BBC heads?
 

Looking into getting some heads from AFR, CNC machined and
ported for my BBC 454.

a little info on the engine. it's a complete High Output build from
GM performance parts, I obvisually want to lose the heads.
I'll need to find a good cam to go with the heads, which is my
next decision, I've been told compcams are great, so what do
you guys suggest?

4.00" bore, 8.5:1 compression, forged steel crankshaft and rods,
forged aluminum pistons, stock all stock, block is cast iron of
course. reccomended rpm is 5500, but I've been told not to
spin it past 6000, so I would say 5600-5800 is as high as
i'll spin it to.

anyways, i'm trying to decide between which AFR's to get, and
don't go off telling me so and so is better, I know i'm going
with AFR's, I don't want your opinion on what BRAND to
get, just which model of AFR heads..

now on to my selection.. going with CNC machined and ported
heads with the competition package.. I've decided to choose
between the two sets of heads which are in the largest portion
of my powerband 315cc and 335cc heads..

______________315cc_________335cc
PowerBand_____2500-6800_____3000-7000
Valves_Intake___2.250"________2.300"
Valves_Exhaust__1.880"________1.880"
C_Chamber_____121cc_________121cc
Intake_.500 lift__353cfm________352cfm
exhaust_.500 lift_271cfm________285cfm

flow is with a 2 1/8th inch exhaust pipe
my exhaust will be hookers with 1 7/8th inch primaries

you can check out the heads over at http://www.airflowresearch.com
under the bigblockchevy section.. for more details...

I'll be glad to recieved any feedback :)

Because of what's in your sig, I'd suggest the bigger heads or possibly the heads that are even bigger (357) :D

heheHEHEHEHEHE:D

shootin for ~760 RWHP baby!

what i'm worried about is getting them too far out of my
powerband, I still want to have power at the lower ranges,
but I don't want all my power to suddenly fall off after
5000rpm.

Yes, I did look at the 357 "Magnum" heads, all three models
of this lineup go for the same price, just shy under 3 grand,
so it's not an issue of price at all, more over what i'm going to
get.

simply, I don't want to lose streetability with huge heads,
the car will be a daily driver, and a track monster, so it's
a compromise, screw gas mileage >)

still suggesting the 357's ? it'll be some time after I get
the car running before i'll install the supercharger..
Oh, and the powerband is 3500-8000rpm for the 357 heads..
they say that displacement and other stuff affects this
band, but to what extent, I dunno. I'm not sure if the band is
a little too high, and how it'll affect my low rpm performance..

I also need to figure out what kinda cam i'll use...

THIRDLY.. jeeze thoughts keep coming, anyone know what kind
of lift I can squeeze away using stock forged steel aluminum
pistons on this block without bending a valve or something?

nevermind I think I answered my cam question...

CompCams Hydraulic Roller w/1.7 rockers PN 01-148-8

rpm range is 2200-5800, .510 lift with 230I/256E duration
110* lobe seperation..

think she'll run fine below that power band? idle is going to
be around 800-1200rpm, it'll be rough, but I still want her to
pull below 1800rpm cause that's where i'm at in 6th going
80 on the interstate :)

don't think i'll hit a piston with that lift... :think:

Scuzzy,

"anyways, i'm trying to decide between which AFR's to get, and
don't go off telling me so and so is better, I know i'm going
with AFR's, I don't want your opinion on what BRAND to
get, just which model of AFR heads.."

Pretty close minded choice here. The AFR's have good advertised numbers so that leads you to a good choice. One thing I would look at is other combos for the $3000 you are going to spend. Do you actually want to hear them?? Most head guys will tell you that a advertised flow number from AFR is not what they flow. One reason head porters don't like them.

You might want to look at the whole flow curve of those AFR heads. The numbers speak for themselves. .300 lift the 315's are 9cfm higher, and @ .400 they are 8cfm higher. Seems pretty obvious to me.

Blower? What kind of blower? a centrifigal or a roots?

That cam...... why? You are using some nice heads here at least with those AFR's. They come with Solid Roller springs good for .700 lift. Even HR springs for that would be good to .600 at least. Your going to miss out on alot of power. 110LSA is too much overlap for a blower on EFI engine. A 230/242 114 LSA (yes basically a CC306) as a Solid Roller will be much more driveable and with .626/.646 lift will be much more powerfull with those heads. Hell even a HR could get you .635/.624 lift with that duration.

