Bence: Those heads are too big!!!!????
#1
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Bence: Those heads are too big!!!!????
Not that I am an expert but I would think those 345cc intakes are too big for your set up. I know you have not started on the motor, hate to see you spend all that time and money on a less than ideal set up. Maybe some other members will have the same or another opinion. :chevy
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Re: Bence: Those heads are too big!!!!???? (69 N.O.X. RATT)
I don't know what heads you are talking about but at 345cc they are toooo big. They will not work below 5000. I have those size intakes and it never worked for me. I am now blown so they work. Forget them on a street machine.
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Re: Bence: Those heads are too big!!!!???? (69 N.O.X. RATT)
Bence. I'm back again. I checked your signature and saw your future Merlin R heads 345 cc. Unless you are going blown, not supercharged blown those heads will be a dog on the street. Even the rectagnular port heads at 325cc are only better then the oval at 6000rpm plus.
Don't do it.
I have been there, done it. Learn from my experience.
Don't do it.
I have been there, done it. Learn from my experience.
#5
Le Mans Master
Re: Bence: Those heads are too big!!!!???? (69 N.O.X. RATT)
I'd say the GM/Edelbrock "rovals" with the matching CNC matched
GM intake. 290 cc is just about perfect for a mid-size big block.
It's kind of an extra big oval port. The intake has a milled down
plenum divider to boost high RPM power.
This is the stuff that feeds the ZZ 502, so it should do the trick...
#7
Le Mans Master
Re: Bence: Those heads are too big!!!!???? (Vetteboy)
I think the Edelbrock version has 2.19 intakes and the GM has either
2.19 or 2.25 intakes. All the exhausts are 1.88
#8
Safety Car
Re: Bence: Those heads are too big!!!!???? (Vetteboy)
Steve:
Those heads do feed the ZZ502...but the 502 only makes 502HP :(
Vetteboy:
It was suggested by Tony(MoMo) that I use the 2.30/1.88 valves. Those are the valves that he will be using on his 600+ HP 427.
I'm still thinking about going with the Merlin 310cc R-Port Heads with 2.25/1.88 valves. :confused:
Those heads do feed the ZZ502...but the 502 only makes 502HP :(
Vetteboy:
It was suggested by Tony(MoMo) that I use the 2.30/1.88 valves. Those are the valves that he will be using on his 600+ HP 427.
I'm still thinking about going with the Merlin 310cc R-Port Heads with 2.25/1.88 valves. :confused:
#9
Le Mans Master
Re: Bence: Those heads are too big!!!!???? (bence13_33)
I'm pretty sure I've seen some magazine build-ups with them that
get the kind of horsepower you're looking for. The GM cam is
pretty mild and I think it maxes out under 6 grand. If you don't think
they'd do it you could step up to the rectangle heads. They've
got the big valves and 315 cc ports.
The main reason I like these heads is that they bolt right on and
they're CHEAP. I got my set for $1500 including shipping. My
Darts cost $2300... My Darts also have raised exhaust ports
which makes header fit a PITA.
#10
Safety Car
Re: Bence: Those heads are too big!!!!???? (Steve439)
Steve:
I'm thinking about going with these heads:
Cast Iron Merlin Rectangle Port Heads
119cc CCs, 310cc Intake Runners, 2.25/1.88 Valves
Those heads come complete and ready to bolt on (they claim 50-100 HP gain over the legendary LS6 heads). The heads cost $1,250 from Jeg's.
What do you think about the heads above?
I think those heads, combined with the Comp Cams 306 solid lifter cam will make some pretty nice power. I plan on revving the engine to 6700 RPMs :yesnod:
I'm thinking about going with these heads:
Cast Iron Merlin Rectangle Port Heads
119cc CCs, 310cc Intake Runners, 2.25/1.88 Valves
Those heads come complete and ready to bolt on (they claim 50-100 HP gain over the legendary LS6 heads). The heads cost $1,250 from Jeg's.
What do you think about the heads above?
I think those heads, combined with the Comp Cams 306 solid lifter cam will make some pretty nice power. I plan on revving the engine to 6700 RPMs :yesnod:
#11
Le Mans Master
Re: Bence: Those heads are too big!!!!???? (bence13_33)
I kinda have to defer on that - I have no personal experience with them.
Hopefully somebody will step in.
But, having said that - these are the classic aftermarket BBC heads.
Anything I've ever read about them was good. I don't think you'd
go wrong with them...
I haven't looked at them in years (I like aluminum heads) but if I remember correctly they have the raised exhaust ports. Other people may disagree,
but I hate raised ports. Remember, since the outside of the head angles, moving the port up also moves it out. Probably no big deal in a Chevelle,
but in my Vette three different brands of headers were just jammed into
all sorts of stuff. It's just too tight in there. Again, I'm not sure if the
ports are raised - somebody else could say...
I could also start a fun discussion by saying that I like the 110 cc
combustion chambers in the GM/Edelbrock oval heads. When I got into
BBCs it seemed like the accepted truth was that open chamber (119)
was good and closed chamber was bad. If you're looking at the classic
"How to Hotrod Big-Block Chevys" I'm sure you've seen that.
But in the last ten years or so it seems like more people are thinking
that small chambers and flat or dished pistons are the ticket. The
thinking is that the big domes that go along with big chambers don't
let the flame propagation (I think that's the right term) work as well.
I think that's the idea behind the 110 cc chambers. They're designed
to give the advantages of the open chamber head but give decent
compression with less dome.
Have you seen the head test in the April 99 issue of Chevy High
Performance? It flow benches pretty much all the popular factory
and aftermarket heads. It's really worth looking at.
