Bigger valves in stock 318 heads?

[1BAD68]

My 318/390 stroker is still running stock heads and although it revs like a maniac and pulls hard, at about 5500+ rpm it seems to kind of go flat like the the valves are floating or maybe it just cant breathe enough.
Running the 1/4 mile this summer a few times I just cant seem to get under a 14.5 ET and I think if it would still pull up to about 6000 rpm I would be in the high 13's.
Anyway, new heads are not in my budget and i'm wondering if they could be machined for bigger valves?
I ported these heads when I rebuilt the engine and I'm running a 340 cam and springs, is there a better cam/springs combo i could be using?
http://www.youtube.com/watch?v=BuPTrsazFCQ

[chargd72]

I would say those heads are limitting you big time.  I put 1.88/1.60 valves in my true 318 with same cam and springs.

Nice run 

[1BAD68]

Did you notice significant difference with those valves vs. 1.78/1.50 valves?
Can the 2.02 intakes from the 340 be machined to fit?

[elacruze]

I'm building a 318 too, just finished putting in 1.88/1.60" valves and blending. Here's the thread-
[/url]http://www.dodgecharger.com/forum/index.php/topic,69895.0.html[/url]


Part of what I'm trying to do is prove that big valves in small-port heads are worthwhile. It's not together yet, so I don't have any data yet.

[elacruze]

Did you notice significant difference with those valves vs. 1.78/1.50 valves?
Can the 2.02 intakes from the 340 be machined to fit?

2.02" intakes will fit in the head and cylinder bore, but I thought them too large for my closed-chamber heads due to shrouding on the quench side. With a set of open-chamber heads I'd have left them at 2.02". 

[1BAD68]

I'm building a 318 too, just finished putting in 1.88/1.60" valves and blending. Here's the thread-
[/url]http://www.dodgecharger.com/forum/index.php/topic,69895.0.html[/url]

Thats a great post, I cant believe I missed it before.

[Nacho-RT74]

I'm building a 318 too, just finished putting in 1.88/1.60" valves and blending. Here's the thread-
[/url]http://www.dodgecharger.com/forum/index.php/topic,69895.0.html[/url]


Part of what I'm trying to do is prove that big valves in small-port heads are worthwhile. It's not together yet, so I don't have any data yet.

fixing the link code http://www.dodgecharger.com/forum/index.php/topic,69895.0.html

[HPP]

You can put bigger valves in them, but they still have tiny ports leading to the valve.

Rather than put the money in to those, you might look at some rebuilt rebuilt 308s, RHS's new casting LAX or MAX heads, or Aerohead Racing Service's budget iron heads. I think most of those are around $400-600 a pair.

[knitz01]

I dont know about your heads but that was a cool run down the strip at WIR 

[1BAD68]

I ran across some "920" heads that have been machined, ported and 1.88/1.60 valves installed.
The price is really reasonable, would these be a good choice? I like them because of the closed chamber and bigger valves.

[chargd72]

Are you sure they are closed chambered?  I thought 302s and 345s were the only closed chamber 318 heads     

[1BAD68]

These are the 920's they were off a 273 in a 67 Barracuda.
Heads have 16 brand new valve guides installed for proper oil clearence, also they have hardened exhaust seats installed for use with unleaded fuel. 3 angle valve job which is cut for the bigger 1.88"/1.6" valves, the port throats have been opened up accordingly to enhance air flow and performance. Valve spring pads have been machined for double springs and the guides have been clearenced for up to .600" valve lift. Both heads were resurface to provide a flat, smooth gasket surface and the chambers are 62cc

[chargd72]

Ok, the 920s were build for 273ci engines.  Those are definitely closed chamber and with bigger valves and the right port job, I say get 'em. 

[elacruze]

If it's 390 cubic inches, I'd probably opt for the 360 heads with their bigger ports.

[greenpigs]

Yep it is 390 CI. Was it 2 issues ago in Mopar Action they tested iron heads for SB and the parts house replacement magnum heads cast in Australia were better than the MP aftermarket heads? I think the thing to keep in mind is that this isn't a 318 anymore and it needs to breath.