200hp V6

[Mr_Roboto]

vortec heads.jpg

With a cam of around 208/208 @ .050 (thinking stock 1994 CPI 4.3 cam) in it, it should surprise many.

This is the big deal with the CPI engines IMO, that and possibly the intake design. (not to discount the Vortec design in the LEAST it seems to actually have very aggressively sized runners as in nearly the cross sectional area of a Vic Jr.) The cam is HOT for a production engine of the era. The heads are slightly better than swirlies but still nothing to write home about. I plugged the Vortec heads into Engine Analyzer Pro once with the CPI cam and it made 257hp with a good exhaust. I could see that not being too far off the mark with a ported exhaust port on them and some long tubes.

[1Gary]

I do think that is brake hp.The flywheel hp ratings ended in the late 70's or early 80's because of insurance reasons and emissions.The details of that was being worked out while I was still working in the dyno rm at the Chevy engine plant.

OK so the boost in performance could be thanks to lightweight components and better camshaft. So what happened after that... Did they go back to heavy stuff and poor cams? Maybe they intentionally restricted the engines (through various means) so that it would get better fuel economy. I wasn't old enough to drive in the mid 90's so I don't know. Was good fuel mileage a big selling feature back then?

Good fuel milage is always a key selling point when dealing with a family oriented vehicle. I don't recall any fuel shortages back in the 90's but I did own a 3/4 ton Chevy pick-up on propane back then.
I must of had a reason for owning that cause, well, propane scares the hell out of me.
I recall in the early 90's that propane was around .20 cents a litre and gas was almost double that.
As more people converted to propane it wasn't long before the oil companies started selling propane at par with gasoline. #-o
A light weight rotating assembly does not do as much for horse power as it does for torque, as it allows for the motor to spool up quicker and in turn bring torque on quicker.
A better cam and heads that breath better will help improve things tremendously.
Torque gets you moving where as h/p keeps you moving.

That's pretty stout when you consider HP vs 262 cubic inch and that measurement is at the wheels and the losses because of that.

I'm sure that's crankshaft h/p not brake h/p.
Jeese Gary, I know your busy and all, but you should know that.

[1Gary]

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.

I think what guys are seeing is a poor man's mod where the Vortec heads increased compression,(V8 wise)but compared to for not much more money,the after market heads flowed tons better.So my bottom line is the Vortec heads don't flow worth a damm.Brodix is the brand I used on my race build 4.3.They do apply to street use as well.Never forget-any engine is a air pump.More air in,more power out.Bottle neck any of it and you give up output.

[MountainManJoe]

I see, so the engine was simply more performance oriented. Usually this means worse fuel economy and more emissions, so that could be why it was later reigned in.

[1Gary]

I see, so the engine was simply more performance oriented. Usually this means worse fuel economy and more emissions, so that could be why it was later reigned in.

That is not factual assuming why GM did anything.

What racing industry do you know embraced the Vortec heads???.


BTW-I sure would love to not see the same tactics you used on AS.It's out of place on this site.The traps you try to set end up getting you caught.I know full well you know what I am talking about.

[MountainManJoe]

Listen closely, old man. I'm going to explain this to you nicely so I can get through your thick skull, and hopefully we can come to some kind of understanding, because I plan to be here on the forum with you.

If you'll read carefully, I'm not presenting anything as fact. That is why my first post was in the form of a question. Imagine that. Using information I gathered from other's posts (such as yours), I was hoping to come up with the best answer I can. In my previous post, I was trying to summarize everything that was said just to have some sort of conclusion. Got that?

Next. I'm sorry, the article I read did not mention any particular racing organisation. I think it was describing it in general terms. I cannot personally vouch for the accuracy of that article.

I'm not sure what tactics or traps you're referring to, but I can assure you that I'm here to learn and discuss, like everyone else. If anybody besides Gary has a problem with the way I post, please send me a PM, because I like it here, and I like the people here, and want to stick around and play nicely with everyone in the sandbox.

Phew! Had to get that out.

