Cam Installed, what’s next?

[mm1077]

Thanks to everyone who helped or offered their thoughts about a month ago : ). Got my new cam installed and things are going well. Truck runs much smoother, easier to tune and my power breaks are working great. Still lacking the takeoff that I’m ultimately hoping for (I’m pretty picky) so I’m looking at 3 options:
-gear change to 3.42 (shop quoted 800)
-gear change to 3.73 (shop quoted 1500)
-replace torque converter with maybe a 1800-2000 and keep existing gear (diy)
- opt. 4 leave it all alone and get A/C lol
*Ive looked at the rpm calculators so just wondering about how the bottom end acceleration feels from real world experience

Anyone have a similar setup to my specs listed below and how do you like it? I drive about 15m on the interstate to work but can take backroads if I want to add a few extra minutes. I plan to drive the truck about 80% of the time,- in town, to cruise-ins, to work, etc…

67swb
275/60 on all 4
350/th350 2400 stall
.60 over / flat top pistons
Vortec heads 2.02/1.60 valves
1.5 roller rockers
Comp xe268 cam
AVS2 650 carb
Dual plane intake
HEI ignition
L/T headers 2.5 exhaust
3.08 gears
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[Tom]

If you just care about off the line immediate accel, then re-gear. You already have a 2400rpm stall according to your specs, which is higher for a street vehicle.

[AcampoDave]

That thing should be a le to smoke a tire as is. I'd check timing curve and AFR ratios before dumping the big bucks.

[mm1077]

Originally Posted by AcampoDave

That thing should be a le to smoke a tire as is. I'd check timing curve and AFR ratios before dumping the big bucks.

That’s what I was thinking just based on the #s. I’m messing with the timing now and trying to tune some more. I think something was wrong with my distributor(my tach was erratic and timing would ‘jump’ every few seconds inconsistently, so I picked up a new one and ill see what happens : )
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[Accelo]

-gear change to 3.73 (shop quoted 1500)

I know it's expensive. Just no way to go fast with 3.08 unless it's a turbo motor.
Purchase the gears and then wonder who changed out the motor when you weren't looking.
Cheers.

[LS short box]

I wonder why the 3.42's are cheaper than the 3.73's? Seems like the same labor and parts cost?

[Accelo]

I believe you have a carrier series change. That should account for the difference.

Didn't say if the current differential is a posi or not.
A one tire firer isn't effective on a truck without any weight over the back.
Cheers

[mm1077]

Originally Posted by Accelo

-gear change to 3.73 (shop quoted 1500)

I know it's expensive. Just no way to go fast with 3.08 unless it's a turbo motor.
Purchase the gears and then wonder who changed out the motor when you weren't looking.
Cheers.

I’ve been starting to lean this direction because I’m pretty sure the truck would feel pretty darn fast by my standards : ) I just need to get over the highway rpm’s at least until I can save up for some sort of OD down the road
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[AcampoDave]

Apart from getting my advance curve set with a cheap balancer degree tape, I got more bang for my buck tuning my 500 cfm Eddy with this https://pe-ltd.com/product/wideband/ than anything else. Out of the box, the carb was too rich, likely in the mid 10's at wide open and mid 12's to 13's at a cruise. Getting it into the 12's and high 14's respectively made a noticeable difference. I First leaned it one step before even checking the AFR so I can't know fro sure what the true outta da box numbers were.

[AcampoDave]

I even made a thread about it http://67-72chevytrucks.com/vboard/s...d.php?t=838553
Edit: BTW when my tach was bouncing erratically, it had a bad ground.

[Dead Parrot]

My mostly stock C10 with a 350/TH350 with 3.42 gears + 235/75-15 tires seems a good compromise between decent take off, highway cruise and load/towing ability.

2nd the thought to get your timing and carb settings dialed in before changing gears/tires/transmission.

Possible your "jumping timing" was the mechanical advance just starting to come in at idle if the springs were too light.

If you really want a snappy jump from a stop, might run the numbers on a set of 4.10 gears with an overdrive trans.

[mm1077]

Originally Posted by AcampoDave

Apart from getting my advance curve set with a cheap balancer degree tape, I got more bang for my buck tuning my 500 cfm Eddy with this https://pe-ltd.com/product/wideband/ than anything else. Out of the box, the carb was too rich, likely in the mid 10's at wide open and mid 12's to 13's at a cruise. Getting it into the 12's and high 14's respectively made a noticeable difference. I First leaned it one step before even checking the AFR so I can't know fro sure what the true outta da box numbers were.

