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Old 12-16-2010, 09:51 PM
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454 heads not sure now

So I've been saving up to get my stock (820 casting) heads worked with 2.19/1.88 valves, new guides, new springs and a mild port job. Well that puts me close to the price of dart 308cc "iron eagle" heads and I've always wanted them.. Also with the tiny chambers of the 820s my CR is hard to get below 9.5:1 (with close to 0 deck and .040 gasket and forged pistons) and I only have 90 octane available. If I switch to the 119cc chambers I get my CR down to almost 9:1.

So my question is based on my specs would it hurt my low end to switch to the iron eagles? I saw a flow comparision between some 049s and the 308s and even down low the 049s got spanked (didn't expect). If this isn't a good idea I'm okay with the 820s. I have a friend that went through UTI and did that hotrod thing and he said he saw the largest overall power gains using the dart heads.

454 30 over
XR288HR
TH350
3.73 r&p
2800rpm stall

Be just my weekend driver, would like good power everywhere and not to rev over 6000rpm. I don't have the cash for brodix and am not a fan of world products or RHS. Would also like to go with iron heads.

Here's the flow comparision: http://www.popularhotrodding.com/tec.../photo_06.html


Thanks,
Greg
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Old 12-16-2010, 10:16 PM
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And the page with the dyno http://www.hotrodders.com/forum/454-...ml#post1350683


I thought the rec ports would hurt the low end power and it didn't in this one.. Leaves me thinking about just goin and doin what I set out to do..



Greg
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Old 12-16-2010, 11:49 PM
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Go with your gut feeling....and the Darts. They will flat smoke all but a pro ported set of your 820's. Just doesn't make good financial sense to pour money into old oval port castings unless it is a very mild build that doesn't require new valves, springs, retainers, guides, etc and machining.
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Old 12-17-2010, 01:13 AM
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I just wanted to hear someone else say that. Wonder how the assembled set would do as is (valve springs and cam). I'll have to look a little more. Thanks for the response.


Greg
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Old 12-17-2010, 07:07 AM
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Just noticed the link I gave was to this page... this is the dyno http://www.popularhotrodding.com/tec.../photo_07.html

I just keep reading about how rec ports are so horrible on the street and the dyno shows an improvement over the 049s
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Old 12-17-2010, 07:17 AM
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820's are good heads. They flow especially well on the exhaust side due to a chamber that has a very unshrouded exhaust valve.

I had a set flow tested a few years ago that had bigger valves and some bowl work (no port work). They flowed 260in/199ex cfm at 0.500" lift. Should be good for 520hp (in theory). Your cam has more lift than 0.500" but I can't remember what they flowed at 0.550". I have the paper work in my garage, I'll try to find it over the weekend.

I would use 9.5:1 cr with a cam that size. (288 degrees). It will not be a problem with pump gas. The late closing point of the intake valve reduces the length of the compression stroke, as the intake valve is still open as the piston is rising in the cylinder during the compression stroke. It is called Dynamic compression ratio and a big cam needs more compression even with pump gas.
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Old 12-17-2010, 07:32 AM
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I've never had oval port heads on my 468 bbc,so I cant comment on them.But,I'm on my second set of rectangular port heads,The first were the 188's that came on the LS-6 crate motor,and they worked pretty darn good from 2000 rpm & up,and the Brodix Race Rites work pretty darn good as well.IMO,having a matching cam is the key ingredient.
Guy
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Old 12-17-2010, 07:38 AM
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Quote:
Originally Posted by ekacpuc
Just noticed the link I gave was to this page... this is the dyno http://www.popularhotrodding.com/tec.../photo_07.html

I just keep reading about how rec ports are so horrible on the street and the dyno shows an improvement over the 049s
The reports you're reading about are most likely comparing OEM iron oval vs. rectangle port heads. The crossover where the rec. heads catch up to the oval ports is often higher than what an engine will see much of the time on the street. But if cammed for the OM rec. ports, an engine will have a peak that the OM ovals cannot reach.

In any event, I don't know what the iron Darts cost (likely less than these), or what cam was used in the dyno comparo, but have you looked at the Profiler aluminum 290cc "ovangular" ("roval"?) port heads?

CC mag did a test w/them recently on a 9.4:1 462 BBC (dual plane intake, '950' HP carb) and made 564 HP @6100 RPM and 542 TQ @ 4500 RPM using a Comp XE284H cam. This engine could be expected to exceed 500 ft/lbs as low as 2800 RPM. The heads came from Dr.J's, cost right at $2K.
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Old 12-17-2010, 07:43 AM
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Yeah I think the 288 is a tad small for the 308s and a tad large for the 820s. I dunno though.

About that dynamic CR buisness. I originally was gonna use a XR282HR but was concerned with the high CR and pump gas bein 90, so I decieded (first asked comp cams) that the 288 was a better option. It also puts the power where I want it (on paper).


I like the idea of working with what I've got actually. I keep just throwing the Dart idea around every once in awile and I'm glad someone who has had them spoke up.


I'd like to have 2.19/1.88 undercut valves in the 820s, give it a bowl blend (machinist not me) and smooth the casting lines in the runners and before the valve seat (in runner). I'll prob get antzy and order the valves and such before I get enough for the dart heads plus shipping to alaska


I'm glad I asked.
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Old 12-17-2010, 07:46 AM
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I think I read a build up somewhere with those. 2g is alot, I was worried about 1500. I guess the saying horsepower costs money is appropriate. I was only trying to hit the 500hp 500tq mark btw (forgot to mention).


I have no idea what kinda match the XR288HR would be with the 820s after thinking about it.
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Old 12-17-2010, 07:54 AM
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im afraid im going to have so much money in my 781's i should have just bought new.
you can sell your old heads to help pay for the new heads.
just curious, why not alum?
ive been looking at the race-rite ovals for a long time.
also any comments on some edelbrock heads?
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Old 12-17-2010, 07:58 AM
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The edelbrocks have a small chamber too (though it is alumium).


I'd rather put my money into a quality iron head then have to skimp (cause I will) and spend 1900 bucks on a "cheap" aluminuim head cause its alum..


I dunno... I guess the worry I have with the 820s is the 255cc intake runner seems a tad small to have any power between 5 and 6g. So I considered some mild port work and uc valves plus a bowl blend
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Old 12-17-2010, 08:09 AM
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So I guess I have a few options

Keep the 820s and work on them ($500 IS another large part)
I think it'd be snappy up till 5000 rpm (though the stall is 2800 rpm)

get darts 308s for 500 more dollars
I wonder if it would be a slug down low and kick in around 5000 rpm? I guess I wouldn't like that

buy the same size chamber but larger runner aluminum edelbrocks and I could prob get away with 87 octane with that cam (I think) but pay $800 more than oem. I do admit 290cc is nice.

Who knows what I'll do. It helped to hear others thoughts on it.


Greg
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Old 12-17-2010, 08:24 AM
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In your other post earlier today, you talk about dome pistons, here you're trying to get your c.r. down?

I just moved from Anchorage, but Coker's did all my machine work on my blown 383 a couple years ago, they're gone now I think, but you should talk to the guys down at Alaska Drag Bike, super machine shop and knowledgeable people.
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Old 12-17-2010, 08:42 AM
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if your only going to spin under 6000 rpm i would just work with what you have, and then could you use some flat-top pistons?
and i dont think all the edelbrock are closed chamber
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