Z head and O head on 1973 340
I was out in the parts shed today and looking over the stuff I'm taking to the swap meet to sell. I ran across some
3671587 casting heads that I thought were late 70's 360 heads. Those castings came on 1973 340's and 73-76 360's. Are they no different than any other 360 head with 1.88 intake valves?
Not any different as far as I know. MoPar head porters can probably really split hairs on the minor differences in different heads that non porters would never see.
I'm thinking I should probably keep them since they could be sent out and prepped and be ready for when I want to get a hotter cam and higher compression pistons.
Or for any other duty I suppose. I don’t see a problem with any head with being prepped for HP usage down the line.
Any insight on mods?
Plunge cut the bowl and blend it? 5 angle valve job?
Port match?
These are all good ideas and it ether costs money, which is your limitation to spend on. (AKA, your call)
I would defer to a head porter on the overall package before doing any work on the head. IF you just wanted a “General HP” head on the shelf ready to go, the I can tell you what I would do though I don’t know if it fits what your thinking now much less down the line years from now. But this is how I myself would prep a stock OE iron head for future HP use.
In rebuilding the head, the deck and intake surfaces are milled flat at there proper angles. All new gear is used. The valve seat receives a multi angle cut to be used in conjunction with the valves selected. Bowl and port work is determined on the level of the future engines performance level. Once you start grinding on the head, it can’t be put back, so.....
Just valve prep for general street use or racing
A bowl porting for general HP street use or light drag.
Fully ported for a street beast or light/medium drag use.
Race ported for racing.
I personally don’t see a need to port a head beyond the intended valve lift. If there is a benefit in flow, that’s fine.
I heard about a mod where the intake pushrod hole can be filled with a rod and relocated so the pushrod pinch can be addressed. I'd like to hear about that or at least get a link so I can read about it. I am guessing you would need some offset rockers from a place like RAS too.
Look up engine masters. Search where Dulcich (sp?) home ported a set of Edelbrock heads for a test of stock vs ported heads on a MoPar 360/408.
Off set rockers arms can be found at Hughes engines. As well as other places.
This trick is normally done on an aluminum head since iron is difficult to work with on this kind of modification. While it is possible to do so, it will more than likely be cost prohibitive.
The trick basically works like this. Fill the pushrod hole, drill the new hole over the amount you wish to move it. This amount may be limited to the amount of a rocker arms off set.
I would not suggest this trick to be done on an iron head. MoPar has done this for you with the W-2 (& 5 aluminum) head. W2’s are still available. The only draw back (stock iron head vs MP’s HP iron head) is expensive rocker gear. You can shop and compare at Summit Racing. Is it worth it? Oh hell yea.
This trick to a OE head. I would not do. Unless I’m building a purpose built trick engine disguised as a stock engine for classes like F.A.S.T. racing or other. If you want to do it for you, that’s fine.
I think I would want to use no lower than a 3.73 gear. 231/237 duration at .050" and .525 lift from Competition Camshafts. The car has subframe connectors and torque boxes. That cam calls for 9:1 compression.
That is a very mile cam, an old common HP street duration (230@050 area) and IMO would not need a radical port modification with its Relatively low lift. The bowl work is responsible for lift until the .400/.450 lift area. Past this point, the port itself becomes more responsible for better flow. How far you want to maximize/optimize the port is your or your porters call. A head porter will know exactly where to stop porting as not to effect the good flowing low lifts. As well as how it would be good or bad depending on the engine size and application.
Would I need to get new pistons or would milling the head surface be required?
I may not be understanding everything that I need to regarding the pistons height in the hole?
I still need to confirm what pistons are in it.
Everything depends on where the pistons sits in the hole now and clearances with the valve to piston. Also, how much gain in compression your after. I’m not really a fan of milling heads to grab more compression. While it is cheap and easy to do this, it often snowballs into milling the intake and/or head to intake surface.
AKA - Mo-work & money.
Knowing where the piston sits in the cylinder requires the head to be off and a bridge with a dial indicator on top.
Can I use a bore scope and determine if they are the factory piston based on the valve cuts?
I am reading that the 340 was 8.5:1 so can I even make that up with head work and gasket and get 9:1?
I probably need to slow down and read more.
A scope to see? Yea, that’s possible and easy enough through the spark plug hole.
A 1/2 point with a head milling? Heck yea. Just mill both sides of the head. Deck and intake sides. Finding a stock thickness head gasket is the hardest part.
The “How to Hotrod my Small block MoPar” or the engines manual will have more on head milling and piston selections for running a desired ratio. These two books are really your best source.
