4.5 Pocket Porting
08-23-2019, 09:40 PM
#1
Rennlist Member
Thread Starter
4.5 Pocket Porting
I know that this subject has probably been beaten to death, but have any of you all tried any basic porting on a 4.5 or 4.7 US head such as some basic pocket porting and gasket matching? I hear that the valve pocket is the best place to pick up some easy hp. I still have a rebuilt 4.5 on the engine stand ( bought it assembled) , but have an itch to unbolt the heads and have a look at the intake and exhaust pockets and runners to see if any easy hp can be made with some basic cleanup. A bit nervous about running a die grinder in the pockets for fear of scratching the new valve job, though. I'm trying to think of some way to protect the valve seats in the process.
I'm not interesting on making the ports bigger, I just want to clean them up so that I can maintain as much port velocity as possible. I had a complete 4.7 Euro top end that I considered bolting on the 4.5 (recently sold these parts) , but I think this would have make the 4.5 run worse, not better, on a street car. From what I have read, 4.7 Euro motors already have a very generous intake valves and runners, almost too big for a 4.7 liter. They would probably work even better on a 5 liter (via a hybrid), but that's just my opinion. I would think that bolting 4.7 Euro heads and intake on a 4.5 might make make it soggy at lower RPM due to a loss in port velocity.
I've been learning as much as I can about head porting, since I made the mistake of "hogging out" heads before as a teenager. It's easy to think that "bigger is always better" when you don't know any better. ( I still don't know crap, but I'm getting there..LOL). From what I can see, the more port velocity one can maintain, the better the low end torque. I never realized that a motor can actually loose hp by bolting on heads that flow too much CFM (too big of runners and intake valves) for the CID of the motor.
I have another 4.7 Euro motor, but I want to leave that engine be; leave it complete. I wanted to do the same with the 4.5, just swap in some 4.7 Euro cams (got them), maybe do some work to the 4.5 heads, like I said, then port match them, bolt on the good S3 exhaust manifolds (got them), bolt on dual Euro exhaust (got it) and let her rip.
I'm not interesting on making the ports bigger, I just want to clean them up so that I can maintain as much port velocity as possible. I had a complete 4.7 Euro top end that I considered bolting on the 4.5 (recently sold these parts) , but I think this would have make the 4.5 run worse, not better, on a street car. From what I have read, 4.7 Euro motors already have a very generous intake valves and runners, almost too big for a 4.7 liter. They would probably work even better on a 5 liter (via a hybrid), but that's just my opinion. I would think that bolting 4.7 Euro heads and intake on a 4.5 might make make it soggy at lower RPM due to a loss in port velocity.
I've been learning as much as I can about head porting, since I made the mistake of "hogging out" heads before as a teenager. It's easy to think that "bigger is always better" when you don't know any better. ( I still don't know crap, but I'm getting there..LOL). From what I can see, the more port velocity one can maintain, the better the low end torque. I never realized that a motor can actually loose hp by bolting on heads that flow too much CFM (too big of runners and intake valves) for the CID of the motor.
I have another 4.7 Euro motor, but I want to leave that engine be; leave it complete. I wanted to do the same with the 4.5, just swap in some 4.7 Euro cams (got them), maybe do some work to the 4.5 heads, like I said, then port match them, bolt on the good S3 exhaust manifolds (got them), bolt on dual Euro exhaust (got it) and let her rip.
08-23-2019, 10:16 PM
#2
08-24-2019, 04:42 AM
#4
Rennlist Member
Better gains can be made by unshrouding the valves in the combustion chamber or even going for a full bowl blend.
I had the bowls blended in my 4.5 engine to fit on a 5.0 better (95mm machined to 100mm) I also had the ports gasket matched.
I also had larger valves installed from a 951 and kept the ports smaller in the head to induce a venturi effect and aid in low end torque because of the increased port velocity at lower RPMs.
Just keep in mind that all 16V intake gaskets are sized for the larger euro runners and you will cause turbulence if you gasket match the head without a euro S intake.
You could get around this by machining the intake as well.
When you machine the heads you should really just be smoothing out the bores and removing casting irregularities and seams to make the flow more linear. Just make sure you don't polish the intake ports.
I had the bowls blended in my 4.5 engine to fit on a 5.0 better (95mm machined to 100mm) I also had the ports gasket matched.
I also had larger valves installed from a 951 and kept the ports smaller in the head to induce a venturi effect and aid in low end torque because of the increased port velocity at lower RPMs.
Just keep in mind that all 16V intake gaskets are sized for the larger euro runners and you will cause turbulence if you gasket match the head without a euro S intake.
You could get around this by machining the intake as well.
When you machine the heads you should really just be smoothing out the bores and removing casting irregularities and seams to make the flow more linear. Just make sure you don't polish the intake ports.
08-24-2019, 11:29 PM
#5
Better gains can be made by unshrouding the valves in the combustion chamber or even going for a full bowl blend.
I had the bowls blended in my 4.5 engine to fit on a 5.0 better (95mm machined to 100mm) I also had the ports gasket matched.
