Are My Heads Holding Me Back???

[ghittner]

I have a set of oval port World Casting steel heads on my blown 489. I am Running a B&M 420 w/ 8 Pds boost and dual 750's Here are the head specs.
[ MERLIN OVAL PORT ]
Cast Iron Big Block Chevy Heads
Merlin 269cc Oval Port heads are excellent for most street-driven big blocks up to 468 c.i.d. They'll out-perform larger heads in many applications because the intake runners have a very high velocity, and the stock 2.190" diameter sized valves have been replaced with 2.300" diameter valves to also improve flow. It's the best of both worlds. True D-shaped exhaust ports help expedite the flow of spent gasses, which also contributes to improved performance. We used these heads on World's own “Daily Driver and Cruiser ”engines because of their excellent low and mid-range torque output. Merlin Oval Port heads are great for towing applications, and have a strong following in the marine market.
030040-2 Solid/Hydraulic Roller Iron Head Oval 269cc Manley Race Master 1.550"Dual150#Seat .650" 119cc
Here is my Hydraulic roller cam
Advertised Duration IN/EX: 304/309
Duration @.050 IN/EX: 245/250
Gross Valve Lift IN/EX: .612"/.612"
Lobe Sep Angle / Intake Ctr Line: 112/110
Valve Lash IN/EX: Hyd/Hyd
RPM Range: 3500-6500
Are my heads holding me back or can I still achieve more power with a few more pounds of boost? Say 10-12?
Thanks.....

[IMPATIENT 1]

there comes a point when a head will only flow so much no matter how much boost you throw at it.i'd say its time to step up to some dart pro1's 325cc heads or possibly 345cc heads. time for bigger heads and little bit bigger cam;) i'm building a blown bbc 475 and i'm runnin 320cc protopline's and a 652 lift blower solid roller cam, blower set to 8-8 1/2 lbs.good luck

[ghittner]

What if I were to change to these World heads? What do you guys think?
Cast Iron Big Block Chevy Heads
When larger displacement engines (468 and up) require additional flow, choose Merlin Rectangular Port cylinder heads. With RightCast® 320cc and 345cc intake runners, you can expect solid gains in air/fuel mixture combustion charges. These heads will really respond to higher compression ratios, and are ideally suited for hot street/strip cars. The larger heads with 345cc intake ports are used successfully on Merlin crate motors with up to 632 cubic inches displacement and can support 760 HP in box stock model!
030630-3 Solid/Hydraulic Roller Iron Head Rect 345cc Manley Severe Duty 1.550"Dual225#Seat .700" 119cc

[Daytona100]

Are you running a bravo 1. What ratio drive and what pitch prop are you running? How fast were you running? Just curious im putting together a similar setup. Thanks Mike:D

[ghittner]

24' Arriva 4500-5000 Pds or so Bravo 1 1.5:1, original Owner, 13 years old, no repairs. 26 prop now at 71 MPH going to a 28 or 30 will get 75 + when I'm done. Now, about these heads????

[VDRIVERACING]

You'll need a new manifold to match the square ports. I almost bought those heads; they would defintely flow more than the ones you have now. I ended up with the RHS heads because they were less expensive and comparable potential. My builder was quite impressed with their out of the box finish.
If you get those heads, try a .650ish lift, 112 centerline range cam.
That said, it seems like a lot of expense and trouble for 4 mph...

[ghittner]

I almost bought those heads; they would defintely flow more. I ended up with the RHS heads because they were less expensive and comparable. My builder was quite impressed with the out of the box finish.
If you get those heads, try a .650ish lift, 112 centerline range cam. Oh, and you'll need a new manifold to match the square ports.
This is what I'm looking for, where did you get them? How much? What HP are you trying to reach?

[VDRIVERACING]

This is what I'm looking for, where did you get them? How much? What HP are you trying to reach?
I bought them direct from RHS. Just check out their website and call them. I think they are about $600 each bare for the iron version. I have a 468 and dynoed over 800HP(the exact number is a closly guarded secret so I don't get intimidated) at 6500 RPM. A couple of guys that build GN race motors said they needed no intake work at all, and there was little they would change on the exhaust side. I didn't have any porting done.
You can spend as much as you want on heads, but I think these are the best value going and are well suited for blower motors.

[TIMINATOR]

The exhaust port is weak on your heads, especially with a blower. The RHS heads have a very good exhaust port. You don't want the large intake ports either, the 312s are fine. Note that the heads all use the same exhaust port. Port there first. TIMINATOR

[WannabeRacing]

Tim is the man. He is right on the mark.
I would stay far away from large cc intake runners with that cubic inch and probable RPM range. They sound cool when talking to everyone on the boards, but will not perform with a smaller well designed runner for your combination. The RHS/Pro Topline heads are very clean from the factory. Very little clean up work needed, lots of meat if porting is desired. There are other heads that come out of that same foundry. But a good, inexpensive, durable head all the way around.
The smaller Merlin rectangle ports are good too. They had a few problems with them five years ago, but not heard bad stuff from then. Again, another durable head.
And like Tim stated, you have a blower. That overcomes intake deficiency. But that air has gotta get out, so working on the exhaust side will give you extra "woomph", and future potential.

[VDRIVERACING]

[QUOTE=ghittner;2556956]I have a set of oval port World Casting steel heads on my blown 489. I am Running a B&M 420 w/ 8 Pds boost and dual 750's Here are the head specs.
While I think about it, ditch the 750's and go for some dominators. Blowers really like those. With regard to the advice on smaller intake runners, I'm sure they mean well...
Consider this: as long as your have positive pressure--boost--in the intake manifold, the induction system is restricting the air flow.

[MACHINEHEAD]

Built a 548 with 269 oval Merlins for a good customer of mine, because thats what he had. Didnt want to use them but we did anyway. 234/242 @.050 Crane hyd. roller, 8-71, Chiller, 8.2 comp ratio, Eddie manifolds, 2x750 and a rectangle manifold and just over 6lbs of boost. Almost 810 HP at 5600. Who would have though. Crazy in a open bow Cole 21 with Imco drive swingin' a lab 32.

[YeLLowBoaT]

i'd buy a intercooler, before I swaped out the heads... its the cheapest hp you will ever buy

[DMOORE]

i'd buy a intercooler, before I swaped out the heads... its the cheapest hp you will ever buy
+1....
I'm running a 420 with a chiller at 10psi, on 91 octane. No problems at all. An intercooler on a boat, just makes too much sense.
Darrell.

[rat tuned]

on a 454" 6 or 8-71 blown pump gas motor at what point should you absolutely step up to square port heads? 5k rpm 5.5k rpm or 6K rpm? if a guy has the merlin oval ports or even 049-781 castings with 2.19-1.88 valves with bowl work how much of a jump would you see with 990's or any decent aftermarket square port head. i'm just curious thanx mike

[ghittner]

i'd buy a intercooler, before I swaped out the heads... its the cheapest hp you will ever buy
No room :o(

[MACHINEHEAD]

Rat Tuned, if this helps. Almost same combo as above but 516 inches 6-71 800 carbs 830 horse with all else the same but with Edelbrock rectangles at 7.8 to 1.