454 with factory H.O. heads?

[East End K5]

I recently picked up a 1980 Silverado 30 with the beefy 454. An old timer at work (who has a 427 and 455W30) asked me to pull the top of motor and check the ports to see if it was an H.O.by looking at the ports. If they were square than it was H.O. if it was oval than it was plain jane. Is this true? I mean..shouldn't this be coded out? Which cars and trucks was this option available. He also wants to give me an edelbrock tarantula for it too that he has no use for.....

[80SPORT]

The rectangular port heads were never available on a truck;you do not have to pull the intake ;just pull a valve cover;the rectangular port heads will have hi perf cast in.
The 1980 should have the peanut port small oval heads ...the trucks switched to the small oval ports about 1975

The square port heads were available from 1965 to 1972 cars with the 4 bolt main perf engines....possibly 73 on Corvette
They were and still are available on crate engines ...and were used on marine engines until the end of Mark 4 production in the late 90s

[East End K5]

thx! Yes, he did mention the valve covers.

[Rpratt]

Originally Posted by 80SPORT

The rectangular port heads were never available on a truck;you do not have to pull the intake ;just pull a valve cover;the rectangular port heads will have hi perf cast in.
The 1980 should have the peanut port small oval heads ...the trucks switched to the small oval ports about 1975

It is correct that they square ports will have hi perf cast in them, but so do the oval ports. Everything that was passenger car had 'hi perf' cast in them. The oval ports are very common, but some are still pretty nice heads. The peanut ports mentioned didn't show up until 90s, and they have a SUBSTANTIALLY smaller intake port than the old 'hi perf' oval ports.

[SCOTI]

Also, just because it has retangular port heads does not make it high perf motor.

More than 1 hot rodder has put retangular port heads on a stock short block only to wind up w/a dud of a motor. Not enough compression, rpm, or valve event timing & those heads won't perform as well as the smaller oval port heads.

[80SPORT]

Originally Posted by Rpratt

It is correct that they square ports will have hi perf cast in them, but so do the oval ports. Everything that was passenger car had 'hi perf' cast in them. The oval ports are very common, but some are still pretty nice heads. The peanut ports mentioned didn't show up until 90s, and they have a SUBSTANTIALLY smaller intake port than the old 'hi perf' oval ports.

OK..lets have some input on this

I am reasonably sure the heads had hi perf cast in only if they were square ports
The blocks had pass hiperf cat in behind the timing chain....even if they were only 2 bolt main

[raceman6135]

Originally Posted by 80SPORT

OK..lets have some input on this

I am reasonably sure the heads had hi perf cast in only if they were square ports
The blocks had pass hiperf cat in behind the timing chain....even if they were only 2 bolt main

Pretty sure you're correct -- oval port heads had PASS cast into them, whereas rectangle port had HI-PERF cast into them. Here's a pic of some 188 heads (basically the same as 990 rectangular port heads) and you can clearly see the HI-PERF cast into them:


And yes, HI-PERF PASS was cast into the timing cover area of pretty much every big block Chevrolet block (except the truck blocks, of course), regardless if they were 2-bolt or 4-bolt main blocks. But, if you already have the timing cover removed, you can look down to the front crankshaft main bearing and see if it's a 2-bolt or 4-bolt block

[Hotrodrobert]

Done lots of BBC. "HI PERF" was cast in the rectangular port heads only.
All 4 bolt main blocks had "HI PERF PASS" cast into the block above the bell housing area. Standard blocks did not have this.
If you have a cast iron intake, it is almost certainly not rectangular port heads. If you have an aluminum intake that is no guarantee either.
Cast intakes and intakes for oval ports often don't cover the upper corners of the rectangular ports so you can have big intake air leaks there.
You can use rectangular port intakes on oval or peanut heads, but seldom will the other intakes work on rectangular heads.

[BigBlocksRule]

Originally Posted by Rpratt

The peanut ports mentioned didn't show up until 90s, and they have a SUBSTANTIALLY smaller intake port than the old 'hi perf' oval ports.

Sorry, but that was about '77, not '90's. The older ones have a casting number ending in 236.

After about '77, you couldn't get a truck with anything but peanut port heads until the late 90's when the L29 came out.

Save your time, unless your engine has been replaced with a performance engine, you'll have small port heads. Swap 'em out for large port heads with no other changes and you'll slow down.

[raceman6135]

The Edelbrock Tarantula intake manifold is a single plane, high RPM intake that is not suited to street driving. The rotated carburetor mounting pad can sometimes cause clearance problems and linkage issues, too, depending upon what you're trying to connect it to.

[cjracing15]

My 83 C-30 has a Gm crate motor installed in it. It was a ambulance at one time and then it done a tour as a rescue truck for several years before I got it. It is a camper special and the rescue squad put in a new crate 454 in it about 1991. They told me that they got the special crate engine from GM what ever that ment. Also told me that it had steel crank and hiperformance heads. I figure it is just a crate motor but how can I find out what I have with out taking the intake off. Motor runs great and I don't want to touch it untill I need too. Thanks

[BigBlocksRule]

cj, just pull a valve cover and post the casting numbers here. If it's a "performance" engine, they'll end in 188.