2.00” or 2.02” intake valve in a 351w D0OE head?

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travis
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2.00” or 2.02” intake valve in a 351w D0OE head?

Post by travis »

This may be a lost cause…

These D0OE heads that I have a ton of hours in I would really like to use. But, when someone in a past life bowl hogged them, they cut all the bottom angles out. My machinist wouldn’t do the VJ for me…said they would be a complete turd with the 1.94” valves in place. I believe these could be opened up for a 2.00 or 2.02 valve but there will be shrouding. Would one of these bigger valves be enough bigger to allow for the bottom cuts to be made?

I’ll have to get them sonic tested to see if it’s even possible to go that big on the valves, but if it is possible will this idea work?
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by mag2555 »

It’s no problem putting in a 2.00” valve and all things being equal that should allow at least a .060” bottom cut to be added.

A 2.00” valve as compared to a 1.94” gains you back like 1/2 a CC in chamber volume so if need be you could unshroud the chamber by that much before resorting to milling the head to get back to your starting point of chamber CCs due to unshrouding work.

How much valve lift will you be running?
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by travis »

I’ve got a couple cams in mind. I’ll have to check my flow bench results but I believe they went turbulent around .650” lift. I’m looking at around .540-.550 lift
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by BillK »

Travis,
Why not pay your guy to just cut one seat and then see how it does. Have him put the seat out as close to the od of the valve as possible.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by Walter R. Malik »

Because of the close proximity of the chamber wall, a 2.02" intake won't flow much more than a 1.96" valve.
On some earlier heads with 18mm spark plugs it is difficult for bigger valves to even fit. There is plenty of room on the exhaust side for using a much larger valve, though.
Doing that sometimes requires a "reverse" dual pattern cam; similar to a turbo cam but with a bit tighter separation.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by mag2555 »

Well you can check what you have to work with now in terms of a 1.94” valve and chamber shrouding.

Place you valve in , set up your flow bench valve opener and measure you clearance between the valve edge and the chamber wall as crank up thru .550” lift.
In a perfect world at each lift point seen you will have just as much valve to chamber clearance.

In terms of the real world numbers and with a 2.00” valve it would be considered good if at .500” lift if you had .400” clearance between the valve and the chamber wall near the spark plug area.

The basic rule of thumb is that the clearance should be = to .20D of the valve at .25D lift.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by steve cowan »

travis wrote: Wed Jun 16, 2021 4:32 am This may be a lost cause…

These D0OE heads that I have a ton of hours in I would really like to use. But, when someone in a past life bowl hogged them, they cut all the bottom angles out. My machinist wouldn’t do the VJ for me…said they would be a complete turd with the 1.94” valves in place. I believe these could be opened up for a 2.00 or 2.02 valve but there will be shrouding. Would one of these bigger valves be enough bigger to allow for the bottom cuts to be made?

I’ll have to get them sonic tested to see if it’s even possible to go that big on the valves, but if it is possible will this idea work?
what size is throat
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by PRH »

If you’re trying to build something “good”, start with fresh heads and do them up the right way.
The “yeh, they’ll work if........” heads go on low buck builds where they just need to run and be somewhat reliable.

Using poorly prepared heads is along the same lines as using the “wrong” heads(maybe even worse).
Especially when you care about the final result.
Somewhat handy with a die grinder.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by travis »

Throat size…something I completely overlooked #-o

Throats are 1.80”-1.84”, which with the current 1.94” valves gives 92.7-94.8%. A 2.00” valve after equalizing all the throats at 1.84” gives 92%…a 2.02 gives 91%. A 2” valve is going to be super tight though, putting the edge of the valve right against the chamber wall, and starts to get into the 18mm spark plug trough.

My wife likes to quote Frozen in these situations. Let it go, let it go…
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by mag2555 »

Well your stuck between the rock and and a hard place!
About all you can do is have a flow test done and see what turns up in terms of reaching your hp goals.

If it where me I would eat the time loss and start over or get some used aftermarket heads that will likely flow more then those ever could anyway!
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by fordified »

Not sure how deep you can cut those castings for new seats, but that may save those heads.

If that’s a dead end, find new castings as others have suggested.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by rustbucket79 »

Unless you absolutely must use these heads, hang them on the wall as the ghost of horsepower past and move on. Even Edelbrock’s heads are a 400 hp choice with zero effort, why not hunt a used set of them down instead?
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by mag2555 »

Installing seats when the throat is so oversized would do nothing but drop off flow numbers that are there all ready.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by n2omike »

D0OE heads have 18mm spark plugs. I have 1.94" and 1.60" valves in a set of 289 heads that share the same architecture and plug size. I don't see how you could go any larger. There's just no room between the valves, as well as between the intake valve and the spark plug. Plus, to enlarge the throat to match the valve size, there's a VERY good chance you'll grind into a water passage. If you have any other options for cylinder heads, I'd look into them.
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Re: 2.00” or 2.02” intake valve in a 351w D0OE head?

Post by Walter R. Malik »

mag2555 wrote: Wed Jun 16, 2021 10:42 am Well you can check what you have to work with now in terms of a 1.94” valve and chamber shrouding.

Place you valve in , set up your flow bench valve opener and measure you clearance between the valve edge and the chamber wall as crank up thru .550” lift.
In a perfect world at each lift point seen you will have just as much valve to chamber clearance.

In terms of the real world numbers and with a 2.00” valve it would be considered good if at .500” lift if you had .400” clearance between the valve and the chamber wall near the spark plug area.

The basic rule of thumb is that the clearance should be = to .20D of the valve at .25D lift.
The PONTIAC valves I have used several times in those and earlier heads are 1.960" intakes and 1.660" exhausts.
With a single pattern or "reverse" dual-pattern camshaft they have been stand-out performers.
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