This intake port mold really tells the story

[blackford]

How does this mold look (see pics below)? Where do you think his port could be improved?

This is a ported '70 351w head (DOOE). 160cc intake volume. I ported these heads in 2002 and they are on a 331 Ford. I never had them flowed, but with nothing radical, the engine is making peak power of 420 HP @ 6500. Power drops off about 30 HP @ 7000. It runs very well and it really loves to rev. This mold was made from a spare DOOE head that I experiment with. If I ever take my heads off, I would not mind spending a few more hours making some port improvements while i'm at it.

Cam is a Comp 282S with 236@.050 and .528 lift. I have Probe 1.7 shaft rockers so the lift is .560 minus lash. I also have a ported and port matched Victor Jr intake, 750 HP carb, 9.7:1 compression and Dougs tri-y headers.

The min CSA in this port was a few inches into the port. It was about 1.72 sq. in. and is it now 1.92 sq. in.

What I did to the port:

• raise the roof of the intake port about 1/8"

• cleanup the pinch area which opened it up to 2.02 sq. in.

• opened up the bowl to 90% of the intake valve diameter

• widened the runner after the pinch and before the turn about 1/16" per side to 1.92 sq. in.

• layed back the short side radius.

What I noticed from the mold:

• The valve pocket around the guide is deeper on one side than the other. Should I deepen the other side?

• The roof of the runner inlet where I raised it has a bit of a curve to the roof and it could be straightened out. Leave it as is?

• The short side radius looks good. Leave it as is?

• Except for the inlet, the CSA through the port is fairly consistent. It varies from 1.92 to 2.16 sq. in.

• The diameter of the bowl is about 90% of the intake valve. Should I try for 91% or 92%? Its only .015 to .030 more

IMG_20220812_135510509.jpg

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IMG_20220812_141304198.jpg

IMG_20220812_135703749.jpg

IMG_20220812_135544131.jpg

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[Ken_Parkman]

The first comment is be very careful porting on iron heads the second time as you have lost your 'zero' point. Unless you know exactly how much material is there don't do it.

The biggest csa is at the valve area and the csa increases around the bend to the exit. This makes flow separation likely above about .25 l/d as the air has to deal with both an expansion and a bend, and does not have the curtain area pinch to control the separation. The cumulative of this is not great so I would not make the bowl any bigger.

In an ideal world you should make both sides the same, but likely there is water between the intake and exhaust ports there, so that is very dangerous. Making the roof straight would probably be a good thing as it would get some csa. Back to where is the water. You have already done pretty good with a 12% csa increase - there is probably not much wall left.

Back to the first suggestion, sounds like it works pretty good as is. Might be best to leave alone.

[modok]

I'm not a ford head expert.....
but IMO that looks very good as-is.

[blackford]

The first comment is be very careful porting on iron heads the second time as you have lost your 'zero' point. Unless you know exactly how much material is there don't do it.

The biggest csa is at the valve area and the csa increases around the bend to the exit. This makes flow separation likely above about .25 l/d as the air has to deal with both an expansion and a bend, and does not have the curtain area pinch to control the separation. The cumulative of this is not great so I would not make the bowl any bigger.

In an ideal world you should make both sides the same, but likely there is water between the intake and exhaust ports there, so that is very dangerous. Making the roof straight would probably be a good thing as it would get some csa. Back to where is the water. You have already done pretty good with a 12% csa increase - there is probably not much wall left.

Back to the first suggestion, sounds like it works pretty good as is. Might be best to leave alone.

Thanks for the comments. I've considered getting a Sonic Checker to validate the wall thicknesses, but they can be a bit pricey.

[blackford]

I'm not a ford head expert.....
but IMO that looks very good as-is.

Thanks. When I pulled the mold out, my initial thoughts were that overall it looked better than expected.

[blackford]

If I find out that there is enough material for me to widen the middle of the runner .025 per side to get the CSA from 1.92 to 2.0 sq. in., should I do it?

Wallace Racing's CSA calculator says I need a little more sq. in. for a 331 spinning 7000 rpm.

The transitions look good as they are now, and I don't want to create a bulge in the middle of the runner. .025 per side is not much though and it could probably be blended. Thanks

[mag2555]

These heads flow about 180 intake cfm in stock form @.500” lift.

Your making of 420 hp suggest that you now have them flowing 205 cfm@.500” lift .

In terms of doing more porting work I would say it’s safe to assume that you have a total of .150” of wall thickness in stock form assuming rust has taken some toll.

This would make it safe to remove .050” to .060” from any port wall .

I know that on a C6FE head I ported ages ago that I had fitted with a 1.94” valve, went 220 cfm@.500” and 227@.600”, peak flow was 234@.700”.

This was by means of a 1.685” throat/ 87% throat, or plus .080” total, thus I took off about .040” per wall with ruff cuts.

This head could have been enlarged safely I bit more I think, but I don’t know how to relate that to your DOOE casting.

