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Discussion Starter · #1 ·
I have L34/L35 heads on my 454 according to the serial numbers. I believe these are 2.06/1.88 valves 100.9 oval port cc. Are these good heads to use on the street for low end torque? And what are 049 and 781 heads?

My 69 chevelle has a 454, 850 Edelbrok Q-jet, RPM intake, pretty lumpy cam (500? lift), mallory dist and coil, flowmaster exhaust, m21 4spd and 4:11 gears. Timing is 15 initial an 40 total. The car runs good and can spin the 8" MT tires some when mashing it at 20 or 30 in first or second but it doesn't seem to have as much torque (G force) as I was hoping for in a BB. Any suggestions or ideas to improve low end torque will be appreciated.
 
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Discussion Starter · #2 ·
I forgot to ask, are their benefits to using open vs. closed chambered oval port heads on the street? Again, I like low to upper range (rpm 0 to 5,000)response.
 

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you definitely want open chamber heads. I don't have time now to get into it but they don't restrict the flow as much as closed chamber heads. besides the obvious thing of closed chamber heads are smaller cc's then open, in my opinion the correct way to make up the compression is in the piston domes. basically figure the compression you want, then use the biggest cc heads you cam get then achieve the compression ratio by choosing the correct cc pistons. the flow is less restricted hence better performance.

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With a BB going to only 5000rpm flow will not be a problem.

There's nothing wrong with closed chamber heads, you are better off being able to have high compression with a flat top piston, than you are with a big dome piston, because the flat top will not disturb the flame travel as much etc.

I would say your current heads are just fine for what you want, no need for larger valves under 5000rpm.

Your camshaft will be what determines your bottom end, can't really tell you much without the specs, but your heads WILL be just fine for what you want.



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Chris Dagenais
'71 Malibu with a home built 454! [email protected]
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Almost every race or street engine I have built was closed chamber. They make more torque will tolerate much more timing and are easier to tune. All of my race engines were big port but even being closed chamber they made good power to 7800 rpm. I am sure Ed will agree. Maybe two in a row we agree on?



[This message has been edited by Mike Feudo (edited 12-14-2001).]
 

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they are actually open chamber heads around 115cc's on average, im running 049's and have PLEANTY of poweer
they are suppose to be one of the best flowing heads that chevy made for the BB. i run mine to 5500 no problem and end up running out of cam before the heads give up. so definately use them.

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I have to agree with Chris and Mike, closed chamber will not hurt at all...but I dont know that you would feel any difference on the street or in your RPM range. I run closed chamber square port, and have all sorts of torque. It used to have flat top pistons, and the CR calculated to only about 8.2/1....I went with forged domed pistons, LS6 equivalent, and CR is now 11.3/1 or so.. CC of my chambers is about 100.8, John
 

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I would keep the heads you already got. I don't understand as too how you are dissapointed in the torque? it seems as if you got plenty if you can spin the tires that easily. the heads should 2.065in-1.72 ex. for valves. perhaps you should do more tuning and bring the advance in quicker(lighter springs in distributer) maybe your cam id too big for maximum torque. with a stick and 4.11's you should be plenty happy. somethimg sounds like it might be mismatched. if you don't have enough compression for your cam the last thing you want is open chamber heads. good luck

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<BLOCKQUOTE>quote:</font><HR>Originally posted by FO_FDYFO:
you definitely want open chamber heads. in my opinion the correct way to make up the compression is in the piston domes. basically figure the compression you want, then use the biggest cc heads you cam get then achieve the compression ratio by choosing the correct cc pistons. the flow is less restricted hence better performance.
<HR></BLOCKQUOTE>


You are certainly entitles to your opinion but your rational is 180 degrees off.


Mike, yes that's two in a row.


John, stay with the heads you have.



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racer's '68

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Discussion Starter · #10 ·
Thanks to everyone for your all you good information.
I've driven 4spd 396's and 427's before. The semi stock 396's (67 & 70 Chevelles) were okay but the stock 427's (425HP), both in full size impala's (66 & 67),were animals. Those 427's are what I use to gauge my cars response, which I believe should be even better due to the modifications, gearing and lighter car.
I will try lighter springs to bring in more timing sooner. If that doesn't work I'll pull the heads and cam to see what the previous owner put into this motor (cam, valves & pistons). Thanks again for all your help.
 

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John, I would. I have alum rect port OC heads , a decent sized cam, excellent compression, and although its a short stroke big port motor, torque is not lacking. Something is wrong here. It could be as simple as your QJ calibration.
 
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Discussion Starter · #12 ·
Gene,
Although I can take most things apart and put them back together, I leave certain things to the experts. I had a good mechanic go over my carb and he adjusted the metering rods, replaced the spring on the power valve and reduced jet size, etc. I also had another expert rewire the car since it was breaking up and was generally wired poorly. The car doesn't misfire, foul the plugs or break up since the rewire but it just doesn't seem to have the tremendous acceleration or g force that I expect in a BB especially with the goodies this motor has.
I had a stock 65 olds 442 (400CI 350 HP), 4spd, 3:90 rear that had greater acceleration and g force than this car does.
 

