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Old 09-04-2004, 11:33 AM
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406 cam/heads combination needed

Hi all... I'm a newbie here and would like some information for replacing my SBC 406 heads and cam. I'm not wanting high RPM's, and former owner simply replaced the cam to a Crane single pattern 228 @ .050, .480 lift, and 112 lobe separation (rpm range listed at 3k-6k). Needless to say, there's no bottom end, and that's pretty much want I want. Here's the present config:

3100 lb, 4-speed, 3.55 rear
.30 over 400
Stroke - 3.75
Rods - 5.565
Rockers - 1.5
Heads - 76cc stock
Pistons - .160" recesssed
Crank - stock cast
Cam - Crane grind 284 H12
Carb - Holley 670
Intake - Edelbrock EPS dual plane
Cylinder pressure 135psi (not much, huh)

Here's my thoughts... Dart Iron Eagle 180cc heads with 64cc chambers. I don't know what the cc dish of the pistons are, but they are the type with no valve reliefs, just recessed (TRW 400NP-30). Not wanting to replace the bottom end at this time. I was hoping someone could calculate the cc's and how much the compression would increase with 64cc chambers. As far as the cam, I was thinking the Crane 262 dual pattern would bring on the power down low, but not sure how well the match is for those heads. I'm open to all suggestions. Tnx!

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Old 09-04-2004, 11:38 AM
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262 with the 180's. Won't be a race car or anything, but it will have power and give you bottom end. Plan on a 5000RPM redline-

K
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Old 09-04-2004, 07:00 PM
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The cam you have is pretty small. Especially on a 406. The Dart 180 cc heads will work, but I would recommend something in the 200 cc range if you are going to bring your compression up.

http://kb-silvolite.com/calc.php

Try to get your compression above 10:1.
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Old 09-04-2004, 09:05 PM
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My concern with the cam is the Crane spec'd RPM range of 3-6k. Seems like other manufacturers with similar specs are 2-5.5k, which has me

My thought on 180cc runners is velocity, plus I don't have a great exhaust system with ramhorns and 2" sidepipes, which is why a dual pattern may do a better job. There's nothing I can do about that, short of tossing the stock sidepipes, and they are way too cool for that... I also would like to keep the compression within reason for iron heads and pump gas. That Crane grind recommends 9.5 - 11. There's got to be a better combination out there to have peak torque at around 3500 RPMs. Without knowing the cc dish (aside from the .160" recess figure), I can't use those 'calculators'. And without going overboard, Dart 180cc heads are probably waaaay better than my stock 1970 76cc truck heads. I thought about a Vortec setup like CHP's article on the "406 Impersonator", but not enough room under my hood. I thought they made great power and they used a Lunati cam with similar specs.

Please keep 'em coming. Tnx!
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Old 09-04-2004, 10:13 PM
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If I remember correctly, my 406 has 12cc dished forged pistons. I used the Vortec 64cc heads, which should give me about 10:1 static. I also used the Comp Cams XE268, which has an advertised range of 1600-5800. I like the combination.

The problem I see with your current combination is your compression is in the basement. I would definitely replace those 76cc heads and go with a 64cc chamber. Those Darts you described should give better low end. The 400 is not a high winding engine anyway.
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Old 09-04-2004, 11:34 PM
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I have a 4.145" bore, (.020" over). With flat top pistons and 7cc valve reliefs, my compression comes to 11.2:1 compression with 64 cc heads.

Don't forget that most cam specs are figured for 350s. The same cam in a 400 is going to make the cam act smaller. You can figure the powerband will shift approximately 400 RPMs.
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Old 09-05-2004, 06:44 AM
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Here's a link to the TRW pistons I have. Any ideas what the cc might be? They really look deep!
400NP-30

I'd like to get some idea of the compression effect of going from 76cc to 64cc heads. Also, do you think simply changing the heads to obtain better flow and more compression will significantly improve the throttle response if I left the existing cam in place?
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Old 09-05-2004, 07:58 AM
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Those pistons would probably get at least into the 9-9.5:1 area, which is good enough for pump gas and the street.

(I know somebody will come back and say they're running 20:1 on regular pump gas.)

I didn't look up your cam, but the increase in compresssion has to help.
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Old 09-05-2004, 10:24 AM
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I would guess those pistons would get you less compression than that.
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Old 09-05-2004, 03:38 PM
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i have a 406 with the trw-speed pro-federul mogul,they started out in life as trw.anyway if you would simply shave your heads and hone the cylinders a little and use new rings there isn't any reson why you can't hit 400-450 horese with the came you have and have 400 lb.ft. of tork starting at about 2000-2500 rpm.i use the power forged L2352F30 pistons.they're forged resonably price and will give you yrs. of service.oh yea the ones you showed from summit are the 1976 style 400 piston. the one i gave reference to is 1970 style and stock will give 9.95-1 c.r. before boring.get rid of the 5.565 rods and use the 5.703.you'll have a whole different animal.its not as nessasary to spen money on techincal parts as a lot of people sometimes think.sometimes your heads might not have the higher flow rating but do have higher velocity.more important to start with the foundation and go up from there.
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Old 09-06-2004, 12:05 PM
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Tnx for the info everybody. I'm really not wanting to pull the motor and start over at this point with a better piston/rod combination, but I agree that may be the best course. I'm guesstimating that the pistons are around 27cc dish if the L2352F30 are at 14cc. I'm tempted just to do a 64cc head swap and see what happens. Decisons, decisions...
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Old 09-06-2004, 12:29 PM
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If your looking for lowend torque I wouldn't drop the dime for big valve large runner heads.Not to mention without headers your not gonna reall see the power potential those heads have to offer.I'd dig up some 64cc 1.94s,perhaps 1.94 double humps or vortecs(if ya don't mind getting a vortec intake).
Also what ever you get you'll need to have your steam holes drilled in the new heads.
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Old 09-06-2004, 12:30 PM
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I like TFS heads for your application, (Trick Flow) excellent velocity and enough CFM to build serious HP as well... and Im pretty sure the price is attractive as well...


I believe Summit racing equipment sells TFS heads..


2wld4u
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Old 09-06-2004, 12:58 PM
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Don't buy 1.94 heads. It will be a serious waste of money.

I have Sportsman II heads 2.02 valves. They came with "big runners". Mine are ported extensively. I haven't lost any bottom end.

People base their opinions on valves size and and runner size with a 350 in mind. A higher compression 406 with its bigger bore size and considerable displacement, will like the bigger heads.
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Old 09-06-2004, 02:58 PM
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Actually I based my opinion on the fact that 1.84 valves give a 350 more lowend than 1.94s.Therefor 1.94s should do the same for a 400.
I'm just not into dropping a grand into heads that are meant for something of a differant purpose.If I wanted lowend I wouldn't drop a grand on heads that make lowend and could make the power if I ever wanted it,I'm gonna save 7 bills and get what suits my current needs.
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