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ARE Heads to Big for 489

 
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mark496
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Joined: 07 Mar 2013
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Location: Beantown
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PostPosted: Thu Mar 07, 2013 3:35 am    Post subject: ARE Heads to Big for 489 Reply with quote

Hello
Getting ready to start build of my first BBC and the engine parts where for a strip car, sadly that car was sold..to pay med. bills so it will now go into a truck..
I'm being told the heads are huge for this APP.
and like feedback on this and if I use them what I'd be really giving up , as I get bench racers say'n I lose some low end and others say'n it'll be a dog till 5500rpm.
the build parts are as follows
454 30 over (489)
forged 4.25" crank
forged 6.3" full floating rods
srp pistons (10.2 to 1 with 118 cc chambered heads)
cam is
The heads are Dart pro 1's 345cc with matching intake
as of now it'll be carb with plans of later moving to injection if and when money tree grows...
have a 850 bearclaw and a 750 demon and a 3310 vac 2nd 750.

Engine will be installed into a chevy truck with a weight of 3900 lb
a th400 3500 stall and 4:11 gear with either 26" tal tire or 29" (still up in the air)

the bench racing I'm getting that should move to 305 cc heads for that c.i.d. and rpm the engine will see 75% of the time...
before I spend another 2-2.5k on heads what am I giving up,if anything with the 345cc heads.. confused...
like to get the compression up a tad also and that require milling as the darts are 121cc chambers..
thanks for any help..
FYI the engine will most likely see my dual stage n.o.s. package if I don't use it on my 355..
also should I move/change to a hyd cam as it'll be more street.. or is that cam mild enough to live ..
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Big Dave
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PostPosted: Fri Mar 08, 2013 9:00 am    Post subject: Reply with quote

Well the general rule is anything under 500 cubes you choose an oval port head. This is why the engineers at Chevrolet chose the Edelbrock RPM Performer heads with a little CNC pocket porting and gasket matching along with bigger intake valves in their 502 cube ZZ 502 motor. The same motor with cast iron rectangular port heads makes 50 horse less horsepower in the range of the hydraulic cam installed (limited to 5,600 RPM).

The 375 horse 396 was equipped with rectangular port heads and solid tappet lifters but it was a dog below 4,600 RPM. Floor it in any gear and you could feel in the seat of your pants when the motor caught up with the heads. From 4,600 RPM to 7,800 RPM it would pull strong. Of course the 375 horse 396 motor only had 320 cc heads.

It took racers about three to four years to notice that the 375 horse 396 motor ran a lot stronger with the 350 horse 396 PASS heads in place of the HiPerf heads it shipped with on both the street and the strip. I suspect your motor will behave the same way.

You are not married to these uninstalled heads as you can sell them and buy aftermarket oval port heads to replace them. That said I noted that you are planning on going with fuel injection (Hilborn, Crower, or EFI?) and adding NOS. That to me indicates that you are more concerned with high RPM operation than with cruising on the street. You will probably miss the heads and regret selling them at least until you try them out to see how they behave.

Only you know how you intend to drive that truck. If it is going to be principally a street vehicle, used for transportation then you will be restricted to 4,800 RPM and below in driving (and a change in heads is advisable). If this is going to be mostly a strip vehicle then you will be fine with what you have if you have a 3,400 to 3,800 RPM converter to match your 4.11 rear gears.

Big Dave
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clay
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Joined: 24 Nov 2002
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Location: South Carolina
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1972 Chevrolet Nova

PostPosted: Fri Mar 08, 2013 1:50 pm    Post subject: Reply with quote

If it was a race engine with high compression I would say try them. I do think you'll be happier with a smaller head though. A 0.030" over 454 is a 468 I believe and I don't think that's enough cubic inches or it'll turn enough rpm to use what you have. I have a good friend that has a mild 454 with factory rectangle port heads and it runs pretty good. However we have never tried oval port heads on it so I have nothing to offer as a comparison. We just built a 540 for the same car and used AFR 325 heads and going by horsepower calculators it makes high 600's for horsepower. I'll be the first to admit I've mostly dealt with small blocks though.
If this is a street driven truck I would go with a hydraulic roller camshaft. My buddies has a mechanical flat tappet and they can be reliable if you dot your i's and cross your t's. Solid rollers make power but have the potential for big problems. Isky and Crower have a solution with the bushing rollers instead of needle bearings but they are very pricey (around $900 I believe). I run one with a rev kit but I drive mine around 500 miles a year and check lash probably every 100 miles and run a rev kit. Rev kits are supposed to help lessen the impact loading on the needles. I also have pressure fed lifters and an oil accumulator that I can prelube the engine. So far so good but years ago I did lose a roller lifter and luckily caught it before any real damage. It wasn't a pressure oiled lifter but regular lash checks caught it. When I freshen it up I'll convert to the bushing lifters. You have to ask yourself if it's worth the risk. In my case I run a small duration (238* at 0.050") but need lift and rpm capability (7200) that is just at the edge of the range of hydraulic rollers or I would run one. Welcome to Smokemup! Clay

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af2
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Location: grassvalley, ca
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1933 Willys Coupe

PostPosted: Fri Mar 08, 2013 7:37 pm    Post subject: Reply with quote

Funny thing to pass on.....
I built a Nova with a pretty bad ass 431 auto that I shifted at 7800+ and ran high 12 with no traction. Then in 1986 my first son came and I sold the car less engine and trans.... The guy that bought it ran a 402 with less head and cam with pretty much the same stall and the same 3.90 gear and ran 12.8 every day with street tires.. The heads were smaller but better to go with the small cam he ran..... Big heads do not mean the car will be faster at all but the combo might..
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mark496
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Location: Beantown
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PostPosted: Sat Mar 09, 2013 5:24 pm    Post subject: Reply with quote

clay wrote:
If it was a race engine with high compression I would say try them. I do think you'll be happier with a smaller head though. A 0.030" over 454 is a 468 I believe and I don't think that's enough cubic inches or it'll turn enough rpm to use what you have. I have a good friend that has a mild 454 with factory rectangle port heads and it runs pretty good. However we have never tried oval port heads on it so I have nothing to offer as a comparison. We just built a 540 for the same car and used AFR 325 heads and going by horsepower calculators it makes high 600's for horsepower. I'll be the first to admit I've mostly dealt with small blocks though.
If this is a street driven truck I would go with a hydraulic roller camshaft. My buddies has a mechanical flat tappet and they can be reliable if you dot your i's and cross your t's. Solid rollers make power but have the potential for big problems. Isky and Crower have a solution with the bushing rollers instead of needle bearings but they are very pricey (around $900 I believe). I run one with a rev kit but I drive mine around 500 miles a year and check lash probably every 100 miles and run a rev kit. Rev kits are supposed to help lessen the impact loading on the needles. I also have pressure fed lifters and an oil accumulator that I can prelube the engine. So far so good but years ago I did lose a roller lifter and luckily caught it before any real damage. It wasn't a pressure oiled lifter but regular lash checks caught it. When I freshen it up I'll convert to the bushing lifters. You have to ask yourself if it's worth the risk. In my case I run a small duration (238* at 0.050") but need lift and rpm capability (7200) that is just at the edge of the range of hydraulic rollers or I would run one. Welcome to Smokemup! Clay


thanks for the welcome..
the engine is a stroker crank 489 if 60 over it be a 496..

most likely look for smaller heads..

thanks everyone
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Sat Mar 09, 2013 7:06 pm    Post subject: Reply with quote

Oops - missed the 4.25" stroke. I would still say go with a smaller head even with a 489. When you get it going or even start assembly keep us posted. Clay
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