beheaded 540

[mrgoslow]

had a question posed to me today and didnt have a good answer. what are the downfalls of running large oval port heads with big valves and all the good work using a bench on a n/a 540, 9.5-1 that will never see more than 6k in a jet? are there tremendous gains at that rpm with 310 ish alum heads? any input would be nice.
thanx.

[UBFJ #454]

310 ish Heads aren't Big Heads ... Actually, they're kinda small these days. Big Heads flow something like 500+ nowadays.

[mrgoslow]

correct, but i guess i wasnt clear. at that rpm (less than 6K) will there be a significant gain between fully massaged large oval (781) w/ big valves and an aftermarket aluminum head in the 310cc range on a 540 ci n/a engine. anyone have any dyno experience which would be relevant?

[UBFJ #454]

To me 310 heads seem a bit small for a NA 540 cid motor, especially at the rpms you say you want to limit it to ... gonna take quite a cam for enough to get into & fill 540 cubes. If you were going to be running even a small blower with mild boost, the 310's might make you happy, but, NA'd ... ??????
If you were building a high compression, NA'd 454 cid with 2, say 750's worked out to maybe 800+, you should be able to get somewhere in the vicinity of 650 Hp with not too radical a cam at the rpms your talking about using the 310's.

[TIMINATOR]

I would use the 310s, the ovals are fine for a 454 at that rpm, but the 540 would like the 310s. I run a 572 at 5800 rpm(rollered,loooong rods,single dominator), and have tried the Canfield 360s,ported Canfield 310s,AFR 335s, and Dart(YUCCCHHH!!!). AFR 335s are IT (for the 572 anyway). JMO, but I HAVE tried it. TIMINATOR

[DeputyDawg]

I'll second the AFR 335s. I have them on my 540! I don't think the 781s would work very well on a 540 even with the 6k rpm limit.

[steelcomp]

For any na motor the key is port velocity, and a good general rule of thumb is the smaller the port giving the best flow no's is going to have the highest velocity. You'll always want to choose the head with the smallest port that will give you the flow numbers you need. You can do a little of your own homework here and check the "selecting the camshaft" thread that Chris Straub has posted, and find what kind of flow you need for your motor at your desired rpm. The Can 310 isa a strong flowing head, and flows better across the board than most 320's and many in the 345 range. Once you choose a head, tyake the time to choose the right cam for your application. It'll give you the most bang for your buck if you're stepping up to aluminum heads. :coffeycup

[steve d]

For any na motor the key is port velocity, and a good general rule of thumb is the smaller the port giving the best flow no's is going to have the highest velocity. You'll always want to choose the head with the smallest port that will give you the flow numbers you need. You can do a little of your own homework here and check the "selecting the camshaft" thread that Chris Straub has posted, and find what kind of flow you need for your motor at your desired rpm. The Can 310 isa a strong flowing head, and flows better across the board than most 320's and many in the 345 range. Once you choose a head, tyake the time to choose the right cam for your application. It'll give you the most bang for your buck if you're stepping up to aluminum heads. :coffeycup
With these larger cubes and na with more velocity, will you gain in lower end torque and less top end?-----Steve

[Liberator TJ1984]

310 ish Heads aren't Big Heads ... Actually, they're kinda small these days. Big Heads flow something like 500+ nowadays.
Scott , what are ya diggin' at ???
my 320's out of the box flowed 403 int and something like 311 on ex.
I'll be in this weekend and got flowbench sheets at home if ya need to look at them.....
thinkin' of goin to different heads???
Gopher
What #'s did Randy pull on your heads since we are talking the same flowbench :confused:

[BrendellaJet]

Im using Canfield cnc 335 on my 540. Should run about 6200 rpm on a B impeller. Hoping for 800 hp. Big mechanical roller cam with jesel shaft rockers and 11.?? compression.

[DEL51]

Bear is not that far off on his assessment. I agree with the 310 canfields. To port out a set of iron oval chevs or merlins, "both" with bigger valves would take alot of labor, produce better flow and beat the square ports up to a point, depending on rpm and cubic inch.You need a dedicated man who is willing to grind on a steel head to make it worth it. Then talk about weight factor.Maybe a set of the Edelbrock semi square port heads would work.Remember, upgrades are easier with square ports.Good Luck,DEL

[mrgoslow]

thanks for all the replys. steelcomp touched on what was steering me toward the ovals. velocity. i guess i have to figure on what i'd like to spend. and now to the "selecting the camshaft" thread.

