in relation to my last post, what do you guys think double hump or vortec ? will be getting them from summit and theirs have .520 max lift on both the vortec and the others. they seem about equal and i will have to swap out intakes anyway (still have cast iron). both have 3-angle valve job. can't decide. any opinions ?

 

The Vortec is the winner in performance.


http://www.chevyhiperformance.com/te...ase/index.html

 

The evidence is clear and that is why I went with Vortec...

 

was kind of thinking that also but just getting opinions of those who have tried it, tks. now on to the cam dilemma.

 

Are the vortec heads the same heads which came on the 99 Tahoe's. with the 350 cuin.?

 

The evidence is clear, a pocket ported set of vintage camel humps is the way to go, (assuming you don't need accessory holes).

 

i have the double hump heads and the only reason to use these is if you want an old school motor OR....you don't want to change to a new intake.....the vortec heads are really good.

 

I only saw the one chart. I assume this was with the camel hump heads. The chart showing the Vortec heads is missing. Without the comparison there is absolutely no clear evidence. At least with the chevy high performance thread, they clearly gave evidence of the flow rates of various heads.

 

The chevy high performance thread is the best evidence I found on the internet, but also personal experience with other people who have installed them. For street use, light to light they have the low end torque I wanted.

The chamber design is hands down better, newer technology, which is more efficient. As long as they are machined to accept springs with lift over .500 they outflow the camel humps.

Oh yea...and they have accessory holes...

 

There are camel hump heads with accessory holes also.

 

I posted the dyno results for my mild 331 CI with vintage camel hump heads.

It is my understanding that the newer ZZ3s and ZZ4s have Vortec heads. Yet, somehow these engines (with another 20 CI and even higher compression ratios) are putting out 50 hp less than my mild combo. So, if those heads are so great, where's the power??? I just get a little unnerved when people contend that the Vortecs are a clear winner when the actual rear wheel hp numbers I've seen never seem to back that up.

My combination:

331 CI, pump-friendly 9.5:1 CR
K&N 14"x4" air filter, Corvette drop base and lid
Holley 600 dp, choke horn milled, polished
1/2" Aluminum open spacer port matched to manifold, exterior polished
Edelbrock Performer RPM, port matched, exterior polished with all extraneous castings and lettering removed
Homemade lifter valley splash shield to keep hot oil off manifold bottom
Camel hump 1.94/1.50 heads hogged out to 2.02/1.60, pocket ported, port matched, pump-friendly hardened seats, 3-angle valve job
Comp Cams 1.52:1 roller-tip rockers
Crane Cam Vintage Muscle 327/350 hp cam, 222 degrees @ 0.05, 0.447" lift (with 1.50 rockers)
Doug Thorley headers, dechromed and ceramic-coated
2.5" mandral-bent exhaust (including tips), 2" cross-over just before rear axle
DynoMax stainless Ultra Flow mufflers
Mallory Hyfire IV CD ignition box triggered off Accel points
Mallory high voltage chrome coil
Mallory spiral-wound coil wire
Mallory solid copper plug wires, ends soldered to wires
Champion plugs
37 degrees total ignition advance (now 34 degrees per Lars tune-up)
Carter high volume fuel pump
Melling high volume oil pump
Open breathers
Polished aluminum high flow water pump
Flex fan with polished aluminum spacer
Polished aluminum one-wire 100 amp alternator
Muncie M-20 CR 4-speed (now Keisler TKO600 5-Speed)
Hurst shifter (Now Keisler With Hurst Tower)
3.70:1 positraction
225/60/15 Firestone Firehawk SZ50s on 7”-wide Western 30-spoke Turbine Wheels

At the time of the dyno pulls, the engine had never been professionally tuned up. Car did 293 ft-lb and 293 hp @ 5,500 rpm on the chassis dyno. Engine pulls to 6,200 rpm and does over 200 ft-lb from 1,900 rpm. This was prior to some clean-up work around the junction of the carburetor and base of the air cleaner that smooths the flow through this area and a Lars tune-up and should be good for a few ponies.

Car has run 107 mph in the high 13's (old, bad tires) at the quarter prior to much of the engine work. Car is extremely streetable and could probably even run 87 octane if it had to. (I can't get the engine to ping no matter how far I advance the ignition.)

The secret to power is in the attention to details!

 

No they do not, they have L98 alum heads which have old chamber design, vortecs out perform them even with less compression

 

Yep. Now take a ZZ-4 and throw a set of Fast-Burn (G.M.) heads on with the matching "hot" cam and clone the 425 h.p. version.

 

I have to chime in here. Stock castings the Vortec heads out flow the double hump heads. That said a set of double hump heads can be worked to put out more power. With pocket porting and the runners hogged out I have seen cars running 10 using the double humps. I worked in a High Performance Machine Shop back in the 70's and that is all we had. You can pull huge power and flow out of a set of these with a little work and get better lift.

 

I was not commenting on the performance of your engine nor on what heads GM uses on their crate engines.

You posted the following:
I did not see any clear evidence. As far as I know, you might have picked up some HP had you switched to the Vortecs.

Double humps may perform as well if ported. The issue is that machine shop work is costly. By the time you buy the heads and have them reworked (cleaning, guides, springs, valves, porting), the user could have purchased new heads. Vortecs have some real advantages and some real disadvantages. They are great for some applications and not a wise choice for others.

 

I live in the Atlanta area and made a trip to the local Summit retail store a couple of weeks ago to inspect the Summit brand heads in particular, as well as to buy some parts. Summits displays samples of their heads, including other name brands. Summit brand camel hump replacements and the Summit brand Vortec replacements appear to be the same casting, but with holes drilled differently to accept the corresponding intake manifold. In addition, it appears the the manufacturer simply drills, or 'hogs out' the intake port roof to achieve a bit of a cathedral shape. Other than that, the heads look the same. The quality looks high and the chambers for both the camel hump replacements and the Vortec replacements share the same, modern, heart-shaped design which were plunge cut for the larger valves. While I did not have a measuring tape to measure the cross section of the intake port, they appeared to be the same with the exception of the previously-discussed cathedral, which I suspect results in the additional 5 CCs for the Vortec replacements.

In addition, visual inspection indicates that the manufacturer is World Products. If you look at the exhaust mounting flange bosses and other markings, they are identical to other World heads, with obvious differences between them and the Dart heads.

I am thinking of buying the Summit camel hump replacements for my Chevelle. I have the GMPP Bowtie Vortecs on my Vette.

Hope this helps.

John

 

If you're looking for more power, I would highly suggest to upgrade to a roller cam using comps retro roller lifters and cam. Lifters just drop in. No block machining needed. It's a no-brainer.

 

I have 2 hump heads only because SCCA rules require them. They are steel, heavier and above 10.5 to 1 compression require some sort of leaded fuel. I change to Vortec in a minute if Street prepared rules would allow it.

 

Those with the Vortecs can you please tell me what plugs you guys use? I use the R44LTS, but they are pretty carboned up and I was thinking of going to a hotter plug.

Thanks, Tony

 

-I have a 385Fast Burn and hot cam Kit


-Spark Plugs: ACDelco MR43LTS Gap @ .045 for HEI distributor