Flow Figures For Gurney-Weslake

Colin Artus · 01-28-05, 01:11 PM

Cfm @28 in.

lift in ex
400 217.9 145
450 231 154.6
500 243.5 161.6
550 252.9 165.3
600 262.8 167.8
650 266.3 167.3
700 263.7

Swirl was only fair but did improve quite rapidly beyond .400 lift.
In theory this flow capacity would support about 550 bhp. The head was not modified/ported beyond manifold matching.
Valve sizes were 2.01/1.6.

Ron Earp · 01-28-05, 01:52 PM

Interesting, not as much flow as a good aftermarket head. But, that is to be expected given all the input into recent designs and that this one is quite old, so, for the time really good. Attached are SB flow numbers for an AFR 225 style head - I'd say the today's comparison for a hot street/race head.

Ron

Cushmancompetition · 01-29-05, 12:28 AM

How many people are running these AFR heads with a 4.125 bore or a 17" extension? Most people dont realize these flow ratings mean very little in the real world. A stock 351c 4v head will flow big numbers and make very little real world HP. Air flow has to be balnced with air speed or velocity to give a real idea as to how much power a head will make over a broad power band. There are alot of better heads out there today than a Gurney-Weslake but most are of the Yates type. With the verticle intake runner these heads have a very high velocity rate which makes alot of power over a broad range. After all they did finish 2nd at Indy 2 years in a row and win Lemans and even a Can Am race. No doubt we have very good stuff available today and plenty of options for everybody.

Brian Kissel · 01-29-05, 05:00 AM

There are several 4.125 bore blocks out there from Ford Motorsports and Dart. And I believe they are talking a " inch and seven eights " exhaust header for flow purposes. I have used AFR's on my CHEVY's with great results. I have used the smaller runners in heavier cars and the bigger ones in light cars and am very pleased with the results.
Regards Brian

Ron Earp · 01-29-05, 08:43 AM

I'll be running 4.125" here in a few months, with AFR heads. I know that the bench numbers don't translate into instant hp or real world results, but, we're comparing two sets of bench numbers here as far as I know and although conditions are slightly different you can get a ballpark idea. As you mentioned, there are a lot better heads out there these days than the Gurney-Weslake heads.

Gary Gibbs · 01-29-05, 10:28 AM

The head comparison ran over a series of articles in Mustle Mustangs and Fast Fords address flow numbers and HP figures for a range of heads. The AFR heads do fairly well against the comp. I do have a set of AFR 225's running on a 4.125 bore Dart block. See my site for info.

RRD · 01-30-05, 12:44 PM

yes, they are old, and yes once again, they did have quality problems with the castings. nonetheless, they can be ported to support a very strong 350" engine. more than that, and they are restrictive compared with newer heads. like most ford heads, they have too much dog leg on the exhaust side; that port, were it 1/2" higher, would be greatly improved. another issue is valve lift. anything over .500, and you'll have to shim up the rocker stands. i recently had a fully ported set get new walves, guides, springs, retainers, etc. i'll see if my head guy saved the flow figures. if so, i'll post them.

Colin Artus · 01-30-05, 02:51 PM

I've got a .600 lift cam with mine and didn't find any problems with valvegear geometry although I would suggest that over the period these heads were made there were quite a few design changes.

Colin Artus

RRD · 02-08-05, 12:26 AM

Colin, sorry on the .500 reference; it is .600. You are correct. I'm trying to locate the flow numbers on my MKIV GW's. If they are found, I'll post them for grins.
rd

RRD · 02-14-05, 01:24 AM

g/w heads went back to stallion racing for new valvegear, will be reflowed for cam fit. will post when i get the numbers.

RRD · 02-23-05, 01:06 AM

my mk iv's are now getting new titanium valves and will be reflowed to fit the right cam. i'll post results, good bad or ugly.
rd

RRD · 03-05-05, 04:35 PM

Gurney Weslake flow @ 28"

Lift Int Exh
.300 167.6 119
.350 186.3 133
.400 219 147
.450 234 157
.500 243.5 168
.550 253 174
.600 267 174

so, here are real numbers from "old style" Mondello port job on a set of G/E MK IV heads. My cyl head guy is going to epoxy in about 30% of the intake runners to increase velocity, that will give much better throtle response and some more power as air will have more momentum moving into chambers on intake stroke.

Colin Artus · 04-13-05, 11:15 AM

Has anybody tried modelling these heads(or any others for that matter) in a software simulation? DynoSim for example?

Colin Artus

jimbo · 10-01-05, 10:08 PM

I think this is fascinating...if you think about how old GW heads are, the flow specs are pretty impressive. And they did make enough power to win a lot of races, if I am not mistaken. So they were the hot setup back then. It took quite a few years to really improve on them. It is too bad they are so rare, they would cost less if they weren't so hard to come by.
Harry Weslake worked on a lot of other engines and is one of the great engineers of that generation. Does anyone know if he is still with us? I have no idea.
How usable GW heads are on the street is an open question. Heads that were not street-usable back then may behave a lot better on an engine with a modern engine management system that can compensate for some of the problems with low flow rates at low revs etc. I am glad someone is trying this stuff- wish I could afford to.

Ron Earp · 10-07-05, 08:49 PM

They are decent on the intake side, but like the majority of performance heads back then for Fords, they are weak on the exhaust side of things. Ford heads are sensitive to exhaust help and if you concentrate work only on exhaust ports in bad heads, like the modern E7 type castings from 85-95 big gains can be had. And they only flowed 30-50 cfm less than the GW heads as cast. I'd think the GW heads could seriously benefit from increased exhaust flow.

They'll certainly be very usable on the street given the fact that the current crop of ally heads for Fords will outflow them and are used on the street all the time.

R

Mike · 10-11-05, 01:36 PM

Ron, I have TFS heads that flow similar numbers. With a relatively mild street cam, I recently pulled 350 hp/350 ft. lbs on a Dynojet. How does this compare to the 'average' STREET GT-40? Just curious what the 'norm' is out there in GT-40 land.
Thanks, Mike