The bottom end.... Forged 1053 Forged Crank, probably the least of your worries. Forged Rods, 4340, shot peened, magnfluxed, they will take a beating in a drag situation I wouldn't be scared to take them to 6500rpm. Forged pistons... Ditto.

315's (not my first choice, but we have no options), the SR 306 type cam, 8psi is going to get you about 800hp SAE at the flywheel around 6000rpm. Sounds good to me. On top of that it should be nice and driveable.

I'd probably rather go with a 305cc head (AFR or Brodix), which is about $1800 and spend the rest of the $3000 on porting. End with about the same volume, just with numbers closer to the 357's, probably 40-50hp there. (only 5-6% in this power level though)

Just thought I would give you some tips because I've been doing alot of Big Block research in the past 8-9 months.

Bret

Thanks for your comments, and yeah I'm kinda closed
minded on it all, I realised that if I didn't stick with a brand
that is known to do well and select something from them
that I would jump around too much trying to follow everyone's
opinions..

so basically I just wanted opinions on this brand. and yeah, I went
back and ran the numbers, looking at the flow and decided on
the 315's for two reasons, i'm in the powerband sooner,
and the flow is better at lower lifts.

blower, Centrifugal, Procharger D-1 @ 16psi.

what about the cam? the blower will come at the later stages
of the engine buildup, when I already have it drivable
and I'm doing just that, driving it.. I wasn't aware if the
heads came with a cam at all, and IIRC valve float begins
at 5800rpm, no? am I completly out of the ballpark here?

I'm still learning myself, I mean it's not like I'm going to go
out tommrow and buy everything and try to put it together
next week. :D I'm looking at a year, maybe more, to learn
everything, all the details.

should I be worried about bending a valve/rod at anything
above .510 lift? assuming I use the stock forged aluminum
pistons, at least I don't THINK i'd hit a valve at that high lift,
but I don't know where my limit is. or how to calculate
that out.

Thanks for your tips, you've been a real help.

I think I did the calculation right... :think:

121cc heads will drop my compression back to 8.3:1 from 8.5:1
less power.. hmm.. hey, less compression = more boost :D

also, you mentioned a solid roller cam.. the block was built
and comes stock with a hydraulic roller, are they preety
much interchangeable or do you have to swap out the entire
valve train?

I'm not much on cams.. or rear ends yet.. we all had to learn
somewhere, right? if I had someone to learn from in my area,
I wouldn't be coming out with all of these stupid questions.. :D

spent the last two weeks reading nothing but forums and
articles, trying to asorb everything I can for my project, but
nothing beats handson experience... you can drop me a msg
on AIM.. 'ScuzzyNova' if you wanna chat further.

A few things.......

16psi is not going to live with that bottom end. You will break things. I gave you 8psi for a good reason. Your also going to need to be a pretty good driver to actually use the 800hp anyways.

The cam doesn't come with the heads. The valve springs do, big difference.

Go look at Brodix.com. Most engine builders and racers have heard of them.

"IIRC" Valve float?

"should I be worried about bending a valve/rod at anything
above .510 lift? assuming I use the stock forged aluminum
pistons, at least I don't THINK i'd hit a valve at that high lift,
but I don't know where my limit is. or how to calculate
that out."

do a search on P/V clearance or piston to valve clearance on advanced tech.

I can tell your kind of new to this. Might not be the best choice to asseble this yourself. I've seen some ASE mechanics put a camshaft and rockers arms in a engine wrong. It's important to the life of the parts and your pocket book to have it done all right.

Bret

thread tag :P

alright, 8psi it is. yeah, I gotcha on the valve springs, I knew
that, I read your initial post wrong, so it seems.

IIRC = If I recall correctly..

Yeah I'm new at this, but I won't be trying to do it very
fast, and I'm going to have help from others who have
done this as well, verbal help at least.

thanks again.

update;

welp, I read up some more on hydraulic rollers and solid
rollers, I like the idea of HR's less noise and maintenance
but it's limitations don't really bother me either, since I won't
be spinning high enough to really encounter them. the SR's
drawback is the noise and continued maintenance requirement
which bothers me a little, but that makes it fun I guess..

