605" Street Hemi Build.

[rev.ronnie]

Very impressive work.

I look at that chamber and wonder if twin plugs would benefit this build. Even with the small dome piston, the bore size being pretty large may like the twin plug.

Thanks!
I don't know how much it would help. Unleaded fuel has a pretty low flash point and there is really no obstruction with the small dome. Compared to a Big Chevy, this is a dream try to fire that mess all from one side...

I know dual plugs are pretty popular on old Harley's. I don't know how much it helped though because half of them I see have the second plug blocked off...

 

[62 Dart Convertible]

Sorry to intrude on the Hemi love fest guys, but I've never understood how twin plugs doesn't produce knock (pinging, detonation), in that knock is explained as two or more flame fronts colliding?!

PS - Great thread Ron, thank you!

 

[rev.ronnie]

Sorry to intrude on the Hemi love fest guys, but I've never understood how twin plugs doesn't produce knock (pinging, detonation), in that knock is explained as two or more flame fronts colliding?!

PS - Great thread Ron, thank you!

Thanks, I hope I'm covering some stuff that normally does not get explained in detail too often.

Dual flame fronts with two spark plugs is different than one spark plug firing into a mixture that has started to pre-ignite at a different part of the chamber.
I think it has to do with the timing of the two flame fronts, working together for a more efficient burn. A rouge flame from heat or instability in the chamber throws a curveball at the burn process.

Some newer cars have dual plugs to help with emissions. Old snowmobile engines did it for more power, for a more complete burn and using all the energy available. It was often a crutch for a bad combustion chamber design.

 

[Meep-Meep]

Thanks, I hope I'm covering some stuff that normally does not get explained in detail too often.

Dual flame fronts with two spark plugs is different than one spark plug firing into a mixture that has started to pre-ignite at a different part of the chamber.
I think it has to do with the timing of the two flame fronts, working together for a more efficient burn. A rouge flame from heat or instability in the chamber throws a curveball at the burn process.

Some newer cars have dual plugs to help with emissions. Old snowmobile engines did it for more power, for a more complete burn and using all the energy available. It was often a crutch for a bad combustion chamber design.

Very much so! The early Porsche 911 race engines had a very deep chamber, and when the compression was raised by increasing the dome (yes, these are hemi head engines), parts of the chamber was shrouded from the plug. Adding the second plug resulted in more power and no detonation. Porsche eventually redesigned the chamber to have less dish, and in the later production CIS engines, they added a quench dome piston. Note pic showing odd piston top profile.

I also believe Tom Hoover commented that he would have added a second plug on the 426 if he could go back and do it again so to speak. Pretty sure Dick Landy ran a twin plug hemi (in fact might have been the first guy to do it).

 

[snakeoil24]

Firing A Hemi with Duel Plugs has risks, with a true Hemi design extreme octane and anti knock additives help. Lead being one of them. Landy and Prudhome where playing with alky Gas blends even in lower classes. Cooling was very important. Alot the newer guys with the small block Semi wedge Motors they refer to as Hemis dont realize that these motors depend heavily on Quench, flat top pistons and polysphere chambers. The Gen two Hemi was designed for brute power and had all kinds of issues with fuel and detonation. My latest motor will be broken in with a blend of race gas. I run a 9.75:1 compression and still know it will be marginal.. These motorsd where here for one reason only to produce brute Power. No Wedge or Poly or Gen 3 can come close.

The early Porche Race engines if I remeber correctly had issues similar to the Hemi, they had hot spots in the cylinders that created predetonation. Correct me if i am worng the early Porches where air cooled, which caused it's own share of problems.

 

[62 Dart Convertible]

Interesting topic, thanks for the information gents.

Meep, at first I thought those pistons had been melted, what an odd dish!

 

[HEMI-ITIS]

What's the weight difference between my stock iron heads & the stage V ?

 

[Meep-Meep]

Firing A Hemi with Duel Plugs has risks, with a true Hemi design extreme octane and anti knock additives help. Lead being one of them. Landy and Prudhome where playing with alky Gas blends even in lower classes. Cooling was very important. Alot the newer guys with the small block Semi wedge Motors they refer to as Hemis dont realize that these motors depend heavily on Quench, flat top pistons and polysphere chambers. The Gen two Hemi was designed for brute power and had all kinds of issues with fuel and detonation. My latest motor will be broken in with a blend of race gas. I run a 9.75:1 compression and still know it will be marginal.. These motorsd where here for one reason only to produce brute Power. No Wedge or Poly or Gen 3 can come close.

