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Old 06-11-2002, 08:56 PM   #1
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Post Edelbrock Performer RPM heads and a 400 sbc

Hey guys. I have a .040 over 350 Chevy in my car now, it has RPM heads, intake, etc (check the sig). Anyhow, I got some new pistons and a 400 core so I am going to build a 406 SBC with 5.7" rods and slight pop-up pistons. I would like to swap bottom ends on my car, plus add a Comp Solid Roller cam XE280 grind. The entire combo should be 11:1 motor with 242/248 duration and about .576 lift, 110lsa solid roller. The question is, I don't think that my Performer RPM heads will flow enough for this motor. I think they will make great power upto maybe 5000 RPM but then will not be great. My first question is does anyone have a 406 sbc with RPM heads at all? If so, what is your motor combination and how well does it run. I will drill the steam holes of course, but I was thinking about porting the RPM heads. Does anyone know can Performer RPM heads gain a fair amount from porting, and if so, what part of them should I work on the most? Or should I just leave them be? Thanks a lot.

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1981 Olds Delta 88 455/th400/3.23 posi

1988 Trans Am WS6, 355/T5/3.27 posi; RPM heads and Intake; Crane Fireball cam; Holley 750 carb; soon Comp RXE294H; th350 & 10" converter.

1994 Trans Am LT1/T56, no cat; Hooker CB; Hotch. SFC and STB; Ripper shifter; Poly mount; Lakewood LCA; K&N FIPK; Hypertech Airfoil; soon to port&polish MAF; Sprint springs & Bilstein shocks; GM Motive 4.10; Hypertech PowerTuner III
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1995 Trans Am LT1/T56, Functional Ram Air Hood and matching CAI, 9" w/4.10s, all free mods, electric WP, Hooker LTs with Hooker CB and OFY, lots of suspension mods
1985 Corvette 406, miniram and EZ EFI, 700r4 with Yank 3600 stall, 3.08 dana 36, dual 2.5" exhaust and 1 5/8s LTs
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Old 06-11-2002, 09:46 PM   #2
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I have performer rpm heads on my 406 in my 79 camaro. They work pretty good for not having done anything to them besides put them on, but I have a buddy that had the same heads on his 406 and then put on some AFR heads and picked up a lot more performance. My 406 is not as built as the one you are thinking of building so I would say port them, or just get some bigger heads. That motor will need as much air as possible. I also have a 406 in my 68 that is similar to the combo you are trying to build, but it has dart iron eagle 230cc heads. They have not been touched as far as porting and that motor made 583 hp on the dyno with a solid cam and about 11:1 compression. Hope this helps. If you want exact specs on either motor let me know.

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Old 06-11-2002, 10:25 PM   #3
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What kind of cam/RPM are you running/shifting at with your 406. You see, I have these heads now. I can use them for now. When I get some more cash, I would like to get better heads. AFRs I would love, but money is the problem. Maybe some iron heads, I will have to think hard. Thanks.

------------------
1981 Olds Delta 88 455/th400/3.23 posi

1988 Trans Am WS6, 355/T5/3.27 posi; RPM heads and Intake; Crane Fireball cam; Holley 750 carb; soon Comp RXE294H; th350 & 10" converter.

1994 Trans Am LT1/T56, no cat; Hooker CB; Hotch. SFC and STB; Ripper shifter; Poly mount; Lakewood LCA; K&N FIPK; Hypertech Airfoil; soon to port&polish MAF; Sprint springs & Bilstein shocks; GM Motive 4.10; Hypertech PowerTuner III
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1995 Trans Am LT1/T56, Functional Ram Air Hood and matching CAI, 9" w/4.10s, all free mods, electric WP, Hooker LTs with Hooker CB and OFY, lots of suspension mods
1985 Corvette 406, miniram and EZ EFI, 700r4 with Yank 3600 stall, 3.08 dana 36, dual 2.5" exhaust and 1 5/8s LTs
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Old 06-12-2002, 03:45 AM   #4
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I am running a Comp cams saturday night special hydraulic with .500 lift both intake and exhaust. I do have 1.6 ratio rockers which makes it about a .533 lift. I shift around 5500. Like you said, thats about the end of the line for the heads (5500 rpm). The car weighs 3800lbs and runs low 12s all day long. It also runs really good on the street. Everyday driver when I am home. If you ned anymore info let me know. As far as iron heads, the dart iron eagle heads flow just about as good as any head out there in the higher rpm range and they are a lot cheaper than the equivalent aluminum heads.

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Old 06-12-2002, 04:59 AM   #5
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I don't know how the 400s react in the upper RPM range. For now, I will use those heads, see what the car can do with the solid roller cam. When money permits, get some good heads and perhaps Victor Junior intake and rev the motor higher.
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Old 06-12-2002, 11:28 AM   #6
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I used to run my old 400 to 6000 and occasionally 6500 even using "shortie" 400-style rods. Don't worry- it'll rev if you feed it enough air. It needs BIG BLOCK amounts of air but you have to flow it though a small block set of heads.