I could go back through my files and look for other dimensions I would have written down for you if you like, as I might still have them.

Just a warning if your working without a sonic tester, that being if you have many hours in these heads and you have Al ready taken off .060” on any port wall that has water on the other side then I would leave the things where you have them now.

Since it sounds like you have a Mule head your working on, then take a reciprocating saw to it and cut it up.

The 2.5 hours of work will give you real good in site as to what you have to work with.

Many general machine shops you might have in your area likely had a big chop saw that can make some starter cuts for you like length wise down the center of a intake and exh port.

This is what I have done.

[steve cowan]

How does this mold look (see pics below)? Where do you think his port could be improved?

This is a ported '70 351w head (DOOE). 160cc intake volume. I ported these heads in 2002 and they are on a 331 Ford. I never had them flowed, but with nothing radical, the engine is making peak power of 420 HP @ 6500. Power drops off about 30 HP @ 7000. It runs very well and it really loves to rev. This mold was made from a spare DOOE head that I experiment with. If I ever take my heads off, I would not mind spending a few more hours making some port improvements while i'm at it.

Cam is a Comp 282S with 236@.050 and .528 lift. I have Probe 1.7 shaft rockers so the lift is .560 minus lash. I also have a ported and port matched Victor Jr intake, 750 HP carb, 9.7:1 compression and Dougs tri-y headers.

The min CSA in this port was a few inches into the port. It was about 1.72 sq. in. and is it now 1.92 sq. in.

What I did to the port:

• raise the roof of the intake port about 1/8"

• cleanup the pinch area which opened it up to 2.02 sq. in.

• opened up the bowl to 90% of the intake valve diameter

• widened the runner after the pinch and before the turn about 1/16" per side to 1.92 sq. in.

• layed back the short side radius.

What I noticed from the mold:

• The valve pocket around the guide is deeper on one side than the other. Should I deepen the other side?

• The roof of the runner inlet where I raised it has a bit of a curve to the roof and it could be straightened out. Leave it as is?

• The short side radius looks good. Leave it as is?

• Except for the inlet, the CSA through the port is fairly consistent. It varies from 1.92 to 2.16 sq. in.

• The diameter of the bowl is about 90% of the intake valve. Should I try for 91% or 92%? Its only .015 to .030 more

IMG_20220812_135510509.jpg
IMG_20220812_135451901.jpg
IMG_20220812_141304198.jpg
IMG_20220812_135703749.jpg
IMG_20220812_135544131.jpg
IMG_20220812_135528600.jpg

Making everything bigger will push peaks up higher in the rpm range.
There will come a point where you would need more lift and duration to help fill the cylinder.
With your manifold porting what size at the opening of the runner.
I understand you are governed by casting thickness in area's, also what size valves ?
Can you run spacer on intake?
Cool little engine for the compression and fun with a stick I bet.

[blackford]

These heads flow about 180 intake cfm in stock form @.500” lift.

Your making of 420 hp suggest that you now have them flowing 205 cfm@.500” lift .

In terms of doing more porting work I would say it’s safe to assume that you have a total of .150” of wall thickness in stock form assuming rust has taken some toll.

This would make it safe to remove .050” to .060” from any port wall .

I know that on a C6FE head I ported ages ago that I had fitted with a 1.94” valve, went 220 cfm@.500” and 227@.600”, peak flow was 234@.700”.

This was by means of a 1.685” throat/ 87% throat, or plus .080” total, thus I took off about .040” per wall with ruff cuts.

This head could have been enlarged safely I bit more I think, but I don’t know how to relate that to your DOOE casting.

I could go back through my files and look for other dimensions I would have written down for you if you like, as I might still have them.

Just a warning if your working without a sonic tester, that being if you have many hours in these heads and you have Al ready taken off .060” on any port wall that has water on the other side then I would leave the things where you have them now.

Since it sounds like you have a Mule head your working on, then take a reciprocating saw to it and cut it up.

The 2.5 hours of work will give you real good in site as to what you have to work with.

Many general machine shops you might have in your area likely had a big chop saw that can make some starter cuts for you like length wise down the center of a intake and exh port.

This is what I have done.

Wouldn't it be better to say that the heads are flowing "at least" 205 cfm to support 420 HP? There are so many more variables such as compression ratio, cam, intake, carb, exhaust port flow, headers.

[blackford]

How does this mold look (see pics below)? Where do you think his port could be improved?

This is a ported '70 351w head (DOOE). 160cc intake volume. I ported these heads in 2002 and they are on a 331 Ford. I never had them flowed, but with nothing radical, the engine is making peak power of 420 HP @ 6500. Power drops off about 30 HP @ 7000. It runs very well and it really loves to rev. This mold was made from a spare DOOE head that I experiment with. If I ever take my heads off, I would not mind spending a few more hours making some port improvements while i'm at it.