I’m going to pick up one of those tapes and check my tdc mark for accuracy tonight- I replaced the damper with one from summit when I was doing the cam. I got the truck running pretty well by ear but the timing #s were really high so something’s not accurate.
Posted via Mobile Device. I’ll take a look at the afr gauges for sure- maybe I’ll add one and vacuum gauge at some point : )

[geezer#99]

Speaking about accurate, if you’re using something other than a piston stop to find tdc then your timing marks could be off 10 degrees.

What was the timing when you set it by ear?

[mm1077]

Originally Posted by geezer#99

Speaking about accurate, if you’re using something other than a piston stop to find tdc then your timing marks could be off 10 degrees.

What was the timing when you set it by ear?

I want to say it was somewhere between 22-26 degrees- that’s where it was showing when I stopped looking and just started using the vacuum gauge anyways. It started fine (starter not lugging) and wasn’t making any noises so I figured something must just be off. Temp and oil pressure were good. I’ve got a piston stop that I’m going to use after work to check it all out
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[mm1077]

Do you think I’d have traction issues daily driving with the 3.73s? I really don’t want to just spin the tires at every red light if it’s raining lol.
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[geezer#99]

My 84 had a stock 305 with 3.42 gears. Had to be careful in the rain. Would light them up with an aggressive tap of the pedal.
What’s your rear tire height?
Going to a shorter tire is like changing your rear gear upward.
Cheap way to test gear ratio effectness.

[mm1077]

Originally Posted by geezer#99

My 84 had a stock 305 with 3.42 gears. Had to be careful in the rain. Would light them up with an aggressive tap of the pedal.
What’s your rear tire height?
Going to a shorter tire is like changing your rear gear upward.
Cheap way to test gear ratio effectness.

28” tire on all 4 (275/60). No plan to ever change it from 15’s. I like the ‘old school’ look : )
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[Accelo]

Moving to a 35" for a 28" tire would make a 25% difference in rpm
Changing from a 3.08 to a 3.73 is a 54% difference.
The truck might look pretty funny if it's not a 4X4.
I used a big tire to get the max change in rpm.

2218 rpm per mile to 2687 with the 28" tires and changing the diff from 3.08 to 3.73.

[AcampoDave]

I had to chuckle at your initial post option #4..... At my present stage of life that one is a no-brainer for me.

[67 twins]

Originally Posted by Accelo

Moving to a 35" for a 28" tire would make a 25% difference in rpm
Changing from a 3.08 to a 3.73 is a 54% difference.
The truck might look pretty funny if it's not a 4X4.
I used a big tire to get the max change in rpm.

2218 rpm per mile to 2687 with the 28" tires and changing the diff from 3.08 to 3.73.

You do realize that a 33" tire is the biggest that will fit without a lift? That's what I'm running on my C20 & believe me you won't get a 35" under there.

[Accelo]

Originally Posted by 67 twins

You do realize that a 33" tire is the biggest that will fit without a lift? That's what I'm running on my C20 & believe me you won't get a 35" under there.

It was an exercise to prove the small improvements possible by a tire size change.

If you want performance gearing is as important as the motor to receive the intended results. I have made all the mistakes. Mostly attempting to save money when I was young and had none.

Our truck 12 bolts are fairly strong. So typically no need to upgrade the type.
Many of our trucks came with 3.70 gears if you are lucky. I also gave up purchasing others 50 years old junk. Seems they all require work of some type.
I would recommend new gears (because of the ratio change required)
And a new carrier to match the decided upon ratio.
However, I am not in the owners shoes. He will have to make the best choice for him.

[AussieinNC]

I would go with the 3.42 rear and standard tires to start.

You already have a higher stall convertor installed.

Just my 2 cents worth

[mm1077]

I got everything all dialed in (what an ordeal- bought a new distributor and turned out something was wrong with it and it took me forever to figure out that was the issue). Truck runs really well now- I can see how some people are totally fine with the 3.08 : ). I’d still like more bottom end take off so I’m leaning toward the 3.73 and then an OD later on. I think if I went with 3.42 I’d always be telling myself ‘ this is cool but man what if I would’ve ramped it up a little more’.
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[Accelo]

With 350hp at the wheels, 3.73's and 295/45/20 tires it's a smoke show from a dead stop. Floored from 25mph it's just barely holding on to traction. With a stock torque converter.
You can do this with less HP if you have a stall converter installed.

Our trucks are extremely traction limited as they are just too light in the rear. Without a Posi you might has well keep the six cylinder IMHO.
I like your plan. Moving to an OD transmission, at a later date, will also get the benefit of a lower first gear, better gas mileage and less motor wear and less emissions per mile. The gift that keeps on giving.
Cheers

[scottofksu]

You might consider a complete swap of your rear end to one with 3.73 gears and posi, if you don't have posi already... A little patience and some good luck and you should be able to find what you want for significantly less than $1,500. You will definitely want to find something that will be "bolt in" so you don't waste any savings in fabrication and hassle.