Top End Speed - The 1947 - Present Chevrolet & GMC Truck Message Board Network

VDOG · 09-03-2003, 02:24 PM

Ok guys, my problem, when im on the freeway speeding (which is a no no by the way) I notice my truck tops out around 85 mph and the engine sounds like its going to blow up.
My truck is a 69, no frills so whatever the gears are there still in there. I did change the trans to a TH350.
Would a 700-R4 help or is it something else?

jmanz69 · 09-03-2003, 02:35 PM

You probably have 3.73 gears in the rear end. With that, you will sound that way at 85 MPH. You probably run about 3300-3500 at 70 MPH, right? If you put in a 700R4 you will gain top end spped because you will slow down the RPM of the engine. With OD you gain some extra room for the RPM. at 4000 RPM you will be going faster. If you got a 700 plus higher gears in the rear, 3.42 or 3.08, you could go even faster. You could just change the gears and not the transmission to accomplish more top end speed. Would probably be cheaper to do that. By the time you buy a 700 core, have it rebuilt correctly, have it installed, have a new driveshaft made, and get a new shifter for the extra gear, you could have bought a new carrier, and ring and pinion, plus have it installed.

Good luck. We can help with all your questions here.

jmanz69

VDOG · 09-03-2003, 02:39 PM

Interesting, so you think my stock plan C-10 came with 3:73's?
I know I can do the test of counting the teeth. But I figured it came with 3:08 with the stock 307 ci engine.

oldsub86 · 09-03-2003, 02:55 PM

How is your engine?
My '86 2WD Suburban with a 350 and 700R4 was topping out around 75 mph. I did some work on the engine - new valve seals, adjusted the valves (obviously I guess after changing the seals), spark plugs, plug wires, new dist cap and it sort of came to life. Not only would it go faster but the mileage improved quite a bit. Not sure if it was any one of those items by itself but whatever it was, it sure helped my top end.

VDOG · 09-03-2003, 03:01 PM

Its a built 283, I do know the cam is too big. The engine was built for a car with a 4speed, thus the big cam.
Also I need to change the exhaust, still running the stock 2 into one with a leak. Got a brand new set of Headman Headers in the garage waiting to be installed. But you cant tell me that changing out my ram horns will give me that much more top end?
Or will it?

*67Fleetsidedream* · 09-03-2003, 03:03 PM

Quote:

spark plugs, plug wires, new dist cap

Basically a tune up, this will really make a difference in a high mileage engine.

tom hand · 09-03-2003, 03:33 PM

A 283 with a big cam should love the tall gears. When you start winding them up, litttle things will kill ya. I would think that motor should do a hundred well before redline. Tune up stuff as mentioned, fuel filters, float level in the carb, and that 2 into 1 exhaust may be hurting you more than you think with that cam.

VDOG · 09-03-2003, 04:13 PM

Well just had a tune up a lil over 2 months ago. Its not my daily driver. Also installed a HEI about 6 months ago. Did I mention that my TH 350 is an automatic if that makes a difference.
Bottom end is slow getting out of the hole also, but once its going then its all good till it tops out.
Maybe it is the exhaust. Thanks guys

lukecp · 09-03-2003, 04:31 PM

It takes power to push these trucks fast, gearing only helps a little bit. This is because of poor aerodynamics. Wind restiance goes up quite a bit above 60mph in one of these trucks. I would say your motor proably needs somemore power. It should be able to go about 100mph with 3.73 gears without rapping the motor too tight. I would say put on the headers and some dual exhaust. It should help out a bit.

