Speedmaster spark plug holes improvement??

[Bobzilla]

These are supposedly copies of Edelbrock LA heads. When I read this thread and started thinking about it, I only had access to Edelbrock Magnum heads. The Magnum style Edelbrock heads do NOT have this spark plug situation.
Last night I dug out my Edelbrock LA heads and checked one of them and found it DOES have this same spark plug situation.
Both styles of the Edelbrock head I tested were with the same RC12YC spark plug, the same number recommended by Edelbrock. So basically this recessed spark plug, as seen from the chamber side, is not something Speedmaster did differently.
Also did a search and found an old thread on this subject on Edelbrock heads.
My LA Edelbrock heads are from around 2003. I wonder if they are still like this, since the Magnum version is not?
Edelbrock 6077 Spark Plug Question

 

[Bobzilla]

Edelbrock Magnum head chamber with RC12YC spark plug installed.

 

[Bobzilla]

Edelbrock LA head chamber with RC12YC spark plug installed.

 

[PRH]

If someone did nothing more than 318will did, and the only upside to it was it made you feel better....... imo, that’s still “mission accomplished”...... since you’ll stop obsessing about it.

Imo, having a proper valve job done will have a much greater impact on power output than what cleaning up those threads will........ or recessing the holes(which I think is just crazy talk).

 

[RustyRatRod]

I am not sure I would "sink the plug" to try to correct this. I think if I was actually going to do something......besides nothing, it would be to go ahead and dress the inside edges of the spark plug hole so that the end of the plug is completely exposed more like Bobzilla's first picture up there ^^^^^^ . I think that would be the "more correct" way to do it, IF you decide to address it at all. In the end, as long as the plug can start the fire, what difference does it really make? None, "I just bet".

 

[gzig5]

Those chambers are shaped very differently. Wonder why? The plug ends up halfway in the wall of the chamber on the LA head.

 

[PRH]

Well, for one...... there’s a 5cc difference in chamber volume.
58cc for the Magnum, 63cc for the LA.

It’s just a totally different chamber.

 

[gzig5]

Ok. Since it’s a performance aftermarket head I would think they would put the better Chamber design in both. Is that much volume difference going to get a stock compression late LA into too much compression?

 

[yellow rose]

I am not sure I would "sink the plug" to try to correct this. I think if I was actually going to do something......besides nothing, it would be to go ahead and dress the inside edges of the spark plug hole so that the end of the plug is completely exposed more like Bobzilla's first picture up there ^^^^^^ . I think that would be the "more correct" way to do it, IF you decide to address it at all. In the end, as long as the plug can start the fire, what difference does it really make? None, "I just bet".

The plug reach in post 53 is better than what was posted in the SM chamber.

On the Edelbrock head you can see the flat of the plug is flush with the end thread in the chamber. On the SM head, the plug is set back, for lack of a better term.

That's not as bad as having the flat of the plug too far into the chamber. That's a real no no.

I just don't like all the sharp edges in the chamber like that. I'd roll them off and not care about the little compression loss.

 

[toolmanmike]

If someone did nothing more than 318will did, and the only upside to it was it made you feel better....... imo, that’s still “mission accomplished”...... since you’ll stop obsessing about it.

Imo, having a proper valve job done will have a much greater impact on power output than what cleaning up those threads will........ or recessing the holes(which I think is just crazy talk).

Agreed. Proper valve job is first on my list. It should be the minimum anyone does even if they are planning on just "bolting them on".

 

[j par]

Agreed. Proper valve job is first on my list. It should be the minimum anyone does even if they are planning on just "bolting them on".

I don't know I think the minimum is just checking them out make sure there's no sticky valves or leaking valves... I think of valve job would be the next step in Improvement.. but we have no side by side comparison on that either just gurus with flow charts...

 

[RustyRatRod]

yellow rose makes a great point about the sharp edges. We all know how crucial eliminating those are for good flame travel and reducing hot spots. There's no question that's an upshot. I don't see anything wrong with doing it at all and possibly even some benefits.

 

[PRH]

The first set of those Ede heads I had in my shop would have been shortly after they came out.
I noticed the spark plug threads right away.
I’ve simply chosen to not do anything about it.

 

[318willrun]

I don't know I think the minimum is just checking them out make sure there's no sticky valves or leaking valves... I think of valve job would be the next step in Improvement.. .

Agree. If I planned on a valve job, I'd had bought them bare and loaded them myself with a good valve job. Each to their own, and there are many opportunities for improvement, but for me these will be replacing stock 360 heads. If they won't outflow an untouched 360 head then SM can shut their doors tonight as far as I'm concerned.

