Anyone using the LS7 heads. Last time I checked assembled heads were not available. How do they compare with AFR 225s or LS6 prepped heads?

 

FYI in case you didn't know; The LS7 heads require a larger bore, I can't remember if it was a 4.100 or 4.125 bore though.

 

There is no comparison. you cant compare them to LS6 heads or other LSx based heads. The design is new. They are awsome to bolt on if you can, but you do have to have the bore for them and the intake manifold.

Rick

 

Think it is 4.125 and the C6R engine bore is 4.185 to unshroud the valves and let this bad boy breathe better.

I'm still waiting for someone to stick a serious cam up this thang and either put some 104 racing fuel or 108 octane E85 in it to take out the advance restriction and see what it will REALLY do. I still think the story my buddy told me (that works for GM engineering) that there's 700 normally aspirated horsepower in the LS7 is true. May not pass any smog tests and may not idle below 1200 rpm or clean up the cam below 3000 rpm, and damn sure won't produce 28 mpg, but it will make the number.

Charlie

 

Thanks for the response Rick. I am aware of the bore size. I have a
C5R block and planning on a 427.

Bear

 

The C5R block was desigen on LS6 heads. Contact Katech for the PP LS6 heads with the 2.1" Exhaust valve 330 flow at 575 lift. KAT-A2698
http://www.katechengines.com/street_...etail.php?id=7

The AFR225 is a good head but the flow does not come close to this special LS6 head.

the LS7 head is for the LS7 block.

 

Now I am getting confused. I thought that the C5R had it's own heads that required the use of a hand built manifold.

How does Katech get a 2.1" exhaust valve in an LS6 head?

Don't the LS7 and C5R blocks have the same demensions? How would the head know it was on an C5R instead of a LS7? Wouldn't it work the same if the bore and stroke the same?

Bear

 

So who's using the katech stage 1 or 2 heads?

 

I think there is a ways to go and a lot more R&D needed before you'll start seeing routine use of these LS7 heads. I know my shop (ECS) tried them on a 402 N/A build for me and after a bunch of time and effort decided that they were just not working out well and they ended up using ETP 215's. I believe Doug Ring (co-owner of ECS) put LS7 heads on his own 447 N/A build and still is not 100% satisfied with the results. I also know of at least 2 Cartek N/A builds (a 441 and a 447) which have employed these LS7 heads and the results have not been what was expected. So, it is not as simple as "slap them on and make big power" as it would seem there are other nuances (cam size?) that need to be experimented with, and that will take time, and time is money. One also has to consider the costs of these heads vs other options out there that are known to work well already.

I do now that A&A Corvette did an N/A 402 with LS7 heads late last year and it made some great numbers on the dyno...there was a thread here on it, but I can't recall all the details. Perhaps Andy has figured out what others have not in getting some serious power out of these LS7 heads. But I haven't heard anything more on this. I'm not sure what's been going on over at LS1 Tech as of late, but I'm certain that if there were some major breakthroughs we'd have hear about it by now.

 

the LS7 and C5-R blocks are much differnt. Besides the differnt alloy the C5-R block is larger, far better oiling and cooling capablites. The LS7 is a street 427, not for racing. For racing or higher HPand TQ ideally the C5R block or a LS2 block sleeved to a 4.0 or 4.125

The LS7 head would work on the C5R block as well as the AFR205. However, the best head is the special LS6 head that Katech makes.

yes the C5-R and C6.R have diffent heads all together but the heads are modfied Katech cast 243 LS6 heads.

The Katech LS6 head with the larger valves also has a diffent injector angle for a unifrom combustion.

 

is the valve grind angle different?

 

There is no comparison to standard LS1 - LS6 architecture....

The LS7 heads, out of the box, flow mid to high 360’s CFM and slightly worked will routinely flow mid 370’s….. and on a full hand reworking our best numbers are just north of 390 CFM.

From a cost solution perspective the new L92 casting, with only a good valve job, will flow north of 335 CFM.

Here’s a dyno graph of an LS7 headed 427 – mods are cam, UD pulley EWP, AR headers…numbers are through cats and on 91 octane!

 

I realize the attributes of the C5R Block after all I bought one, but I do believe that they can be set up with the same bore and stroke as the LS7 and then matched with the LS7 heads which come with 2.20 intake and 1.61 exhaust valves along with 283 cc runners. Lingenfelter does a LS7 package using these heads with no mention of porting along with a streetable cam and headers and tune to get 534 RWHP.

Who says the Katech special LS6 head is the best? Who I running them? What kind of power do the put down? According to the Katech web site there is no mention of 2.1 exhaust valve, that is bigger than I have ever heard of for an LSX engine.

I have a friend that had the C5R heads on his 427 and there was no factory intake manifold that would bolt to it. He had to have an aftermarket intake made.

Also I think that AFR suggest using the AFR225 head on the large bore engine not the AFR205.

 

The intake valves are 2.100, exhaust 1.550.

 

DOH got them switched.

 

Wonder what happened to the torque above 5000 rpm? I suspect the person who finds a way to get more air flow on this bad boy pulls that curve up. When the torque curve comes up, so will the horsepower. I think the number goes above 600 when that happens, and with enough cam and flow begins to squeeze 700, albeit at or above 6800 rpm.

Charlie

 

The cam is probably on a tight lsa.