290 vs. 820 Heads - Chevelle Tech

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post #1 of 19 (permalink) Old Mar 23rd, 10, 11:45 PM Thread Starter
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Tony
 
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290 vs. 820 Heads

I am thinking about buying a 1970 454 LS-5 engine. I am waiting on the block ID numbes and date codes. He says it has 820 heads. I thought a 1970 LS-5 had 290 heads. Did they make any 1970 820 heads? What is the difference between 290 heads and 820 heads?
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post #2 of 19 (permalink) Old Mar 23rd, 10, 11:49 PM
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Re: 290 vs. 820 Heads

According to the source I have 820 heads are 1971 402/454 oval port open chambered heads. The 290 heads are 1969-70 396/402/427/454 oval port closed chambered heads.

A 1970 LS5 would be 3963512 casting with two bolt mains. I'm sure you already knew that. There are a couple different engine suffixes used.

1966 Charger (383, 727 Torqueflight)
1970 SS 454 Chevelle (LS5+2, M22, 3.31 12 bolt)
1971 Malibu (350, M22, 3.31 12 Bolt)

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post #3 of 19 (permalink) Old Mar 24th, 10, 2:17 AM
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Re: 290 vs. 820 Heads

the rated CR of an 1970 LS-5 is 10.25:1 with small domed piston, 101cc chamber.
for 1971, the 820 head has 112 cc nominal (114 more common)
figure factory was .023 deck height
dome at -13.8

see what you come up with
http://www.kb-silvolite.com/calc.php

George Kettler
o 70 Elky 496 #074 AL heads with porting, 10.3:1 CR, Straub HR 237/241* .617/.570 107 race weight should be 3895#. 3500 or better stall, 3.90s
o 68 Vette 427/M-20/3.36 23 year owner
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post #4 of 19 (permalink) Old Mar 24th, 10, 3:13 PM
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Michael
 
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Re: 290 vs. 820 Heads

Aren't the 290 heads 109 cc?

1966 Charger (383, 727 Torqueflight)
1970 SS 454 Chevelle (LS5+2, M22, 3.31 12 bolt)
1971 Malibu (350, M22, 3.31 12 Bolt)

I'm looking for a girl with a car, and a house..........with cable.

http://s160.photobucket.com/albums/t164/MEJ1990TM
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post #5 of 19 (permalink) Old Mar 24th, 10, 10:36 PM Thread Starter
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Re: 290 vs. 820 Heads

The seller tells me the heads are date stamped 2-28-70. Is that possible? How would the performance compare between 290 and 820?
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post #6 of 19 (permalink) Old Mar 24th, 10, 11:27 PM
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Michael
 
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Re: 290 vs. 820 Heads

Yes, that is possible. I don't think there is any way to know for sure whether they are 402, or 454, heads though.

1966 Charger (383, 727 Torqueflight)
1970 SS 454 Chevelle (LS5+2, M22, 3.31 12 bolt)
1971 Malibu (350, M22, 3.31 12 Bolt)

I'm looking for a girl with a car, and a house..........with cable.

http://s160.photobucket.com/albums/t164/MEJ1990TM
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post #7 of 19 (permalink) Old Mar 25th, 10, 3:46 AM
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Re: 290 vs. 820 Heads

My 820’s on my 71 BB are dated F – 70 and my car was a very early car. So I would think those dated 2 - 70 are for a 70.

71 Malibu 400 B B Conv _72 GS 455 Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out and loudly proclaiming: "WOW! WHAT A RIDE!!"
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post #8 of 19 (permalink) Old Mar 25th, 10, 4:27 AM
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Re: 290 vs. 820 Heads

This shows 820's as 1970 and 1971 402 and 454 open chamber.

http://www.roadsters.com/bbc/
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post #9 of 19 (permalink) Old Mar 25th, 10, 9:28 AM Thread Starter
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Re: 290 vs. 820 Heads

Thanks for the link. Is the performance of an open chamber 820 head less than a closed chamber 290? Which head is the correct head for a true 70 LS-5?
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post #10 of 19 (permalink) Old Mar 25th, 10, 9:51 AM
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Re: 290 vs. 820 Heads

IMHO 290 is the true correct head for an LS5 .

Here's what Mortec one of the chevy motor/blocks/heads/casting id info websites states:

3964290....69-70...oval..CLOSED..396, 402, 427, 454, 101cc chamber
Large or small hex spark
plugs used


3993820....71......oval...OPEN...402, 113cc chamber, 255/114 ports

================================================== ===========Now ack
OK,now back to my take on this.

In 1970 bbc's l34 396 & ls5 454's came with 290 small chamber lrg oval port heads & approx 10.25.1 compression.

The larger chambered 820 lrg oval port heads were used on 71 bbc's due to emmissions laws for 71 which dropped compression from 10.25.1 to approx 9.0 comp.

The only big difference bewteen the the 290 & 820 heads is mainly the combustion chamber size being larger and that its now also an open design that may breathe a bit better. But both the 290 & 820 heads are roughly comprable/= perf wise given same compression & all else like cam/intake/carb etc being = too. So if you use the proper larger domed pistons to get the compression back up in a 71 bbc motor the 820 heads will perf just as well as the 290s do on a 1970 or older bbc l34 or ls5 motor with stock pistons.