 

[j par]

Agree. If I planned on a valve job, I'd had bought them bare and loaded them myself with a good valve job. Each to their own, and there are many opportunities for improvement, but for me these will be replacing stock 360 heads. If they won't outflow an untouched 360 head then SM can shut their doors tonight as far as I'm concerned.

All they have to do for me is match the performance of the 596 mildly ported heads I have now and be 50 lbs lighter...

 

[toolmanmike]

I don't know I think the minimum is just checking them out make sure there's no sticky valves or leaking valves... I think of valve job would be the next step in Improvement.. but we have no side by side comparison on that either just gurus with flow charts...

Gee, I think the machine shop guru will find tight or loose guides when they take the valves out for the valve job. The valve job is the first modification. The checking out goes without saying.

 

[318willrun]

All they have to do for me is match the performance of the 596 mildly ported heads I have now and be 50 lbs lighter...

I would think they'll offer you some gain. I know you had some porting done and 2.02's installed, but I can't believe your 596 heads will match these unless you had some extensive porting done. Means my heads are stock 1.88's, I should have a big improvement.

 

[PRH]

Personally....... I’m looking forward to 318will and jpars “bolt ‘em on and go” results.

That’s as good of a “real world” test as there is.

Plus, it’s two rather different combos.
360, low cr, small cam, auto..... vs ......408, higher cr, TR, solid cam, stick.

The set that went on the 360 here last spring had nothing done to them that would have made any difference in power.

They aren’t going to fix a lousy combo though.

I think 318wills test will answer some questions about how they’ll match up with the combos that are on the milder end of the scale.

 

[j par]

Personally....... I’m looking forward to 318will and jpars “bolt ‘em on and go” results.

That’s as good of a “real world” test as there is.

Plus, it’s two rather different combos.
360, low cr, small cam, auto..... vs ......408, higher cr, TR, solid cam, stick.

The set that went on the 360 here last spring had nothing done to them that would have made any difference in power.

They aren’t going to fix a lousy combo though.

I think 318wills test will answer some questions about how they’ll match up with the combos that are on the milder end of the scale.

Any feedback from the set that went on the 360 last spring?..

 

[PRH]

It was dynoed, ran fine, but didn’t make very much power(330-ish hp).... and they came and got it.

I have no idea what happened after that.

TQ-345@3000(start of pull)
TQ-367@4600(peak)
HP-331@5200(peak)
HP-317@5600(end of pull)

 

[j par]

It was dynoed, ran fine, but didn’t make very much power(330-ish hp).... and they came and got it.

I have no idea what happened after that.

Yes that seems a little low I guess..
Do you remember the cam specs?..

 

[PRH]

Comp XE268.

There are more details on one of the many SM head threads.

 

[j par]

Comp XE268.

There are more details on one of the many SM head threads.

When I looked that cam up on the comp website they had a Dino pull and it showed just about the same results you had. On a mildly built engine.. I think it said something about Dart RT heads or something?
My cam has just about the same lift(after its last regrind), but I'm using 1. 6 to 1 rocker so I get a little bit more out of it. also my duration has another 10 degrees at least at 50..
Again I never bought the Speedmaster heads trying to light the world on fire or take me to the next level... I've always wanted aluminum heads and always looked at the Edelbrocks but could never afford to pull the trigger.. if I'm anywhere in the ballpark out-of-the-box I'll be plenty happy....

 

[PRH]

I estimate that a more well thought out overall combination of parts could have bettered that 331hp by another 40-50hp without really spending any more $$$.
Mainly, compression and the intake manifold.

The XE268 in a small block with half way decent heads is an easy 1hp/ci cam.

What I’d have changed:
-Make sure it was an honest 9.5-10:1
-RPM A/G intake
-prepped/blended heads
-small street solid lifter cam

I’d have been looking for over 400hp out of that.
A hyd might get you there if the lifters were cooperating.

 

[j par]

I estimate that a more well thought out overall combination of parts could have bettered that 331hp by another 40-50hp without really spending any more $$$.
Mainly, compression and the intake manifold.

The XE268 in a small block with half way decent heads is an easy 1hp/ci cam.

Well I have plenty of the two mentioned LOL... I'm not really dead set on which head gasket I'm going to use until I pull my current heads off. Paperwork says .010 above deck which is basically the .010 they shaved off the deck.. I have in mind a simple 8553 gasket, but again until I get the motor out on my stand and the heads off I'm Not Dead set..