P-51 heads

I just mounted a set with Kaase hardware and it was plug and play. No cutting guides, bending and welding. I didnt even need to push the guides around to get the geometry straight. After the issues with SCJ's this was a surprise.
If this is normal and you are considering SCJ's save yourself the extra four hours altering the guides and just buy the P-51s.

Now we'll see how much it picks up.

Dave De wrote:I just mounted a set with Kaase hardware and it was plug and play. No cutting guides, bending and welding. I didnt even need to push the guides around to get the geometry straight. After the issues with SCJ's this was a surprise.
If this is normal and you are considering SCJ's save yourself the extra four hours altering the guides and just buy the P-51s.

Now we'll see how much it picks up.

So when are you planning on hammering down on the loud pedal, for the comparison?

Should be testing at Milan next Saturday. Im street legal so I   will do a little testing on the street even though its not very good.
Cant go wot on the street.

Nice, My street strip s#{t runs a go cart tire and trying to go WOT with a frosted SB is reminiscent of John F and Tony P for the title, hooks on the track though, we will see when the BBF is installed

Anxious to see how the new P51's work out

That sounds good, I have a set of P-51 heads to install soon, never had any aftermarket heads before these.

you have to flycut the pistons?

8liter wrote:you have to flycut the pistons?

If you are running OEM style pistons the will need a p51 relief cut, if your are buying pistons make sure to get the p51/SCJ reliefs

I'm sure it'll fly. If I remember right, the P-51's came out a week after I bought the SCJ's.........naturally.

Dave De wrote:Should be testing at Milan next Saturday. Im street legal so I   will do a little testing on the street even though its not very good.
Cant go wot on the street.

Bada Bing Bada Boom should fly nice work Dave

Dave are you dragging it to BC then heading out... Should have the old farm truck ready in a few weeks...

I will be loading up after BC and heading to the track.

I finally have a P-51 comparison to my previous SCJ-b heads. It has been a difficult season where the first time out I blew the drive shaft slip yoke and destroyed the tail shaft, bent the main shaft and trashed the case on the C6. In any case the car has picked up less than a 1/10 where it would go 9.32 average to now 9.24 with a best today at 9.20 and 145.6 mph. I might get a few 1/100s with some more tuning. I was thinking there would be more change. The mph only went up 1mph. Shifting at 6300 gives the best et.

Stats
580 cubes, 13.4 comp, 3100 pound car, both heads were ported and the SCJ heads have 2.25 valves.

Im okay with the package because my SCJs will be used on a new 560 motor for my Torino to get it into the tens.

Dave De wrote:I finally have a P-51 comparison to my previous SCJ-b heads. It has been a difficult season where the first time out I blew the drive shaft slip yoke and destroyed the tail shaft, bent the main shaft and trashed the case on the C6. In any case the car has picked up less than a 1/10 where it would go 9.32 average to now 9.24 with a best today at 9.20 and 145.6 mph. I might get a few 1/100s with some more tuning. I was thinking there would be more change. The mph only went up 1mph. Shifting at 6300 gives the best et.

Stats
580 cubes, 13.4 comp, 3100 pound car, both heads were ported and the SCJ heads have 2.25 valves.

Im okay with the package because my SCJs will be used on a new 560 motor for my Torino to get it into the tens.

My neighbor had similar results with this swap.

Dave De wrote:I finally have a P-51 comparison to my previous SCJ-b heads. It has been a difficult season where the first time out I blew the drive shaft slip yoke and destroyed the tail shaft, bent the main shaft and trashed the case on the C6. In any case the car has picked up less than a 1/10 where it would go 9.32 average to now 9.24 with a best today at 9.20 and 145.6 mph. I might get a few 1/100s with some more tuning. I was thinking there would be more change. The mph only went up 1mph. Shifting at 6300 gives the best et.

Stats
580 cubes, 13.4 comp, 3100 pound car, both heads were ported and the SCJ heads have 2.25 valves.

Im okay with the package because my SCJs will be used on a new 560 motor for my Torino to get it into the tens.

both heads ported, to what extent ? what was the flow difference between the 2 heads?

Dave De wrote:I finally have a P-51 comparison to my previous SCJ-b heads. It has been a difficult season where the first time out I blew the drive shaft slip yoke and destroyed the tail shaft, bent the main shaft and trashed the case on the C6. In any case the car has picked up less than a 1/10 where it would go 9.32 average to now 9.24 with a best today at 9.20 and 145.6 mph. I might get a few 1/100s with some more tuning. I was thinking there would be more change. The mph only went up 1mph. Shifting at 6300 gives the best et.

Stats
580 cubes, 13.4 comp, 3100 pound car, both heads were ported and the SCJ heads have 2.25 valves.

Im okay with the package because my SCJs will be used on a new 560 motor for my Torino to get it into the tens.

What this tells me is that there is something else in the package beside the heads which is holding this back.

rmcomprandy wrote:

Dave De wrote:I finally have a P-51 comparison to my previous SCJ-b heads. It has been a difficult season where the first time out I blew the drive shaft slip yoke and destroyed the tail shaft, bent the main shaft and trashed the case on the C6. In any case the car has picked up less than a 1/10 where it would go 9.32 average to now 9.24 with a best today at 9.20 and 145.6 mph. I might get a few 1/100s with some more tuning. I was thinking there would be more change. The mph only went up 1mph. Shifting at 6300 gives the best et.

Stats
580 cubes, 13.4 comp, 3100 pound car, both heads were ported and the SCJ heads have 2.25 valves.

Im okay with the package because my SCJs will be used on a new 560 motor for my Torino to get it into the tens.

What this tells me is that there is something else in the package beside the heads which is holding this back.

Good point.

The SCJs were to flow over 385 and the P-51s have data sheets that show 425. When I first ran the P-51s I used 1.8 rockers and the car slowed down a little or there was no change over the SCJs. I went back to 1.73 rockers and it picked up. This cam is intentionally compromised to be small for reliability. Could my full 4" exhaust with Flowmaster 44s be an issue? The mufflers have the second baffle knocked out.
I thought that with 580 cubes it would pick up more because these heads are ideally suited for less displacement. Then with 10 percent more flow it would like to run higher and it really doesnt. I think that if I were to have dyno'd each setup there wouldnt be much difference in power.

Well at least ive got the SCJs for the other motor now.

Your cam is probably not allowing you the advantage the p-51 head has to offer.

Same

A cam with less duration is required?

I'd ditch the Flowmisers for a "straight through" type...or use no muffler at all.

Dave De wrote:A cam with less duration is required?

Whats in it now? My bet its too small.

richter69 wrote:

Dave De wrote:A cam with less duration is required?

Whats in it now? My bet its too small.

You'd probably lose ... 278/290 @.050"  is not what is holding it back from making power at 6,500 RPM; though something else might be.

mine was a hell of a lot bigger than that.........


...... and there may be other issues


also it aint like he went from a procomp

Interesting comparison. You can compare flow curves, dyno tests etc., but there is nothing like an ET slip to see what if any you have gained or lost.