VDOG · 09-03-2003, 04:40 PM

Thanks 72 custom. I did make a carb change to open my secondarys up sooner, that helped a bit. In fact, I can chirp second gear were as before, I needed some warter on the ground to burn out. LOL!
Not a major issue, but trust me, it made me want to keep this motor. Keep it long enough to put into another project, like a 64 nova. LOL

gmc67swb · 09-03-2003, 06:54 PM

WHAT KIND OF DISTRIBUTOR ARE YOU RUNNING. I KNOW STOCK HEI'S START TO PETER OUT AROUND 4 TO 4500. ALSO , IF YOU'RE NOT GETTING A FULL 12V TO THE HEI, IT WON'T PERFORM AS WELL AS IT SHOULD.

jhwkns · 09-03-2003, 07:13 PM

Good Call gmc67swb... The HEI could be hooked to the resistor wire.

hgs_notes · 09-03-2003, 07:20 PM

I've had mine well over 100 mph, more like 120. I've got a 283 bored .040, deck milled, stock dished pistons, crane RV cam, rhoads lifters and 1.6:1 aluminum roller rockers on screw in studs. I run headers into a cheap kit dual exhaust w/out a crossover. Holley 4150 4 barrel, HEI distributer.TH 350 tranny with a shift kit. I lowered it about 3.5 inches also. 265-70-15's in back.

When I had the three on the tree, I had a real monster cam (rumpity rumpity), and could smoke a set of 295-50-15's for half a block and about 50 mph in 1st gear. Had a q jet carb that had manual secondaries and wished I'd never got rid of it. That thing was awesome. Went to the automatic and had to detune the cam so it would idle in park.

Now back in high school whenit was a stock beater 307 that had a questionable cylinder or three, crappy exhaust and even crappier tires, it would top out at about 85 mph. Point is, if you want speed, you'll have to work for it with the little engine that could(283).

HG

VDOG · 09-03-2003, 07:35 PM

Quote:

Originally posted by gmc67swb
WHAT KIND OF DISTRIBUTOR ARE YOU RUNNING. I KNOW STOCK HEI'S START TO PETER OUT AROUND 4 TO 4500. ALSO , IF YOU'RE NOT GETTING A FULL 12V TO THE HEI, IT WON'T PERFORM AS WELL AS IT SHOULD.

Im using an Accel HEI, bought it brand new.

VDOG · 09-03-2003, 07:38 PM

Quote:

Originally posted by hgs_notes
I've had mine well over 100 mph, more like 120. I've got a 283 bored .040, deck milled, stock dished pistons, crane RV cam, rhoads lifters and 1.6:1 aluminum roller rockers on screw in studs. I run headers into a cheap kit dual exhaust w/out a crossover. Holley 4150 4 barrel, HEI distributer.TH 350 tranny with a shift kit. I lowered it about 3.5 inches also. 265-70-15's in back.

You and I are basically running the same engine. Even down the roller rockers. Man this is driving me crazy, cause I know this engine is much faster than its going.

hgs_notes · 09-03-2003, 10:14 PM

Another thought, checked your fuel filter lately? I had this problem with a toyota celica years ago.

Put a tachometer on it and see where your actual rpm's are at. It may be just gearing, but doubt it.

Another real dumb thought, are you positive the tranny is shifting into its highest gear?

HG

crazy longhorn · 09-03-2003, 11:38 PM

I think its just a matter of tuning your combo to its full potential

I ran a 60 over flatop 283(300hp /350 heads, 350hp 327 cam, 600 dp holley, headers/turbo muffs with dumps). It ran a M 21 muncie behind it with 3.73 gear in the rear......not much for low end tork, but it ran like stink from about 3500- 6800 rpms! Flat open on the hyway would set the speedo needle on the M in the MPH(a little past straight down).....about 120, my guess? Those little engines love the revs! I would go for the headers & better flowing muffs to start with, then get into any ign recurve, & carb setup. Good luck,crazyL

kaycee · 09-03-2003, 11:44 PM

I would say you have like a 2:80 gear setup I have a mild 350 with 3:73 and I have not found the top end yet, I had the speedo allmost back around to 0 before I let out of it.I would check the rear gears and find out what the hell you have.And I would put duls on it for sure.

