Will unmilled C head ports mate up to an unmilled 7111 OK without milling or porting of either? Which has the larger ports, the heads or the intake? Also, just how tall are the 7111's in relation to air cleaner and normal hood clearance.

 

From what I've read, the intake ports need to be enlarged to match up with the head ports.

As for hood clearance, you didn't say what vehicle you have. On my 71 Cutlass Supreme there's ample clearance, but if you have a TA with a shaker scoop it likely won't work without modifications.

 

Considering it for 403 in a ‘79 Buick Estate Wagon. From what I understand the 7111 is the only one that will come close to working with a C head so even it has to be modified apparently. Just one of the options I’m considering. Thanks

 

I have a ported RPM intake matched to the big block heads for sale...

Why are you considering big block heads? Might be at a loss if you're just throwing them on a factory deep dish piston engine. Even with the reduced airflow, a set of 65-72 330 or 350 heads will pick up the compression. You're already losing .023" from the new head gasket if you choose to swap to big block heads which would bring that 7.9:1 compression down even more.

 

As said without KB, Arias, Diamond or the pistons Cutlassefi sells, you will stay at 8 to 1. My understanding is that the 403 came with Felpro head gaskets factory and the C heads will be 82ish CC. My 4A heads were 86CC, so there would have been a slight gain. I put on #8 heads on my 403 which seem to measure77 to 78CC, measured two sets vs the 79CC factory spec.

 

Several notes.

1) No matter what, the intake ports on the intake need to be opened up. The small block intake is much shorter than the big block. The 7111 has enough material to be opened up so the port sizes match. I suppose you could run it without doing that, but there'd be some terrible intake turbulence. It only takes about an hour with a regular die grinder and a decent aluminum carbide.

2) Most Edelbrock Olds intakes come out of the warehouse with rather poor machining. The intake flanges generally need to be milled ~0.030", possibly more depending on what all has happened with the block and heads. You *might* be able to get the intake to seal without getting it machined, but it'll be a trial.

3) 7111 raises the carb about 2"? ish?

As mentioned, the general combos are:
a: stock short block with earlier small block heads
-OR-
b: flat top pistons with big block heads

Stock short block with big block heads will get you a better exhaust port, but not worth the effort.

 

I guess because I read it on the internet Guess too that I had forgotten the part about needing the flat head pistons. I had found a set of C's just thought I's inquire as to whether or not to consider them. Thanks for straightening out my thinking.


So noted, THANKS!!

Well that puts my 2 months of googling and internet searching in a nut shell for me doesn't it? Honestly I think my brain is getting on overload and it is all beginning to run together.

Thanks for taking the time to straighten this Olds 403 newbie out guys.

 

Being the fact that it's going in a wagon I'd do small block heads with a 7111 and properly tuned carb. That'll give the best bang for the buck in my opinion.

 

Hey Mark, I am leaning toward that option too but have posted much more info that may help us determine the best approach in this new thread. https://classicoldsmobile.com/forums...1/#post1191934

I'd be happy to communicate more with you via email if you think this is something you could help me with, ie parts as well as possibly the actual build. Look over that new thread and lets get together.