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New motor,or lower gears,or both

6.2Blazer said:
3.73 gears and 35's isn't that bad of a combination on the highway...Keep in mind the the OP mentioned maintaining speed on hills while driving on the highway and not fourwheeling or taking off from a stop..
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...towing a 4000lb+ boat. If it was unloaded, sure, 3.73's and 35's would be fine. Plenty close to my 3.42's and 33's. I get "great" economy BTW, and I can climb any mountain pass here at 60-70MPH, but not towing.

I don't think of OD as a factor when towing. If you are towing, and need the RPM's, it or you downshift. No different than with a manual. The difference is, with OD, you can get the 1:1 ratio in a range that isn't pushing the engine to its RPM limits at hill-climbing freeway speed (via gearing). Gearing is an all or nothing proposition without OD...either you deal with extremely high RPM's at freeway speeds, or you deal with sluggish performance.

I just calc'd the numbers:

Assuming 1:1 (excludes torque converter slippage which is probably a factor) the OP is turning 2148RPM at 60MPH now.

With 4.88's, 35's, and the 4L80E (for an OD example), the 1:1 RPM becomes 2811...but OD puts it back to 2192, almost identical to what he is running now.

No one here is likely to argue that 2800RPM is too high to run a SBC, GM didn't. Not what I want to run all day, every day, but if that's what it took to pull my load through steep terrain at a more reasonable speed, and I could cut that RPM nearly a third with one gear shift, I'd take it. I don't think it's likely the SBC is ever going to feel like it's a powerhouse pulling that load, but increased mechanical advantage is going to help.

In the past I thought 4.88 was a crazy ratio to run. With OD, it makes absolute sense, especially for guys running larger tires. Being able to run those gears, with large tires, and pull the same RPM's as you did with 3.73's, is kind of a no-brainer IMO. The benefits to steep gears are many, the penalties are none if you have the OD to make up for them.
 
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Im leaning towards a new engine first.Im an old schooler 1st and foremost and don't care for ls engines.I love the procharged bbc in my 56 stepside,but it gets 4 mpg cruising on the freeway so that's out of the question. Im thinking about a gm crate 350 with 300hp/ft lb tq. That's about double the hp of the stock 74 350.If I need gears after that, that's ok too.Not super concerned with mpg,just don't want to go 25 mph thru the hills/turns around lake Berryessa.
 
dyeager535 said:
...towing a 4000lb+ boat. If it was unloaded, sure, 3.73's and 35's would be fine. Plenty close to my 3.42's and 33's. I get "great" economy BTW, and I can climb any mountain pass here at 60-70MPH, but not towing.

I don't think of OD as a factor when towing. If you are towing, and need the RPM's, it or you downshift. No different than with a manual. The difference is, with OD, you can get the 1:1 ratio in a range that isn't pushing the engine to its RPM limits at hill-climbing freeway speed (via gearing). Gearing is an all or nothing proposition without OD...either you deal with extremely high RPM's at freeway speeds, or you deal with sluggish performance.

I just calc'd the numbers:

Assuming 1:1 (excludes torque converter slippage which is probably a factor) the OP is turning 2148RPM at 60MPH now.

With 4.88's, 35's, and the 4L80E (for an OD example), the 1:1 RPM becomes 2811...but OD puts it back to 2192, almost identical to what he is running now.

No one here is likely to argue that 2800RPM is too high to run a SBC, GM didn't. Not what I want to run all day, every day, but if that's what it took to pull my load through steep terrain at a more reasonable speed, and I could cut that RPM nearly a third with one gear shift, I'd take it. I don't think it's likely the SBC is ever going to feel like it's a powerhouse pulling that load, but increased mechanical advantage is going to help.

In the past I thought 4.88 was a crazy ratio to run. With OD, it makes absolute sense, especially for guys running larger tires. Being able to run those gears, with large tires, and pull the same RPM's as you did with 3.73's, is kind of a no-brainer IMO. The benefits to steep gears are many, the penalties are none if you have the OD to make up for them.
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Back in the day it was common for trucks to have 4:56 gears with no overdrive..especially 3/4 ton and larger ones...though the engines had to wind up high to get to top speed ,which was limited to around 60 mph with stock tires,they seemed to tolerate the higher revs pretty good,especially the small blocks..long stroke straight sixes and big blocks,not so much..but gas mileage was not much of a concern back then,when gas was like 3 gallons for a dollar..
 
