Gen III Hemi LSA vs wedge engine.

[cpearce]

Are there different requirements for LSA on a Hemi head vs wedge heads? As I learn about the newer gen Hemi engines I am finding they have different requirements and characteristics than LA engines, which I am familiar with. I see many of the cams in the aftermarket have wider LSA's than I am familiar with. Realizing a lot has to do with idle quality and EFI, I wonder what carbed requirements are like? On other forums, member's have indicated Hemi engines generally prefer a wider LSA than wedge heads. What are some experiences of FABO member's?

 

[cpearce]

Buehler, anyone?

 

[dusterdoug]

I think it’s pick your poison. There are carbed gen 3 hemis that make good power at 108, and at 112 in NA applications. Of course if you have any forced induction you want a wide LSA.

But you are correct, most shelf grinds are wider.

If you want a more educated opinion, call the folks at MMX (Modern Muscle Extreme). Great service without trying to sell you something that you don’t need.

 

[273]

Don't know about hemi's and LSA probably like you said most run wider for efi reasons, LS guy's run wider because piston to valve clearance also, don't know how the hemi is on that front ?

From what I've heard hemi's like/need less overlap which could lead to a wider LSA.

 

[cpearce]

From the little I have found on the subject, piston to valve clearance is an issue as overlap increases. I have also found information that Hemi's need less overlap due to the ports flowing straight on from one to another.

What I have not found much of is dyno testing on Gen 3 Hemi engines where camshaft swaps are done to test LSA. Frankly many of the test I have come across are not using what I would really call aggressive cams. Perhaps due to the engines being EFI and not needed, supercharged applications, or simply lack of variety of grinds. I realize I will be in a minority with my build of naturally aspirated with carbs, or possibly carb style EFI.

 

[racerjoe]

From the little I have found on the subject, piston to valve clearance is an issue as overlap increases. I have also found information that Hemi's need less overlap due to the ports flowing straight on from one to another.

What I have not found much of is dyno testing on Gen 3 Hemi engines where camshaft swaps are done to test LSA. Frankly many of the test I have come across are not using what I would really call aggressive cams. Perhaps due to the engines being EFI and not needed, supercharged applications, or simply lack of variety of grinds. I realize I will be in a minority with my build of naturally aspirated with carbs, or possibly carb style EFI.

I'm no expert, but most of the shelf cams you will find are for a stock piston. Which means a narrower LSA can lead to PTV clearance issues like you mentioned. There's plenty of options out there now and several of them are very similar specs. It is also easier to tune EFI if you have good manifold vacuum.

 

[cpearce]

I'm no expert, but most of the shelf cams you will find are for a stock piston. Which means a narrower LSA can lead to PTV clearance issues like you mentioned. There's plenty of options out there now and several of them are very similar specs. It is also easier to tune EFI if you have good manifold vacuum.

I will be having pistons made, my wrist pins are .688", to keep them lighter and out of the rings. The cam will be factored into piston design.

 

[408 swinger]

I have two 6.1 engines, one stock stroke, the other a 426. The 426 has a 107, and, the stock stroke has a 110. They both run very well. The stock stroke 6.1 has just under .550 lift. The clearance is just enough.

 

[cpearce]

I have two 6.1 engines, one stock stroke, the other a 426. The 426 has a 107, and, the stock stroke has a 110. They both run very well. The stock stroke 6.1 has just under .550 lift. The clearance is just enough.

Where are the cams from? Do you mind sharing some details on your 426?

 

[67Dart273]

You guys are depressing the old man and making him drool at the same time!!!

 

[408 swinger]

Where are the cams from? Do you mind sharing some details on your 426?

They are both Hughes cams. Unfortunately, he dumped all his gen 3 availability.
The 426 is 4.08 bore, 4.08 stroke. Heavily modified early heads. Johnson juice lifters, stock rockers and shafts, Stanke collars and tie bars. Tall Ritter drag pak intake. Had a 1050 Dominator on when I raced it in my Dart. I now have a 1000 cfm competition series Thermoquad that will take its place.