I was about to re install the J2 intake manifold on my Rocket motor when I decided to check the ports against the gasket. The gasket was pretty close to the port shape of the heads. The intake manifold was another story. I didn't think to take any pictures so nothing to show. I cleaned off the intake ports and brushed on some machinists blueing. When it dried I bolted the intake gaskets to the intake. Then took a scriber and scribed the port shape of the gasket to the intake. Out came the air grinder with a carbide burr in it. I opened up the ports in the intake manifold to the scribe lines, which match the gasket. I really don't know if this helps much, but I have always done this whenever I removed the intake manifold. What is your experience with this. Does it help any?
Only port match if the head is smaller than the manifold. If it is the other war round than the intake creates "anti-reversion" dam [which can be desirable at low velocity] Do not gasket match the intake and head ports ,it is ok if the gasket is slightly larger. When idiots do this ^^^ they stall the air velocity by creating the reverse effect of a venturi [think of 2 trumpets facing each other] I have seen the results of simple DIY gasket port matching on a flow bench and the CFM went down slightly. If you do get the urge to hogg out the ports , trace the intake face onto paper and superimpose this to the head face. Don't use the gasket as a template
I've done it to just about every motor I've built. From mild street and up. Seen dyno tests and on a dyno with a hot street motor it was worth almost 20 horse. Cheap horsepower.... ....
So you've built an engine and dyno'd it. Then pulled the heads and intake off , dis***embled and port matched them. then re***embled and dyno'd the engine again Almost 20 hp gain from just port matching and nothing else. I've seen bigger gains because the savvy dyno operator re-installed the distributor in a different position
Years ago I funnel ported some old bb chevy oval port heads to match a rectangle port TR2X Edelbrock tunnel ram Worked pretty good .
There's a bunch of guys that have run rectangle port intakes on oval port heads for various reasons, and the results are surprisingly good. Not saying it's ideal, but the airflow through a port can be counterintuitive. Unless one does a real world test, there's no way of knowing, but in your case, (Olds), it probably can't hurt.
The ports on both my Cad. engines were miss-matched almost 3/8", intakes ports were high on one side and low on the other. Didn't hog them out, just made them match. I've port matched every "performance" engine that I had the heads off of for 60 years now.
I've used the grinder on some sbf heads in an attempt to use '77 air pump heads and went through a port, ruining the head. Not that ruining the heads was a bad thing in reality. Just made me buy a pair of aluminum Edelbrock heads, which are working out quite well with roller rockers. The gaskets matched perfectly to the heads and extremely close with the intake manifold. I'm not going racing, just want to enjoy my hotrod sooner than later.
In my nearly 60 years of building engines, port matching I rarely do and depends on the characteristics of the engine. To me, it is all about intake velocity and fuel suspension. In some cases, I agree with @Kerrynzl in which port matching can be detrimental. I have had numerous discussions with the Martins about Nail Head engines along this line. 250/292 Chevy engines lump port pieces are a good example of enhancing velocity. Shorter stroke/ high rpm motors may benefit along this line, especially for racing.
depends on application , stock or mild motors, usually like intake a little smaller than head. Some aftermarket intakes are so horrible that they need cleaned up regardless , like this Olds victor
Not on a street motor. I don't drag race. I would inspect the gasket match on the dirt track motors, but unless the mismatch was radical, I didn't do it.
Yes. I try to leave a Venturi effect if I can. At low to mid rpm where we all drive it defiantly helps..
I think it can help most any motor breath better, so I do it. Many aftermarket manifolds are made with smaller runners near the flange with the intent to port match, so I like to check to see what's going on. I've always used the method Smokey describes in his book of secrets, and feel better knowing what I have.
Don't know if they have "wot stonps "up here in Washington State but I'm not taking any chances. I'm going to port and polish my Hemi.
Smokey sez...Several techniques can be used to transfer the shape of the port entry to the manifold flange. We usually paint the head surface with machinists' blue and bolt the manifold in place with a gasket clamped between the two surfaces. When the ***embly is taken apart, the port openings in the gasket can be trimmed to match the bluing impression. The gasket will then serve as a template for shaping the port opening. Once the runner entry shape is defined and enlarged, the entry should be blended smoothly back into the runner. You should watch the crossectional area, however, and try to minimize sectional changes as the flow moves along the runner and into the port. It is very important to not enlarge the crossections here, because this will reduce the flow velocity. If anything, it would be better to let the crossection get a bit smaller here. This will act as a slight venturi to increase the velocity as the flow transitions into the manifold. You cannot get carried away with this, but it will help a little to maintain the flow velocity.