[Kabey's Van]

I would love to join in and say something but I have a ribeye on the BBQ right now.

[doyoulikeithere]

Well, not wanting to spend a ton , I would recommend the Vortec heads over the earlier heads to anybody! and a 200HP motor would be no prob at all.

The CPI Cam is awesome compared to a VIN Z.

If I Gary has more money than brains, then ya - aftermarket heads, hell why not get an aluminum bowtie block 4 bolt mains stroker crank etc.!!

and a chrome diff cover and a chrome tranny pan too. Woo-Hooo!

er-um, I dont think thats what this thread was supposed to be about though.

[1Gary]

Mike-I went down "that" road with one 4.3.Learned V8's are cheaper to build.

Heck the one 4.3 cost us almost three times a normal race 383 would have cost and almost my partnership.But that is my learning curve back then.

Sure not all members are for the V8 route and I totally agree with you,you can do a build up on a semi stock format.It's not any different than any other build.The exception is as you go for more with the 4.3's it gets expensive in a hurry.My big 4.3 was a 4.155 bore and a 4.00 stroke.That bowie block I had was 75lbs more than a bare block 350.Same old-how fast do you want to go-how much do you want to spend??.

I got a 1994 CPI and it is once leaned on some is pretty fast for what it is.Over 4,000lbs too.

[MountainManJoe]

Here ya go, Gary. I googled up the Vortec article that I was referring to earlier.

"The newly redesigned Vortec cylinder heads were intended to replace the swirl-port Throttle Body Injection heads that were previously used on GM 350 trucks. What got the power merchants attention was the increase in horsepower from 200 to 255 solely based on the power generated by these heads. By the time you purchased a used double hump cylinder head and had it reworked, the cost was the same as buying a new Vortec head that produced more power. Circle track racers were tossing their double hump heads as fast as they could buy the new Vortec heads."

http://www.onedirt.com/tech-stories/eng ... evy-heads/

Again, I wasn't old enough to drive in 1996, so I can't speak for the accuracy of the article, so don't shoot the messenger. I'm just passing along info, as you so often do. I can say that I enjoyed the article because it was easy to read, had nice pictures, and I learned a lot of history.

[JoeJITSU]

vortec heads.jpg

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

We have a 1995 Vortec.
Now can you tell me what I need to get to 300+ horsepower?
I want to have the engine overhauled soon and maybe I can get them to build it for me. Thank you

[MountainManJoe]

what kind of engine is it?

[doyoulikeithere]

We have a 1995 Vortec. Now can you tell me what I need to get to 300+ horsepower? I want to have the engine overhauled soon and maybe I can get them to build it for me. Thank you

Just ask him what he would do to build a 400 HP 350 SBC, and then ask him to do the exact same kinda stuff to your 4.3..

[maestro]

chevymaher, you mentioned that you have a big exhaust on your van. My '93 is due for a new muffler and tailpipe combo which got me to wondering what you've done... could you elaborate please?

[chevymaher]

It is a TBI Factory van. The casting numbers on the block and heads matched a CPI sonoma engine. Which I needed the block to rebuild mine. It is all factory now except the block and cam. It came factory with the 3 inch single exhaust. 94 CPI exhaust is what the exhaust parts guy came up with when I replaced some of it. TBI exhaust did not fit. It has since been undercoated get the rust off. It has a Thrush glasspack on it and new tailpipe. The rest was factory.

Sometimes the factory literature isn't what they came with. I got one and my parents owned it since it was new. According to the vin search I did. There were 45 other vans exactly like mine.



This is the factory exhaust with a glasspack. Cam and ported heads, intake and exhaust manifolds. It gets with it. The mini mouse runs fine if it is cared for and about.

[youtube]http://www.youtube.com/watch?v=1hun4QS7oY0[/youtube]

Same exhaust with the factory engine, before modifications. Before the oil cooler line ruptured and it needed bearings.

[youtube]http://www.youtube.com/watch?v=Cgygj6DGS0I[/youtube]