Will 781 heads support a 496 motor?

J

JimBiron

Member
At the risk of getting thrashed I thought I'd ask this question here. I'm going to build a 496 vs. a 454 but don't have the extra $$$ for a new set of heads. Will the 781 BBC heads I have (2.06 intake) support the 496 Cu In motor or is there a limit at some Cu In below that?
I know its a relatively subjective question and thre are a lot of variables but for now I think I need to stay with the 781s.
If it can't support a 496 at some reasonable rpm then do I bowl blend and go to 2.19 valves or just keep saving? (I don't know the cost of the additional head work)
 
http://maliburacing.com/patrick_budd_article.htm

read this

yes, if the rest of the combos set up correctly and the heads are mildly reworked they will prove to be a decent choice on a 496 BBC
the key is getting the rest of the combo, IE COMPRESSION,CAM,INTAKE,HEADERS,DRIVE TRAIN GEARING AND TIRES/SUSPENSION set up to handle what can be MASSIVE MID RPM TORQUE
concentrate on building power in the 3500rpm-6500rpm band, with the max compression the cam sellected will tollerate, and gear the car to match that rpm band and youll generally find youve got a decent combo

BTW theres several threads on sellecting gearing, and getting TRACTION , don,t think so much about spinning it into the upper rpms as much as using the tq and launching hard, those heads on a 496 can easily support over 550-600hp if set up correctly
 
Thanks Grumpy.
I'm looking at the Ohio Crank site and may be going for one of their rotating assemblys. What's your take on a decent 'street' motor for my 66 BelAir with a M20 and 3.73 gears.

On another note what if I stayed with my 454 and the 8.25:1 compression. Is there any hope for a 8.25:1 motor? :roll:
 
JimBiron said:
Thanks Grumpy.
I'm looking at the Ohio Crank site and may be going for one of their rotating assemblys. What's your take on a decent 'street' motor for my 66 BelAir with a M20 and 3.73 gears.:
Click to expand...

decent for WHAT application,??
a 454 -496 BBC can have almost anywhere between 240hp-900 PLUS hp depending on components used, I can give you I 496 BBC combo thats fairly cheap to build that I used in several cars , and that will work ok in your manual trans/3.73 rear gear car but it won,t get great mileage or be particularly street friendly, and it will require high test fuel,but it will move the car right along and not cost you a huge amount?

JimBiron said:
On another note what if I stayed with my 454 and the 8.25:1 compression. Is there any hope for a 8.25:1 motor? :roll:
Click to expand...


sure, but if you stay at 8.25 cpr...... ID be thinking about this...

http://store.summitracing.com/partdetai ... toview=sku
 
let me address the 2nd comment from you first...
Evil Grumpy. :D

On the first comment on the cost effective enging build I would be very interested. I've got a 454 with 781 heads but I am consideraing all options.
Thre is a builder in VA that can put together a 496 for around $4500 that seems decent. I have done business wit hthen before and gotten a decent 383 for $3995. (all inclusive)

So, Do I want to build or not? Please let me know what your, cost effective, setup looks like and I'll make a decision.

BTW- This is a... "go to the car shows" car that I want to sound like it has some ooph. It will not make it to the track... I've had just too many broken parts over the years and replacing any more will hurt my retirement. :eek:

Been racing for the $$$ with my 59 vette (F/S and I/S) my 60 brookwood (O/S) and my 69 camaro (ss/d) and also bracket racing with my 57 chevy. It does hurt when you break some parts. I personally knew some of the NHRA record holders back in the early 70's... Geez. I miss those days. Its only been the last year or so I decided to get back in the saddle... and I don't have a clue about the newer LT1 LS1-7 and LSX motors... Its hard to teach an old dog new tricks.
 
JimBiron said:
JimBiron said:
let me address the 2nd comment from you first...
Evil Grumpy. :D

On the first comment on the cost effective enging build I would be very interested. I've got a 454 with 781 heads but I am consideraing all options.
Thre is a builder in VA that can put together a 496 for around $4500 that seems decent. I have done business wit hthen before and gotten a decent 383 for $3995. (all inclusive)

So, Do I want to build or not? Please let me know what your, cost effective, setup looks like and I'll make a decision.

