516 heads-porting/unshrouding valves

[PRHeads]

This is a 346 head, but will give you an idea......
If you do more than this for a mild small cam build, you’re probably wasting time and wearing out tools for no gain.

Stock pinch = .975”
Reworked pinch = 1.060”
The pinch work was a 7cfm gain.
(My recollection is that the 516 head has a wider pinch area than the later heads)
With a back cut OE 2.08” valve the port in the pics flowed:
237@.400/251@.500/260@.600

For comparison, a gently used 452 head(factory valve and valve job) flowed:
206@.400/222@.500/225@.600



For another comparison....... the big valve 906’s I had on my old 448, that made 535hp and ran low 11’s....... that I ported before I had a flow bench, and just used some guidance from a guy who did porting for a shop I was working at........ the 8 cylinder average(which I determined later on after buying a flow bench) was...... a whopping 239cfm.
I had spent quite a bit of time on those too.

 

[Mark Barnes]

This is a 346 head, but will give you an idea......
If you do more than this for a mild small cam build, you’re probably wasting time and wearing out tools for no gain.

Stock pinch = .975”
Reworked pinch = 1.060”
The pinch work was a 7cfm gain.
(My recollection is that the 516 head has a wider pinch area than the later heads)
With a back cut OE 2.08” valve the port in the pics flowed:
237@.400/251@.500/260@.600

For comparison, a gently used 452 head(factory valve and valve job) flowed:
206@.400/222@.500/225@.600

View attachment 934831 View attachment 934832 View attachment 934833 View attachment 934838

For another comparison....... the big valve 906’s I had on my old 448, that made 535hp and ran low 11’s....... that I ported before I had a flow bench, and just used some guidance from a guy who did porting for a shop I was working at........ the 8 cylinder average(which I determined later on after buying a flow bench) was...... a whopping 239cfm.
I had spent quite a bit of time on those too.

How much grinding did you do in those bowls, or is it more polish than grind?

 

[steve340]

Just a bit of trivia about hogging to much out or concentrating solely on flow numbers.
I saw an interview with John Kaase and he commented the heads with the biggest flow numbers did not necessarily make the best power during dyno testing.
It seems counter to most wisdom but if he said it you could bet money he is right.

 

[wyrmrider]

I had a whole pallet of 526 and earlier heads walk off with some scrap guy. about a half were the ones with no stands that I was hoarding for the retro crowd
no max wedge but some were 300's
Not only will they not make the most hp they will be even worse on most torque

 

[69Bee]

Any pics that show what you did UNDER the valves?

Sorry, it took a while to locate some. I take a lot of pics for my business facebook page. Usually you deshroud valves because you are installing larger valves in, and as you surmised, I open up the throat also.

 

[PRHeads]

How much grinding did you do in those bowls, or is it more polish than grind?

Uuuumm....... you don’t gain 35cfm from a little bit of polishing.
The polishing is worth next to nothing.

It mostly just makes the pics look nicer.

 

[Mark Barnes]

Uuuumm....... you don’t gain 35cfm from a little bit of polishing.
The polishing is worth next to nothing.

It mostly just makes the pics look nicer.
That's why I asked. Because you can't tell from the pics how much work was actually done. Maybe someone can, but I can't.

View attachment 935091

 

[zyzzyx]

69Bee's pic's look like he bored the diameter all the way down until the tool hit the bottom???????
Kind of a super sharp turn there! PRHeads pc looks much nicer for flow.

 

[Dodge Bros]

If the machine shop did a cut like 69 bee to open up the bowl for the large valves you may just be able to smooth out the cut into the ports and have some respectable gains.

If the shop just did an angle from the seat you have more work that needs to be done in the bowl to find any flow. With the cam your running there is no reason to get carried away porting.

 

[Mark Barnes]

If the machine shop did a cut like 69 bee to open up the bowl for the large valves you may just be able to smooth out the cut into the ports and have some respectable gains.

If the shop just did an angle from the seat you have more work that needs to be done in the bowl to find any flow. With the cam your running there is no reason to get carried away porting.

Ok. So what type of cam WOULD require more porting? I have no problem changing cams and porting....

 

[69Bee]

If the machine shop did a cut like 69 bee to open up the bowl for the large valves you may just be able to smooth out the cut into the ports and have some respectable gains.

