Talking about heads

hound dog · #1 (**permalink**) 07-09-2003, 06:25 AM

I've seen several threads talking about "what heads to use on my small block 427 stroker" and some of the answers have set me to thinking (dangerous). If we assume that cubic inches are cubic inches regardless of what size block they are in, why does anyone even consider the smaller flowing heads such as the Edelbrock Performer for a 427? And the GT40 heads must be nothing but a waste of money. These heads are made to try to get some torque from the 302-351 engine sizes, certainly not proper for the 427 engine size. A quick look at the AFR website for a comparison of head flow rates for different size engines can be a real eye opener. For instance, the MAXIMUM flow for a small block Ford head (225cc) at .600 valve lift is 315 cfm regardless of cubic inches. They don't have a big block ford head on their sight but the MINIMUM size big block Chevy head has a flow rate of 358 cfm at .600 valve lift. I realize that valve diameter and other factors have an impact on engine performance also but given these numbers it would seem that there aren't any heads made for a small block Ford that will make the most of the 427 cubic inches. I have a 393 in my cobra and I bought the Vic. jr. heads and I'm not sure I have enough yet. Opinions? Is my thinking all screwed up?

h dog

Roscoe · #2 (**permalink**) 07-09-2003, 07:29 AM

Take a look at the AFR 205's

Roscoe

Tony Radford · #3 (**permalink**) 07-09-2003, 07:33 AM

h dog, I've been spending a fair amount of time lately on this issue myself. Go to the fordmuscle.com site. They have an interesting article on a small block Ford head shoot out. As I mentioned on a previous thread, I'm trying to decide as to whether I want to replace my TFS heads or not. I've concluded that my Twisted Wedge Heads are as good as I can get without changing the port profile (racing heads). Are you doing your own engine work? I've got Southern Automotive here in the Atlanta area doing my engine. Bill produces a 427 stroker as a standard product that makes pretty good HP while maintaining good street manners. He does a fair amount of port work on the heads beyond what comes with the head. The two head shoot out articles lead me to believe that the Edelbrock heads don't make the top of the list. I've written them off entirely. Fortunately for me, the Twisted Wedge heads are rated pretty highly. With all the addtional work that SA does to them, they should be OK. My concern at the moment is with my headers. I have the standard 1 1/2" tubes which (according to many opinions) are a bit restrictive for a stroker. Trying to upgrade these are tough and expensive. I'm beginning to believe that it's best not to understand this stuff, just drive the car and get off on the radical (though perhaps not optimum) performance.

hound dog · #4 (**permalink**) 07-09-2003, 08:42 AM

Tony,
Yep, built my own engine about a year ago. Runs great and a lot of torque with the stroker. And it all fits nicely into the Unique (nice choice by the way). Before I built my engine I spent some time in the Dyno 2000 program trying different heads/cams/strokes/etc. I sort of concluded that there wasn't a lot of difference that I would notice between the top heads driving them on the street. I went with the Vic. jr. because I thought they may work and fit better with the Vic. jr. intake that I used. I would do it again. Actually a head similar to the 4V Cleveland with the large valves and high flow might make a better head for the 427 but I don't think anyone makes one like it and I wouldn't try adapting the Cleveland heads to the Windsor although it is done successfully. My point was that there are no small block 427 heads that flow as well as big block 427 heads and is that a problem? Are we leaving something on the table with the 427 small block?

wilf leek · #5 (**permalink**) 07-09-2003, 09:26 AM

One issue worth considering is that rpms are limited by rod ratio considerations on stroker sb's. Certainly, I keep mine down to 6000 max, even though the forged items in the bottom end might take more. (4.03" bore, 4" stroke, 6.2" rods). I specc'd the cam and top end accordingly, no point in having a valve train good for 7500.

Given this, ultimate flow rates may not be such an issue, since only when building a screamer might you actually need the massive flow rates.

The concept of a stroker "Cleveor" is certainly interesting, I wonder if there would be enough cubes to overcome the low rpm issues of the 4V heads?

hound dog · #6 (**permalink**) 07-09-2003, 11:38 AM

Wilf,
From what I can find, the 4V Cleveland heads flow about 273 cfm at .600 lift. It would be easy for someone who knows what they're doing to massage a set of these heads to flow well in excess of 300 cfm at .600 intake lift. They should be easily the equal of aftermarket heads in flow capacity. However, other factors such as chamber design is a whole new subject. Anyone know what the Yates heads flow?
h dog

Roscoe · #7 (**permalink**) 07-09-2003, 11:53 AM

http://www.airflowresearch.com/

hound dog · #8 (**permalink**) 07-10-2003, 08:00 AM

OK, just to stir the pot one more time I have taken the Dyno 2000 data that I have for my 393 using Lunati roller cam, Victor jr. heads and intake and given it a 4.190 stroke to make it a 427.6 cubic inch stroker. These are the numbers I got; max hp 506 @ 5000 and 5500 rpm (slightly less than the 393), and 564 lb/ft torque at 4000 (about 40 more than the 393). Now if I replace the head flow data with the data for the MINIMUM AFR 305 cc chevy head (no BB ford data) I get the following; max hp 583 @ 6000 rpm and max torque 592lb/ft at 4500 rpm. Both of these numbers are significantly increased over the small block heads. Now we all know that such a head design doesn't exist for the small block engine but it does show that existing heads do not supply enough cfm to justify stroking the engine to 427 cu. in. If someone had a nice set of aluminum Cleveland 4V heads that they could have ported, etc. to get the same airflow numbers as big block heads, then I think you could start to justify stroking the small block to 427. Otherwise I'm not sure it's worth the money. And Roscoe, the AFR heads do show an increase in HP over the Victor jr. also.
h dog

scottj · #9 (**permalink**) 07-10-2003, 08:30 AM

The design of the stroked 427W is not suited to high-perf. Long strokes, with their high piston speeds make inefficient use of cylinder head potential. Small bores shroud valves and limit valve size, again limiting cylinder filling potential.

The 427w IS suited for low RPM torque, street-performance, and the available heads are well suited for that.

If you want a High-perf 427 small block you should be looking at a race block with the 4.125 bore. There are a number of small block heads available for those that flow upwards of 400cfm and make well over 800 hp on a 430 small block with a single 4150 Holley.
Scott