BTW- This is a... "go to the car shows" car that I want to sound like it has some ooph. It will not make it to the track... I've had just too many broken parts over the years and replacing any more will hurt my retirement. :eek:

Been racing for the $$$ with my 59 vette (F/S and I/S) my 60 brookwood (O/S) and my 69 camaro (ss/d) and also bracket racing with my 57 chevy. It does hurt when you break some parts. I personally knew some of the NHRA record holders back in the early 70's... Geez. I miss those days. Its only been the last year or so I decided to get back in the saddle... and I don't have a clue about the newer LT1 LS1-7 and LSX motors... Its hard to teach an old dog new tricks.
Click to expand...

Finally I should add that I'm looking for something in the 400-475HP range. Anything more is gravey.
Click to expand...

Hey... should I consider the 588 for that matter?
 
LETS keep the cost low, Have the guy building your 496 stick some 11:1 cpr pistons, a decent set of scat 7/16" 6.385" rods that match those 871 heads in it and clearance, and set up the springs for the valve train on the (do a bit of bowl and chamber clean up work )mildly reworked stock heads for a .650 lift flat tappet solid lifter cam, do a 3 angle valve job,then throw THIS CAM in a properly set up 11:1 cpr 496 and add an EDELBROCK RPM AIR GAP INTAKE and your going to get what your looking for

http://survivalmotorsports.com/ChevroletBBCams2.html

Chevrolet Performance Camshaft; Part Number SS4265 $74.95
lifter-type
Solid
Big Block 1967-93 396-454; intake-duration@.050 lift 264; exhaust-duration@.050 lift 274; intake-lift .612; exhaust-lift .637; lobe sep angle 108


ITS more cam than you need but it will sure lope and build decent hp, and it will sound good in that 496 and won,t cost you that much either
 
this will be a good place to look into detonation, with a static cpr of 11:1 that cam will be at a dcr of very close to 8:1-8.2:1 depending on several factors like head gasket, quench, etc, which should run decent on pump high test.
now the rather obvious question is why not just drop the static cpr a bit, its because your TORQUE AND THROTTLE RESPONCE is closely related to the cylinder pressure which you generally want as high as you can get it WITHOUT GETTING INTO DETONATION ISSUES

heres where you get the valve timing info if you don,t have it, and IVE always installed most flat tappet cams 4 degrees retarded

http://www.crower.com/misc/valve_timing_chart.html

heres more info, youll want to read thru.

viewtopic.php?f=50&t=671

viewtopic.php?f=50&t=499

this cam (below) will also work,really well, if you use a bit of octane booster, and probably give more off idle responce and tq, but its more prone to detonation

Chevrolet Performance Camshaft; Part Number SS4254
lifter-type
Solid

Big Block 1967-93 396-454; intake-duration@.050 lift 254; exhaust-duration@.050 lift 264; intake-lift .587; exhaust-lift .612; lobe sep angle 108

HEY GRUMPYVETTE, WHY DID YOU SUGGEST THE CAM BE INSTALLED RETARDED 4 DEGREES ?

if that's the case, would you expain why?"

(1)it tends to lower the tendency toward detonation on pump gas if you get a bad batch, as it bleeds off just a bit more low rpm cylinder pressure., add 4 degrees of retard to your calcs and see what I mean, then run it both ways on DD 2000 and see the differance it makes
(2) it moves the whole torque curve about 200rpm higher.
(3)many cams have an extra 4 degrees advance built into them at the (DOT-TO_DOT) install position, thats there to boost low rpm tq at the expence of the upper mid range and peak hp, something than many cam companies do to compensate a bit for the vast majority of guys who consistantly select cams a bit larger in durration than IDEAL for the application, or tend to ignore the fact that a cars generally used by most customers far more often on the low and mid rpm band than they will admit..
(4) in this case youll need the upper rpm tq far more than the off idle tq.

WHEN YOU SELECT THE CORRECT CAM FOR THE APPLICATION, and installing the cam strait up, or retarded 4 degrees tends to make sence
 
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