Or if in your case you 70 ls5 moor still has stock pistons with stock dome design/size you can simply remove the 820's and install a set of 290's and your good to go.

The reverse of that would be for example if you had a 71 bbc that came with 820 heads you can simply install the smaller chambered 290 or 063 or 215 heads all being small comb chamber lrg oval port head designs with closed chambers to get the compression back up to the factory rated 10.25.1. Thats because those 71 motors still had the same dome size & design pistons that were used in the 1970 l34 & ls5 bbc motors . It was just the larger chambered open chamber design of the 820 heads that lowered the comp & helped the 71 bbc's meet the newer emmissions regs for those motors in that timeframe.

Now onto the supposed 820 head 2/70 casting date,maybe the prior owner could have mistaken a 3 or an 8 for a 2 because 2-Feb 70 seems kinda early for the larger 820 heads that were not supposed to neever be on any 1970 l34 or ls5 pass car motor to be going onto them.

I have been working on thses motors for just shy of 40 yrs and have never seen 820 heads on a known/verified 70 bbc. But i have obviously not seen every bbc motor built in 1970 either so i guess you never know what may have happend at the factory esp with respct to a very late built 1970 bbc pass car motor.

But possibly if the date on your 820's is correct maybe gm was already mfg the 820 heads in 2/70 to meet truck emmissions regs that can be stricter/comming in a yr ealier then for the pass cars and thats why you have 820 heads dated 2/70. Or who knows,maybe GM was simply casting the 820 bbc heads months ahead in 1970 to get a jump on the 1971 builds which could be possible,crazier things have happend over the yrs.

But normally the earliest you should be seeing 820 heads on the chevelles/pass cars would be for the new 1971 pass car's bbc motors for early production of new 1971 cars built in mie-late july or early august 1970 for early built 71 pass cars to hit the sales floor.

You really need to pull the valve covers and very that head casting id & date code for yourself and if its truely 2/70 cast date look into if either trucks got those heads in 70 or if gm was casting the heads months earlier then normal to get a jump on things which i have never heard of happening but again,you never know.

Scott

SCOTT
1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)
2009 HD ELECTRAGLIDE CLASSIC ULTRA (GOT 11/14 W-9,700 miles)

Last edited by SWHEATON; Mar 25th, 10 at 10:18 AM.
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post #11 of 19 (permalink) Old Mar 25th, 10, 11:18 AM Thread Starter
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Re: 290 vs. 820 Heads

Thanks for the input. It sounds like the heads are more than likely 71 heads. The owner is suppose to be sending photos of the date stamp for my review. My car is a true 70 SS LS-5 with a build sheet. It was a frame off restoration it is in great condition except it currently has a 71 402 in it. I am looking to try to find a true LS-5 date correct 454 engine and I hope it will increase the value significantly over having the 71 402 in the car. Any Thoughts? I am not looking for a race car just a solid driver. Any suggestions of were to look?
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post #12 of 19 (permalink) Old Mar 25th, 10, 4:37 PM
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Re: 290 vs. 820 Heads

If you're planning on driving it, I don't think "value" should be quite so much of a concern.

OTOH, alot of those earlier motors cannot be used to any great extent on modern pump gas. The valve seats need lead to lube them. They didn't start induction-hardening them until ... about 71. Plus, the earlier design heads are more prone to detonation. IOW, at the same compression, the 820 heads are better for a DD, regardless of which casting will ulitimately make more HP in a go-for-broke HP situation. "More HP" isn't necessarily the right criterion for evaluating heads in all cases.

That said, unless it's a totally all-original, numbers-matching, unmolested, flawlessly perfect specimen, having the wrong head castings shouldn't affect the "value" very much; especially if the "correct" heads would render the car unseable and the "wrong" heads would let the owner enjoy the car in some way beyond merely admiring it sitting in the garage.
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post #13 of 19 (permalink) Old Mar 25th, 10, 10:12 PM Thread Starter
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Re: 290 vs. 820 Heads

I am diffinitely going to drive the car. I just want to make a good decision on which head would be the best. It sounds like you would prefer the 820 head over the 290 head unless it was a matching numbers original car which mine is definitely not. Is that right?My current 402 is a mild low to mid 300's HP engine. I am not looking for a race car just a fun driver with a little attitude. I considered a "crate motor" but thought the original block would be more appealing if I decided to trade or sell the car at some point in the future.
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post #14 of 19 (permalink) Old Mar 25th, 10, 10:34 PM
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Re: 290 vs. 820 Heads

Right, I think that's about it.

BBC heads have such a HUGE variety with all sorts of things different about them. There aren't a whole lot of "bad" ones, and just about any of them are "good" in some combo or other. The toughest things to watch out for, like the hardened seats, don't really show up in flow or HP numbers; and some of the ones that make the best racers are no good on the street, and vice-versa. 820 is one of the street-freindliest ones IMO. Maybe not the "max HP" type of choice although not too far off either, but a good all-around driver.
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post #15 of 19 (permalink) Old Mar 26th, 10, 7:08 AM
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Re: 290 vs. 820 Heads

If it has 820 heads,its more than likely a 1971 LS5 unless someone swapped out the heads.
In my experience,the closed chamber heads like alot of timing (38* to 40*) and the open chamber heads run better with less.
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