#12
Burning Brakes
Re: Bence: Those heads are too big!!!!???? (69 N.O.X. RATT)
Well I'm going with the stock 781 heads. I'm going to have them (may do it myself) ported and polished, and put 2.19/1.88 valves in. As far as I know, the combustion chamber is 118cc. My only question is, how the heck can I increase my compression without having a HUGE dome on the piston, which would surely smash into the valves. I want to get up to 10:1 compression, but when I plug it into all the calculators, I need a 100cc combustion chamber just to get 9.5:1. I've also heard that milling heads is a bad idea, and plus, it makes it hard to line up the intake manifold.
What gives?
What gives?
#13
Melting Slicks
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Re: Bence: Those heads are too big!!!!???? (ddn)
ddn
Use the smaller closed chamber heads like 215, 063, 702, 206 or 802. That is what I am doing.
I am also using the 2.19 valves, with a street port to clean them up.
Terry
Use the smaller closed chamber heads like 215, 063, 702, 206 or 802. That is what I am doing.
I am also using the 2.19 valves, with a street port to clean them up.
Terry
#14
Burning Brakes
Re: Bence: Those heads are too big!!!!???? (trw)
trw, Unless someone wanted to trade me or something, I'd rather just keep the heads, supposedly they are very good stock heads, money is a factor.
Check out:
http://maliburacing.com/
Check out:
http://maliburacing.com/
#15
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Re: Bence: Those heads are too big!!!!???? (ddn)
ddn
Your in the catch22. I bought a set of 215 heads (at my machine shop) for $200. For the cash that is the cheapest way to get compression.
You might be able to trade heads or buy some and sell yours.
Terry
Your in the catch22. I bought a set of 215 heads (at my machine shop) for $200. For the cash that is the cheapest way to get compression.
You might be able to trade heads or buy some and sell yours.
Terry
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Re: Bence: Those heads are too big!!!!???? (bence13_33)
For the size motor you're building the smaller rectangular ports will be best. The Merlins and Dart iron heads are great. You will need to check on the exhaust ports. I know the Merlin ovals I had were in the stock location. Everythiing fit fine. make sure they haven't changed design. The ex. port of the Merlins is an excellent D-port design and is where much of the power is made.
Be careful going too large on valve size on a 454 bases engine. A 4.250 bore can shroud a huge valve. In many cases the head will flow more air when actually bolted on the engine with a smaller valve. Pontiac guys have seen this for years. Add up the totals...2.30 intake+ 1.88 ex= 4.180. That leaves .070 to divide 3 ways between the two valves and on either side of them to the wall. That ain't much! Now, understand that the big block cants it's valves and tilts them on their axis to gain more clearance from the wall, so you actually have more than this but you see the issue. Now stick the same head on a 4.500 bore and bingo there is .320 to divide between them all. Much better.
What gears are you willing to run? You need to be thinking 4.56-4.88 final drive ratio to take advantage of this setup. If you aren't able to get it into that 6500 range as you cross the line the car will be a pig. The rectangular ports will have a hard time gaining rpm against 3.55 gears unless you do install the 6 speed.
Remember Chevy did lots of things to crutch the big heads for the street. Very wide LSA on relatively mild cams was the biggest. When you change these things the character of the engine changes drastically too.
My 427 peaked HP at 5850 but still managed low 11's all day long. And that's with ported oval ports. The rpm range you're talking about shoud get you deep into the 10's with a 454 if you're willing to build the car around it. But be aware that at the rpms you're talking about, street manners are tough to get with the equipment required to make power at that rpm. You can easily run 10's with an iron head oval port 454 if you want to without twisting it so high and busting stuff.
Either way, plan on some pocket porting work on those iron heads. They are great raw material but need some serious hand finishing inside. Don't just bolt them on out of thebox. You'll be leaving lots of power on the table.
jim
[Modified by 427Hotrod, 1:11 PM 11/24/2001]
Be careful going too large on valve size on a 454 bases engine. A 4.250 bore can shroud a huge valve. In many cases the head will flow more air when actually bolted on the engine with a smaller valve. Pontiac guys have seen this for years. Add up the totals...2.30 intake+ 1.88 ex= 4.180. That leaves .070 to divide 3 ways between the two valves and on either side of them to the wall. That ain't much! Now, understand that the big block cants it's valves and tilts them on their axis to gain more clearance from the wall, so you actually have more than this but you see the issue. Now stick the same head on a 4.500 bore and bingo there is .320 to divide between them all. Much better.
What gears are you willing to run? You need to be thinking 4.56-4.88 final drive ratio to take advantage of this setup. If you aren't able to get it into that 6500 range as you cross the line the car will be a pig. The rectangular ports will have a hard time gaining rpm against 3.55 gears unless you do install the 6 speed.
Remember Chevy did lots of things to crutch the big heads for the street. Very wide LSA on relatively mild cams was the biggest. When you change these things the character of the engine changes drastically too.
My 427 peaked HP at 5850 but still managed low 11's all day long. And that's with ported oval ports. The rpm range you're talking about shoud get you deep into the 10's with a 454 if you're willing to build the car around it. But be aware that at the rpms you're talking about, street manners are tough to get with the equipment required to make power at that rpm. You can easily run 10's with an iron head oval port 454 if you want to without twisting it so high and busting stuff.
Either way, plan on some pocket porting work on those iron heads. They are great raw material but need some serious hand finishing inside. Don't just bolt them on out of thebox. You'll be leaving lots of power on the table.
jim
[Modified by 427Hotrod, 1:11 PM 11/24/2001]