BigBK5 said:
Im leaning towards a new engine first.Im an old schooler 1st and foremost and don't care for ls engines.I love the procharged bbc in my 56 stepside,but it gets 4 mpg cruising on the freeway so that's out of the question. Im thinking about a gm crate 350 with 300hp/ft lb tq. That's about double the hp of the stock 74 350.If I need gears after that, that's ok too.Not super concerned with mpg,just don't want to go 25 mph thru the hills/turns around lake Berryessa.
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That sounds like a good plan to me. @Bent77 bought a GM engine for his to get a good torque number and keep some of the same parts. Be warned though , the one he bought has raised exhaust ports and required headers.
 
dyeager535 said:
...towing a 4000lb+ boat. If it was unloaded, sure, 3.73's and 35's would be fine. Plenty close to my 3.42's and 33's. I get "great" economy BTW, and I can climb any mountain pass here at 60-70MPH, but not towing.

I don't think of OD as a factor when towing. If you are towing, and need the RPM's, it or you downshift. No different than with a manual. The difference is, with OD, you can get the 1:1 ratio in a range that isn't pushing the engine to its RPM limits at hill-climbing freeway speed (via gearing). Gearing is an all or nothing proposition without OD...either you deal with extremely high RPM's at freeway speeds, or you deal with sluggish performance.

I just calc'd the numbers:

Assuming 1:1 (excludes torque converter slippage which is probably a factor) the OP is turning 2148RPM at 60MPH now.

With 4.88's, 35's, and the 4L80E (for an OD example), the 1:1 RPM becomes 2811...but OD puts it back to 2192, almost identical to what he is running now.

No one here is likely to argue that 2800RPM is too high to run a SBC, GM didn't. Not what I want to run all day, every day, but if that's what it took to pull my load through steep terrain at a more reasonable speed, and I could cut that RPM nearly a third with one gear shift, I'd take it. I don't think it's likely the SBC is ever going to feel like it's a powerhouse pulling that load, but increased mechanical advantage is going to help.

In the past I thought 4.88 was a crazy ratio to run. With OD, it makes absolute sense, especially for guys running larger tires. Being able to run those gears, with large tires, and pull the same RPM's as you did with 3.73's, is kind of a no-brainer IMO. The benefits to steep gears are many, the penalties are none if you have the OD to make up for them.
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Not sure if you are in agreement or not with my comment (3.73 gears okay with 35" tires on the highway), but will specify that my comment is based on NO overdrive transmission. I agree with the above that low gears are great if you have an OD transmission to lower the RPM on the freeway. I think that the OP would be helped by going to the combination of an overdrive transmission with lower axle gears. But based on the my opinion of the benefit vs. cost and time that dropping in a different engine is the best way to start out. There is a lot of cost and time involved in swapping transmissions (especially if you wanted a 4L80E in an old truck) and then also swapping axle gears, then you are still stuck with a low HP older engine. Speaking of OD transmission I wouldn't count out a 700r4......heck of a lot easier swap in these trucks. Personally have had good luck with 700r4's in mine and my dad's vehicles. Back in high school I spent a lot of time going to USAC midget car races all over the midwest with a racer and he used a Suburban with a built 350 and 700r4 as a tow rig pulling a tandem axle enclosed race trailer. He always used OD when towing and ran it for years and only retired that rig because it started rusting out.

Regarding a previous comment about older trucks used to come with 4.56 gears, I remember those days. Back in high school I worked on farms and construction so drove a lot of 1-ton trucks with 4.10 or 4.56 gears. They needed those gears to deal with the low power engines, they didn't spend much time on the freeway (overall average speed much lower), and the biggest point is you were lucky to get 100,000 miles out of an engine before they were completely ragged out. Nowadays 100,000 miles is nothing.
 
I think im going to get the 290 hp 350. I bought a crate motor for my 56 years ago from the local chevy dealer and it was a little more expensive than summit but the lack of shipping charges/driving up to sparks NV made it a wash. Most of the induction I can reuse on the new motor(600 holley,performer intake) and my billet specialties valve covers.If I still need gearing after that I will farm that out,dont have the patience for that.lol
 
Just FYI, check ebay. I know for my L31 crate it was cheaper by $1-200 than summit and other online retailers. Apparently that specific dealer bought them by the truck load, so was able to price them better. I think it was Radley Chevrolet. Probably them or others doing the same with other crate engines.

I don't know if shipping got messed up or not, but it was shipped to my door and I didn't pay anything extra for that. I would have paid $50-100 more to save the hassle of having to drive to get it.

