ed,
I am curious of your opinion of the following. I know we have discussed at length the oval port vs. square port. in your application, if you were to keep your compression the same but use a piston and also change to 119cc open chamber heads what would the result be? if you were to rev your motor to 6500 rpm instead of 6000 would there be an advantage as long as your cam would make power? the reason I ask this is that I collect and read every book and magazine article I can get on big block chevy's. some of the builders that prefer the use of open chambers are lingenfelter and also traco engineering. it seems that most of the books suggest open chambers for more horsepower because there is less valve shrouding. does this supposed advantage only happen at high rpms(over6000)? I for 1 have had good luck with closed chamber motors as far as detonation is concerned. I am no expert but just a back yard mechanic and between myself and a couple of buds put together about 5-6 motors over the years. our current toy is a racecar that goes 10.4 but has 12-1 comp, big solid roller, OC square port heads and all other race goodies. the performance of your car truly amazes me. I for one look forward to continuing this discussion in an intelligent and respectful manner. just some food for thought, thanx all

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1969 SS 396

I basicly heard the same thing regarding open chamber heads and thats why I went with 119cc merlins(before listenig to the other side of the fence). Eds comments got me thinking along the same lines as you. One thing though is I need to run higher domes to get my compression up and less dome is better. http://www.chevelles.com/forum/frown.gif Just cant win. Although....I THINK I have figured out something though.....if you run a supercharger then you can run without domes and big cc heads and rec ports(wouldnt have to worry about volocity would you?)...hmmmm....possible next buildup??? Why must everything be a compromise??? I am interested in hearing the dissusion on if open chamber heads are all that. Hope this discusion dosnt erupt into a my combo is better than yours. Ill wait till your brain stops chewing.....

I've also read that a small dome isn't too bad as it promotes swirl. I built my motor around the same principles. I built a 454 but used keith Black hypereutectic pistons because I really only want a quick street car. I hoped that a tight piston clearance would keep my leakage to a minimal amount. it has a 1/4" dome and gave me about 10.5-1 comp with my 781 heads(117cc). I sought out certain part numbers because of all I read. now I'm thinking would I have gained that much if I kept everything the same and used a closed chamber head and piston combo. perhaps we need to see if cc heads are only good to a certain rpm. i've had great luck on a couple of closed chambered head motors. but these were street cars that were in the low 12 sec range.

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1969 SS 396

ratuned, I know this is WAY off the subject, but what kind of tires are/where you running on those low 12 second street cars? I am sorry, I know this is way off the subject, but this is something I am currently working with, setting my car up for a 396 that should be in the mid-low 12 second range, but will be a 95% street car. I am planning on running 295/50 BFG Radial T/A's,(would like to stick with a street radial, and not a drag tire)with an M-21 4-speed and 12 Bolt Posi, with 3.73's. Whatcha think? Thanks man for all your help!
Jim(The '68 Malibu and SS396 Guy)

hi jim,
those times were on slicks. I would use 2 sets of tires. it will be tough to hook a big block street car with a 4 gear on radials. lotsa fun but tough. you might want to try a set of MT ET streets for the track and just messin around. put the others on for loner trips. good luck

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1969 SS 396

The Openchamber heads gains in flow test becasue of unshrouded vlaves. but that can be done in a closed chamber head to. When we start talking about flametravel etc, the closed chambers are better, you can have a little dome, a little chamber , making a good force on the right position on the piston. You can do that on a openchamber too but its much harder and you cant buy that stuff. It must be a matched piston to its matched head. In sweden SAAB has gone far with this and studies flametravel alot making electronic systems for them making them very effective.

But there isnt so much gain that everybody should thrash their opennchambers and start porting and modyfying closed chambers. You have a slight gain and if it what it takes to win go for it, otherwise skip it.

No, but I think the point BottleRat missed in the last around is that the "Bigley Special" may or may not be the only 9-10 second combination out there, but it certainly is the optimal choice for a street/strip car.

Cant swing it right now, but I'd sure like to see someone with a 496+ Bigley Special tucked into their engine bay that looks just like a stocker 325-350 hp mill. Very cool to roll up and run a friggin DEEP 11 with a showroom looking ride. Drawing thru a Qjet no less!

Very cool! http://www.chevelles.com/forum/cool.gif

(maybe if FMO ever hits 10 http://www.chevelles.com/forum/wink.gif )

But i digress, would like to hear more on advantages of open chamber heads as observed and measured vs closed...



[This message has been edited by 427L88 (edited 01-05-2001).]

oh no i did'nt miss it L-88, i could'nt agree with you more. if you want a good reliable street mill. then 1320s setup is the way to go. it's just not the only way.

and to bring you up on current affairs ed's not running a quad on his current setup he run's a HP 900 or 1000 CFM holley.

ratuned, we've built identical motors and installed them in virtually identical Chevelles. Using my old hydraulic cammed version of the 454. Mine with the closed chamber and the other, '71 Chevelle with open chambers. Both oval ports of course with identical porting/valve job by the same guy. Close chamber motor was about 3 tenths quicker and 4 MPH. Run side by side, same day.