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no need to gang up on me
i am comparing open vs closed chamber heads with totaly equal final compression ratios. for the street my research has shown me that you can get away with higher compression with lower octane gas by using open chamber heads and fitting domed pistons to the non shrouded area around the valves. this allows for the same quench area as in the closed chamber heads but it keeps the fuel charge cooler to avoid detonation. also open chamber heads, due to the unshrouding of the valves, breath better. you don't have to rely on just looking at them to see this, it has been proven. again I am talking around 5500rpm only. if yu guys are talking race fuel and higher rpm then i think this information might not hold true. I'm running #781 120cc extremely ported heads with +20cc pistons for a 9.5CR. I guess the proof for this combo will be on the dyno.
also john h get you heads cc'd you can not go by what the books say they are by the casting.

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1970 Chevelle 454 Wagons haul A$$ in style! "The Chopped Suburban". to see some goto
www.EINSTYN.com FO_FDYFO = four-fifty four! TC#1460, VCEA#2
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by FO_FDYFO:
i am comparing open vs closed chamber heads with totaly equal final compression ratios. for the street my research has shown me that you can get away with higher compression with lower octane gas by using open chamber heads and fitting domed pistons to the non shrouded area around the valves. again I am talking around 5500rpm only. if yu guys are talking race fuel and higher rpm then i think this information might not hold true. <HR></BLOCKQUOTE>


Again I disagree.

Closed chamber cast iron heads, pump gas, 10.7:1 compression.

Less dome,, less chamber volume, more efficient combustion, better flame front, less prone to detenation.

The chamber can be laid back for better unshrouding of the valve.




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I guess we are going to have to friendly disagree about the "more efficient combustion and better flame front"
I think that's what open chamber gives you. GM changed to open chamber around 1970 to get a more efficient combustion (which meant cleaner, less emissions) at first they did it to lower compression because they could not run on low octane fuels. then they were able to bring the compression ( & power) back up by filling the open chamber heads back up with piston volume. producing cars with higher compression that could still run on low octane fuels without detonation. GM spent millions, I have several books that state this and I have talked to professional builders that have proven this over and over and swear by it. maybe we are all wrong? that's ok.

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1970 Chevelle 454 Wagons haul A$$ in style! "The Chopped Suburban". to see some goto
www.EINSTYN.com FO_FDYFO = four-fifty four! TC#1460, VCEA#2
 
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Discussion Starter · #16 ·
Thanks for all the good information. I guess this is a difficult topic that may have more than one good answer depending on your experience.
My own limited experience driving BB's was making me think I needed to change the oval cc small valve heads for the same heads that were used on the Hi Per 427 and 454's. The performance they delivered on the street was awesome. I believe they were cast iron rectangle cc heads with the bigger valves.

Thanks for all the valuable info on the different heads.
 

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Let me throw this one in there. Why don't Chevrolet put closed chambered heads on their 502's? If they thought they would make more power and burn better they would put those on the 502 502hp engine wouldn't they? Does anybody have an answer for that question? It would be interesting to hear from Gary at GM.

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69 Malibu 454 10.00 to 1
2400 stall with 3.73
284XE Cam 049 oval heads
2.19 & 1.88 valves 850 dp
1.71 60' 12.42 ET at 108-110
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<BLOCKQUOTE>quote:</font><HR>Originally posted by plain 69:
Let me throw this one in there. Why don't Chevrolet put closed chambered heads on their 502's? If they thought they would make more power and burn better they would put those on the 502 502hp engine wouldn't they? Does anybody have an answer for that question? It would be interesting to hear from Gary at GM.<HR></BLOCKQUOTE>


I do.


Let me answer a question with a question.

If open chamber heads made more power, don't you think I'd be running them? Not only that but let's say they do how much quicker and faster do you think I'd run with my junk yard, boat anchor heads and RV motor. 10.40's, 10.30's, 10.0's?


Now for the answer to your question all you'd have to do is search this topic and you'll find I explain it fully.


It's thinking like this that has many wondering just how I run as quick as I do with such a seeming mild combo and without all the go fast goodies.


Remember too as I have posted before, NHRA Pro Stock engines as well as other professional class engines have a combustion chamber shape and volume that is far closer to "closed" than it is to "open".

Now for the vast majority here open chamber heads are easier to locate and will perform just fine. However if you're looking for free HP and lessen the possibility of detenation, then a closed chamber head is the way to go.

Somethings to think about!

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racer's '68

[email protected] n/a
1.38 60 foot
3900 lbs.
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[This message has been edited by racer1320 (edited 12-19-2001).]
 

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Ed,
have you ever tried open chamber heads with a matching piston, so that you had the same compression but with open chamber oval port heads? I know you love the closed chamber heads, but good cores are drying up and I wonder if there would be any real difference. Also, GM went to the open chamber supposedly to increase performance by unshrouding the valves, so wouldnt laying the chamber back in effect be making a "semi open" chamber to do the same thing? What octane pump gas do you use?

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Dave
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Ed this is your Christmas present I am defending you against the onslaught. I have run both types in race motors but always closed on a street engine. The closed chamber builds more torque over a wider range and will tolerate much more timing if set up with min. deck. The open chamber has a much narrower power band and is very detonation prone, In its power range the open chamber will make more power but requires high rpm to do it. On a street strip car I would always use closed chamber heads. I might not us Eds oval ports but closed chamber would be my choice.
 
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