If the shop just did an angle from the seat you have more work that needs to be done in the bowl to find any flow. With the cam your running there is no reason to get carried away porting.

I always blend the bottom to remove the ramp at the bottom. I also don't usually go this far down, I think this was the first one after getting the bit.

 

[PRHeads]

The bottom line is, you’re not going to learn how to port heads from a thread on the Internet.
These types of threads are really only useful if someone already has some previous experience grinding on heads.

Something like a BB Mopar 516 used in a mild street application doesn’t need a bunch of porting to get satisfactory results.
Just blend away the sharp edges and abrupt transitions.

If you really just don’t know where to begin.......I’d suggest buying one of the porting books by Vizard.
Those are pretty straight forward and will give a novice some useful straightforward guidance.

It’s also important to keep in mind that the best heads in the world won’t fix a poor combination........ but a good combination can run really well even with fairly modest heads...... if those heads are factored into the final plan.

As an example, on a flat top, zero deck, properly machined 440 short block with a hot cam, good intake manifold, appropriately sized headers and a good carb........ mildly reworked 516’s with 2.14 intake valves....... you could very easily make over 450hp(even more if a big enough cam were used).
And that would be with heads that only had a few hours of porting done to them(4-5hrs for the pair).

A combo like:
Comp XE285HL/Howard’s 721201-08/Voodoo 704/MP 484 or 509, RPM or SD intake, Brawler 850 carb, 1-7/8” headers, zero deck, heads milled to 82-ish cc, ported to flow in the 250@.500 range.

 

[IQ52]

Dwayne is so correct. Here are some dyno runs switching from stock 906 heads to some mildly ported 516's. See posts #43 & 44 for the cylinder head swap results including the airflows for the ported 516 heads.The final compression ratio in these tests was below 8:1.

https://www.forabodiesonly.com/mopar/threads/dyno-testing-a-stock-1972-440.249866/page-2

Also because I don't try to teach porting I refer others to this set of articles now posted online about porting big block Mopar iron heads. It's a place to start for free.

https://www.hotrod.com/articles/cylinder-heads/

https://www.hotrod.com/articles/cylinder-heads-ii/

https://www.hotrod.com/articles/cylinder-heads-iii/

We have used our ported 906 heads to achieve over 700 HP normally aspirated on 91 octane pump gas.

 

[Mark Barnes]

IQ, PR, Dodge Bros and anyone else that responded with info-
Thank you all so much. I had (some) head work done previously, and you all have provided the missing pieces that I need to move forward. My goal is to wring out as much HP/TQ as I can from the parts that are currently in my possession, and add as much power as I can with additional bolt on components, until my wallet gives out (no doubt sooner than later). Wanna give my son something to smile about after I'm gone. Believe me, I'll be asking LOTS more dumb questions....

 

[BSB67]

I'm not a head porter, and don't own a flow bench. But I've been around it for a long time and here is a key observation.

Before you spend time grinding, have a plan to make sure you'll have a good set of head with quality work from the machine shop. I mean new valves, back cut, new guides, a real competition valve grind with narrow seats and maybe a 30° seat angle. Good work and good parts are not cheap. This will do more for performance than amature porting on marginal heads.

 

[Dodge Bros]

As far a what head flow and cam is appropriate. We set goals based on the entire combo. Start with the head flow you have. I will use my 516s as an example. 240 cfm at .500”

superflow hp equation
.26 x #cylinder x cfm= appr 500hp

a lofty goal on a 240 cfm headed street engine, do able though.

next find max rpm for your street engine
Hyd cam use 100% eff as a goal

Roller cam w/wider LSA, solid flat tappets with narrow LSAs. 110%

Roller /narrow LSA use 116%

http://www.wallaceracing.com/max-rpm.php

100% eff, 394 cid, 240 cfm= max rpm 6350

Pick a cam that has the lift and duration , with engine components that will make it to 6350 rpm. That would take at least a Lunati 276 or 284 to hit the rpm. Still won’t hit 500 hp. That would take a bigger cam yet.

From there we use the cam and cams intensity to find SCR, DCR and V/P index.

There is more than one way to build power. You can build a lot of power with a small cam with lots of lift and area under the curve, like a hyd roller cam that has a lot of lift. The lift can tend to move the power to lower rpms and make more average power. But you have to manage the compression or you will be mixing race gas in the tank. Or you can go the other way and with a less aggressive cam and increase the compression. Which is closer describes the hft cam with 10scr in a 383 with 516 heads.