This topic has been discussed here before to which I responded.

To achieve the same compression with the closed chamber requires less dome which yields better flame travel and results in more efficient combustion. All this spells more power.

The close chamber heads and small headers are KEY to my performance and yes they are less sensitive to detonation.

BTW in a previous post I explained why all the aftermarket heads are of the open chamber variety.

This topic is also being discussed at www.dragraceresults.com. (http://www.dragraceresults.com.)

Check this link www.dragraceresults.com/ubb/Forum2/HTML/000931.html (http://www.dragraceresults.com/ubb/Forum2/HTML/000931.html)

Don't take my word for it. These guys are bracket racers more than hobbyist. Some big names frequent this board.


Gene, it seems Joe G. built a 496 more or less to my specs. Now he's looking for a roller(another car) that can handle the power. http://www.chevelles.com/forum/biggrin.gif


bottlerat, currently using a Pro-Systems prepped 1000HP. This piece was worth .03 in 60 feet and .06 at the stripe over a "out of the box" 950HP. Max effort piece that cost $1,100 and not for everybody. However IMO, Patrick James is the best custom carb builder in the country. His customer service is second to none. I did some R&D for Patrick so it was a learning experience for both of us.

The 950HP is worth about a tenth and 1 MPH over the Q-Jet.



[This message has been edited by racer1320 (edited 01-05-2001).]

BottleRat, no I know he doesn't but you could easily run an 800 cfm QJ and make your 500+ HP and still look bone stock.( exe headers) Too cool.

i'm with ya L-88, very cool

Ed, Just curious but if you were to consider taking the streetable factor out of your combination and wanted to see just how quick the sled would go with this size engine, what do you think you would do? More compression, more cam, more gearing, more converter, better cylinder heads? Just pondering the next step if it were a consideration. Due to the weight factor do you think the current combo is the best combo and nothing other than a bigger big block would work it?

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http://msnhomepages.talkcity.com/yosemitedr/quintillis/index.html

Glenn, in my post - "Somethings to think about" I gave an example of a '68 Chevelle with a 467 running 10.50's that is not streetable but "looks" every bit the part. This car is a real sleeper yet sports 14:1 CR, Brodix BB-1 heads, huge roller cam, 5500 stall converter and 4.88 gears. So without going to a bigger big block this is about optimum with a 467 at nearly 4000 lbs. running on the motor, built with off the shelf parts. I suppose with components like custom port lay out one off heads, more compression and a Inverse Flank cam it's possible to run even faster. But the question remains why all this for a 2 ton "race car". Kind of a oxy moron. This is a motor that will be apart every weekend.



[This message has been edited by racer1320 (edited 01-06-2001).]

I guess if we had all the time ness, our own machine shops and dyno, a person could tweak the engines power and torque curve to get some real world h.p. in the appropriate rpm for a heavy weight machine. Hey that sounds like my dream, no job, enough money and plenty of free time, LoL!!
By the way Ed, isnt that other chevelle lighter than your car? Since your making about 550hp
what is he makin with all the "race" hardware? Doesnt sound like much more unless the engine chassis combination isnt wrung out yet.

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http://msnhomepages.talkcity.com/yosemitedr/quintillis/index.html

Glenn, his piece is dialed in and weighs about 3700 lbs. I would guess he makes about 40HP more at the rear wheels.

[This message has been edited by racer1320 (edited 01-06-2001).]

Glenn,
Nothing to do with this topic, but I just spent about 15 minutes going through your website. I tracked the history of your car from 1974 to present. Very nice. I like that "Inna-Godda-Davita" thing in the background also.

Jim

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My 70 Chevelle (http://www.angelfire.com/pa4/jim/)

Thanks Jim, I've had this car about 25 years
and its been fun! I could write a book about its history.

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http://msnhomepages.talkcity.com/yosemitedr/quintillis/index.html

Glenn,that's one for the history books!! Too friggin' cool! http://www.chevelles.com/forum/biggrin.gif I really enjoyed the history of your LS-6,and that Nova is pretty damn wild!

The web site is basically a photo album of our cars and some friends rides, the midi music is just to keep things interesting while the pages load.
The red 71 nova SS is my sons car, it runs pretty good for a 3700 lb "street" (well a little bit), car. With an LS-7 and oval port Merlin heads it runs 9's on 180 shot.

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http://msnhomepages.talkcity.com/yosemitedr/quintillis/index.html

[This message has been edited by GlennLS-6 (edited 01-06-2001).]

Glen, those are some awesome cars!!! Just wanted to say that your page is way cool!!-joel

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Speedster-T/C#980 1968 SS396/325 CHEVELLE