454 heads and blocks [Archive] - Chevelle Tech

: 454 heads and blocks

Dec 12th, 08, 5:41 PM
Someone mentioned 454 heads with cast numbers:

049 and 781 are good
236 and 360 are not as good
What about 045 heads? good or not as good? Is there a more complete list?(mortec, thanks Mike)

Blocks the same thing.
512,289,959,445 are good. but why?

Could someone help me decode these as to why they are good or not as good.


Dec 12th, 08, 5:58 PM
What are you trying to do/build ?
The terms are more like good & better ,not necessairly good or not.
The good/no good is relevant to the intended use - ie :
cruse/street only
strip only

Look around on Mortec (http://www.mortec.com/bbc.htm) to see what the original applications were for the blocks/heads your questioning.

Dec 12th, 08, 6:20 PM
hey mike,

Thanks for the response.

Looking to give an engine to my builder. I guess i'm trying to get the most horsepower for the least dollar. Building a mostly street car and I don't mind spending 4g but 8-12 is out. I checked Mortec and the only thing it says about 045 heads is that they are for the 454.

My questions still remain though. How come someone said that 781 heads are better than the 236 heads for example. what's the difference? It could all be irrelevant since I don't even know if they'll work for a high horse application.

Dec 12th, 08, 6:52 PM
For high HP application's ,there's a lot to consider.
chamber size/shape ,intake port flow,exhaust port flow ,valve shrouding and more.
Take a look at PG 11 on for some BBC flow data:
http://racingfeed.com/downloads/chevy_flow_data.pdf#search=%27cylinder%20head%20fl ow%20data

Dec 13th, 08, 12:07 AM

Seems that you are still curious.
I am "that someone" mentioned here, post #1

Those blocks, in that order...all are very good just the 512 and 289 are preferred for casting and machining accuracy. 959 and 445 are plenty good, just not as good. Unlike some brands....there are none to avoid! Just if I had a stack of blocks to pick from, a 512 or 289 would be preferred. I built a 959 the other week for my 70 Elky, no problems at all.

Please consult any of the numerous BBC books.
Refer to the BBC INFO thread, top of the ENGINE area, pictures there that I posted, added to what was there to square away those seeking basic BBC Knowledge.....
There are three size / configuration intake ports on heads and intake manifold runners
Rectangular port HUGE PORT
Oval port Good-sized port
Peanut/truck port Small port

The 781 and 049 are OPEN CHAMBER OVAL PORT
The 236 and 360 are OPEN CHAMBER Peanut Port (PP)
I have not seen an 045 head.... I do have my suspicions that it is an OPEN CHAMBER OVAL PORT HEAD with small valves for a HD truck application...

In a nutshell....the BBC heads are famous for their free-flowing intake configuration.
The 236 and 360 heads have the Peanut Port (PP), smallest of the bunch. As this is mostly a PERFORMANCE-oriented group, plus the heads made for the Chevelles back in the day were either oval or rect port from the factory, the PP heads are looked-at as boat anchors by most here. The bottom line here is that for a cruiser with 3.08 gearing, the guy who seldom goes to the strip, someone looking to destroy tires at the burger joint....the PP heads are certainly viable.
Anyway, back to your question
In the mid 70s, BBCs got discontinued as car engines. Chevy re-designed the heads to work better for their only purpose...truck engines. Truck engines need low rpm torque. So, long story short, will simply state that a small runner has high velocity and keeps the fuel air mix suspended...great for power and somewhat better economy in an engine that will seldom see north of 3500 pm. Lots and lots of PP headed engines in Pickups, Suburbans, motor homes....

The problem is that guys with their souped up 454 cars and 4.11 gears.....the 236 and 360 PP heads...the intake ports more or less give up the ghost at around 5000 rpm....regular oval port heads run good to 6000+ and the rect port heads shine above 3000 rpm.

I do understand that typical improvements like big valves, bowl blending under the valves also work well for Peanut Port heads. VortecPro can get these puppies to hum. I also think a small BBC like a 396 or 402 would like the smaller intake runners....plan to experiment some day.

Dec 13th, 08, 1:07 PM

Wow, I really appreciate the informative post. That really helped me. That is what Team Chevelle is all about.

I checked the 045heads on mortec and all it sais is open, oval, 454, 78-87year.??

Dec 13th, 08, 9:09 PM

I have not seen '045' heads.....industrial or truck application I'd guess.....

Big Blocks are pretty cool engines. By swapping pistons and heads around, you can get just about any desired CR you require.

Stock late 70s and up truck engines have advertised 8.5:1 CR. If you pull one apart, measure the volume of the chambers, measure how far in the hole the pistons are...the majority will be in the 7.9--8.2:1 range. Lotsa guys, myself included, take the smogger shortblocks, install early closed chamber heads 96-101cc (shaved you can get the small ones to 94cc, the larger 101 cc heads down to 97cc), maybe throw a shim head gasket in there.... With the small shaved heads, shim gaskets, you'll be looking 9.4:1. This is with the factory flattops. I went 101cc head, no shave, stock 77 slightly dished pistons, stock head gasket, have 8.8:1 cr.

TC member FRYNTYR, aka Doc Smokum, aka Darryl, took some early heads, shaved them to 94cc, added big valves, did a basic port job.....thew them on "FourEightyNine" BrIan's 489" Rat......he's running 10.2s at 124.......

Most guys like the open chamber (OC) heads and domed pistons. The OC heads flow a little better from the get-go.

The Rect Port heads come on all the high perf engines. Sadly, the intake runners are oversize, more suited to engines 500" and larger. Sure, they will work on 396/402s, 427s and 454s but they will give up a lot of low-end torque, especially the 396/402.
As the Rect port heads came on the legendary cars, the cost for these heads with the right part number and date is out the roof.