Is it worth the effort to port match an air gap intake manifold to 3904392 Al heads? The heads appear to be untouched but they don't match the gasket very well. The Edelbrock manifold ports aren't very consistantly shaped either. I noticed most modern heads are port matched to the gasket. Any suggestions?

TT

 

It may not always be "necessary", but I'd feel like I had cut a corner if I didn't properly match the intake to the heads on any sort of performance build. That said...

First, I'd hope the intake requires more work than would the heads. Then, if these heads are indeed '67 L88/L89, aluminum, closed chamber, rectangle port BB's, dated from back in the day, are you really sure you want to touch them? If you're OK with that, I'd tend to err on the side of caution should you choose to do very much to them, concentrating pretty much on any gross irregularities from small port to small port, and from large port to large port. It is NOT necessary to hog things out to the gaskets. Besides, achieving a proper match is all about the transitions from the intake runners into the ports, so don't get caught up in how big are the port cross-sections of modern heads.

FWIW, the more aggressive you get with enlarging any port cross-sections at the gasket, the more blending them well into the head ought to be done so as to not introduce a sharp variance to the rate of taper flow will encounter just after the runners enter the ports.

Yes, one could do even more, but IMCO any further into it than this, and we're talking more about head porting than we are runner/port matching. Hope that's worth more than you paid for it.


TSW

 

I got the heads in 1977 for $315. I think they may have been surfaced or slightly milled. I can't find a correct date stamp with a letter prefix. They are stamped on the intake surface with 22068 which I doubt is a factory stamp. The casting# is 1967 L88/L89. So with that said, I should probably leave the heads as is and just do some minor grinding to the manifold ports?

TT

 

YES!!!!!!!!

Don't end up kicking yourself later for not doing it now while you can!

God bless, Sensei

 

Whether its worth it or not is up to you.
If you do it, and your lucky, you might get an extra 10hp.

 

im with skunkworks.......

 

As long as you manifold ports are smaller than the head leave them alone. You can match ports all day long because one thinks it looks better, but unless you flow the together what ever you do is just a guess!

 

The intake runner ports are definitely smaller than the head ports. Some of the head ports have a 1/8" chamfer or bevel at the entrance. It seems they were cast that way because the left and right are the same. I never touched them but I don't know their history pre 1977. It doesn't make sense to match the intake runner to the head opening when there is a gross transition at the head port entrance. I'll post a photo if I can.

TT

 

With Skunkworks. Don't port the heads. Don"t gasket match anything. What I did was take a piece of thin cardboard and put it on the head flange. Then I took a sharp exacto knife and cut the bolt holes out. Inserted short bolts and used the exacto knife to cut the cardboard out to match the head ports exactly. Then I bolted the cardboard to the intake and darkened the area that needed to be port matched on the intake with a marker. Then removed the cardboard template. Using a dremel I removed material till the darkened area was gone. Then I worked my way into the port of the intake making sure I transitioned it well into the intake with no visable restrictions. This matches the intake port to the head port exactly without ruining the heads for a later sale or in my case changing the flow characteristics of my competition ported AFR heads. As long as the gasket opening is very slightly larger so it don't protrude into the port opening anywhere your good to go.

 

My Vic Jr intake was matched to my AFR227's by AFR. I had them flowed with the intake resulting in only a 3% loss with the intake bolted to the heads on a flow bench

 

I'm not going to touch the heads. Perhaps they are too valuable as is. I have already made a template of the head ports and have marked the intake for removing a little material from the intake ports per 63 mako.

TT

 

63mako outlined for you a good explanation of how to properly go about the actual process of matching an intake itself. I might add that I place the intake on with the cardboard templates located as gaskets, marking them for reference, so I can ensure that I've precisely registered them with both the intake and the heads.

In my previous post, I should have made the point that the same goes for working intake runners...

 

Those suggesting that the manifold port being smaller than the head port is okay don't have a full understanding of airflow dynamics. That explains why you can port and end up with 3% less flow.

It seems to make sense that a small intake port leading into a larger head port would work because there is no physical restriction to flow. But in reality, cylinder filling efficiency is also based on velocity. The flow path must gradually be REDUCED throughout the run. This increases velocity so the A/F mixture is accelerating into the cylinder. If, as the mixture enters the head, the size of the path opens up, the airstream stalls and flow is reduced.

If you are worried about the value of your heads, leave them alone. But if you are going for performance, you absolutely must portmatch (also unshroud valves, blend bows, polish chamber and exhaust port, smooth short side radius). Otherwise, you are just leaving HP lying on the bench.

In the C4 Corvettes, GM was able to add 30 HP to one model (I forget which one) by porting and polishing.

God bless, Sensei

 

Depends on the gasket.

Each cross section has its own rpm range.

 

I was told by a world record holder for the 8th mile a while back,that port matching is one of the best things you could do for your engine.Ive been doing it ever since then,engine does seem to be stronger after doing it,but i have no proof of it,Its just the seat of the pants feel.

 

I agree for drag racing because flow is everything but I would not on a street driven car because the step will actually help further atomize the air/fuel ratio.. If you start smoothing runners on a street car the fuel wont atomize like it needs too... Smoothing to much can even cause fuel puddling at idle, which obviously will cause idling problems and intial acceleration issues until the fuel starts flowing again.. Stall converters help elliminate that issue on drag cars..

Here are 2 things I wont do on a street car
1. Smooth intake and head runners
2. Use racing fuel (racing fuel burns colder and slower). The hotter and faster the burn, the more power it will produce. I also know a guy who holds the world record in stock class boat racing and he says the lower the octane you can run, the more power it will produce because it burns faster & hotter. There are also articles floating around on this..

 

I have to differ with ya,port matching is the important one not polishing,have you ever checked the port match up with the after market stuff out there now?its bad,sometimes you can cover up 1/4 of your port and block air flow which will reduce performance.Its a good practice to check port match up.Stock engine i would agree with you,usually match up is close.

 

I was just about to say pretty much the same thing. Interestingly, Reher-Morrison has found that a miniature corrugated pipe type texture in the intake runners actually improves flow at high intake runner/port velocities. (High intake runner/port velocity is your friend.)

And, having the A/F charge run into a substantial impingement on its way to the valve from the carb introduces all kinds of disturbances which harm runner/port flow efficiency. If such is "needed" to improve fuel atomization you've got problems which would be better addressed by other means.

As for a step from smaller runner to larger port, many years back, Edelbrock experimented with raising the floor of the runners approaching the larger ports (some ~3/8" or so) in an attempt to level out flow between the two types on the old TR-2X tunnel ram (if I still had one I'd post a pic). In practice, this didn't actually improve anything as it only made the better ports less efficient. If it had been the thing to do, you'd best believe this practice would have become wide spread. It's not.

Finally, it's worth noting that efficient ports don't do anything to hurt fuel economy; that's more a function of other variables, the weight of ones right foot being prominent among them.

 

You mean like nitrous
All nitrous does is further atomize AF (hence the reason they refer to it as a fogger) so there is room for more and the more atomized AF you stuff in a combustion chamber, the bigger the boom.. Modern tech has also yielded further designs such as injectors (mist sprayers), valves and combustion chambers to help further atomize AF ratios for more power and improved gas Mileage.. Back in the early 70's even Bill Jenkins knew that if he further atomized fuel he could make more power so he began experimenting with screens under the carb..

 

Done deal. Matched the intake to the head. Pretty easy with a die grinder and a fluted bit. Hopefully I'll have good results. I finally took off the TM2-R Tarantula single plane Iv'e had since 1977.

TT