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Discussion Starter #1
My build is as follows
A460 block @ 4.440"
Scat 4.5" forged crank
Scat 6.8" h beam rods
Probe dish pistons 12.2 to 1 compression - I thought!!!!!!!!!!!!!!!
Blue Thunder B cylinder heads [chebby exh] unported 65cc I thought!!!!!
Victor with a 1000 cfm 4150 holley
camshaft is a Chet Herbert grind .715/.716, 271/280 @ 0.050" 109 lobe center
Jomar Girdle
Wider cam bearing [Randy Malik]
MSD ignition c/w crank trigger

So of to the dyno I go.
It made 726 hp and 720 ft/lb which I was reasonably happy with. But we had a problem
with one chamber that had been repaired from my last blow up, the seat kept moving
around where it was welded and couldn't get it to stay sealed.

I asked a few questions on the forum and got a few replys with sugestions and
help.(thanks guys)
One of the people who offered help was uncle Charlie.
Once I was pissed off enough with my **** heap I decided it was time to replace
the cylinder heads.

I contacted Charlie and after a bit of deliberation we decided on P-51's.
Charlie got the heads from Lem with all the hard ware I needed and ported the heads
and even put hardened washers in the heads so as I could use my existing heads studs.
The heads flowed as follows

Intake
.100=72.9, .200=168.5, .300=261.6, .400=343.9, .500=390. .600=406.3. .700=408.3, .750=410, .800=41.1cfm
exhaust
.100=56.9, .200=109.6, .300=155.1, .400=187.8, .500=207.5, .600=235.1, .700=251.1, .800=258.1 cfm

So I received the heads and was impressed. I measured the BT chambers and they weren't what I thought they were. They were 70cc. So I had the p-51's machined to 65cc so as my compression was were I wanted it(12.2to1)

Other than new pipes because the exh flange being different and 5cc in the chamber, of coarse I had to re-cut valve reliefs, nothing else changed.
Back to the dyno and what a difference.

836 hp and 770 ft/lbs. 116 hp gain!!!!!!!!!
The car weighs about 2400#, I haven't had a chance to weigh it since I changed from a d1ve block to the A460. The best it went was 9 flat on a bad track.

First pass with the new combo off the trailer 8.60 @ 157 mph.
Very happy. I got to say special thanks to Charlie and Lem. They are stand up guys.
I'm here in Australia and I can just email/pm Lem or Charlie and some times I get stuff quicker than ordering it here in oz. And always ready to answer questions. Thanks again guys.

So the only thing I'm still thinking about is how much I'm still leaving on the table using a 4150 style holley instead of a 4500 style.

Cheers Colin
 

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Do the 4500 style, talk to Lem or Charlie about a Quick Fuel setup. I think you will be pleased over the 4150 style.
Nice numbers, by the way.
 

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Colin,

Thanks for posting your results. I'm pleased that you are pleased.

Guys,

I've known about Colin's new engine for a couple of months now and have encouraged him to post a thread about it. I appreciate him doing so. Let me add that in the beginning Colin was pretty head strong about just getting a new set of Blue Thunder heads with the Chevy port. I have ported and flowed several sets of the B.T.s in the past. I called a couple of different B.T. dealers and tried to get Colin a set. I was told that B.T. was out of them and that it would be at least 6 months and probally longer before they would make any more of those heads. So at that point we started looking at other options and I suggested to Colin the P-51 heads. I was pretty sure that they would make more horsepower, due to their better mid-lift flow numbers on the intakes. Remember now, the B.T. exhaust flows really good with that raised port Chevy bolt pattern, so we were taking a hit there, with the switch to the P-51 heads.

Long story short, Colin trusted me and a new set of ported P-51 heads was on it's way across the big pond. Colin still has some Hp left on the table; a bigger cam, and a bigger carb would surely help, along with more compression. But the point is, he gained 110 Hp and 50 lbs.ft. of torque with this head swap. In addition to dyno results, his e.t. slip shows a 4 tenths reduction on the first pass afterwards. I was really impressed and the Sunday morning after breakfast at the Winter Tech Seminar, I was pleased to tell Jon Kaase about it.

Colin, we're proud of you and happy for you! I hope you win a bunch of races this year!!! Now then, hows about a nice picture of your car posted in this thread??

Take care,
 

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.

836 hp and 770 ft/lbs. 116 hp gain!!!!!!!!!

So the only thing I'm still thinking about is how much I'm still leaving on the table using a 4150 style holley instead of a 4500 style.

