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  #31 (permalink)  
Old 12-20-2010, 07:55 PM
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I agree after seeing that picture, that head is a turkey, not a desirable chamber shape at all. Not a head I would be using on an engine where I wanted to push what I can get away with as far as fuel octane minimums. Quench virtually non-existant no matter how close you get the piston to clear the head.

Maybe a bit outside the topic, but I do have to say this, and it may be because I am more of a racer than a street rodder, ...but I have yet to see an Oval port headed BBC that impressed me, no matter what fancy work was done to the head.....and I've yet to see a Rectangle port head BBC that had poor low end torque(427 or bigger). Cubes over 420 and airflow is torque. Every Rectangle head BBC I've been around will flat blow the tires off, from a stop or from a 25 mph roll, it doesn't matter which.

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  #32 (permalink)  
Old 12-20-2010, 09:11 PM
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So there's a possibility of after working on getting the quench just right that it detonates?


With an XR288HR and aluminium heads what would be my limits on static CR with 90 octane?


I GUESS I could save and get some edelbrocks (110cc) or brodix (119cc)

Last edited by ekacpuc; 12-20-2010 at 09:18 PM.
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Old 12-20-2010, 09:30 PM
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Heck the brodix are 119cc and with 18cc dome set of probes, 0" deck and 040 gasket that gives me a 9.54:1 CR. Since the brodix race rites are alum could I get away with 87 octane (If I HAD to)?


Just not sure of what to expect by changing to alum. I'm guessing based on what I've read a 10:1 with my cam would be good for 92 octane using alum heads?


Greg
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  #34 (permalink)  
Old 12-20-2010, 09:56 PM
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You could consider the ProComp BBC head, a engine builder member here has had really good results with multiple sets of them performing well and holding up. This BBC head I have also seen on other forums as doing well, often exceeding expectations hp figures into the 700's.

Shoot a PM to member "BOBCRMAN@aol.com" here at Hotrodders about the ProComp BBC head, he has experience with it. There is also info on them at heads-up racers site www.yellowbullet.com and the machinist/engine builder site www.speedtalk.com in the General Engine forum.

I've used a couple sets of the SBC ProComp heads without problems, I buy them bare and pick the quality of parts to finish them so I have some control, the pre-finished complete assemblies from ProComp seem to be a little too low in valvetrain part quality but the casting is fine. I wouldn't hesitate to use a BBC set based off what I have heard.
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Old 12-20-2010, 10:59 PM
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his box is full for PMs


I see alot of mixed reviews. I put alot of chinese junk on my V.W and really really regret it. I'm lookin more, like you said its bad reviews on the valve train. I wonder what they flow? I see on jegs you could get a bare set non ported for just under a grand or they have stage one two and three versions (same price though prob junk). I dunno...


Greg

Thanks for the idea though, scares me buying a "inexpensive" set of aluminium heads..
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  #36 (permalink)  
Old 12-21-2010, 02:11 AM
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Okay so I found info on the procomps and they're rectangle ports, I'm hoping for ovals. Nice flow numbers though.

So with that said... I found 2 sets of ovals that I'm interested in. AFR 265cc cnc'd combustion chamber version and Brodix 270 race-rites. I was originally thinkin the brodix but then someone in another forum was talkin about the AFR265s and they have some IMPRESSIVE numbers.. They're also the same price as the brodix as cast version.


What I'm goin for here is a nice oval port set of alumium heads without going MUCH over 2g. I see that with the AFRs 112cc chamber I get a 9.76:1 CR zero deck and speed pro 13.8cc dome. The brodix gives me a 9.54:1 CR with a 18cc domed set of probes. I'm trying to get it to run nice on 90 octane gas, it would be a plus to be able to run 87 though if I had to.


Is 9.5:1 or 9.7:1 low enough with aluminum heads to run 87? If both same answer then maybe I'll pick one over another due to piston quality (probes or speed pros) and valve relief room. I'll just take a little more time and get the "good stuff"

I hear the speed pros are heavy and have shallow valve reliefs. The valves are kinda big in both heads but lift will be .521/.54 so maybe since that isn't too much it wont be a worry? The probes I do admit are expensive but if its whats right..

so is there any reasons of why to pick one combo over another? I'm iffy because I don't know what the shape of the brodix chambers are but I'll bet they'll flow nice with a low domed set of speed pros. On that note the AFRs may not like the probes large done. Any thoughts?


Greg
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  #37 (permalink)  
Old 12-21-2010, 05:08 AM
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Quote:
Originally Posted by ericnova72
I agree after seeing that picture, that head is a turkey, not a desirable chamber shape at all. Not a head I would be using on an engine where I wanted to push what I can get away with as far as fuel octane minimums. Quench virtually non-existant no matter how close you get the piston to clear the head.