09-03-2003, 02:24 PM	#1
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Top End Speed Ok guys, my problem, when im on the freeway speeding (which is a no no by the way) I notice my truck tops out around 85 mph and the engine sounds like its going to blow up. My truck is a 69, no frills so whatever the gears are there still in there. I did change the trans to a TH350. Would a 700-R4 help or is it something else?

09-03-2003, 02:55 PM	#4
oldsub86 Registered User Join Date: Dec 2002 Location: Canada Posts: 695	How is your engine? My '86 2WD Suburban with a 350 and 700R4 was topping out around 75 mph. I did some work on the engine - new valve seals, adjusted the valves (obviously I guess after changing the seals), spark plugs, plug wires, new dist cap and it sort of came to life. Not only would it go faster but the mileage improved quite a bit. Not sure if it was any one of those items by itself but whatever it was, it sure helped my top end. __________________ 1968 Chevy - 292 with a powerglide

09-03-2003, 03:33 PM	#7
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	A 283 with a big cam should love the tall gears. When you start winding them up, litttle things will kill ya. I would think that motor should do a hundred well before redline. Tune up stuff as mentioned, fuel filters, float level in the carb, and that 2 into 1 exhaust may be hurting you more than you think with that cam. __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

09-03-2003, 04:31 PM	#9
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	It takes power to push these trucks fast, gearing only helps a little bit. This is because of poor aerodynamics. Wind restiance goes up quite a bit above 60mph in one of these trucks. I would say your motor proably needs somemore power. It should be able to go about 100mph with 3.73 gears without rapping the motor too tight. I would say put on the headers and some dual exhaust. It should help out a bit. __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

09-03-2003, 06:54 PM	#11
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	WHAT KIND OF DISTRIBUTOR ARE YOU RUNNING. I KNOW STOCK HEI'S START TO PETER OUT AROUND 4 TO 4500. ALSO , IF YOU'RE NOT GETTING A FULL 12V TO THE HEI, IT WON'T PERFORM AS WELL AS IT SHOULD. __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

09-03-2003, 02:35 PM	#2
jmanz69 Careful, they attack... Join Date: Aug 2001 Location: Waterford, MI, USA Posts: 1,107	You probably have 3.73 gears in the rear end. With that, you will sound that way at 85 MPH. You probably run about 3300-3500 at 70 MPH, right? If you put in a 700R4 you will gain top end spped because you will slow down the RPM of the engine. With OD you gain some extra room for the RPM. at 4000 RPM you will be going faster. If you got a 700 plus higher gears in the rear, 3.42 or 3.08, you could go even faster. You could just change the gears and not the transmission to accomplish more top end speed. Would probably be cheaper to do that. By the time you buy a 700 core, have it rebuilt correctly, have it installed, have a new driveshaft made, and get a new shifter for the extra gear, you could have bought a new carrier, and ring and pinion, plus have it installed. Good luck. We can help with all your questions here. jmanz69

09-03-2003, 02:39 PM	#3
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Interesting, so you think my stock plan C-10 came with 3:73's? I know I can do the test of counting the teeth. But I figured it came with 3:08 with the stock 307 ci engine.

09-03-2003, 03:01 PM	#5
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Its a built 283, I do know the cam is too big. The engine was built for a car with a 4speed, thus the big cam. Also I need to change the exhaust, still running the stock 2 into one with a leak. Got a brand new set of Headman Headers in the garage waiting to be installed. But you cant tell me that changing out my ram horns will give me that much more top end? Or will it?