I agree with the info on the Iron Eagles. They made SHOCKINGLY more power out of the box than my home-ported 882 castings. Probably 90% as good as a set of aluminum AFRs, if I had to guess. But if you already own the Edlebrocks- use them! You can buy better heads later as money permits.

BTW- This is IMPORTANT! You don't need pop up pistons to make 11:1 compression. The extra cubes build a LOT of compression. The problem is getting compression LOW ENOUGH! 64cc heads, flattops and you're already slightly over 11:1, even without decking the block or using a thin head gasket.


[This message has been edited by Damon (edited June 12, 2002).]
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Old 06-12-2002, 10:18 PM   #7
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I know, compression will be freeking high. I have 70cc chambers and will use Fel-pro thicker gaskets, but I bet still over 11:1.

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1981 Olds Delta 88 455/th400/3.23 posi

1988 Trans Am WS6, 355/T5/3.27 posi; RPM heads and Intake; Crane Fireball cam; Holley 750 carb; soon Comp RXE294H; th350 & 10" converter.

1994 Trans Am LT1/T56, no cat; Hooker CB; Hotch. SFC and STB; Ripper shifter; Poly mount; Lakewood LCA; K&N FIPK; Hypertech Airfoil; soon to port&polish MAF; Sprint springs & Bilstein shocks; GM Motive 4.10; Hypertech PowerTuner III
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1995 Trans Am LT1/T56, Functional Ram Air Hood and matching CAI, 9" w/4.10s, all free mods, electric WP, Hooker LTs with Hooker CB and OFY, lots of suspension mods
1985 Corvette 406, miniram and EZ EFI, 700r4 with Yank 3600 stall, 3.08 dana 36, dual 2.5" exhaust and 1 5/8s LTs
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Old 06-14-2002, 01:55 PM   #8
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Old 06-15-2002, 02:21 PM   #9
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11:1 is WAY low from what you'll have...

with zero deck, 0.04" gasket, 64cc head, and 4vr (guess @ 6cc) FLAT-TOPS will give you 11.5:1
Start adding a dome, and you're soaring into mid 12:1! With the cam you mentioned, you'd have to run race gas.
Granted, a 400 does need more cam duration to feed the cubes, and that duration will need additional compression to give a good crankng psi, but not that much...

With a 10-15cc dish, you'll be right around 11:1 with a 64cc head. Then run a cam in the 245-250@.05 range, but with a slightly wider LSA than usual (like 112+). This will give you a later intake closing to keep cylinder pressures under controll.
The old LT1 cam, or factory 'off-road special' would be good cams for a street-driven high compression, big cube motor. Just run high ratio rockers, because those cams run kinda low lift...

To answer your question about the head flow, I agree. Flow tests I've seen don't make the RPM's look very special at all - maybe a bit better than world S/R torquers (which have the same runner size BTW)
With the high compression the RPM heads will give you, you'll have to use a larger cam to keep away from detonation. BUT the large cam is going to want higher rpm's, which the Eddy RPM heads won't be able to support...
If you've got them, run them for now, but save for new heads as soon as you can.
Something with 200cc runners at least (World, Dart, Pro Topline all have good heads for a budget in this range)

Also, when you're buying new heads, you need to decide on chamber size.
On the one hand, you can buy larger 68-72cc heads and run flat-tops with a reasonable CR.
But, OTOH, you could also get dish pistons, run 64cc heads, and have the option of putting larger heads on later to drop the CR, and running a blower/turbo!
I'd go for option 2 Click the image to open in full size. They also say that the small chamber/dish piston is more effecient... (as long as the piston still gives quench area - a 'D' dish - we're not talking stock bathtub pistons here!)
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Old 06-15-2002, 09:46 PM   #10
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I think I got the combo down. It'll be a 406, I already have the small dome pistons and rings so I don't really have a choice of getting new ones, I already have the comp solid roller cam, which I also don't have much choice of new one, but I think instead of the RPM heads, I am going to run MoTown 220cc with 72cc chambers. I think the compression should be close to 11:1 then and I am hoping the flow will work ok and the power should be good. I am going to get the heads last, see how much I can sell the RPMs for and how much money I got. Because if I can, I want Dart Iron 215 or 230 cc alluminum heads.

------------------
1981 Olds Delta 88 455/th400/3.23 posi

1988 Trans Am WS6, 355/T5/3.27 posi; RPM heads and Intake; Crane Fireball cam; Holley 750 carb; soon Comp RXE294H; th350 & 10" converter.

1994 Trans Am LT1/T56, no cat; Hooker CB; Hotch. SFC and STB; Ripper shifter; Poly mount; Lakewood LCA; K&N FIPK; Hypertech Airfoil; soon to port&polish MAF; Sprint springs & Bilstein shocks; GM Motive 4.10; Hypertech PowerTuner III
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1995 Trans Am LT1/T56, Functional Ram Air Hood and matching CAI, 9" w/4.10s, all free mods, electric WP, Hooker LTs with Hooker CB and OFY, lots of suspension mods
1985 Corvette 406, miniram and EZ EFI, 700r4 with Yank 3600 stall, 3.08 dana 36, dual 2.5" exhaust and 1 5/8s LTs
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Old 06-15-2002, 09:46 PM
 
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