[steelcomp]

Don't compare the oval port GM's to the Merlin ovals. The Merlin ovals will out-flow GM rect. port 990's, but they also are a LARGER port than the GM oval port. Apples and oranges. You won't be able to port a set of GM oval port heads to run good with a 540 at 6000 rpm. You could have a real snappy 540 with the Merlin ovals, but it would probably run out of breath at 6K, unless you cammed the snot out of it, but then your power would most likely be above 6K. I'm betting the Canfield 310's are going to be a good choice for this motor. Too much flow and you're not opening the valve enough to get any port velocity (with a properly matched cam). With heads, bigger is definately not always better.
Something to remember. Cyl head mfgr's are trying to build heads that they can sell to a LOT of people, which means they are building heads, trying to cover a wide range of applications. Even with the different selections of port sizes that we have today, production heads are still going to be a compromise at best. There's a lot more to a port than just size and flow numbers. Runner shape, port contour, cross-sectional area, where the largest cross section is located, all are critical factors in a port's design, and each engine will require different things in all these areas. For one head to be optimal for many engines is really impossible. But they're getting MUCH better.
If you're really serious about getting the best performance from your hard earned $, then take the time to do your homework, like mrgoslow. :wink:

[mrgoslow]

steel, every seen/heard good results out of running an oval T/R on rectangle heads to increase velocity

[steelcomp]

steel, every seen/heard good results out of running an oval T/R on rectangle heads to increase velocity
With the GM heads on a Jet, small cubes (454 range) it's not a bad isea. Never seen the results, but I'd bet it would be an improvement. If your set up is right, and you need the rect ports, then you most likely need the rect port manifiol, but if you're trying to crutch a too-big port, I think it's a good idea, especially on a Jet where your rpm's are going to stay low.

[blowngas]

Mr Goslow, I've used to run one on my old lake motor with dolled up oval ports----would turn 7200 rpms----you are welcome to try it if you go the oval port route----would be interested on how it would stack up against kenneths dart manifold setup

[steelcomp]

Mr Goslow, I've used to run one on my old lake motor with dolled up oval ports----would turn 7200 rpms----you are welcome to try it if you go the oval port route----would be interested on how it would stack up against kenneths dart manifold setup
Was that a jet or v-drive?? How big was the motor? With that rpm I'm thinkin v-drive, which isn't really a fair comparison. Jets don't have the luxury of gearing for rpm, but that still sounds like a good running oval port motor!

[GofastRacer]

With the GM heads on a Jet, small cubes (454 range) it's not a bad isea. Never seen the results, but I'd bet it would be an improvement. If your set up is right, and you need the rect ports, then you most likely need the rect port manifiol, but if you're trying to crutch a too-big port, I think it's a good idea, especially on a Jet where your rpm's are going to stay low.
That's nothing new, back in the 80's one of the big name outfits used to make an oval port manifold to use with the square port heads, be damned if I can remember who it was though, I'll have to look thru some old catalogs, maybe I can find something on it, or somebody on here ought to remember that!..

[steelcomp]

That's nothing new, back in the 80's one of the big name outfits used to make an oval port manifold to use with the square port heads, be damned if I can remember who it was though, I'll have to look thru some old catalogs, maybe I can find something on it, or somebody on here ought to remember that!..
I know Edelbrock was (still is, maybe) making a "Street TR" that was oval port. I see the small block one in Summit and Jegs, but not the BB one. Now THAT would be a good jet tr.

[wet77]

I am going to run some 325 dart pro1's heads on my 540 victor jr intake and 850 single carb .
Running aggressor B cut bronze impeller with inducer.
Will let you guess know what the #'s are after the dyno run and later in the boat for rpm..
Boats a 21' daytona

[blowngas]

I know Edelbrock was (still is, maybe) making a "Street TR" that was oval port.
that's the one I have and yes it was in a flatbottom---was pulling 15 over gears with a small prop---would rpm like crazy, but only run 78 mph---most everyone would hand me my butt----then went blown, and now its the other way around!!

[mrgoslow]

wet, now im more curious how you like the b in that 21 ftr. as for heads, probably going with canfiled cnc'd 310's.