C6AR-R Porting and valve sizing

[677litre]

I picked up a set of 14 bolt C6AE-R today that need rebuilding but overall in good shape. Yes I'm aware money is better spent on some Edelbrocks but lets for a moment disregard that, partly because I want to stay true to the stock look for the year I'm restoring and second I like the challenge of getting what I can out of old iron within reason, it's a street car not a drag racer.

Looking for links to porting these specific heads, pictures are always nice. I know about the exhaust lip to be removed.

With a 30 over 428, dual quad low riser intake, what are the largest and/or most beneficial valves I can install? With stock piston? Aftermarket pistons required for larger valve relief for largest valves installable?   Note: I may still go the stroker kit route for the extra cubes.

I'm going with a roller cam, haven't decided specs yet, open to suggestion on that as well. Pump gas friendly.

Thanks.

[Phil Brown]

The set that I got have a 2.09 intake and a 1.75 exhaust
There close but they don't touch   
Just some "cleanup" in the ports. There on a 4.250 bore motor and make good power

[My427stang]

I have run 2.15/1.67 in iron heads and they work well.  Bigger exhaust valves will get real close to the bore and can hit with a lot of lift.  Bigger intakes will fit, but there is debate on whether it helps as it gets closer to the bore.  In a 428, I'd likely go 2.15/1.67 and then focus on the valve job and the rest of the bowl to make a nice smooth path to the new valves.

[677litre]

Recommendations on where to buy decently priced complete valves, guides etc etc?  The local machine shop will just be buying and marking up the same stuff so they told me they don't mind me buying all the parts myself.

Refresh me on the thermactor port bumps in the exhaust, they can be ground smooth correct?


With regards to the R heads specifically - how large can you take the exhaust before it is an issue.  I know there is not much meat on the one side of the valve seats.  It also sounds debatable whether installing new exhaust seats is necessary if not needed with so little there to hold the seat in place.


The links in this old thread are long gone dead and I was wondering if anyone has any old the old pics and info discussed?

http://www.network54.com/Forum/74182/thread/1156317484/C6AE-R+exhaust+hump+removal

[jayb]

I think Barry R sells the valves you want.  A lot of people just go up to CJ sized valves, which are 2.09/1.65, and that's a pretty good improvement.  Not sure how big you can go with the exhausts on those heads...

Yes, you can grind the thermactor bumps out of the exhaust ports, and that would be one of the first things I'd do if I were you. 

[677litre]

Thanks Jay,  just to be clear on the thermactor bumps, they are just solid as part of the castings and not hollow on these right?  That is, they can be completely ground down to port size without worrying about breaking through correct?

[fastback 427]

You can also try www.alexparts.com for what you need. I've ran a few sets of his valves, retainers, seals and locks with good results. Cheap prices with quick turnaround.

[677litre]

You can also try www.alexparts.com for what you need. I've ran a few sets of his valves, retainers, seals and locks with good results. Cheap prices with quick turnaround.

The Link seems to be broken.

Edit: I found the right link.  Thanks.

http://www.alexsparts.com/

[677litre]

Is it worth going with 11/32" guides and valves?

[ScotiaFE]

If your going to do a nice valve job/upgrade go with a 45* seat on the intake.
A stock CJ intake seat is 30* and not the best starting point for serious upgrades.

[Phil Brown]

Thanks Jay,  just to be clear on the thermactor bumps, they are just solid as part of the castings and not hollow on these right?  That is, they can be completely ground down to port size without worrying about breaking through correct?

                                                                                                                                                          Mine were solid , gone now  I don't think any were hollow but I could be wrong

[My427stang]

Just for reference, here is a C8AE-H with 2.15/1.67s in a 4.05 uncut 390 block.  You can see there is a ton of room for the intake valve even in the small bore, but you can also see the exhaust gets tight, and gets tighter with lift.

I like the Alex's parts CJ valves for a budget build, but I am not sure they have 2.15 intakes.  If going that route, and it assuming it isn't a big power maker or racer, I'd likely go with their CJ valves, my hunch is the money would be better spent on the valve job and bowl work.

If it's a hotter/higher RPM motor, I'd likely spend the money for Ferrea or some other higher end component.  FWIW I run Ferrea in my Mustang, but I did try the Alex's parts stuff in my 445 truck motor, it never sees north of 5000-ish.  Have had heard only good things about Alex's cheap valves from others too

[677litre]

2.15/1.67s look like they might be perfect for a 4.160 bore 428 though?  i could see going bigger but there doesn't appear to be much more without the valves touching?  I'll contact Andy's but it looks like they only sell certain sizes.  If I go the Ferrea route is there a supplier you guy recommend?

With regards to the factory cast but not machined  thermactor ports on these,  I'm still not sure if they are solid or actually open on these castings.

[Joe-JDC]

When you say roller cam, are you talking hydraulic or solid?  If you are going to use a large exhaust valve, then you may consider notching the bore of the cylinder just under the exhaust valve in each corresponding bore.  The 427 MR did this from the factory.  It will help unshroud the exhaust valve at lift.  Also it will be beneficial if you are going lift numbers near or over .600" on the exhaust.  Just don't cut into the ring sealing area.  Joe-JDC

[Phil Brown]

Interesting photo showing just how offset the valves are in the bore. Next time mine is down I'am going to have to see how tight it is around the exhaust on the larger bore
I do agree port and bowl work probably better spent money