I have an 84 Z with an L69, and again am considering using Vortec Heads.

They are said to have a combustion chamber of 64cc. Someone told me that in actuality is more like 61cc. But for the time being, let's assume 64cc.

Without milling the heads to have a 58cc combustion chamber to maintain my 9.5:1 ratio how much HP would I lose due to compression compared to if I had them milled?

Basically, how much does .5:1 in compression cost or benefit you as far as horsepower goes?

Everything else I have read about these heads makes good sense. The only problem is the change in compression ratio and the negative effects that milling can possibly cause. The only work I'd like to have done is porting and polishing/valve job type stuff.

 

There are other negatives to Vortecs: Special intake manifold required, no exhaust crossover passage for the EGR valve, the need for self-aligning rockers, .450" valve lift limit.

Scoggin-Dickey sells the heads with an "install kit" that includes the intake, gaskets & rockers. About $700.

For the same money, you could get a set of World Products S/R Torquer 305 heads that are made for a 305. Added benefits include screw-in rocker studs (vs. the pressed-in studs of the Vortecs), valve springs that can handle more lift, no need for a special intake manifold or rockers.

But, word is the extra flow of the Vortecs over the stock heads will more than make up for the loss of compression. If you want the flow and keep the compression, go with the Worlds and have them pocket ported (you say you've done that yourself - Standard Abrasives Deluxe Porting Kit includes great instructions for full porting and polishing jobs), or shave the Vortecs (might as well get them machined for the screw-in studs while they're at the shop).

I'm running that 9.5 CR with 7 degrees advanced base timing using regular gas with absolutely no pinging problems (I polished the chambers as well). I'm fairly certain I'm not giving up any flow or power to the Vortecs.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4, 2300 stall TC. Ported World 305 heads, Crane PowerMax 2050 cam. ZZ3/4 intake, oil pump, pan & baffle. Accel HEI SuperCoil & module. Hooker 2055 headers, 3" Catco cat & 3" catback w/dual-opposite Flowmaster 80. 2.93 limited slip. Spohn SFCs waiting to be installed. AMSOIL syn lubes bumper-to-bumper. Daily year-round driver. Best ET, speed TBD...
57 Bel Air, my 1st car. '66 396, 9.7:1 forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 700 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

[This message has been edited by five7kid (edited December 11, 2001).]

 

five7kid,

I had also thought about the Torquer heads but I thought that they didn't flow as well. What are the comparisons between the two....intake runners and so on? It's all about flow!

I knew about the intake (I doubt that I will keep my current carb/intake combo) but wasn't aware that the lift was so limited. One question....

The stock springs are good for .450, but can you get higher lift out of better springs or is that about all the heads themselves can take?

My other thinking was that with the Vortec heads is that I could re-use them on a 350 or maybe even a 400!

OK......intake runners for the World Products Torquer 305's is 170 cc.

Vortec intake is also 170 cc.

Good information to have. Price is a difference intially...World Products $364.99 @ jegs. Vortec heads are $228.75 @ Scoggin-Dickey! Of course with the Vortec you have to purchase a new intake and rocker arms.

With that in mind, using a .028" on the Vortec heads, the compression would still be just over 9to1.

I have a magazine article somewhere that compares the two sets of heads, along with comparing several others...I'll have to find it and put the information on here.

57, are you happy with the World Products heads?

 

Jegs is overpriced. You can get an assembled pair from Competition Products for about $650. I got mine unassembled because I wanted to do the porting, and I upgraded the springs for higher lift (thought I was going to use a ZZ4 cam when I ordered them), so my price was slightly different. But, it was in the $600-range with shipping (I think assembly adds ~$40-$50/head).

The S/R 305's probably don't flow any better (if any) than the Vortecs out of the box. But, they respond very well to some porting work (notice every evaluation/use of them in the mags have them pocket ported). I figured about a 10% increase in flow over the values published by World when inputting for Desktop Dyno. The actual may be more. I'm sure they flow more than the CHP "My Generation Camaro" based on the pictures they had of their pocket porting job.

I did all my mods in one shot, so I can't say how each part is contributing to the package. But, I can say that I am quite pleased with the package.