Here's a section shot of the 5364 casting providing an inside look behind the bulge. I don't have the 2716 head sectioned yet.



Richard

 

I have a set of the 823 castings here & they don't flow as well as the previous castings... Anyone else notice this?

 

Richard any comment on the 823 casting numbers? I have a set that will be here tomorrow via FEDEX that I've been over for the past 2 months and I was going to send them out for an exhaust CNC rework.

 

I have no knowledge of the 823 castings. If anyone wants to send one to us I'll test it and report the results.

Richard

 

Richard, could you do just an exhaust CNC for me? I'm going forced induction and I'm planning on leaving the intake as cast. Also could you ask your GM buds how many different castings they are and is the 823 the finial release since Elwood just got his from SDPC last week?

 

Yes I could machine just the exhaust ports for you. I have some minor details to sort out with the exhaust program, but it doesn't have anything to do with the finished part. I could machine a pair of heads for $350. That includes re machining the seats as well. Our target flow for these ports will be 240cfm@.650" lift. I'll have some more info on that by early next week. It'll take about 3-5 days to work the heads through the shop.

Richard

 

what are the casting dates ? and which is the oldest and which is the newest

figures GM comes up with something good , then has to fark it up for everyone

 

SWEET... Richard, you will be hearing from me soon! I bought 1.6 Titanium exhaust valves but they have 11/32 stems. Could you over size ream the guides with the Serdi and install bronze bushings or should I do that here before I send them to you?

Frank

 

OK you ask, so I asked....here is the response from the team at GM Performance Parts;

There are currently two different castings. We have a couple foundries and the tooling carries different numbers. I've been assured that the design of the ports and the water jackets are the same, but there are just casting process differences causing the differences that the consumers are seeing. Flow testing in stock unported form shows slight flow benefits to one vs. the other, however not enough to have any real impact on performance.

When the castings are CNC'd and the port is done correctly the flow numbers will not be affected even though some of the port will not be touched by the cutter.

We do not have control of which foundry we (and the consumer) get them from.




It's all good

Robin

 

Thanks Robin! I was just checking to make sure I couldn't have done better before I machined them.

Frank

 

Robin, you have a PM.

 

Would it matter if you had one casting on one side of the motor and another casting on the other side?! a Mismatched set!?

 

Thank you for your prompt response Robin. Your exctly correct about the port not cleaning up 100%. My reason for bringing this up at all is to gain better awareness of possible differences to port wall locations. You mentioned that there are two castings being made, yet we have 3 different casting numbers. Can you let us know which 2 of the 3 casting numbers are being used?

Respectfully,

Richard

 

Richard

I agree with you on the number of castings. I have an L92 engine here with the 823 casting number. After I posted about the 2 I sent another request to GMPP noting that there are 3 numbers not 2. I will eventually have the 823's off and compare them to the 5364's that I have that are bare castings.

I'll start looking for some of the 2716's when I can. Still I don't think that it amounts to anything worth the effort.

I will advise when I hear more.

Thanks

Robin

 

i got my 823's today from SDPC. do all the intakes runners have "lumps". just wondering. mine have the lump like the 5364's do on the exhaust runner from the best i can tell

 

My 823s have those 'bumps'.

 

Yes they do

Robin

 

Thank you for your assistance with this Robin. I'm not really concerned about the performance differences in the as cast version, I feel the same as you on the minor difference in flow. Rather my main concern is will I need to make separate exhaust port programs for the different numbered heads due to casting wall thickness differences and the proximity to water jackets? I suppose I can port them and then saw each head apart and measure, but it'll cost valuable time not to mention money. Again, thank you for helping with this issue.


Both numbered head castings I have appear to have the same bubble in the intake port roof to accommodate the spring pocket.

Richard

 

ok well thanks for the info guys.

Nick

 

My 5364 post CNC. Looks like the lump is virtually gone.