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Subject: oval port vs. square port

Original Message
Name: JJ
Date: January 29, 1998 at 13:37:54
Subject: oval port vs. square port
Comment:
Any recommendations on oval vs square port heads for a street/strip application? What castings should I use?

Response Number 1
Name: Mark
Date: January 30, 1998 at 10:59:12
Subject: oval port vs. square port
Reply:
Oval ports are good up to about 6-6500 rpm. It has been said that they actually outperform the rectangle port head up to about 4000 rpm. I don't have any part numbers, but you can't go wrong if you can find a set of oval port heads made around 70-72. They are open chamber and work great with cams up to .500-520 lift and compression ratios around 9-10:1.
If you are serious about power, square or rectangle port heads are the way to go. They are good to 7500. I think all of Chevy's rectangle port head engines had at least 11:1 compression and a solid lifter cam with lift of at least .520.
You really can't go wrong either way. Just make sure that whatever you decide, make sure the rest of the engine is matched to the heads.

Response Number 2
Name: paul
Date: January 30, 1998 at 12:42:59
Subject: oval port vs. square port
Reply:
JJ,
It depends on how you plan to use the car. If it is a street car that will go to the track on occassion I would recommend oval ports. Rectangular ports have too much volume for the typical street car setup. They make power in a much higher rpm range, and will give soggy bottom end results when matched with typical street components. With some work, stock oval port heads will work well if on a budget. Of course “some work” is a relative term and one could easily spend more than what an assembled set of Merlins cost and not realize the same performance.
There are a number of quality aftermarket heads (both cast iron and aluminum) to choose from. I’ve seen some original G.M. hi-perf. heads at swap meets that need complete rebuilding that cost as much as a new set of aftermarket heads that are ready to go.
Oval ports are by no means wimpy, there are some pretty stout race cars running them.
Good Luck!

Response Number 3
Name: Jack
Date: January 30, 1998 at 23:13:06
Subject: oval port vs. square port
Reply:
Soggy bottom end from a Big Block Chevrolet just because it has huge amounts of port volume using rectangular port heads? May it never be! Big Blocks can have the plug wires pulled on 4 cylinders and still have good bottom end! All joking aside, I'm running a 408 with sq. ports, a big cam, LS6 intake, 750 Holley, TH400 and 1800 stall and 3.08 12 bolt on 28 inch tall tires. It gets 15 - 17 mpg and runs low 12's on street tires.

Response Number 4
Name: JOE HARRISON
Date: January 31, 1998 at 05:53:55
Subject: oval port vs. square port
Reply:
for the money and easy to find look for some 049 casting large oval port heads they have 119cc chambers and work really good with this chamber all you have to do is buy the right piston for the copmp. ratio you want do a little bowl work and go with stock size vavles for a street car or 2.19 1.88 if you plan on some strip duty. you can find these heads for about $100.00 ea. and thats complete if you want to sve money hard seat them and a 3 angle grind and a performer or performer rpm intake a 750 holly or carter or q-jet and a comp 268 cam and you will have enough bottom end your friends will ask be asking you to sell them your left overs.

Response Number 5
Name: Keith Tedford
Date: January 31, 1998 at 05:56:46
Subject: oval port vs. square port
Reply:
Over the years I have had 396 and 427 engines with rectangular port heads and there is definitely no soggy bottom end. If there is then start looking at cam timing, ignition timing, jetting or carb size. Magazine writers have claimed that the big port heads suffer at lower rpm but I wonder at how much practical experience they have had. Big ports will definitely hurt highway mileage. Jack and I seem to have had the same experience. Big ports really like lots of cubic inches.

Response Number 6
Name: Hollis
Date: January 31, 1998 at 14:41:36
Subject: oval port vs. square port
Reply:
I have a set of oval ports w/ 119cc combustion chambers when used with a set of trw forged pistons part #L2465F THIS COMBO MAKES 9.5 TO 1 COMPRESION WHICH IS VERY STREETABLE AND WILL RUN ON PUMP GAS WITH NO PINGING, IF INTERESTED IN THESE HEADS PLEASE FEEL FREE TO E. MAIL ME

Response Number 7
Name: Al
Date: February 19, 1998 at 10:27:27
Subject: oval port vs. square port
Reply:
Like everyone else has said, you really have to consider the application but I also want you to consider what you already have and your budget. I build alot of motors for both street and track applications. The square ports need alot of cam and some reasonable gear to be worthwile on the street. If you have not invested in any parts yet you should really look at the aftermarket. I just finished a 454 with 11:1 compression, Dart Merlin Oval ports, which have alot smaller intake runners than the GM squareports and a comp cams solid with 629/605 lift & 260/266 duration at 50 on a 108 for a street Camaro. The duration may seem a bit long for a street car but with an 850 Holley on the Dyno it made over 540 HP and had a pretty flat torque curve from 2600 to 6400 and peaked at 522 Ft lbs. at 4900. Best of all in the car the motor was pretty docile and could be driven anywhere and the car ws solidly in mid to high 10's at 3400 lbs. Also, noone has mentioned that all the factory installed castings have two good and two bad runners on each head. Two runners have a dog leg and two are straight, not great for flow of fuel distribution, not to metion all the protrusions for thread castings and the non hardened exhaust deats in the earlier heads that are not compatible with unleaded gas. The Dart heads have four runners with a straight shot at the valve in each head and no thread casting protrusions and are unleaded ready. E-mail me if you have any questions, I'll even send you a copy of the dyno sheet if you want it. Good Luck !!

Response Number 8
Name: Al
Date: February 19, 1998 at 10:30:56
Subject: oval port vs. square port
Reply:
Like everyone else has said, you really have to consider the application but I also want you to consider what you already have and your budget. I build alot of motors for both street and track applications. The square ports need alot of cam and some reasonable gear to be worthwile on the street. If you have not invested in any parts yet you should really look at the aftermarket. I just finished a 454 with 11:1 compression, Dart Merlin Oval ports, which have alot smaller intake runners than the GM squareports and a comp cams solid with 629/605 lift & 260/266 duration at 50 on a 108 for a street Camaro. The duration may seem a bit long for a street car but with an 850 Holley on the Dyno it made over 540 HP and had a pretty flat torque curve from 2600 to 6400 and peaked at 522 Ft lbs. at 4900. Best of all in the car the motor was pretty docile and could be driven anywhere and the car was solidly in mid to high 10's at 3400 lbs. Also, no one has mentioned that all the factory installed castings have two good and two bad runners on each head. Two runners have a dog leg and two are straight, not great for flow or fuel distribution, not to metion all the protrusions for thread castings and the non hardened exhaust seats in the earlier heads that are not compatible with unleaded gas. The Dart heads have four runners with a straight shot at the valve in each head and no thread casting protrusions, and are unleaded ready. E-mail me if you have any questions, I'll even send you a copy of the dyno sheet if you want it. Good Luck !!

Response Number 9
Name: Pat
Date: March 15, 1998 at 10:10:33
Subject: oval port vs. square port
Reply:
just purchased anew crate 454\390hp which has had 219\188's installed in head casting #14092360. would anyone be able to tell me the chamber and runner specs on these heads? Thanks

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