09-03-2003, 04:13 PM	#8
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Well just had a tune up a lil over 2 months ago. Its not my daily driver. Also installed a HEI about 6 months ago. Did I mention that my TH 350 is an automatic if that makes a difference. Bottom end is slow getting out of the hole also, but once its going then its all good till it tops out. Maybe it is the exhaust. Thanks guys

09-03-2003, 04:40 PM	#10
VDOG Grand PooBaa Member Join Date: Jan 2001 Location: LA, CA Posts: 5,302	Thanks 72 custom. I did make a carb change to open my secondarys up sooner, that helped a bit. In fact, I can chirp second gear were as before, I needed some warter on the ground to burn out. LOL! Not a major issue, but trust me, it made me want to keep this motor. Keep it long enough to put into another project, like a 64 nova. LOL

09-03-2003, 07:13 PM	#12
jhwkns Registered Cruiser Join Date: May 2002 Location: Las Vegas NV Posts: 2,230	Good Call gmc67swb... The HEI could be hooked to the resistor wire. __________________ I intend to live forever. So far, so good.

09-03-2003, 07:20 PM	#13
hgs_notes GEARHEAD Join Date: Aug 2003 Location: MN Posts: 6,126	I've had mine well over 100 mph, more like 120. I've got a 283 bored .040, deck milled, stock dished pistons, crane RV cam, rhoads lifters and 1.6:1 aluminum roller rockers on screw in studs. I run headers into a cheap kit dual exhaust w/out a crossover. Holley 4150 4 barrel, HEI distributer.TH 350 tranny with a shift kit. I lowered it about 3.5 inches also. 265-70-15's in back. When I had the three on the tree, I had a real monster cam (rumpity rumpity), and could smoke a set of 295-50-15's for half a block and about 50 mph in 1st gear. Had a q jet carb that had manual secondaries and wished I'd never got rid of it. That thing was awesome. Went to the automatic and had to detune the cam so it would idle in park. Now back in high school whenit was a stock beater 307 that had a questionable cylinder or three, crappy exhaust and even crappier tires, it would top out at about 85 mph. Point is, if you want speed, you'll have to work for it with the little engine that could(283). HG __________________ If no one knows what you're doing, they can't tell you you're doing it wrong HG's Dream Car Build - Shelby Cobra Kit Build your own adjustable track bar 71 Long Fleet C/10 72 Jimmy 4x4 (Junkyard Jimmy) HG's Plow Truck '78 K35 Dually Bigass Farm Truck HG's thread of miscellaneous stuff

09-03-2003, 10:14 PM	#16
hgs_notes GEARHEAD Join Date: Aug 2003 Location: MN Posts: 6,126	Another thought, checked your fuel filter lately? I had this problem with a toyota celica years ago. Put a tachometer on it and see where your actual rpm's are at. It may be just gearing, but doubt it. Another real dumb thought, are you positive the tranny is shifting into its highest gear? HG __________________ If no one knows what you're doing, they can't tell you you're doing it wrong HG's Dream Car Build - Shelby Cobra Kit Build your own adjustable track bar 71 Long Fleet C/10 72 Jimmy 4x4 (Junkyard Jimmy) HG's Plow Truck '78 K35 Dually Bigass Farm Truck HG's thread of miscellaneous stuff

09-03-2003, 11:38 PM	#17
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	I think its just a matter of tuning your combo to its full potential I ran a 60 over flatop 283(300hp /350 heads, 350hp 327 cam, 600 dp holley, headers/turbo muffs with dumps). It ran a M 21 muncie behind it with 3.73 gear in the rear......not much for low end tork, but it ran like stink from about 3500- 6800 rpms! Flat open on the hyway would set the speedo needle on the M in the MPH(a little past straight down).....about 120, my guess? Those little engines love the revs! I would go for the headers & better flowing muffs to start with, then get into any ign recurve, & carb setup. Good luck,crazyL __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

09-03-2003, 11:44 PM	#18
kaycee Registered User Join Date: Jan 2000 Location: Wyoming USA Posts: 2,446	My Turn I would say you have like a 2:80 gear setup I have a mild 350 with 3:73 and I have not found the top end yet, I had the speedo allmost back around to 0 before I let out of it.I would check the rear gears and find out what the hell you have.And I would put duls on it for sure. __________________ 2001 Silverado K-1500 2005 FXDWG stage3 69 CHEVY Short/Step 327/4L60 373 posi 63 IMPALA 327



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