Cheers Colin
Nice numbers, are you still using the Herbert cam ?

4150 vs 4500 what rpm are you reving it to? If it's 6,500-6,750 I'd say your leaving 25-35 hp on the table vs a 1,050 dommie . Just a WAG. ;)
It would be interesting to see what type of vac numbers you're pulling on the top end.

G-Code
 

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Improvement

My build is as follows
A460 block @ 4.440"
Scat 4.5" forged crank
Scat 6.8" h beam rods
Probe dish pistons 12.2 to 1 compression - I thought!!!!!!!!!!!!!!!
Blue Thunder B cylinder heads [chebby exh] unported 65cc I thought!!!!!
Victor with a 1000 cfm 4150 holley
camshaft is a Chet Herbert grind .715/.716, 271/280 @ 0.050" 109 lobe center
Jomar Girdle
Wider cam bearing [Randy Malik]
MSD ignition c/w crank trigger

So of to the dyno I go.
It made 726 hp and 720 ft/lb which I was reasonably happy with. But we had a problem
with one chamber that had been repaired from my last blow up, the seat kept moving
around where it was welded and couldn't get it to stay sealed.

I asked a few questions on the forum and got a few replys with sugestions and
help.(thanks guys)
One of the people who offered help was uncle Charlie.
Once I was pissed off enough with my **** heap I decided it was time to replace
the cylinder heads.

I contacted Charlie and after a bit of deliberation we decided on P-51's.
Charlie got the heads from Lem with all the hard ware I needed and ported the heads
and even put hardened washers in the heads so as I could use my existing heads studs.
The heads flowed as follows

Intake
.100=72.9, .200=168.5, .300=261.6, .400=343.9, .500=390. .600=406.3. .700=408.3, .750=410, .800=41.1cfm
exhaust
.100=56.9, .200=109.6, .300=155.1, .400=187.8, .500=207.5, .600=235.1, .700=251.1, .800=258.1 cfm

So I received the heads and was impressed. I measured the BT chambers and they weren't what I thought they were. They were 70cc. So I had the p-51's machined to 65cc so as my compression was were I wanted it(12.2to1)

Other than new pipes because the exh flange being different and 5cc in the chamber, of coarse I had to re-cut valve reliefs, nothing else changed.
Back to the dyno and what a difference.

836 hp and 770 ft/lbs. 116 hp gain!!!!!!!!!
The car weighs about 2400#, I haven't had a chance to weigh it since I changed from a d1ve block to the A460. The best it went was 9 flat on a bad track.

First pass with the new combo off the trailer 8.60 @ 157 mph.
Very happy. I got to say special thanks to Charlie and Lem. They are stand up guys.
I'm here in Australia and I can just email/pm Lem or Charlie and some times I get stuff quicker than ordering it here in oz. And always ready to answer questions. Thanks again guys.

So the only thing I'm still thinking about is how much I'm still leaving on the table using a 4150 style holley instead of a 4500 style.

Cheers Colin
Colin,
Real nice improvement. What are the flow numbers on your old unported Blue Thunder B heads? Did you upgrade the camshaft and try a Dommy?
Gary,
 

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Real nice Colin . When I switched to the 4500 from the 4150 on my 466 I picked up a tenth of et. I was surprised to say the least. I am sure your combo would need more carb.

I would like to try a set of p-51's someday after running Charlie's 533 with the scj's I was really impressed . I ran beside a light weight tube chassis probe at the nmra race last year at Bowling Green during time trials. We both ran a 5.26 1/8 mile , he was running a 572 with A - heads though . I could not believe an oem head would even hang with a- heads much less run beside them.

If you put Kaase , Charlie , and Lems heads together you have a recipe for horspower no doubt !
 

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Just to bring everything into focus.............

My build is as follows
A460 block @ 4.440"
Scat 4.5" forged crank
Scat 6.8" h beam rods
Probe dish pistons 12.2 to 1 compression - I thought!!!!!!!!!!!!!!!
Blue Thunder B cylinder heads [chebby exh] unported 65cc I thought!!!!!
Victor with a 1000 cfm 4150 holley
camshaft is a Chet Herbert grind .715/.716, 271/280 @ 0.050" 109 lobe center
Jomar Girdle
Wider cam bearing [Randy Malik]
MSD ignition c/w crank trigger

So of to the dyno I go.
It made 726 hp and 720 ft/lb which I was reasonably happy with. But we had a problem
with one chamber that had been repaired from my last blow up, the seat kept moving
around where it was welded and couldn't get it to stay sealed.

