Dry fitted a set of SBO Edelbrock 61035 heads and 7111 intake manifold today w/o gaskets on a '68 350 block. I'm trying to learn so have some questions...

1. The intake bolt holes barely align w/ the threaded holes in the heads. The bolt is tight to the "bottom" of the through hole in the manifold in order to line up w/ the head. When the head gaskets are in place this will help, but the intake gaskets will counteract that. Probably won't be a problem per se, but thought this was odd. Is this normal?



2. Regarding port matching intake ports on the head and intake - the head ports are larger in both dimensions then the intake. Is it advisable to enlarge the intake's ports to match the head's ports if the head ports are larger?
Head - 1.51" x 2.53"
Intake - 1.24" x 1.90"

3. The exhaust ports on the aftermarket heads are shaped differently (more more square vs rectangular) than those of the stock manifolds or the stock #5 heads. Why would that be, and is there a benefit to port matching the exhaust ports to the header or manifold used?
**EDIT** - per the instruction sheet that shipped w/ the heads "EXHAUST HEADERS: Any header or manifold designed for original equipment heads will fit the Edelbrock Oldsmobile Cylinder Heads. Exhaust ports are CNC profiled for optimum performance and should not be enlarged to fit the header gaskets"
61035 Head: 1.62" x 1.51"
#5 Head: 1.4" x 1.9" 2.66
Exh Manifolds: 1.53" x 2.1"

4. Misc question on two threaded holes in the lifter valley. What are these for - they appear to tie into the cam bearing area?

 

I used a brand new Chinese copy of the 7111 intake with the 61035 Edelbrock aluminum heads, it bolted right on with no drama. I used the Edelbrock composite intake gaskets, ports perfectly matched the heads, block was decked .016" and .040" thick Mr Gasket MLS head gaskets were used. No leave the intake ports stock, except for a bigger cubic inch or high compression, big cam small blocks. Don't mess with the floor of either port, the exhaust especially. The floor was raised to remove a dead spot in the port. I thought only the 330 block had those, the factory used separate side shim intake gaskets with a bolt in valley tray.

 

Yes, it’s advisable to open up your intakes runners to roughly match the size of the larger intake port on the head.
you generally want to increase the size of the intake runners as far into the manifold as possible, for a smooth transition,.
I don’t think you want a small volume of air suddenly being dumped into a larger space, the flow would cause a pressure loss.

I’m not sure I’ve seen someone run cast-iron manifolds on aluminum heads, but I imagine it’s been done.
conversely, your exhaust head port will be trying to push through more air into a smaller restricted space in a manifold.

those two holes in your lifter galley are for a stock oil baffle. it will keep hot oil off the bottom of your intake and redirect it down to the rotating assembly

 

Smooth taper makes intuitive sense to me, but how does this relate to MCSA effect on powerband? In this case I would be porting the manifold runners. The MCSA (I believe) is in the head itself near the turn to the intake valve, so I porting the manifold shouldn't have any impact on this, correct? Just trying to understand if there are likely downsides to doing this.

This engine didn't have that during teardown. I tried to find an image online to know what I'm looking for and didn't find any stock OEM examples, but did find this:
This looks simple enough to make - is this what I'm looking for?

 

What is your combination? Mine is very mild, 9.3 to 1 and a 218/218 .541/.541 112 LSA hydraulic roller cam. I didn't even notch the center divider on the intake, just used the thick open gasket. These heads are very sensitive to timing compared to iron heads. I can only run around 20 base at 1000 rpm, it didn't like 25, made the idle less stable. Mark made the most power at 40 degrees on his low compression mule. I am adding a mechanical advance limiter, my doesn't like the close to 40 at 4 to 5000 rpm HEI adds with 91 non ethanol. See what the experts suggest.

 

Another question - the combustion chamber has a very rough cast texture to it. Does that serve a purpose, or is it just additional machining that Edelbrock opted to leave up to the end user? Is it typical to smooth/polish this surface?

 

Pretty much all Non-CNC’d chambers will be like that. Natural casting texture.
As far as Port matching, if you have a mild combination, I really wouldn’t lose any sleep over it. When I do the port match, I do it small smaller than the head itself anyway. That can help the reversion a bit.
When I tested these Heads five years ago, my port matched RPM only picked up about 12 or so over the non-port matched one. Again, I wouldn’t lose that much sleep over it if it’s a mild build like my test mule was.

 

The bolt-in lifter valley tray was not used on the later engines, but the holes are still there. My 70 block had them and they were not threaded, so in order to use them you need to thread the holes while being careful not to contact the cam bearings.

 

The intake bolt holes are oversized for exactly this reason. So long as you can get the bolts started by hand, it is a non-issue. Fitment without the gaskets installed and compressed doesn't mean much. The height of the intake bolt holes in the head above the deck surface obviously vary both with head gasket compressed thickness and with machining on the block deck and the head deck.

 

Regarding polishing out the casting flash in the chamber, would you characterize that as likely to have a negative effect on torque/power, no effect, or possibly a positive effect?

Is this the test mule you are referring to?
https://classicoldsmobile.com/forums...umbers-164172/

When you say "I do it smaller then the head itself anyway" - you mean that you don't open up the intake port quite as large as the port on the heads? Roughly how far back into the intake from the gasket surface to you blend?

 

Yes, about a 1/16 smaller all the way around. You can remove any sharp edges if you like.

 

If you really want to learn like you say…what you need to do is slot your intake manifold bolt holes and RAISE your intake as much as you can, double gasket or triple if you have to. preferably get the intake up so the roof of the intake port is at the roof of port in the head.

once you get that sorted out, fill the floor of the head with epoxy to the height of the intake floor straight in.

do not open up your manifold in the position it’s in now to match the head..that’s a big TQ killer. that head is big TQ killer as it is on 350 cubes. if you don’t want to be disappointed, do what I suggested.

 

You can still make real decent tq with this head on a stock stroke 350. I did, it’s on here. 465hp, 465tq. Those are 383 SBC Chevy type numbers, with 20ci less.

 

That is why I am curious what his compression and cam are. These are a nice head and definitely not for those with empty wallets. They are definitely different in the timing they like, much less than the 1964 iron chamber design. The Progression distributor or SEFI with timing control to dial it in is a good idea. Even my Qjet was surprisingly rich with these new heads.

 

Why do you think that was?

 

A much more efficient chamber is my guess. You tell me Mark.

 

Nope. Stronger signal at the boosters. The heads will retain better vacuum vs irons than some believe.

 

Very interesting. It would explain why it was rich across the board. The timing is also tough to figure out, too much timing runs shitty at idle and popping back through the intake trying to run 40 WOT on 91. Too little at idle, also a shitty idle. These heads really are the 3 bears, it needs to be just right. Also it gets to operating temp much quicker than the iron heads but doesn't overheat, that must be a thermal efficiency thing.

 

As I mentioned before, I put in just about as much timing on any of these new heads as irons or any previous aftermarket head. I’m not seeing as much of a difference as other people are stating.

 

You can only go by what the dyno tells you the new heads like with 93 octane. It could be the Chinese HEI as well as the factory HEI is adding the 2 to 3 degrees in the 4000 to 5000 rpm they usually do. A Progression ignition is way to go, especially with these new heads. I have spent enough, massively over my budget, going with free by adding a stop on the advance plate.