[ho428]

I'm sure someone has done this before, looking for info and feedback.
Put a 2.20 intake in a small valve head and leave the 1.66. Say in a set of 46's, fully ported and race prepped.

433 cu in, 4.155 bore running a Performer RPM intake. (dual plane mandatory)
RPM range 4000-7000+

[steve25]

The stock average factory iron head wall thickness of.180" will not really allow a full on, maxed out porting job to take full advantage of that 2.20" valve and the throat size that should be used of 1.98".

The largest throat size that can be used in a D port high comp head is 1.850", and even this makes for a good risk of grinding thru a port wall once everything else is made as big as it needs to go.

If your talking about the low compression 46 head from a 74 GTO then due to its lower as cast short turn height, using a throat size of even only 1.750" makes no sence!

In my opinion in a high comp D port head it makes no since to use a Intake valve of more then 2.14" , especially if you want to some day have enough meat to do a freshen up valve job!

[ho428]

69 #46 heads.
I could just upsize them to 2.11's but was wondering if going to the 2.20 and leaving the 1.66 would be better than the 2.11-1.77 on a road race engine.

[ho428]

The past Winter has been spent swapping over the brakes, wheels and tires from 17" to period correct 15's. Now I've got this 433 short block I was planning to install some newer KRE's on, but to run with SVRA I need Iron heads and a dual plane intake. HSR and VDCA allow me to run Aluminum heads/single plane so I was thinking of using D ports for an SVRA engine since they'd be more of an occasional event at bucket list tracks.
The KRE's I have on the car now are D's so it's be a fairly simple swap to pull one engine for the other, events are weeks to months apart.

The valve size question came about due to running across a bare set of 69 46's, which should yield about 11.5:1
Finding something like bare 13's, 48's or 62's is hit and miss since I'd scrap whatever parts are in them anyway.
From what I understand the castings, ports and runners are very similar between the 46's and 48's, but there is a lot I don't know.

[cfmcnc]

Originally Posted by ho428

69 #46 heads.
I could just upsize them to 2.11's but was wondering if going to the 2.20 and leaving the 1.66 would be better than the 2.11-1.77 on a road race engine.

Go to the bigger intake valve with corresponding port crossection work .OK to stay with the 1.66 EX.Have made 1138HP with 1.66 EX NA.

[steve25]

Come on Bill!
Where talking about factory iron heads here with a 1.66” valve , and yes I have seen a NA motor with a aftermarket head with a 1.600” valve top 1000 hp also!

Some facts here once again are needed to be gone over.

With just a custom 2.14” intake valve in a 68 and up iron head the chamber needs to be unshrouded ( especially if well ported ) and in a very special way to only remove the minimum amount of CCs if your not looking to have to mill the head a lot to get back to your starting compression ratio.

If you step up to a 2.20” valve then the CCs needed to be removed is even greater!

The valve bowl porting work for a 2.20” valve needs to be done in a way to guide a good chunk of the added flow out into the center of the bore, so you had better have a flow bench at your constant disposal to guide you in the right direction.

The great thing about doing all the porting and chamber work needed to start to take good advantage of stuffing a 2.20” valve into a iron head is that the flow numbers between the all important.200” to .400” lift can be made massive !

You could probably get by means of working on a mule head first to make mistakes on ,maybe 170 cfm @ 28”@ .200” and by .400” 255 cfm.

The large flow numbers like this at .200” would likely make for too large numbers down at .050” and .100” so a 30 degree seat would not be the way to go.