Apples to oranges unless they all compare at the same RPM's.
Is there no way to limit results to 4000 rpm? (or whatever you intend as a shift point)

Yes, I would say you've done a good job.
The real thing to compare is the area 'under the curve' of the actual results, not some computer that is making too many guesses/assumptions.
Driveability is what's important.
A huge dip in the torque curve is a fatal flaw in a DD... especially a tow rig.
Your torque numbers indicate a healthy improvement over stock even though peak torque remains the same.

Have you ever heard the expression "suck it and see"???

I can't limit the output of the dyno programs, nor change the range that CamQuest uses for its average - whatever that is. But, I can change the range I calc the averages since I'm doing that in a spreadsheet. I'll change the range to 2000 - 4000 from the 2000 - 5500 I'm using.

Agree that "area under the curve" is the key, which is why I've been giving averages as they approximate that. But, I'll input the new #'s and provide curves and let you do the integration visually. I get curves out of Desktop Dyno that are very good but can't be easily output to get them here, and the CamQuest charts are laughably small so are almost useless. And, another function of DD I like is the ability to put the output of up to 4 engines on the same chart for comparison.

As for "suck it and see", I do recognize the term awa the meaning. And, I may well do that with these heads. However, the benefits of the GT40's are so tantalizing that I'm holding out hope that someone will offer me a set at a reasonable price. And, the $300 pair may be them although I still have the other leads being run to ground. But, those benefits may not be that obvious to y'all until I get the charts done and posted. Soon!

if your running windows 7, hit start and type in "snipping tool" and you can select a part of the screen, save it as a picture, and upload it to here.

Which is why they are such a popular upgrade. :-X22

I can't imagine what you have into these heads.
Certainly a LOT more than $300 if you're paying yourself $5 an hour (plus burrs & rolls, cobbling together a tool post grinder and flowbench testing...

Pretty sure that I said early in this thread that you couldn't get me to grind on a set of iron heads unless class rules dictated it.

But for you, I'm sure it was for the experience.
It is an intriguing quest, but tough to justify re-inventing the wheel.


Gary,
RELAX.
Enjoy your grandchildren. :)
The heads aren't going to grow up off the bench and start a life of their own.

Muscletruck: I'm running XP on 2 machines & Vista on another, and that's just the Winders machines. Thanks, but I don't really like the way Desktop Dyno presents the info on their charts, so prefer to input the data itself into a spreadsheet and create the charts the way I want them, as below.

Jim: I'd rather not consider how much time I have invested in these heads. But, at $5/hr I should have gotten aftermarket. Fortunately I don't have to pay myself and have enjoyed doing this and consider it a learning experience - and learn I have.

And, as said before, I've learned that you are better off starting with a head that flows decently out of the box than trying to take what is arguably the worst-flowing head Ford made for the small-block and make it flow reasonably.

As for the grandkids, we are leaving Wednesday and won't be back for about a week, and even when we get back I'll have other things between the heads and me. Hopefully I'll have time to read the book on flow awa keep up with responses on FTE.

But, 'tween now and Wed I hope to get a few things documented so I'm ready to work instead of compute when I get back. Toward that end I've put the Desktop Dyno HP and torque #'s into a spreadsheet and created a chart that helps see the "area under the curve". But, you'll notice that info from CamQuest is missing. That's because it doesn't provide power figures at each RPM but just gives peak and average #'s. I can't put that into a chart, and the chart they give is the size of a postage stamp and shows just one engine. So, we'll stick to DD for the chart.

And, before I put the chart in I'd better document all the parameters that begat the #'s:

• 351W with a .030" overbore
• Performer intake on CQ and dual-plane on DD
• 600 CFM 4bbl carb
• Small-tube headers with no cat and muff's
• Comp Cams' XE250H cam
• 8.5:1 compression ratio
• Stock valve sizes in each head

Here's the results, but I should explain that "Hybrid" means stock D8OE intake and my ported exhaust - just an attempt to figure out whether it is the intake or exhaust porting that helped:
EDIT: Chart deleted as it was incorrect. See later post.

