires for weight. We aren't turning the motor anywhere near 6600 through the lights however, that's what the engine builder said we should be going through the traps at. We also have a 2.75 1st gear.

Will, what are you 60' times?

impstocker · 05-16-2014, 07:03 PM

OK, trying to remember my 60' times were in the 1.55 to 1.65 range, but I use to spin the tires a lot due to running a stick shift and not sorting out the clutch completely. I ran a McCloed Rev_Lok adjustable with around 650 lbs of pressure and a 14 lb flywheel. With the TH 350 auto I expect the 60' times to be better. So you can't rev 6600 through the traps?

Will L 65 impala I/SA in progress

impstocker · 05-16-2014, 07:08 PM

People have told me that motor should not be turning over 5500 to 5800 - they say I am past my torque curve, but of course that advice came from a local SS Ford racer- he also told another fella with a stick MoparCuda stocker to run a 30lb flywheel! that car would leave way to violent, he runs a auto now.

Will Lamprecht, I/SA Impala

05-15-2014, 07:40 AM	#1
impstocker Member Join Date: Dec 2008 Location: Wingdale, NY Posts: 302 Likes: 27 Liked 53 Times in 16 Posts	4:56 or 4:88's Big Chevy ? Good Morning, Started to prep my 12 bolt for installation but did not like the way the preload felt, so I will go through it. Now I have a chance to install the 4:56's instead of the 4:88's I ran the 4:88's in my 68 Impala I/S car with the 396/325 combo. Going through the traps on a good run was 6600 RPM but this was a stick car. I will be running the same 396/325 in my 65 Impala but with a Turbo 350. I expect to RPM higher now with the converter on the far end, would the 4:56's be better? I know when I come close to 7000 RPM with that motor it loses power. I also run 30" tires. Racing weight will be the same as the 68 Impala - heavy! 4095 lbs in I/SA Any input would be appreciated! Will Lamprecht - NED 65 Impala in progress I/SA

05-15-2014, 01:54 PM	#2
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Re: 4:56 or 4:88's Big Chevy ? Will, this is the same question I have. We run pretty much the same combo as you do but, in K/SA Chevelle Wagon and weigh 4255 w/driver. We run a 402/300 BBC with a 350 trans. We currently have a 4:56 in it but, I am not happy with the 60' foot times. We also have a 30" tall tire. I thought about going to a smaller diameter tire but I don't think it will be enough. I'll be interested to see the comments. __________________ Nelson Kowal Stock 345 Last edited by njk53; 05-15-2014 at 01:57 PM.

05-15-2014, 02:41 PM	#3
Todd Hoven Guest Posts: n/a	Re: 4:56 or 4:88's Big Chevy ? I made the same change last year when I went from a manual to an auto trans. I had a 5.0 gear and went to a 4.56 along with a radial tire, and that gave me the same trap rpm. If your happy with going through at 6600 I'd go with a 56 or a 33. Good luck

05-15-2014, 09:26 PM	#5
impstocker Member Join Date: Dec 2008 Location: Wingdale, NY Posts: 302 Likes: 27 Liked 53 Times in 16 Posts	Re: 4:56 or 4:88's Big Chevy ? Thanks everybody for the input. The TH 350 does have the 2.75 first gear- No, the motor lays over after 6800 - with the stick I did try a pass shifting at 7000 and the car slowed down 2 tenths! I seem to get the same idea Todd gave me- use the 4:56's, now i just got to find that set i have! Wow, that Chevelle station wagon can be that heavy! I had to put 135 lb ballast bar in the back to make the 4095 weight for I/S Will Lamprecht- 65 Impala in progress-

05-16-2014, 08:12 AM	#6
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Re: 4:56 or 4:88's Big Chevy ? We also put a ballast bar in the station wagon. That is what the NHRA requires for weight. We aren't turning the motor anywhere near 6600 through the lights however, that's what the engine builder said we should be going through the traps at. We also have a 2.75 1st gear. Will, what are you 60' times? __________________ Nelson Kowal Stock 345 Last edited by njk53; 05-16-2014 at 08:15 AM.

05-16-2014, 07:03 PM	#7
impstocker Member Join Date: Dec 2008 Location: Wingdale, NY Posts: 302 Likes: 27 Liked 53 Times in 16 Posts	Re: 4:56 or 4:88's Big Chevy ? OK, trying to remember my 60' times were in the 1.55 to 1.65 range, but I use to spin the tires a lot due to running a stick shift and not sorting out the clutch completely. I ran a McCloed Rev_Lok adjustable with around 650 lbs of pressure and a 14 lb flywheel. With the TH 350 auto I expect the 60' times to be better. So you can't rev 6600 through the traps? Will L 65 impala I/SA in progress

05-16-2014, 07:08 PM	#8
impstocker Member Join Date: Dec 2008 Location: Wingdale, NY Posts: 302 Likes: 27 Liked 53 Times in 16 Posts	Re: 4:56 or 4:88's Big Chevy ? People have told me that motor should not be turning over 5500 to 5800 - they say I am past my torque curve, but of course that advice came from a local SS Ford racer- he also told another fella with a stick MoparCuda stocker to run a 30lb flywheel! that car would leave way to violent, he runs a auto now. Will Lamprecht, I/SA Impala