Big Block Oval Port Heads Questions [Archive] - Chevelle Tech

: Big Block Oval Port Heads Questions


shrado
Apr 29th, 00, 9:36 PM
When did oval port heads go to the peanut port shape?I have a 454 with 781 heads-date code late 1976-never seen the ports thou-will it have big oval or peanut ports?When did hard seats come from the factory?1972?I have casting #6272292 heads with a L 3 71 date code(late 1971)would they possibly have "hard seats".What is the best cam for my 9 to 1 compression,.060 over 454 with the 292 heads,Q-jet carb,stock intake off 350hp 396,1&7/8 headers,1500-5500 rpm, in a 72 chevelle with 350 turbo & 3.08 gears?

BBC DON
Apr 30th, 00, 8:46 AM
I am not sure when the peanut port head came out, but I would guess around the mid 80's. As far as the 781 heads, they are a great factory oval cast iron head. Your 292 heads are openchambered oval port heads, which show to be 113 cc combustion chambers, but are probably larger. As far as which cam to run, I would seek the advice of one of the major cam manufacturers. But with 9 to 1 cr, and with 3.08 rear gears, I would stay fairly conservative, as far as duration goes. Hope this helps, Don http://www.chevelles.com/forum/smile.gif

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Don McGowen
1970 SS El Camino
Gold #179

IgnitionMan
Apr 30th, 00, 11:59 AM
All production big blocks went peanut starting with first 1975 engine off the line, Sept., 1974. Only rectangle port BB's produced now are performance crate engines.

Hard seats on exhaust only didn't come from GM until 1988. Initial hard seats were just induction hardening of the head metal, no inserts. Inserts started in 1996.

[This message has been edited by IgnitionMan (edited 04-30-2000).]

DZAUTO
Apr 30th, 00, 4:51 PM
I believe the BB 366 came out about 68 and as far as I know they all had the peanut port heads which were shared with some of the other BBs. I am sure that ONLY big trucks (bigger than 1ton) got BBs with peanut port heads, but I can't say for sure just which truck series. Any truck, 1ton and smaller, as far as I know got the "regular" type oval ports. The purpose of the peanut port was to produce lots of port velocity at low rpm. The BBs with peanut ports were designed for lots and lots of low end pure lugging torque and they died about 4000rpm.
And don't be mistaken that a BB truck engine which never saw the high side of 4000rpm is in excellent shape. They produced tons and tons of stress on the crank main webs. Especially if the engine was a high mileage engine. If you get a BB out of a BIG truck, be sure to have your machinist inspect it thoroughly.

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Tom Parsons

[This message has been edited by DZAUTO (edited 04-30-2000).]

IgnitionMan
Apr 30th, 00, 11:49 PM
At this point, I think we should all get to agree with the port terminology of BB cylinder heads.

All dimensions are darn close if not right on, it's from memory. Rectangle is 2.125" tall x 1.240" wide, Oval is 1.900" tall x 1.065" wide, Square (peanut) is 1.065" tall x 1.065 wide. All refer to intake port configuration, not plug thread/jacket types used. Rectangle and oval were used from production inception in 1965 to 1974, then the only BBs were in trucks, and went to square (peanut) port heads, all of them past 1975. No peanut intake port heads were used or produced before 1975.

Large truck 366 and 427 tall deck engines all used Oval port heads, all years, all pickup 454's changed to square (peanut) port in 1975.

Sorry, Tom, that's the way all the Chevy people I have ever known and I have ever referred to them as. No fights, please.

shrado
May 2nd, 00, 8:26 PM
well I took the intake off my 1976 454 and it has the large oval port heads!(casting # ends with 781)I double checked the date code -I 17 76-.How do you explain this.The engine came out of a truck which was formally a diesel powered rig-so I have no idea where the 454 came from originally.I guess its possible the "76"is a "70" but it sure looks like a 6-or am I totally wrong how to read date codes?

DZAUTO
May 3rd, 00, 5:27 AM
Iman,
The terminology/dementions that you stated are EXACTLY as I know them. Only the years/application is where I may be off. Admitedly, it has been a while since I last saw a set of 366 heads, but they appeared to be the really small (peanut) ports.

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Tom Parsons

mr 4 speed
May 3rd, 00, 7:27 AM
<BLOCKQUOTE>quote:</font><HR>Originally posted by shrado:
When did oval port heads go to the peanut port shape?I have a 454 with 781 heads-date code late 1976-never seen the ports thou-will it have big oval or peanut ports?When did hard seats come from the factory?1972?I have casting #6272292 heads with a L 3 71 date code(late 1971)would they possibly have "hard seats".What is the best cam for my 9 to 1 compression,.060 over 454 with the 292 heads,Q-jet carb,stock intake off 350hp 396,1&7/8 headers,1500-5500 rpm, in a 72 chevelle with 350 turbo & 3.08 gears?<HR></BLOCKQUOTE>
I would go with a Crane grind,272 Duration(216@.050)515"/515" I/E,112 LSA.I've had very,very good luck with this grind.Can't remember the part #,but it is cam/lifter kit.Check a Summit or Jeg's catalog.I once put that cam into an 8.5 to 1 '71 454,with an M21 and 3.31's with stock exhaust manifolds and it pulled REAL well.All in all,a nice street cam.I think it would work well with your gears.I'd probably go with a mild stall convertor(2,200 max)


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1970 Chevelle SS396/L78/M21/4.10
1969 Corvette L46/M21/4.11
1982 Oldsmobile Cutlass 350 Olds,Th350(daily driver)
"Be aware of the possible ramifications of the potential outcome"

[This message has been edited by mr 4 speed (edited 05-03-2000).]

Kevin
May 3rd, 00, 8:23 AM
I'll second what Mr. 4-Speed said. I ran the exact combo in my '71 SS and those 292 heads have hardened seats (as do all '71 and later heads). Their ports aren't as large as the 049 castings though.

shrado
May 6th, 00, 7:25 PM
can anyone tell me why after all that is stated above I have large oval port heads with a casting date of late 1976?

Jerry Huber
May 7th, 00, 6:29 AM
I reply only because I am doing the same thing with 454 heads.Reference book BB Chevrolet Parts Interchange Manual shows 336781 oval/open on 73-84 454 and 386781 oval/open on 73-79. It also says peanut ports started in 86. Also check www.mortec.com (http://www.mortec.com) it says about the same thing.

68396
May 8th, 00, 9:14 PM
The peanuts were made as far back as '75. I owned a '75 Caprice that had the original matching #'s 454 and it had the peanuts.

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A bought lesson is worth two or three free ones.