As you see, DD says the GT40's and Thumper's heads outclass my heads by quite a bit, and the 40's beat Thumper's down low where it really counts. Having said that, CamQuest gives different #'s in some cases, so it would be appropriate to document that. The biggest difference is in the output using Thumper's heads, with CQ showing 303 HP at 5000, but DD showing 279 at 4500. I do know that CQ has a pick for a Performer intake, but DD only has one dual-plane intake choice. Perhaps the better intake allows the engine to take advantage of the better flow. Dunno. Anyway, the table follows and I'll stop typing here and call it a night. But, your comments will be appreciated.
EDIT: Chart deleted as it was incorrect. See later post.

Try bumping the CR to 9--9.25:1, see where that puts you.

You didn't lose anything to the stock heads, and it seems you have a solid 10 to 40 more horse from 3500 up.
Hard to understand why CQ puts the averages so close together.

Jim - Bumping the CR was my next step, and boy am I glad I did as I discovered an error - the GT40 run on DD had been done at 9.18:1 CR while all the others were at 8.5. And, that explains why the 40's came so close to Thumper's on DD but not CQ, as I had the CR at 8.5 in CQ.

But, I've now realized, I can't use the same CR for all of the heads, as I have been doing, as the combustion chamber sizes vary. For instance, the D8OE's have 69 cc chambers, the E7TE's and early GT40's have 61.5 cc chambers, but the later GT40's have 64.5 cc chambers.

Using DD's CR calculator with the pistons zero-decked, a .039" head gasket, and 12 cc valve relief, the compression ratios are:

• D8OE: 9.2
• Late GT40's: 9.6
• Thumper's & early GT40's: 9.9

Given all that, I've deleted the two charts from my previous post. I'll have to re-run, populate the spreadsheet, regenerate the charts, etc. I hope to get that done later today and then will post the results. Sorry for the confusion, but I don't want mis-information to be on our forum, especially with regards to Thumper's heads that he is selling.

I'm thinking 10:1 is a little too much on pump gas.
Question zero decking the GT40's...


Sorry for the short reply, from my phone at lunch...

I'm with you on the 10:1. I'm not comfortable with more than 9.5:1, and kinda like the 9.2 the D8OE's would give.

Which raises the question of quench vs CR. Is it better to go with the .039" quench area and 9.2 CR, or .059" quench area and 9.5:1 using early GT40 heads? IOW, to get to 9.5:1 using early GT40 heads with 61.5 cc chambers it takes dropping the piston .020" below the deck but still using a .039" gasket and 12 cc valve relief.

The reason I ask is that I'm not knowledgeable on the benefits of quench. I understand what it does, but not how much it does, maybe I should say. But, I can see the benefits of CR from the dyno program #'s for HP and TQ, and don't know how to compare.

Maybe when I rerun the #'s I should limit the CR on the GT40's and Thumper's to 9.5:1 since that's all I'd like to run, and that'll give us a much more realistic comparison. But, I'll document that doing so gives up .020" quench which, btw, is exactly the difference in the two sets of pistons I have.

Thoughts???

.059" is not quench.
.040 and under is where it's at.

The .020" of your other pistons would probably get them close to 0 deck without cutting the block.
That's the point.

Look back to what Stangrcr1 said about "you have more to gain from compression even if you have to retard the timing"
(to a point...)

If the pistons you have put your quench too tight for operating clearance you could always run a thicker head gasket. (and reduce the CR as well)
But then you have to pay attention to pushrod length and other variables too.

Just mocked-up the engine and it looks like I'll need to deck the block:

• Driver's side: #5 is down .045" & #8 is down .047"
• Passenger's side: #1 is down .033" & #4 is down .035"

If I were to run the lower pistons I'd have an 8.5:1 CR, and the .020" higher pistons would give 8.8. Obviously neither is what I'm looking for as the CR is too low and there's no quench.

But, the plot thickens as my machinist doesn't deck blocks - doesn't have the equipment with which to do it. So, I'll have to call around Tulsa to find someone that does and what the price is.

