Rebuilt Replacement Engine

[97c1500]

Would the 3.42 gears be good enough with the hot cam and also could I get by with just changing ring gear and pinion since the rear end is still good in the truck? And I believe I just might try this before the motor swap. The reason for removing the original 350 is the valve guides are bad, done replaced valve guide seals but still smokes from time to time on take off. and when i sold it one time the guy had a dumbass **** put a starter on and they busted the outer side of the block so i got the one bolt holding it up and another long bolt going up the side of the block keeping the starter from twisting.

I personally would run a 3.42 because it a good blend between high gearing and low gearing
and for the cam what are you looking for high rpm power or low rpm grunt because you can't have both

 

[Badass69]

With your tires I would run 3.73 personally. It's a nice all around gear ratio for pretty much anything. The 3.42's in my 94 are okay..... but the 3.73 in the 96 is about perfect. I run 3.42's in my Caprice but its all highway with a 27" tall tire. Tire height comes into play with gear choice too, and with 29" tall tires, I vote 3.73.

Here is a ZZ4 to LT4 Hotcam comparison in a ZZ4 crate. The link is missing from my original thread for whatever reason.

http://www.cis.udel.edu/~davis/z28/buildup/cam/

He is making 336 lb ft at 2000 rpm with the crappy old L98 heads. The Vortecs will do better than that, hands down with the more efficient fast burn chambers that the L98's lack. The engine is making 8 more lb ft with the LT4 Hot cam than it was with the ZZ4 cam at 2000 rpm. The ZZ4 then matches the output of the LT4 at 2500 rpm with the LT4 walking away from it from there on. Sounds like enough low end to me as a stock L31 won't do that. That guys peak was at 3500 rpm and it was flat from 3000-4000 rpm. The LT4 Hot cam is a decent torque producing camshaft, hence why the Impala, Camaro and Vette crowd really don't like it because it runs out of steam around 5500 rpm. The only reason to run a ZZ4 cam is if you get it for free imo. Otherwise it's not a very good cam for much of anything.

Now that said even the XR 264 Comp I was going to run would be a decent choice for just torque and mid range power. It would work well in a truck as well.

Here is a 264 roller in a 350 with Dart SR torquer heads and just an Edelbrock performer intake.

http://www.compcams.com/v002/Pages/394/XR264HR-10.aspx

It makes over 400 lb feet from 2800 to about 4300 rpm. Even at 2 grand is about 360 lb ft. Decent torque grind. If you are super worried about idle vacuum and the 110 LSA they also grind the cam on a 112 LSA and market it as a L98 torque cam.

http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=194&sb=2

That's the F body variant of it. I own both the versions of the XR 264 myself...... and don't want either anymore so any takers? lol.

If you are dead set on 3.42's you can grab a new ring and pinion but it's easier to just find a junkyard diff for your truck as there are literally millions of them out there.

 

[jeff's88silverado]

^ Since your running both sets what is the rpm of both sets of gears at 60-65 mph

I personally would run a 3.42 because it a good blend between high gearing and low gearing
and for the cam what are you looking for high rpm power or low rpm grunt because you can't have both

I'd perfer a little more low end torque but yet not kill my gas mileage by it topping out to quick. If it helps I generally on average drive 60-65mph But I want good pick up and go when and if i need it.

 

[97c1500]

^ Since your running both sets what is the rpm of both sets of gears at 60-65 mph



I'd perfer a little more low end torque but yet not kill my gas mileage by it topping out to quick. If it helps I generally on average drive 60-65mph But I want good pick up and go when and if i need it.

Then i would run a zz4 with 3.42s i'm sure others will disagree though
also my truck has 3.42s and at 70 my truck is at 2000 rpms so MPG will still be decent and 3.42 rear ends are around 250-300 all day long near me

 

[Badass69]

^ Since your running both sets what is the rpm of both sets of gears at 60-65 mph



I'd perfer a little more low end torque but yet not kill my gas mileage by it topping out to quick. If it helps I generally on average drive 60-65mph But I want good pick up and go when and if i need it.

Around 1800 rpm in the 94 and around 2000 rpm in my 96. My old 92 had 3.73's( turning around 2 grand at 65 mph) and got better mileage than the 94 ever has. Both were TBI 350's and the 92 had the handicapp of being a 4X4 and a long box. I have to be careful to get more than 17 mpg out of the 94 ( it gets 18-19 if you drive like a grandpa) but the 92 got around 18 mpg all day long, without any special driving considerations. It's a fair comparison as the tires on the 92 were 225/75R16's that are only 29.28" tall.

The 96 is better on fuel than the 94 but it's also a Vortec truck so it's not 100% fair.

 

[jeff's88silverado]

how are yall both running 2k at 65mph but both of you have different gear ratios?

and with the extra power of the new engine it shouldn't have to work as hard either way. So it should be alright on gas either way i go.

But what will make one set of gears better than the other. I do want good low end torque but also want it run at least 100-120mph at or below 4k

 

[jcro61]

maybe different tire sizes

 

[jeff's88silverado]

maybe different tire sizes

I didn't think of that for some dumb reason. What size tire are yall running I wanna see whats the closest to mine.

 

[97c1500]

how are yall both running 2k at 65mph but both of you have different gear ratios?

and with the extra power of the new engine it shouldn't have to work as hard either way. So it should be alright on gas either way i go.

But what will make one set of gears better than the other. I do want good low end torque but also want it run at least 100-120mph at or below 4k

typo on my part

 

[jeff's88silverado]

typo on my part

what size tire you run and rpms you run at 65mph