I asked a few questions on the forum and got a few replys with sugestions and
help.(thanks guys)
One of the people who offered help was uncle Charlie.
Once I was pissed off enough with my **** heap I decided it was time to replace
the cylinder heads.

I contacted Charlie and after a bit of deliberation we decided on P-51's.
Charlie got the heads from Lem with all the hard ware I needed and ported the heads
and even put hardened washers in the heads so as I could use my existing heads studs.
The heads flowed as follows

Intake
.100=72.9, .200=168.5, .300=261.6, .400=343.9, .500=390. .600=406.3. .700=408.3, .750=410, .800=41.1cfm
exhaust
.100=56.9, .200=109.6, .300=155.1, .400=187.8, .500=207.5, .600=235.1, .700=251.1, .800=258.1 cfm

So I received the heads and was impressed. I measured the BT chambers and they weren't what I thought they were. They were 70cc. So I had the p-51's machined to 65cc so as my compression was were I wanted it(12.2to1)

Other than new pipes because the exh flange being different and 5cc in the chamber, of coarse I had to re-cut valve reliefs, nothing else changed.
Back to the dyno and what a difference.

836 hp and 770 ft/lbs. 116 hp gain!!!!!!!!!
The car weighs about 2400#, I haven't had a chance to weigh it since I changed from a d1ve block to the A460. The best it went was 9 flat on a bad track.

First pass with the new combo off the trailer 8.60 @ 157 mph.
Very happy. I got to say special thanks to Charlie and Lem. They are stand up guys.
I'm here in Australia and I can just email/pm Lem or Charlie and some times I get stuff quicker than ordering it here in oz. And always ready to answer questions. Thanks again guys.

So the only thing I'm still thinking about is how much I'm still leaving on the table using a 4150 style holley instead of a 4500 style.

Cheers Colin
So basically, you went from a stock set of BT Heads to a set of ported P-51 Heads and raised your compression a couple points. That netted you 100+ hp. That's very good, and is to be EXPECTED.

A set of BT 'B' Heads will flow almost identical flow on the Intake port(405-410 @ .800"), with SUPERIOR flow(55-60 cfm+ for around 315 cfm) on the Exhaust. Along with the compression increase, I'm sure the power increase would have been the same, or BETTER. Re-flycutting the Pistons(which lowered your potential compression gain), would not have been necessary unless a Cam change would have required it.

BT 'B' Heads are in stock currently, and are available both as stock, or fully ported pieces.

JMO. RR
 

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Very interesting read there.

Is this a pump fuel engine? I too am in Australia and plan on running about 12.9:1 on my new engine. It seems Australian and American fuels differ significantly. I have read on this very forum that even 12:1 is considered too much for American pump fuel but many alloy headed combos here run more compression than that.

If you were able to keep the seat in place, would you have persisted with the Blue Thunders? I will be running the BT B's that went 409 @ 800 which I am very pleased with. I can't seem to find many blokes running these heads.

Can anyone suggest what sort of power this engine would make with a sheet metal intake and a pair of 4150's? It is basically what I intend on running.

Is it fair to assume the BT B's are a better shape and outflow the P51's on the exhaust? Can someone provide some info on this?

What car is it going into?

Race ya later.
 

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Very interesting read there.



I will be running the BT B's that went 409 @ 800 which I am very pleased with. I can't seem to find many blokes running these heads.

Is it fair to assume the BT B's are a better shape and outflow the P51's on the exhaust? Can someone provide some info on this?
Here is my experience after 4 years running the same basic combination with BT 'B's, and doing MANY sets of these heads for customers.

"A set of BT 'B' Heads will flow almost identical flow on the Intake port(405-410 @ .800"), with SUPERIOR flow(55-60 cfm+ for around 315 cfm) on the Exhaust."

That is what we routinely get out of them. By the way, I use a welded Weiand TR with 2-1,000 cfm Holley HP's and Shear Plates on mine. Don't think a Sheetmetal Intake is required for 410 cfm and 850 hp. Money is better spent elsewhere. JMO

RR
 

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Here is my experience after 4 years running the same basic combination with BT 'B's, and doing MANY sets of these heads for customers.

"A set of BT 'B' Heads will flow almost identical flow on the Intake port(405-410 @ .800"), with SUPERIOR flow(55-60 cfm+ for around 315 cfm) on the Exhaust."

That is what we routinely get out of them. By the way, I use a welded Weiand TR with 2-1,000 cfm Holley HP's and Shear Plates on mine. Don't think a Sheetmetal Intake is required for 410 cfm and 850 hp. Money is better spent elsewhere. JMO

RR
How much does the exhaust port affect horsepower?
 

