Chevy & GMC Vans

Here's a question for all you hot-rodders and engine builders.

If I'm not mistaken, between years 1992-1994, GM put 200hp CPI (L35) 4.3's in these vans. It was a vast improvement over the previous TBI models that produced 170hp at most. Then in 1996, GM introduced Vortec heads which were supposed to improve combustion efficiency. But these only produced 190hp and peak torque also fell by 10lb-ft. I'd like to know what specific engine traits gave the 200hp engines that extra power, and why they dropped it in 1995. Was it dictated by oil prices?

The L35 heads were made to flow better than the earlier heads, why they don't produce more power than a Vortec head, I dont know. Never bought into the Vortec thing anyway, I think it was all a bunch of hype.

Peter

Timelessbeing-I would think the CPI is apart of the answer.

Actually the 96+ 4.3 Vortec head flows identical to the L31 head. They share the same weak exhaust ports as the 350 heads. I would open the heads up in a heart beat and run 2.02/1.60" valves in them. GM Powertrain released Vortec 4.3s with spreadbore single plane manifolds on them for marine use. I would secure one and run a well tuned Q-Jet on it. Use a 1985 vacuum/mechanical advance distributer with a small block roller cam gear on it. The stock pistons should be trashed for a set of flat-top pistons, which will increase the compression ratio from 9.4 to 10.3:1 with the vortecs 64cc chambers. With a cam of around 208/208 @ .050 (thinking stock 1994 CPI 4.3 cam) in it, it should surprise many. A 350 of the same build would be about 415-425 HP. The 4.3 will make around 310-315 HP while maintaining good driveability and fuel mileage. from the S-10 forum well thats my motor the one they describing I have had it apart and seen it.It a good runnin 160 hp
Pocket Ported 1992 L35 (CPI) heads
Stock valve size,
28” of water

Lift Intake Exhaust
.050 31.9 24.4
.100 63.9 50.6
.200 126.1 95.1
.300 175.7 120.5
.400 204.8 137.2 Stock 1996 vortec head flow
28” of water

Lift Intake Exhaust
.050 31.7 25.4
.100 63.6 52.1
.200 127.9 96.8
.300 179.4 130.9
.400 223.2 147.5
.500 227.7 156.3
.500 221.3 148.6

I believe it is a combination of fuel/pollution control and mechanical parts.

The CPI engines from that era (92-95) are not only a psuedo multipoint FI, But, they had a much hotter cam + lightweight hypurtectic pistons, lightweight crank & lightweight rods.

I dont think the 96+ 4.3 had that kind of hotter style cam or the lightweight anything, and I would bet the computer chokes the hell out of it too, but I'm a bit lost after 95, so I could be wrong.

And, Ya, he is right, a good HEI distributer, and well tuned Q-Jet on a marine or edelbrock manifold will make a 95 engine scream ! There's no computer to hold it up.

1Gary wrote:Timelessbeing-I would think the CPI is apart of the answer.

Can you elaborate, Gary?
I thought the trend towards finer control over fuel injection was to gain efficiency. Hence going TBI=>CPI=>CSFI=>MPFI=>Direct injection.
It allows the computer to calculate precisely how much fuel to inject into each cylinder. After all, the CPIs batch fired, so wouldn't that waste a lot of fuel?

I got the CPI motor, Big exhaust, monster TBI intake and I am supposed to believe it puts out the same hp as a saturn 4 cylinder.Those cars are a lot lighter and the day a V-6 saturn beats my van I will junk it.

Kabey's Van wrote:Never bought into the Vortec thing anyway, I think it was all a bunch of hype.

I read on the internet that Vortec heads were really popular when they first came out, especially in the racing industry. Simply by swapping heads, they could dramatically increase horsepower.

chevymaher wrote:I got the CPI motor, Big exhaust, monster TBI intake and I am supposed to believe it puts out the same hp as a saturn 4 cylinder.Those cars are a lot lighter and the day a V-6 saturn beats my van I will junk it.

If you have 94 with stock TBI, you do not have a CPI engine.

the 94 TBI will have the good heads, but does not have the same hotter cam + lightweight hypurtectic pistons, lightweight crank & lightweight rods that the CPI motors (VIN W) did.

Yes I do look at the picture I posted that the engine in mine.Eyebrow heads countershaft motor Non CPI did not have the eyebrows.Same valve covers.Dealer told me it a conversion van with drivetrain upgrades.Ive got pics from when I did the intake gaskets it clear those the heads I got.It isnt rocket science to see that big countershaft balance in there.My frame is the same as a 97 got 7.5 inch wide rims.This thing got upgaded in a big way.S-10 forum claiming that if it had the heads and counterbalance it was a CPI motor with TBI

Chevymaher,
Perhaps you're talking about the GM GenII Ecotec 2.4L in the Saturn Ion, which can produce 175hp. However, it only produces 164 ft-lbs of torque @ 4800rpm. A Vortec 4.3 produces peak 250ft-lbs torque @ a much lower 2800 RPM. That's why you can smoke a Saturn off the line. But he may catch up to you down the road. I'm a bit confused with your mixture of CPI and TBI. If you have a non-stock engine, then none of the numbers I've mentioned mean anything.

My brother got a saturn twin overhead cam not the ion.That thing wont touch the van from a 60 MPH kick down.And yes this thing left stock a while back.It all stock parts but they have been modifyed.I have dremel tools and aint afraid of them.Non stock timing Blocked EGR exhaust is altered These things run alot better tuned

doyoulikeithere wrote:hypurtectic

Hypereutectic. It's a mouthfull.

chevymaher wrote:My brother got a saturn twin overhead cam not the ion.That thing wont touch the van from a 60 MPH kick down.

http://en.wikipedia.org/wiki/Saturn_I4_engine#DOHC_LL0
Only 124 hp and 122 ft·lb torque

Says 145 hp on the valve cover.145-160 that about the same