I'm going to go to compcams sometime soon and get a custom
HR built with +.600 lift and longer duration with 114* LSA, since
they don't offer anything around that area..

plus, for the pocketbook it'll be better, since I don't have to
change the entire valvetrain around for a SR, the Gm Gen6 block
is already built with high performance HR valvetrain parts. at
most i'll need stronger rockers... oh, would I need to change
out the springs on the 315cc heads to work with a hydraulic
valve train? or will thoese springs and 1.6/1.7 roller rockers work
together?

Hmm.. :think:

Feel free to throw in your opinions, just don't call me stupid, I
already know that. everyone has to learn somewhere.

Concerning big blocks......

For clarification... the bore is 4.25" & stroke 4".

The .510 lift cam you list is definitely not aggressive by any means. I run a 220/230 .525 lift in my 4x4 427 pickup. The heads you list are not matched to your cam. If in a light car, a 234/242 with .600-.620 lift (over 10# boost & 6500rpm) is very possible or milder like 226/234with .580-.600 lift (under 10# boost & 6000 rpm). Any half decent built big block will spin 6000 easily & 6500 with good factory components.

Those big rectangle port heads are not well suited to throttle response or low speed drivability (under 3000), nor are they required for a low rpm blower motor. They are more geared to big cams .600-.700+ lift & 4000+RPM usage. Those low speed recommendations they give are very generous. The 357's would be nce on a 1000HP 7000RPM motor. A good oval port head will net more drivability & still make killer HP. Compared to small block heads which are considered huge at 220cc intakes, big block oval ports average 260cc & rectangles 300 & up. Remember the charger will extend the rpm range of the heads to a degree.

Is your engine a GM performance crate motor? Which one? If it a newer crate motor with the factory aluminum heads... they are made by Edelbrock for GM & are a great head for drivability. Big valve & mid size oval port. If adding a centrifugal charger, 700 HP is obtainable on the stock engine.

More than 12# is asking for trouble on your relatively stock engine...... yes the engine is 4-bolt with 7/16" bolt rods & 5140 forged crank, but not an all out race motor. Start with a 450hp 8.5:1 motor & add 10# intercooled boost & you have over 700HP on pump fuel. For a blower motor, stay conservative on heads & cam & you will be happier.

thanks much for your reply. yeah the bore is 4.25" and stroke
4". I caught that just a few hours back.

yes, it's a GM performance crate engine, the High Output 454..
the cam on it, however... well.. the specs say

Lift: .510" Intake, .540" Exhaust.
duration is 211* Intake, 230* Exhaust

The block must not be one of the newer ones, which is why
I want to do away with the heads, one I need rectangle
ports for the intake that i'm going to use, two they're
not aluminum, they're iron. three they're heavy as hell..

so you see why i'm doing away with them, the cam is not agressive
the heads most likely are oval and won't work with my intake
which is a must.

I'll get a rev kit for the roller to prevent float, with that I should
spin to 6200, but it all depends on how I dyno. the cam i'm
shooting for is what SS suggested.

Duration: 230I/242E
Lift: .626I/.646E
LS Angle: 114*

within that range, i'll talk to some compcams people and see
what they suggest, take there numbers, and shoot a little higher.

oh, does anyone know if it's possible to do math calculations
to figure out if you'll hit a valve with a certian lift?

I want an agressive motor, but I don't want to lose driveability,
so like you said, i'm going conservative, 315cc heads, I won't
gag the motor.

but my main points here is that the supercharger will not be
apart of the initial build, that's coming down the road. secondly
I don't care about gas mileage, with fuel injection i'll always
doing better than an equally carbed motor. you're
right about the comparison of headsize compared to the block,
however most people get the 190cc heads for there SBC.

Similarly (sp?) I'm getting the 315cc heads for the BBC, both are
considered the smaller class heads for the blocks, so my goal
here isn't "the bigger the better" but "the right part for the job"

am I making any sense? :think:

so my main worry now is if i'll hit a valve with this lift, if not
how far do I have to go before I do end up hitting a valve. Hehe

not trying to create the fastest cat on the road, just a beast
that will make some money. :D

thanks for your comments guys, I went to other boards and
got: zilch.