Giving new life to GT40X heads

[Carnut1]

So, what do you think is more accurate, smoke on a static flow bench, or a proper CFD model.......?

Warp, who determines a "Proper" cfd model and how is it determined as accurate? Thanks, Charlie

[David Vizard]

So, what do you think is more accurate, smoke on a static flow bench, or a proper CFD model.......?

Warp,

Good question. First I have never had access to CFD programs anything like as powerful as those used in F1. So within the context of what I have had access to I have seen the CFD and the smoke tests show recognizably similar results on most occasions - but not always. When you get a steady state CFD simulation produce different results to a smoke test which do you believe??

Again within the context of what we are doing here the smoke results are as real as they can get. The ~CFD results are only as good as the program produces. They can be wrong under certain circumstances but currently whats in use by top teams is pretty damn good - but I cannot afford such programs. However I can afford 'smoke' and the results I have seen over the years have shown to be totally positive.

As you are most certainly aware one of the big advantages with CFD is we can 'flow' the system with the piston in place. A difficult but not totally impossible thing to do with a real world flow test.

Where as I cannot practically recomend every porter buy a CFD program costing tens of thousands I can usefully suggest they add smoke testing to their test regime.

DV

[David Vizard]

Here is the before and after port energy. As can be seen the port energy is up a decent amount indicating that we have a more functional port velocity/flow combination. From this graph we can expect the heads to perform substantially better than in the stock form.

The next question we can ask ourselves now is how capable are they compared to other heads. This is where we look at the 'specific port energy' of the ports.

Next graph will be just that.
DV

[Carnut1]

David if the 289 heads that I worked up will be dynoed a part of me would love to see the ported heads vs. stocker 289 heads even with upgraded valvetrain. I know it would be costly but would be interesting. Thanks, Charlie

[David Vizard]

Here is the specific port energy of our reworked GT 40 heads. So how does it rate?

From the curves it can be seen that we now have more effective ports. These results indicate we can expect a before and after test to show the modified heads functioning significantly better. I would say the any low speed reduction of torque from the bigger (about 4-5 cc) modified port to be minimal to non-existent while peak torque and hp to go up considerably. My guess is the mods are worth about 25-30 hp minimum on Andy's 393.

As I have said before this test allows us to compare porting results across the board. so how do the modified GT 40 heads stack up?

Unfortunately only fair to middling.

What we are seeing here is less than 20 ft-lbs per square inch of valve per foot length of port. A good record setting PS head will push the curves up close to the top of our chart here.

Now I may hear some comments like 'you can't compare a purpose built ProStock head to a performance head bases on a production based head casting'. Well actually we can. That does not mean we will meet ProStock levels here but it does give a valid target to shoot for. That said the numbers that this graph gives can be very helpful at identifying port sizing/flow situations so as to better refine them.

For more on this go and check my 572 BBC posts.
DV

[David Vizard]

Sorry for the lapse reporting progress here but Andy and I have been up to our ears with flow bench work for my Ford book. Just want to thank Andy for the many hours help here.

The progress on this now multi-faceted project is that we are now decided on a port design for the GT40 /E7TE heads(which Charlie is just finishing up) and the GT40 heads that I am doing. These will be tested on a really low buck 347 with a stock Crown Vic 107 LCA cam courtesy of Dave McLain.

Below is a shot of the GT 40 head that I have almost finished. Note the polished seats. The polished area below has yest to be roughed up to a 40 grit finish.

I will post the finished flow, efficiency,velocity,port energy and specific energy curves soon but, for now, it is worth mentioning that we succeeded in making the 1.94 intake valve appear to the cylinder as a valve of at least 2.05 dia.

DV

[Boz-Race Engines]

Hi DV, i would love to be able to purchase your program, if and when available

[Casper393W]

These heads will make that 347 scream! I can't wait to see them on the dyno....

[Carnut1]

These heads will make that 347 scream! I can't wait to see them on the dyno....

If these are going to go "heads up" against the E7TE 's I am finishing expect a battle! Thanks, Charlie

[Casper393W]

LOL......

[Carnut1]

No shame in losing if you are the underdog!

[Casper393W]

Hey I thought the GT40X's were the underdog.....I am amazed what you pulled from those E7's!

[Walter R. Malik]

Will there be a high ratio, 1.72/1 is pretty common, bolt-down rocker arm be used for these dyno tests ...?

That Particular O.E.M. hydraulic roller camshaft only has .237"/.247" lobe lift and the O.E.M. intake valve lift of .379" won't tell much about any improvements from any upper lift airflow gains. Even .407" valve lift won't be near enough.

That low lobe lift is why that camshaft is such a good candidate for regrinding with its 104/111 center-lines.

There really are no aftermarket cams in the correct range with a tight enough separation but, I have tested a bunch for that type application and a decent running catalog unit is a Lunati #20350712, old #61012.

[David Vizard]

These heads will make that 347 scream! I can't wait to see them on the dyno....

If these are going to go "heads up" against the E7TE 's I am finishing expect a battle! Thanks, Charlie

Charlie,

Having appreciated your head porting skills I would expect nothing less!

[David Vizard]

Will there be a high ratio, 1.72/1 is pretty common, bolt-down rocker arm be used for these dyno tests ...?

That Particular O.E.M. hydraulic roller camshaft only has .237"/.247" lobe lift and the O.E.M. intake valve lift of .379" won't tell much about any improvements from any upper lift airflow gains. Even .407" valve lift won't be near enough.

That low lobe lift is why that camshaft is such a good candidate for regrinding with its 104/111 center-lines.

There really are no aftermarket cams in the correct range with a tight enough separation but, I have tested a bunch for that type application and a decent running catalog unit is a Lunati #20350712, old #61012.

Walter,
AS ever thanks for the useful input. The second round of testing will be with a higher lift valve train so we should cover your suggestions in that respect. As for rockers we will go for the highest we can find stock then aftermarket. The aftermarket ones will be Scorpion.

Thanks
DV