I'm not posting to ignite a battle over physics or theories, frankly I don't quite understand it myself, but you MIGHT be better served with a larger carb as well. Or at least trying one if you have access. GM felt running 800CFM carbs on the smaller engines (Chev 305's in trucks and Olds 307's in cars) was a good idea, and testing by other folks like Vizard on less mundane motors showed torque increases as carb CFM went up. Given that the Monte SS was running a 305 with 750CFM at the same time, 350 trucks were running 750CFM carbs, and GM was trying hard to make the 305 equivalent to the 350, I'm guessing it had something to do with torque as well. It's a very messy subject, but having seen all those factory engine and carb combinations myself, whether they make sense or not, GM did it. The calculations for carb size vs. RPM were revised/improved years back for different applications, it's likely for the same reasons. Given what carbs cost nowadays, I don't think I'd throw a new 750+CFM carb on there in the hopes it helped, but if I could borrow one to try, I certainly would.
 
2800 rpm is low for a sbc, especially if it is stock. You have to spin them faster to make full power. Gearing and number of gears is king as well. My 88 K5 with a stock tbi engine, 35 inch tires and 3.73 was a dog. I upgraded to 4.88 gears and it makes all the difference for normal driving. The 700r4 is actually useful now (OD was only good at 75 mph with stock gears) and there is much better power at lower speeds. The power band on the new gm 350 tbi is 3,000-4,000 rpm. It is fairly weak below that and really drops off after. Of course it doesn't have much power either.

My towing is done with my 79 C20: built 406 sbc, th400, gear vendors, 4.10, 33" tires. This one has good torque at 2k rpm and starts to wake up at 2500 rpm, but is happy to spin at 4500+ as long as you want and still pulls hard at 5000 rpm. The roller cam isn't aggressive, but has a great torque curve. Being able to split gears and have 6 forward choices makes a big difference. I'm also pulling a trailer that weighs 8500 pounds loaded. Engine should make around 400hp and 500 torque, but it only has a 600 cfm edelbrock carb. and under 5000 rpm, it should be enough air, but then again, big carbs with the right tuning can really help smaller engines.

Go for all the power you can from a new engine, and then seriously consider a trans upgrade for OD and gear swap to get full power at any speed (as much as possible, anyway).

While I wouldn't be caught dead driving a toyota, the towing capabilities and power output of 2000 and later trucks is much better than stock square bodies. My next truck will be a 2000 and later diesel. As much as I like the square body trucks, they will never be able to compete for a total package including a nice ride, quiet in cab, space, towing capacity and fuel mileage. There will always be compromises to have a cool old truck. Choose what aspects are most important and consider your budget, and modify from there.
 
I’d go the engine route as well. 3.73 and 35s isn’t horrible if you gave the power to push it. Your 40 year old engine is tired. And was not much power from the factory.
 
Ordered gm performance 350/290 hp today from summit,going to pick it up Friday.Will drive up thurs night and stay in Reno. Went to stealership yesterday and they want 3300 for the same motor otd.I paid 2600.So basically I will get everything needed for motor swap(new water/fuel pump.starter,flexplate,balancer,etc) for less than what just the motor costs at stealership. And a free room at Grand sierra.I am assuming my stock converter will be ok? thoughts?
 
I would think your stock converter is fine. If it’s got some miles on it, you can send it to a reputable torque converter company for a rebuild

I like PTC in Alabama
 
If the trans was solid before it maybe ok. You will find out for sure once you put the new engines power to use. If the trans is still stock and no rebuild that long, it may be he next thing to go.
 
BigBK5 said:
Ordered gm performance 350/290 hp today from summit,going to pick it up Friday.Will drive up thurs night and stay in Reno. Went to stealership yesterday and they want 3300 for the same motor otd.I paid 2600.So basically I will get everything needed for motor swap(new water/fuel pump.starter,flexplate,balancer,etc) for less than what just the motor costs at stealership. And a free room at Grand sierra.I am assuming my stock converter will be ok? thoughts?
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Where are you driving up from to Reno?
I am going to Reno 2-3 times a week from Morgan hill CA, truck and trailer with liftgate.
 
Fairfield CA.Me and the old lady go to Reno several times a year,hence the free room.Thanks for the offer tho imiceman44
 
BigBK5 said:
Fairfield CA.Me and the old lady go to Reno several times a year,hence the free room.Thanks for the offer tho imiceman44
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Wow I am finding many guys close to me now.
I even found 2 guys right here in Lincoln.
Anyway if you ever need anything from Reno I go there all year long with a big rig.
 
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