35% off SpeedMaster

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chrispy1971gtx said:
Yea, I'm measuring +.010 "
Click to expand...
If you're there, then a standard Felpro kit gasket (PN 8553PT) will work out and give a piston to head clearance of .040" + or - a bit. Nice for a quench gap. Just be sure that you are at .010" on ALL cylinders. (With a nominal deck height, those pistons ought to stick up around .018" above deck.) I personally would check how much that changes with piston rock at the upper and lower edges those forged pistons typically have some pretty loose clearances and will rock more than cast or hypers.

Your static CR computes up around 9.8-9.9 with the 65 cc SM chambers, that head gasket, and the 2316's out of the deck by .010". That's a tad more than the actual production 340 SCR, and may end up being a pretty nice spot to be in IMHO, depending on what you plan to use the engine for.
 
MOPAROFFICIAL said:
The high end 1.937 or so, that will make the rocker tips rollout worse than already is.
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This 1.937" is referenced from where? Some standard spring seat height below the center axis of the rocker shaft? Just trying to get that dimension fixed in my head....
 
For whoever has one of these (PRH)?), would you mind checking the OD of the intake seat and letting me know? Tnx
 
I just got my set of heads over a week ago.
Took some 'purdy' pics for the archive but didn't have time to take them apart yet.
 
I bit the bullet on the heads and ordered the cheaper 65cc heads. I got the off amazon, thru Jegs, so .... if I figure I might not use them, I can easily send them back...plus I got the amazon points. LOL.

@nm9stheham, thanks for they reply/info!

I picked up this 73-340 over Christmas for $250. So the plan is to run it in a MINT-66 4door coronet with mainly some used parts on hand. 4:10 8-3/4, some cheap headers (bought a set of chinese magnums to tryout) and something along the lines of a .474 Hemi grind cam/727 shift kit and maybe get in the high 12's. A new track is coming to town.
 
Initial report was the car picked up .28.....but he was running into a 15 mph head wind.....did not go to the track this weekend....will see him and the car this weekend to see the time slips.
 
Was this a test where the combo went from unported speedmasters to cnc ported speedmasters....... and no other changes?
 
A brief update on the SB speedmaster rpm copies I had here in the shop.
A little backround.......

Someone brought a nearly completed, fresh 360 to a friend of mines shop...... to have it finished up and dynoed.
He’s not totally “fluent” in Mopars and I got a call about what the heck that thing would use for plugs.
I gave him a number, and he was like..... nooo nooo, these are the huge plugs like an old ford.
I had him tell me where the heat crossover in the head went.
As I suspected, it went into water..... and a search of the casting number revealed they were indeed the industrial heads with small ports and valves.
Calls the customer with a few options, the decision is made to get some SM heads.
I checked them over, all seemed fine.

The motor had arrived with the steel PRW rockers installed, it all fit fine with the OE heads.

The springs that came on the SM heads are only 1.440 diameter, and the valve tip stands well proud of the retainer.
But apparently ...... the rockers won’t clear the retainers as they are.
The underside of the rocker contacts the top outer edge of the retainer.

I gave him an old Crane gold rocker to try as a test piece to see if it cleared or not.

I’ll update once a solution is arrived at.
 
I used some Comp magnum rockers on mine.. the speedmaster rockers didn't fit properly.
 
PRH said:
A brief update on the SB speedmaster rpm copies I had here in the shop.
A little backround.......

Someone brought a nearly completed, fresh 360 to a friend of mines shop...... to have it finished up and dynoed.
He’s not totally “fluent” in Mopars and I got a call about what the heck that thing would use for plugs.
I gave him a number, and he was like..... nooo nooo, these are the huge plugs like an old ford.
I had him tell me where the heat crossover in the head went.
As I suspected, it went into water..... and a search of the casting number revealed they were indeed the industrial heads with small ports and valves.
Calls the customer with a few options, the decision is made to get some SM heads.
I checked them over, all seemed fine.