My machinist used to bolt the heads on the engine with used gaskets , then bolt the intake on with used gaskets and drill a 1/8" hole through the intake into the head where no water or oil was, two holes per head. Once it was back apart, two 1/8" alignment pins located the gasket perfect so we knew just how close the alignment was. The pins were used on ***embly to locate the intake back in alignment. If it was off, first thing to cut was the head, match it to the gasket and blend the cut as far back into the port as you could so the walls were straight from gasket into the bowl area. In this case, straight like body work, one continuous level surface with no divots or bulges. The intake was trimmed to make the walls straight back to the carb area. It was better to have a smaller intake opening than flared ports. It also mattered which side of the curve the mismatch was on, the outside curve where most of the air flow goes needed to match up, the inside curve could be off as long as it was smaller than the head.
I tend to follow the idea of direction. Intake a wee bit smaller, exhaust manifold/header as big as I can get it. Unless the engine is gonna live at WFO when you're putting it to work then a pure match isn't helping. Reversion is real and the "cleaner" you can keep the Intake charge the better. My race motor was about .050 smaller all around at the Intake, my headers welded and hogged out almost an ⅛ all around. I ran a 1050 Dominator. My carb bores were way cleaner than that of all the other guys I was racing with, even the ones running the same cam. There's were a bit sooty just below the venturis whereas mine was almost nothing. I credited the headers being more responsible for that than the intake but I gotta believe both played. FWIW...
I matched some heads to a larger intake once, and enlarged a much smaller intake part way to some larger heads once. But generally I just check that the intake isn't larger than the heads (no step to restrict flow that direction), then bolt it all together and don't worry about it.
Hello, For all of us teens with high performance v8 motors, porting/polishing the heads was the "go to" item to increase horsepower. From 283 SBC, 348 Impala, Olds v8, Pontiac v8 and others, if you wanted to go faster than what other motor modifications done, porting/polishing the heads was it. Luckily, the now, famous Jocko’s Porting Service was located within the far boundary of Bixby Knolls. For us it was a few blocks North of our usual cruising grounds and across the street of the “hot rod central” of the area. For blocks, the Cherry Avenue Drags was located South of the “hot rod central.” If we went North on Cherry Avenue we came to a row of shops from chrome accessories, to muffler shops, to tire/wheel alignment, to custom manufacturing ch***is, parts, etc. There were also transmission shops and custom wheels, too. But, across the street, in a plain building was Jocko’s Porting Service. We knew from the local Lion’s Dragstrip racers, Reath Automotive, Joe Mailliard, Speed Engineering (local Bixby Knolls racers McEwen/Legrand) groups that porting makes more horsepower almost instantly. It was worth the cost and wait to get it done. Plus, no one knew what was done to increase horsepower as it was done inside of the motor casing. A Speed Engineering product from McEwen/Legrand on Junior Thompson's Studebaker 283 motor. The top speed shops and racers all swore by the porting/polishing service. A smooth flow is the goal and this is the service done to make things move smoothly. It does not seem so, but every teen hot rod sedan that was fast had the porting service done at Jocko's. Jnaki So, yes, match your manifold, but since everything is apart, take it to get the professional porting/polishing service done. Yes, no one can see the work done. But, it is your performance motor and what was done that is the important thing. YRMV https://www.jalopyjournal.com/forum...seven-chevy-post.635978/page-11#post-15570442 There is nothing better than a set of clean, newly ported and polished heads sitting on a table gleaming on a cold winter night. I could not wait to install it on our 283 SBC motor. Despite our mom coming in to yell at me for bringing in a “dirty old car part on her clean card table… ha! After several months, the same heads worked well on our new build to a blower spec SBC motor now up in size to 292 c.i. and a 671 supercharger on top. "Smooth flow = more power instantly..."
The Jalopy Journal
