What are your thoughts about putting 2.19/1.88 valves in a closed chamber BBC head. Do you think the chamber wall should be laid back to unshroud the larger valves, or put them in and let it be? I am concerned with compression and how many cc's I would gain in the chamber from laying the chamber wall back. If it needs to be laid back how much larger will this typically make the chamber? Thanks in advance for any advice.

they don't need to be laid back, but you will need to notch the top of your cylinders to accomodate the correct amount of flow around the valves.

I opened up my 290 closed chambers a little and polished the chambers when I did mine. I had the heads resurfaced .008", but don't know how much they were cut before so can't report total that have been cut. Wound up at 104CC finished. If you are starting with closed chambers and a matching small dome piston, I doubt you will miss the .2 decrease in compression, unless the motor was only an 8.5 motor to start with. A much bigger detriment to compression is having any more than .042 piston / head. Stock specs sit the piston down about .020 for use with a .022 steel heads gasket. Alot of guys never cut the block and then use the .041 FelPro gasket. That .019 difference is significant. Stack that up with an unshrouded chamber and the CR falls way down.

Hey Chad, if you ran that 7.39 @91 with the current config I'd leave the durn thing alone!

Horror stories about breaking through the wall into the water passage just behind the ex valve abound on this deal. Beware.

Alot depends on the casting. The super early small chambers can get to water (although I just had a set that was fine) The later 215 style works great with bigger valves.

I have 2.19/1.88 in my closed chamber/ported heads and they are fine,been running them for about 3 years now.

Originally posted by Patrick O'Rourke:
I have 2.19/1.88 in my closed chamber/ported heads and they are fine,been running them for about 3 years now. Did you unshroud the chambers? What size motor?

These heads are the 3904390 casting off of a 67 396/427. Heads have already been shaved .035 giving me 10.25:1 with L2240NF30 TRW pistons. I have also put the Manley Race Flow valves and bronze guides. I have not cut the block and the pistons do set down more than I would like, but I am using the .020 Steel Shim gasket. I have talked to numerous racers and some say lay the walls back, some say you don't need to but it may be a bit useful, then another guy that I race with said to "ditch" cut the wall just above the seat area and blend it in. The "ditch" cut would keep from gaining too many cc's in the chamber. I am up in arms whether our not to do this. The car does run good numbers for a roller cammed bone stock headed 396, and it is deadly consistant. I just like to tinker, but I can't convince myself that this mod will be worth it. I'm sure it may be worth around .1-.2 in the 1/8th, but then again that may be wishfull thinking.

RMCHEVELLR :cool:

The motor is a 454, 30 over, I did the porting, my friend the machnist did the rest, including putting the heads together for a hundred bucks, thats why he's my friend. The parts list for the motor is on my web site under photos/Eng. Specs. I did not go into specifics just major things.

Are the old -206's OK for bigger valves??


Bttt, never heard of "ditch-cutting" the walls of the chamber's just above the valves so that you get a "rolling" relief??

But I kinda like it b/c aren't some intake bowls done this way just below the last taper cut below the seat from the factory on other motors??

But don't know how to get them equal w/o alotta hassle??

pdq67

67,

Just saw you page, we have basically the same motor. RIght now I am running a hyd flat but have the same Comp Solid Roller in a 110LSA sitting on the shelf. Running a 3.73 w/ street tires though. I am going to try to restrain myself from doing anything but a cam change and see what the results are. At least that's the intention.

my 702's (around 100cc's) have Manley 2.19's and 1.88's, mildly ported and unshrouded. The machinist is a friend of the family and said there was no problem with the water passages.