And now, back to the charts and tables. I believe I have them corrected and have added some info. What follows is a "printout" of two tables - the first has all CR's at 8.5:1 while the 2nd varies the CR's to what I believe they would be if I built the engine with that head, as follows:

• Stock and hybrid would be 8.5:1 as I wouldn't bother to deck the block
• Ported is my D8OE's and with the work I have in them will probably zero-deck the block, giving 9.18:1
• The GT40's & Thumpers are calculated at 9.5:1. If the heads were the later model GT40's with 64.5 cc chambers the CR would be 9.6, but if they were the small chamber 40's or Thumpers, all of which have 61.5 cc chambers, the CR would be 9.9:1 if zero-decked, and that's too much. So, I wouldn't even deck the block but would just install the taller pistons giving a deck-height of -.020ish, which gives 9.5:1. However, that would kill the quench.

So, here's the table printout:
https://www.ford-trucks.com/forums/p...ictureid=82873

Here's the chart with all CR's at 8.5:1 in order to allow comparison of the effect of the head's flow:
https://www.ford-trucks.com/forums/p...ictureid=82874

And here's the chart with how I think I would build the engine with each head:
https://www.ford-trucks.com/forums/p...ictureid=82875

With that much difference in heights, I would be measuring stroke, rod lengths, piston top to pin height, bearing thicknesses, everything. There should not be that much difference. I would not run parts with that much difference. It is possible that the block has that much difference, but I would recheck everything.

I also balance to within 1/10th of a gram for all rotating sets(piston/rings/pin/rod/bearing).

The reasoning for this is simple. If everything is the same, the engine will run smoother. A smoother engine looses less power to rotating pumping losses on average and makes more power than an unequal motor.

Any machinist that can bore and hone a block should be able to deck and line hone and more, or I would be looking for someone else. Just my opinion.

Power(hp/tq) is a mind altering dilema. How much is enough?
Dwell on it too much and you loose sight of the original objective.

.012" difference in deck between banks?
Something is definitely up with that.

I've seen them out of line front to back, but never that far out side to side.

I talked with Eric, the engine builder that did the flow work for me. He hasn't seen a block that far out, but he has seen them out almost that much. He gave me the name of the guy that does his machining and thinks I can get the block squared for $90.

Then there's what Stang said so well: "Power(hp/tq) is a mind altering dilema. How much is enough? Dwell on it too much and you loose sight of the original objective." I agree, and there's a plan that is slowing taking shape in my ancient mind. It looks to me like 69 cc's is almost the sweet spot for combustion chamber size since it lets you zero-deck the pistons and, with a .039" headgasket, get a quench area of that size as well as a compression ratio of 9.18:1. And, as luck would have it, D8OE's are said to have 69 cc combustion chambers, although I've as yet not cc'd them.

The larger GT40 heads with their 64.5 cc chambers give 9.61:1, which is high although maybe livable with good quench, but the 61.5 cc'd Thumper and earlier GT40 heads give 9.9:1 and that seems too much. I would have to get lucky and locate a set of the larger GT40's, but only the 96 & 97 Explorers had those so the odds aren't good.

Given that, it looks like I should have the block cut to put the "stolen" pistons as close to zero as reasonably possible. I'll probably put the other 4 pistons in and measure their deck height, but it looks to me like the block is the issue since so far it is fairly consistent side-to-side. That'll give me a good # to tell the shop how far to cut the block. And, if by the time all of that is done I haven't found the needle-in-the-haystack set of GT40's, I'll put my massaged heads on.

However, since I left some of my valves at Eric's and have to go back, I'll probably back-cut a valve or few and have him test my ported head with them. Maybe I can get the best of both worlds - flow at low lift via the back-cut valves and decent flow at high lift as a result of the porting.

How does that sound for a plan, Stan?

Does cutting the block then require cutting the intake? Seems to me the intake would sit a little higher in the valley after a decking cut. Would the bolt holes line up?