I'd like someone knowledgeable in this area to explain to me why a 376ci LS3 motor is able to use a cylinder head with a 260cc intake runner volume perfectly fine. And on the other hand an older 350 or 383 SBC would never be able to run a 260cc head on the street. What changes give the LS3 this ability to run larger port volume heads?

 

The head flows better and electronic fuel injection. I have a 406 sbc with a large solid roller and big dart heads and it idles and drives fine with efi. BTW I do not consider myself knowledgeable in this area.

 

Runners are different shapes and lengths as compared to the old stuff. Kinda like comparing small blocks and big blocks...

 

Guys, the OP had sent me a PM asking for my input mentioning his question in this thread....I thought it might be helpful to share my answer publicly for the benefit of others.

The new heads are certainly larger but flow a bunch more than the older heads at comparable volumes (or when you compare CSA versus airflow).....they are more efficient and have higher airspeeds, BUT....they aren't as efficient as a clean sheet aftermarket head design....they are just alot better than stuff the factory put out 15+ years ago.

Our 230 cc head flows the same peak number with better lows and mids and does it with 30 less cc's and a much smaller intake valve. We also have alot more exhaust flow which helps.

Do the new LS3 heads work?....do they provide good value.....yes....most definitely, but they do come with their share of compromises.

The other issues are that the old school engines were built on much more narrow LSA's.....the wider LSA's help to reduce overlap and keep the engine alot smoother and more tractable around town.

Also, the intake manifold design of the new Gen III engines is also a huge help. Equal length runners that are almost twice the length of the unequal length runners of the old school engines your trying to compare.....that helps a great deal in building more more low speed torque offsetting some of the losses inherent in the large port CSA.

Muck lighter weight ring packs also freeing up a bunch of power and enhancing fuel economy.....and of course the EFI deal is huge. We aren't trying to atomize fuel thru a carb and a large lazy inefficient intake port.

Lots of unique attributes that all add up to making a large port much more tractable and civil out in the real world but that still doesn't mean that scenario provides the ultimate solution. Drive the same package with a similar flowing head some 30 cc's smaller and you will experience exactly what I'm talking about.....just ask Pat G!!

https://ls1tech.com/forums/dynamomet...k-results.html



Cheers,
Tony

 

Thanks Tony! I always wondered why that was for quite a long time, then it struck me to ask on ls1tech!

 

What kind of heads does AFR make for an LS3 motor?

Do they Port LS3 head?

I have a 2011 SS Camaro L99 I'm about to do a DOD delete Head and Cam combo I drive it every day. I know to have Patrick spec the cam. I just need to know what to do with the Head.

If I sound like a Pilgrim sorry and please pass the Stuffing... HELP.

 

Yea the gen 1 stuff is terrible on the exhaust flow...those two center exhaust ports being side by side def dont help the cause!

 

First, you might want to make your own thread so you don't hijack this guy's thread, but to answer some of your questions here it goes.

I don't think AFR will port anybody's head but their own. They do not make a rectangular port head for L99/LS3/L92 motors.

Only Mast Motorsports and PRC make an aftermarket casting rectangular port head, but PRC (Texas-Speed) and WCCH will port your factory casting for you.

Hope this helps.

 

I apologize for hijacking the thread, I'm new.

Yes it did help.

Thank you

 

lower cc = higher compression ratio

 

Talking about runner cc here, not chamber volume. Runner size has nothing to do with compression ratio.

 

Talk about reviving threads!