Maybe a bit outside the topic, but I do have to say this, and it may be because I am more of a racer than a street rodder, ...but I have yet to see an Oval port headed BBC that impressed me, no matter what fancy work was done to the head.....and I've yet to see a Rectangle port head BBC that had poor low end torque(427 or bigger). Cubes over 420 and airflow is torque. Every Rectangle head BBC I've been around will flat blow the tires off, from a stop or from a 25 mph roll, it doesn't matter which.


I didn't see your post.


This is what I found out:

http://www.chevelles.com/forums/show...=1#post1345377

The guy had horrible troubles and 30 hrs of portwork to get it to flow what they're suppose to.



Greg

Last edited by ekacpuc; 12-21-2010 at 05:27 AM.
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  #38 (permalink)  
Old 12-21-2010, 01:31 PM
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I don't understand why, if you're limited on octane, you insist on using domed pistons? You can build to make power with lower c.r.'s. Just curious.
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  #39 (permalink)  
Old 12-21-2010, 01:39 PM
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i thought flat top pistons had better flame travel anyway?
but i could be wrong!
educate me, anyone.
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Old 12-21-2010, 01:47 PM
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Just a note, the Chevelles.com thread you linked in is more than 3 years old, the heads have improved since that introductory batch. Some of the more recent posts there show quite a few people using them on motors very similar tou yours with no problems. I will say I feel the Procomps are not for the bolt them on out of the box crowd, they are better off with someone who likes to port match, bowl blend and generally look things over closely and pay attention to valvetrain goemetry.

There are also Patriot Heads, they are a bit better than ProComp but still in the budget catagory.

You can't really go wrong with either of your proposed set-ups for AFR or Brodix heads, both should run fine on 89 octane, maybe even 87 octane due to the tolerance the aluminum material provides.

The Probe piston will likely have more piston to valve clearance than the Speed-Pro, but Speed-Pro has redesigned a lot of thier pistons abouta year ago with skirt coatings and bigger valve releifs, but I haven't looked at a set of them in that time so IDK. You could also look at the Keith Black/ICON line of forged pistons, they are nicer than TRW/Speed-Pro.
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  #41 (permalink)  
Old 12-21-2010, 01:50 PM
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Quote:
Originally Posted by matts37chev
i thought flat top pistons had better flame travel anyway?
but i could be wrong!
educate me, anyone.
Very hard to get much compression in a BBC with a flat top piston because the typical open chamber factory and aftermarket head cc of 119cc or more. Almost has to be a 489 or bigger stroker to get above 8.5-1 compression with this large a head chamber and flat tops. It's not as simple as a SBC with flats.
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Old 12-21-2010, 04:57 PM
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Truthfully I'm just difficult.. I figured that if I shoot for the 9:1 range I'm competitive and okay on poor gas (with Iron). Problem is with the 820s its hard to hit 9:1 and don't think that I could mill the 820s enough without a negitive affect (valve shrouding, intake manifold matching, ect) and use flat tops to hit the 9:1 I wanted. Now I'm thinking its worth looking into aluminium.


. I didn't think about the fact that's a 3 year old thread. I'm okay with taking heads to a machinist (he does stock stuff though) but I'm new at this so I myself may not catch a problem. Like until now on the 820s I never noticed how messed up of shape the chamber is. They flow like 781s but don't have the nice shape.

I'm hoping to find a aluminium head that don't have to port to get it to flow nice. Porting is expensive I'm noticing (including shipping too).



Thanks,
Greg
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  #43 (permalink)  
Old 12-21-2010, 05:50 PM
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Quote:
Originally Posted by ericnova72
Very hard to get much compression in a BBC with a flat top piston because the typical open chamber factory and aftermarket head cc of 119cc or more. Almost has to be a 489 or bigger stroker to get above 8.5-1 compression with this large a head chamber and flat tops. It's not as simple as a SBC with flats.
that didnt really answer my flame travel in the combustion chamber question.
i was thinking if hes buying heads anyway he could get some smaller than 119cc
(im also trying to learn, building a bbc myself)
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Old 12-21-2010, 07:10 PM
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With flat tops I need approx 100cc chambers to get a 9:1 cr


Greg
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Old 12-21-2010, 07:19 PM
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I shoulda added that what I found in that range is alum edelbrocks. I read that if you want 9:1 pump gas use iron but if you use alum with 9:1 it sheds heat too fast.

Edelbrock rpms flow charts are sad.
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