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Not as much as the Intake does, but my current engine puts out 840 hp @ 6800 rpm. Oh, and it's 514 cubic inches, not 557. It's the ratio between Intake and Exhaust I look at, among several other things. On the P-51's mentioned that would be 63%(411 In x 258 Ex). A typical BT 'B' would be >75%(405 In x 312 Ex). Any Head that is over 70% is good, and 75% is certainly VERY GOOD. These BT's typically attain 77%-78% when ported properly.

Don't want to participate in a pissing match. I just want to point out that comparing ported Heads to unported Heads and their effect on power production isn't like comparing apples to apples. Hope this info is of use.

RR
 

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I don't have a dog in this, but after reading all of this post it looks to me, that all that has taken place is someone changed heads and gave us all a lot of good info, that was well documented. I didn't see it as comparing two heads.

I say this taking a chance Mr. J.S. may call me a Charlie Evan's *** kisser , but I could give a **** less.

R.R.

Two points of compression does not come from 5 cc's less combustion chamber volume, and when you take out the 2 cc's for the new valve reliefs it's only 3 cc's which , if my math is right is only 4 tenths of one point of compression.

Give the man a pat on the back and dispense with the drama, or do a back to back dyno test and then give us the numbers.

This is just my two cents and no way reflects the thoughts of Charlie Evans. Nor were there any *** kissing going on. Don't want anyone jumping to wrong conclusions .
 

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I don't have a dog in this, but after reading all of this post it looks to me, that all that has taken place is someone changed heads and gave us all a lot of good info, that was well documented. I didn't see it as comparing two heads.

I say this taking a chance Mr. J.S. may call me a Charlie Evan's *** kisser , but I could give a **** less.

R.R.

Two points of compression does not come from 5 cc's less combustion chamber volume, and when you take out the 2 cc's for the new valve reliefs it's only 3 cc's which , if my math is right is only 4 tenths of one point of compression.

Give the man a pat on the back and dispense with the drama, or do a back to back dyno test and then give us the numbers.

This is just my two cents and no way reflects the thoughts of Charlie Evans. Nor were there any *** kissing going on. Don't want anyone jumping to wrong conclusions .


Well, first of all the BT's are sold as 78cc Heads. I'm sure we can all do that math as compared to 65 cc's.

Second, I didn't mention ANY NAMES at all. Just wanted to point out that what happened WASN'T A MIRACLE.

RR
 

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Well, first of all the BT's are sold as 78cc Heads. I'm sure we can all do that math as compared to 65 cc's.

Second, I didn't mention ANY NAMES at all. Just wanted to point out that what happened WASN'T A MIRACLE.

RR
We all know what they are sold as , he said in his post he thought they were 65 but turned out to be 70 cc .

I don't think anybody thought it was a miracle, what is was, is what it was, just facts .


Thank you Colin............
 

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Discussion Starter #19
A bit more info. When I first contacted Charlie I wanted to just replace my BT heads with a new set, which Charlie was HAPPY TO DO. Mine were the first series so I was going to have to replace both. I wanted to stay with them because it was a fresh build, I had replaced everything, the only thing I saved from the previous blow up was the head castings, sump, cam and manifold. This was about May last year. Charlie rang around ( I think he spoke to Barry R)and couldn't get any heads and they couldn't give a availiability.
So that is why I went with P-51's.

Blake you were right, my BT heads were supposed to be machined to 65cc but when I took them off I measured them @ 70cc. So I had the P-51's machined to 65cc.
I have no flow # for the BT's. But as I said "they were unported out off the box."

A couple more things I found on the dyno, the engine liked 33° timing and we also found it liked spacers under the carby. We first had a 2" then we put a 1" as well and it liked that.
We didn't keep trying more spacers because I can only use 1 spacer on the car so it would have been pointless. I used Shell RF100 which basically avgas.

This thread was just to document my build with some dyno figures and some et slips, not to compare the heads. It would not be a fair comparison.

I'm just luck after all the money I had just spent to re-build after the blow up my wife said to me "buy new heads if that's what it takes to get it fixed."
Between my house and the closest championship track there is only 2 sets of traffic lights, but an 8 hour drive between the lights.(Melbourne to Sydney)

Charlie I will try to get a picture posted.
Busta, I got a almost new stud girdle to suit BT heads if your interested.
 

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The in to Exhaust Ratios are BS, Proper Camshaft timing Pretty Mutch negates it.
 
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