The motor had arrived with the steel PRW rockers installed, it all fit fine with the OE heads.

The springs that came on the SM heads are only 1.440 diameter, and the valve tip stands well proud of the retainer.
But apparently ...... the rockers won’t clear the retainers as they are.
The underside of the rocker contacts the top outer edge of the retainer.

I gave him an old Crane gold rocker to try as a test piece to see if it cleared or not.

I’ll update once a solution is arrived at.
Click to expand...
So is the valve centerline to rocker shaft centerline distance too close? Or closer than stock? That seems odd....which I assume is why you are mentioning it...
 
nm9stheham said:
So is the valve centerline to rocker shaft centerline distance too close? Or closer than stock? That seems odd....which I assume is why you are mentioning it...
Click to expand...
(i know you quoted prh) the stock rockers fit the speedmaster heads when I first had everything setup and before I went to roller cam. But the speedmaster rockers themselves I think are the issue, they didn't fit the factory heads either.
 
nm9stheham said:
Roger... but PRH states that steel PRW hit the retainers..... that is what seems baffling.
Click to expand...
I swear the PRW and the Speedmaster rockers are almost identical at least the "stainless steel" ones.. They lack the notch (or it's not big enough
) that the higher quality rockers have to clear retainers.

like these
Mopar fits Chrysler SB 318 340 360 1.5 Stainless Steel Roller Rocker Arm... | eBay
and these
PRW 3231811: PQX Shaft Mount Rocker Arm Complete Kit Mopar 273-360 | JEGS
 
If you stick to 1.437 springs and comp 740-16 retainers n super locks and inside the factory stem height range.. you clear the comp, prw steel rocker just fine...

That's not always realistic, so you now you need to relocate the shaft away... and hey..what the scrub looking like on the valve from the roller? Offset toward the exhaust side of the head? Wide, narrow, in between?

A geometry kit that moves the shaft away would fix the scrub and the spring diameter limitation/interference issue.
 
I just got my Speedmaster heads this week. I got the cheapest assembled version. Took them over to a buddy of mine today and had him do a visual, as he used to have a engine shop back in the day. I mentioned the rather small spring package and he went into a box and pulled out a brand new Z28-350 spring and retainer and it was identical. Hence the .500 max lift. These also have 11/32 valves. An Elgin Z28 spring kit is about $55 bucks, lol. Chevy cheap. I installed a set of 273 rocker arms, and the clearance is fine. But the spark plug counter bore.....well its missing when compared to stock LA heads.
 
A brief update(but probably not the last one).
The Crane gold rocker clears just fine.
Not even close.
The two arms/struts that extend out from the main body of the PRW rockers have much more of a curved arch shape to the underside of them than say a Comp rocker.
That’s where the contact is.
When the underside of the PRW rocker body contacts the retainer, the roller is about .100 from contacting the valve tip.
Apparently the shaft to valve dimension is just closer enough than the stock heads to create this issue, along with perhaps the stock heads had the valve tip sitting even more proud of the retainer(I never saw those heads).

That bottom of the strut area of the Comp lifters is straight, not curved.....so they would also clear just fine.
 
are you talking about the self aligning fulcrum ?
 
A little follow up......
A few pics:

6202FFAE-435E-4D9A-9314-55270238638F.jpeg


C613BD52-DDA9-436F-88DE-16904207AA87.jpeg


4A2C2BC4-4183-494C-B409-B14F214C7675.jpeg


5495A086-ED87-480A-8652-66DF82B3642C.jpeg
 
Here a pic of a Comp Pro Magnum:

What you can’t see in this pic is there is also a spring relief cast into the body.

63E5DAB6-97C3-4040-AEEB-16738913898A.jpeg


Notice the difference in the relationship between the adjuster cup and the roller tip between the two rockers.
The PRW rocker has the roller higher up vs the center of the shaft, so the rocker has to be rotated down farther for the tip to contact the valve, which results in the contact with the retainer.
 
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