This intake port mold really tells the story

[mag2555]

What throat percentage is that port using Chad?

There looks to be a good amount of bias there that if he where to go for that would take him into a water jacket.

[SpeierRacingHeads]

What throat percentage is that port using Chad?

91.5 with out valve deducted

[mag2555]

And this is with what size valve Chad?

[SpeierRacingHeads]

And this is with what size valve Chad?

2.08

[mag2555]

In regards to the OP of this string, I think your at the point now where to make us of the flow there that you have you need a intake manifold with a bit more taper to lower peak velocity somebody because your really not going to get any more minimum port area out of that casting.

Also as posted before and maybe first and foremost, those headers need to go!

1 5/8” headers where never invisioned carring Hp numbers well to 7000 rpm with 289 cid breathing trying to breath thru them, no less 331 cid!

[mag2555]

Thanks Chad!

[SpeierRacingHeads]

But to the OP. The roof needs some luvin.

[blackford]

But to the OP. The roof needs some luvin.

I did take the curve out of the roof that you can see in the port mold before getting the head flowed. The roof contour looks more like your Profiler rendering. What volume is that port?

[mag2555]

I hope Chad reply’s,to your question, but with its 2.08” valve and it’s 1.90” throat diameter it’s got to be over 190 CCs in port volume.

In terms of your iron head you really don’t have anything more to work with and still be safe from blowing out a port wall.

What you can do is tweak at this point to trade off some flow numbers at .050 to .100” lift for a smidge more high lift flow.

This can be done by blending off/ reducing the depth of some of your bottom cut of your valve job around the short turn.

This needs to be done carfully and parallel to the inclination of the valve.

If for example your bottom cut is ,060” or more tall I would start by blending off .030” of it.

How tall is that bottom cut now?

[BobbyB]

But to the OP. The roof needs some luvin.

I did take the curve out of the roof that you can see in the port mold before getting the head flowed. The roof contour looks more like your Profiler rendering. What volume is that port?

Great job! Do you have a port mold of the head as it was flow tested?

[blackford]

But to the OP. The roof needs some luvin.

I did take the curve out of the roof that you can see in the port mold before getting the head flowed. The roof contour looks more like your Profiler rendering. What volume is that port?

Great job! Do you have a port mold of the head as it was flow tested?

I'm sorry I don't. I ran out of silicone mold material. The biggest difference between the mold in the pic and port as it was flowed was that the min CSA of 1.92 was increased to 2.00 by widening the port in that area an additional .030 per side and taking the curve out of the roof near the inlet.

[BobbyB]

Ok, thanks anyway. When do expect to get them running on the engine?

Do you expect to make other changes before trying them?

[blackford]

Ok, thanks anyway. When do expect to get them running on the engine?

Do you expect to make other changes before trying them?

I was looking at the head and the valves today and I noticed that they did NOT backcut the valves like we discussed. So low lift flow can be better.

I had the shop cut the valve seats (3 or 4 angle) before they flowed them. Now that the seats are there I can see that there is room to open the throat a bit more. In some areas, it's only 88% to 89% of the valve diameter so I could open this up a bit more. This was an area of the port that I had to be careful with while porting since the 1.94 valve seats had not been cut yet.

This exercise was an experiment. I got a spare head to port the same as I did on a pair of DOOEs 20 years ago plus I made some new improvements. For curiosity sake, I had this test head flowed. The ported DOOEs are on the engine now (minus the port improvements), but I don't think I am going to pull the heads just to make the improvements since I think it would net me only something like 20 HP or less so it's not worth it at this time.

[mag2555]

Back cutting the valve is a always a good thing for the exh valve, but for the intake it can be a double edged sword.

The back cut always helps to re-atomize wet flow, but the added overall air mass can send a port into tumble if your right on the edge of such.

[blackford]

Back cutting the valve is a always a good thing for the exh valve, but for the intake it can be a double edged sword.

The back cut always helps to re-atomize wet flow, but the added overall air mass can send a port into tumble if your right on the edge of such.

That's opposite to everything i've read. It's good for the intake, but could increase reversion with the exhaust.

I'm curious about you mentioning how my Doug's Tri-Y headers are not good. Is it high rpm where they are not fitting the bill? How much of a difference would long tubes make? Do you have a header recommendation?