Cam is a Comp 282S with 236@.050 and .528 lift. I have Probe 1.7 shaft rockers so the lift is .560 minus lash. I also have a ported and port matched Victor Jr intake, 750 HP carb, 9.7:1 compression and Dougs tri-y headers.

The min CSA in this port was a few inches into the port. It was about 1.72 sq. in. and is it now 1.92 sq. in.

What I did to the port:

• raise the roof of the intake port about 1/8"

• cleanup the pinch area which opened it up to 2.02 sq. in.

• opened up the bowl to 90% of the intake valve diameter

• widened the runner after the pinch and before the turn about 1/16" per side to 1.92 sq. in.

• layed back the short side radius.

What I noticed from the mold:

• The valve pocket around the guide is deeper on one side than the other. Should I deepen the other side?

• The roof of the runner inlet where I raised it has a bit of a curve to the roof and it could be straightened out. Leave it as is?

• The short side radius looks good. Leave it as is?

• Except for the inlet, the CSA through the port is fairly consistent. It varies from 1.92 to 2.16 sq. in.

• The diameter of the bowl is about 90% of the intake valve. Should I try for 91% or 92%? Its only .015 to .030 more

IMG_20220812_135510509.jpg
IMG_20220812_135451901.jpg
IMG_20220812_141304198.jpg
IMG_20220812_135703749.jpg
IMG_20220812_135544131.jpg
IMG_20220812_135528600.jpg

Making everything bigger will push peaks up higher in the rpm range.
There will come a point where you would need more lift and duration to help fill the cylinder.
With your manifold porting what size at the opening of the runner.
I understand you are governed by casting thickness in area's, also what size valves ?
Can you run spacer on intake?
Cool little engine for the compression and fun with a stick I bet.

Manifold opening is port matched and blended and is about the same CSA as the head opening or 2.3 sq. in.
Valves are 1.94 intake and 1.6 exhaust.
I don't have the necessary hood clearance to use any spacer.

Yes, it is a little screamer and loads of fun to drive with the manual trans.

[mag2555]

Another certainty is those headers are a pretty good cork in the overall flow system above 5800.

You might address that first because any more porting work will only increase the cork factor of those!

[blackford]

Another certainty is those headers are a pretty good cork in the overall flow system above 5800.

You might address that first because any more porting work will only increase the cork factor of those!

My poor little Doug's Headers get no love! I went to Dougs (not Doug Thorley) 20 years ago when I first built the engine. They were in Anaheim close to home. I had already ported the heads and the exhaust port outlet was now 1.48 x 1.12. I had them bring out a few different 1-5/8 headers for me to look at...tri-ys and long tube. The only header that had a large enough opening that I could port match to my exhaust port were the Tri-Ys so that's what I got. On the dyno, the engine peaks at 6500 rpm and dips only about 30 HP at 7000. Given this, could the headers be that bad above 5800?

[mag2555]

I don’t hate them as I have used them myself on folks builds.

The fact is that at your rpms even a decent header ( as you stated, tad bigger then your ported exh flange) with a merge type collector will pick you up 12 Hp .

[blackford]

Quote from my original post:

What I noticed from the mold:

The valve pocket around the guide is deeper on one side than the other. Should I deepen the other side?

The roof of the runner inlet where I raised it has a bit of a curve to the roof and it could be straightened out. Leave it as is?

The short side radius looks good. Leave it as is?

Except for the inlet, the CSA through the port is fairly consistent. It varies from 1.92 to 2.16 sq. in.

The diameter of the bowl is about 90% of the intake valve. Should I try for 91% or 92%? Its only .015 to .030 more

I left the valve pocket as-is. I straightened out the roof and lightly touched up the short side radius. I also increased the min CSA from 1.92 to 2.0 sq. in. and opened up the bowl to about 91%.


I took the head in to be flowed on an SF600. The results are fantastic!

Exhaust @28 in
.100 49.5
.200 97.6
.300 132.2
.400 152.9
.500 173.3
.600 179.0

The exhaust had a 1-5/8 test pipe attached to simulate my headers. Exhaust valve is 1.600" dia. Exhaust port volume is 62 cc. Exhaust flow is just about what i've seen from other ported DOOE heads.

Intake @28 in
.100 60.4
.200 119.7
.300 177.2
.400 214.5
.500 240.9
.600 243.5

Intake port volume is 162 cc. Intake valve is 1.940" dia. Based on what i've seen, most ported DOOE heads flow around 220-225 cfm. The highest i've ever seen was 252 cfm (I got 249 cfm @ .8 lift...does that count?). I can't believe I got over 240 cfm out of the intake port at .500!

The shop said that my intake/exhaust flow ratio is in the optimum range right where you want it to be. Using a single pattern cam, like I did, would be a good choice.

These heads are outflowing several aftermarket aluminum SBF heads! How about that!

[SpeierRacingHeads]

Here is a scanned image of my ProFiler Ford. Maybe you see something you can apply.