[Rar_421]

Picked up a set 4x4h heads, including new 2.11 valves since this was a 1.96 head where can I get the correct seats and also want to have new guides installed.All the local shops are busy with dirt track engines so I want to save time by bringing the heads and parts in,thanks

[steve25]

If your just adding bigger 2.11” intake valves that’s all you need as you exh seats may just clean up with out going thru the factory hardened area and then having to install a seat(s).

The best way to deal with the guides is to have just a sleve installed and if a shop is equipped to instsllbthat type of guide then they have them on hand and there is no point to your buying them!
If the shop try’s to sell you on knurling the guides to regain a good fit then find another shop, period!

Those 4H stamped heads are over 100 CCs in chamber volume so you will need to mill them a good amount to work well with a 421 cid motor!

[Rar_421]

The heads will be going on a 400, can the 1.96 seat be cut to fit the 2.11 valves or do I need to get larger seats? First Pontiac rebuild, replacing my 350 in a tempest,I'll be asking alot of questions thanks

[steve25]

There are no seat incerts so to speak in Pontiac D port heads, so your small valve 4X heads are the same casting wise but for being machined for the smaller intake valve and having pressed in rocker studs instead of the needed screwed in rocker studs which by the way should be corrected for at the machine shop if there equipped to do so.

Originally these 400 motors with heads of these chambers had only 8.2 compression.

The main issue I see for your plans to use these size chamber heads on a 400 is getting a decent compression out of them, like 9 to 9.5.

I am not home as I post this to have access to all my needed info, but off the top of my head I will say that if your looking for a nice 9 to 1 compression out of the motor, then even with boring the motor .030” over you will need like a 85 CC chamber.

This means that your heads being about 103 CCs would need to get milled .030” or more!

[Rar_421]

These heads have the factory screw in studs,I'm fine with cr under 9-1,it's just a daily driver,work car actually,the 2.11 ferrea's were included with the engine I bought

[steve25]

Ok, your golden, you will just also then need to get the valve guides cut for positive type seals since those 2.11” valves will not have the needed second groove for the valve seal O ring in the retainer, and if your running new exh valves it will likely be the same deal!

I would not run anything bigger duration wise then something like the factor 066 cam with the compression your going to have without some head milling.

[Cliff R]

4X were among the first heads with factory hardened exhaust seats. They are prone to cracking so make sure you have them checked. They aren't as bad as the 7M5 heads that had the larger valves in them. Something to be learned from all that when it comes to using factory induction hardened seat heads.

For what you are doing there is no need to install larger valves but if you already have them they woln't hurt anything. On the exhaust side I'd just stick with the 1.66 valves instead of grinding away at the seats for the larger 1.77's. The biggest cam I'd would use in a "mild" 400 build under 9 to 1 compression is the Crower 60240. It is an EXCELLENT cam for the later 400 engines with the 5C and 6X heads on them and low compression.

It specs at 210/221 @ .050" on a 112 LSA. Of all the cams I've used in those engines over the years it will be the biggest one you can manage without a lot of gear and converter.......Cliff

[steve25]

As Cliff mentions, these heads are prone to cracking if over heated, and especially if when in a over heated condition you add water to the cooling system that is not hot and then start the motor as in what normally takes place during a break down on the side of the road.

Such a action just makes the head contract at a rate so fast that it has no other recourse by to crack!
This fast temperature change will crack just about any iron head, no less ones that have Induction hardened seats as in your 4 X heads!

Since it seems that these heads 95% of the time when they do crack, do so from the exh valve seat area on out to a head bolt hole or a water passage .

You can greatly reduce the chance of this taking place by taking the time and using a stone in a Dremel tool to roll over the sharp edges where these holes and passages meet the head deck surface.

A .015” roller over is all thats needed and this rework I would concider mandatory especially if these Induction hardened type heads get even just a .002” clean up mill done to them!

[Rar_421]

The engine I bought came with new 2.11 &1.66 ferrea valves so that's what I'll be using and a 68' intake,thanks guys!

[steve25]

Ok, so the machine shop as I posted will need to cut all 16 of your valve guide tops for positive type valve seals if such has not been done already.
You want to us a comp cams seal for a .530” guide and a 11/32” valve.