The early Porche Race engines if I remeber correctly had issues similar to the Hemi, they had hot spots in the cylinders that created predetonation. Correct me if i am worng the early Porches where air cooled, which caused it's own share of problems.

Yep, 426 hemi's have no real quench to help out the burn. But Porsche managed to create a quench dome piston for a hemi head. The problem with this profile is it interferes with the valve timing on the older mech FI cams. And yes, all 911 flat 6 cars are air cooled up to 1997 (highly sought after 993 model). Not trying to make this a Porsche thread, but as the saying goes "good information is where you find it."

 

[rev.ronnie]

What's the weight difference between my stock iron heads & the stage V ?

I will weigh one of each tonight and let you know. They will be bare casting weights.

Here is an interesting piston designed by Aruzza/McCandless. It has a dome that mimics a Stage V chamber for quench. This is probably a great piston for a high compression Hemi. John and Herb are well known for their contributions to Hemi engine performance.

(The photo is from John Aruzza's website.)

 

[rev.ronnie]

What's the weight difference between my stock iron heads & the stage V ?

Stock head 59.75#
Stage V head 25.55# ported, finish machined

Both heads bare.

 

[rev.ronnie]

The final step on the heads after the finish porting. Installing brass sleeves in 4 pushrod holes. We burn though on these 4 when porting to get the cross section wide enough with the big valve .

 

[snakeoil24]

Rev Ronnie beautiful work youhave done!

 

[aldal]

Can a guy use stock valve covers with the Dvorak stands?

 

[rev.ronnie]

Can a guy use stock valve covers with the Dvorak stands?

Yes. It's usually big springs that hit.

 

[rev.ronnie]

Machining the timing gear for a torrington bearing. It seems impossible to find a 3 keyway billet timing set for a Hemi with a bearing. They all want to sell you a 9 keyway set.

I avoid 9 key gears at all cost. They are very hard on the snout radius. Callies will not warranty a crank that has had one installed.

 

[Meep-Meep]

So what's with the 9 keyway sprocket? If there is interference with the nose radius of the crank can't you just cut a larger chamfer on the sprocket? Or do the extra keyways make the sprocket weak?

 

[HEMI-ITIS]

Yes. It's usually big springs that hit.

There is a modification for that:blob1:


Called heat&beat:icon_smile:

 

[2059]

been following this in order to learn some things. Isn't designing a "quench piston" like "tail wagging the dog"?

Yep, 426 hemi's have no real quench to help out the burn. But Porsche managed to create a quench dome piston for a hemi head. The problem with this profile is it interferes with the valve timing on the older mech FI cams. And yes, all 911 flat 6 cars are air cooled up to 1997 (highly sought after 993 model). Not trying to make this a Porsche thread, but as the saying goes "good information is where you find it."

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BTW Hemi-itis. nice mods...

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superior work rev..

 

[rev.ronnie]

So what's with the 9 keyway sprocket? If there is interference with the nose radius of the crank can't you just cut a larger chamfer on the sprocket? Or do the extra keyways make the sprocket weak?

The key ways cut in the gear create many stress risers on the face of the crank snout, even if the radius clears. These stresses have been known to cause snout breakage. Callies addressed this years ago, and sent out a bulletin with every crank.
On some 9 keyway units, I have seen the press fit go away after running to the point where the gear is loose. This leads to chatter witnessing and timing chain runout. I would prefer a single keyway if I could find one. I'd rather use offset bushings to correct cam timing.

- - - Updated - - -

There is a modification for that:blob1:


Called heat&beat:icon_smile:

It makes it look tough as hell too!

- - - Updated - - -

been following this in order to learn some things. Isn't designing a "quench piston" like "tail wagging the dog"?

- - - Updated - - -

BTW Hemi-itis. nice mods...

- - - Updated - - -

superior work rev..

Thanks I think the quench comes into play with the really big domes. On a lower compression deal, there isn't the dome for it, and less problems with detonation. You are correct though, the big dome creates it's own problems that you have to sort of "fix" by having the some big enough and close enough to the head to get quench.

It's a viscous tail chase, that's for sure.

 

[rev.ronnie]

Finally got the camshaft!... Now its time to mock up for rod to cam clearance and get pushrod lengths.

Turns out the factory got 6 of the 8 pushrod holes are off little off. I will correct that.
Also, I'm going to add. 010" to the rod/cam clearance. It's at .050" now. It won't even affect the rod weight and balance.

Piston to valve and overlap clearance are great. No problems with this mild cam.

The timing gear alignment came in perfect. Always check this.

More to come!