I also had larger valves installed from a 951 and kept the ports smaller in the head to induce a venturi effect and aid in low end torque because of the increased port velocity at lower RPMs.
Just keep in mind that all 16V intake gaskets are sized for the larger euro runners and you will cause turbulence if you gasket match the head without a euro S intake.
You could get around this by machining the intake as well.
When you machine the heads you should really just be smoothing out the bores and removing casting irregularities and seams to make the flow more linear. Just make sure you don't polish the intake ports.
I had the bowls blended in my 4.5 engine to fit on a 5.0 better (95mm machined to 100mm) I also had the ports gasket matched.
I also had larger valves installed from a 951 and kept the ports smaller in the head to induce a venturi effect and aid in low end torque because of the increased port velocity at lower RPMs.
Just keep in mind that all 16V intake gaskets are sized for the larger euro runners and you will cause turbulence if you gasket match the head without a euro S intake.
You could get around this by machining the intake as well.
When you machine the heads you should really just be smoothing out the bores and removing casting irregularities and seams to make the flow more linear. Just make sure you don't polish the intake ports.
08-27-2019, 01:15 AM
#7
Rennlist Member
Thread Starter
Thanks Blake. I had a Euro S intake but I sold it on eBay a few months ago. The buyer had a ported 4.7 US car and wanted to bolt it on. What I was thinking is to just match the intake ports on the 4.5 heads with the stock 4.5 intake the best that I can, and either make new gaskets that actually fit the size of the ports (they are just paper, afterall, correct?). This would work wouldn't it?
One concern that I would have is that bolting on a 4.7 Euro S intake on a 4.5 US motor would reduce port velocity at low RPM. One would almost need to put the motor on a dyno to find out for sure. Plus, the intake ports on the Euros are so much larger than the 4.5 US ports that I would think that you'd have to to hog the intake ports in the head to make them fit the Euro intake.
What I do like about the 4.5 versus the Euro 4.7 is that the compression is lower in the 4.5 I would think that one could run 87 octane in a 4.5 motor, versus a 10:1 Euro motor which surely prefers 91 to 93 octane. With the lower compression one can run more valve timing. I have a Ford 351W is 10:5 :1 compression with aluminum heads. I could never get this motor to stop rattling from detonation short of putting a lopey cam in it. Sure, I could retard the timing, but that kind of defeats the purpose of having higher compression. Having to always run the expensive fuel gets old fast. I don't know how the 928 guys with a 4.5 liter run superchargers on them without race fuel. Check out this BOOST Compression Ratio tool - https://www.rbracing-rsr.com/compression.htm A motor with 8.5:1 static compression running just 5 lbs of boost at zero altitude (basically at the coastline) goes from 8.5 to 11.39:1! How do you 928 blower guys do this on pump gas? Anyhow, I am getting off topic here. Thanks!
One concern that I would have is that bolting on a 4.7 Euro S intake on a 4.5 US motor would reduce port velocity at low RPM. One would almost need to put the motor on a dyno to find out for sure. Plus, the intake ports on the Euros are so much larger than the 4.5 US ports that I would think that you'd have to to hog the intake ports in the head to make them fit the Euro intake.
What I do like about the 4.5 versus the Euro 4.7 is that the compression is lower in the 4.5 I would think that one could run 87 octane in a 4.5 motor, versus a 10:1 Euro motor which surely prefers 91 to 93 octane. With the lower compression one can run more valve timing. I have a Ford 351W is 10:5 :1 compression with aluminum heads. I could never get this motor to stop rattling from detonation short of putting a lopey cam in it. Sure, I could retard the timing, but that kind of defeats the purpose of having higher compression. Having to always run the expensive fuel gets old fast. I don't know how the 928 guys with a 4.5 liter run superchargers on them without race fuel. Check out this BOOST Compression Ratio tool - https://www.rbracing-rsr.com/compression.htm A motor with 8.5:1 static compression running just 5 lbs of boost at zero altitude (basically at the coastline) goes from 8.5 to 11.39:1! How do you 928 blower guys do this on pump gas? Anyhow, I am getting off topic here. Thanks!
Trending Topics
08-27-2019, 04:42 AM
#8
Rennlist Member
Join Date: Feb 2011
Location: Mostly in my workshop located in Sweden.
Posts: 2,226
Received 442 Likes
on
244 Posts
The 928S where S stands for "sport" has 25% more power than the tired 4,5 L. That is a huge difference.
The 4,7 L intake port with the larger 45 mm intake valve flows quite well, it is not easy to improve upon.
Åke
08-27-2019, 01:07 PM
#9
Rennlist Member
Thread Starter
Nice build!! Also, I agree, the S motor is more powerful. I have one of those, too, in an 84 Euro. I'm just trying to see what upgrades I can make to a 4.5 I bought from a guy that is completely rebuilt for my 79. I think 300hp is doable with just a little work. Fill the tank with cheaper 87 and run the **** out of it. 91 or 93 is fine if your not going to drive the car a lot, but take it on a nice long trip for a few thousand miles and pumping in high test really starts to suck.The guy I bought the 79 from took it once on a 10K mile trip. I'd like to do something like that....