If your goal is say 400 hp. Work backwards with that calculator and find what the head flow and max rpm would be. Then pick your components accordingly. Depending on your goals, you may not need any head work.

Our 70 Cuda went 11.60s with stock 906 heads. The 240 cfm 516s I have would have ran at least that in that car with the same set up.

 

[RemCharger]

We have used our ported 906 heads to achieve over 700 HP normally aspirated on 91 octane pump gas.

Thats what I enjoy hearing! 440 inch or bigger? Im working on 440 MW Chrysler project.

 

[PRHeads]

For mild street builds I approach it differently than Dodge Bros.

I look at the overall combination that will be used in the “car”.
If it’s a heavy vehicle that will be running tall gearing, low stall speed, exhaust manifolds, a/c, etc...... then it doesn’t matter that you have great heads that need a lot of lift and long duration to take full advantage of the heads.
Trying to maximize engine output will just result in a car that’s a dud to drive...... even if it does make nice power at 6300rpm.

Honestly assess how the vehicle will be used, what gears you can live with, how much stall you can tolerate, etc....... then select an appropriate cam to suit those needs.
Then you can evaluate how much porting is necessary to make good use of that cam.

If it’s a “race car”, it’s actually a much simpler process.
Get the heads to work as well as practical....... then the formulas come into play with where the power will peak, how much power, etc..... then you get a cam to work within that rpm range, and then gears & converter to keep the motor in the sweet spot.

 

[Mark Barnes]

As far a what head flow and cam is appropriate. We set goals based on the entire combo. Start with the head flow you have. I will use my 516s as an example. 240 cfm at .500”

superflow hp equation
.26 x #cylinder x cfm= appr 500hp

a lofty goal on a 240 cfm headed street engine, do able though.

next find max rpm for your street engine
Hyd cam use 100% eff as a goal

Roller cam w/wider LSA, solid flat tappets with narrow LSAs. 110%

Roller /narrow LSA use 116%

http://www.wallaceracing.com/max-rpm.php

100% eff, 394 cid, 240 cfm= max rpm 6350

Pick a cam that has the lift and duration , with engine components that will make it to 6350 rpm. That would take at least a Lunati 276 or 284 to hit the rpm. Still won’t hit 500 hp. That would take a bigger cam yet.

From there we use the cam and cams intensity to find SCR, DCR and V/P index.

There is more than one way to build power. You can build a lot of power with a small cam with lots of lift and area under the curve, like a hyd roller cam that has a lot of lift. The lift can tend to move the power to lower rpms and make more average power. But you have to manage the compression or you will be mixing race gas in the tank. Or you can go the other way and with a less aggressive cam and increase the compression. Which is closer describes the hft cam with 10scr in a 383 with 516 heads.

If your goal is say 400 hp. Work backwards with that calculator and find what the head flow and max rpm would be. Then pick your components accordingly. Depending on your goals, you may not need any head work.

Our 70 Cuda went 11.60s with stock 906 heads. The 240 cfm 516s I have would have ran at least that in that car with the same set up.

This is exactly the kind of response I was looking for. A basic guideline to get me on the ballpark. I can handle the work part. Practical experience with Mopars is where I come up short. Thanks!

 

[Mark Barnes]

For mild street builds I approach it differently than Dodge Bros.

I look at the overall combination that will be used in the “car”.
If it’s a heavy vehicle that will be running tall gearing, low stall speed, exhaust manifolds, a/c, etc...... then it doesn’t matter that you have great heads that need a lot of lift and long duration to take full advantage of the heads.
Trying to maximize engine output will just result in a car that’s a dud to drive...... even if it does make nice power at 6300rpm.

Honestly assess how the vehicle will be used, what gears you can live with, how much stall you can tolerate, etc....... then select an appropriate cam to suit those needs.
Then you can evaluate how much porting is necessary to make good use of that cam.

If it’s a “race car”, it’s actually a much simpler process.
Get the heads to work as well as practical....... then the formulas come into play with where the power will peak, how much power, etc..... then you get a cam to work within that rpm range, and then gears & converter to keep the motor in the sweet spot.

"Heads to work as well as practical". All I ever wanted.