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Topic Review (Newest First)
03-28-2013 03:50 PM
techinspector1
Quote:
Originally Posted by captainbob View Post
He says that these heads are pretty much the same as the original 327 heads... with the exception of having hardened valve seats, larger valves and the bolt holes in the front of the head for accessories, says they are late heads.
882's are not "pretty much the same as the original 327 heads". Not even close from a combustion chamber volume standpoint. Most of those earlier heads were 64 cc's or smaller. The larger chambers in your 882 heads are what is producing the very low static compression ratio of your motor.

Quote:
Originally Posted by captainbob View Post
He said that there will not be any loss of compression and will not be a problem unless the engine is overheated.
There is a large difference between the static compression ratio that you would have had by using heads with smaller chambers compared with the static compression ratio you have now with the larger chambers. That won't be a problem for you though, as you have indicated that you will be happy with a power range of idle to 4000. Just make sure that is the range of the cam, so that it is compatible with the low static compression ratio, like the cam I linked or something very similar. More cam than that will extend the intake valve closing point too far and leak off most of the compression in the cylinder, leaving you with a weak-suck operation.

Quote:
Originally Posted by captainbob View Post
For my use..I only want to drive the truck normally and it is not meant to be a high performance engine. With that said, I think, since I have never used the engine before, I will not know any difference anyway.
Sounds right to me.

Quote:
Originally Posted by captainbob View Post
I don't want to go to aftermarket heads, so what is the other choice anyway..he said Vortec heads are the ones with issues and would not be a good choice for me.
L31 Vortecs would have been one of the better choices in my opinion. With the proper pistons, the motor could have been built at a pump gas compatible 9.5:1 static compression ratio with a tight 0.035" to 0.045" squish, making more power and better fuel mileage than your present setup. Many Chevy heads, including the ones your shop used and the L31's are thinwall castings that are prone to cracking if you get them too hot.

Quote:
Originally Posted by captainbob View Post
How many cars and trucks were produced with these heads and how many actually had any issues? I don't even know if that info is available.
Perhaps it is assumed that I want a high performance engine, but I don't. I just want a good solid motor for my truck. I have had several 70's model trucks and cars with 350 engines that ran for many miles with no problems except burning a ton of gas. So, I am going to stick with what I have and hope for the best.
Thanks again, Bob
OK cap'n, have a great day.
03-28-2013 03:08 PM
captainbob Well, techinspector1, I appreciate all the work you put into the reply. I also spent some time reading most of the same quotes on the internet when it was brought up. It was rebuilt by a professional shop that only does engine and head rebuilding. They have been in business since the 40's. I had a Jeep engine rebuilt there with good results and have no reason not to trust them.
Ok, just made a call to the rebuilder and talked to the person that rebuilt the engine. He says that these heads are pretty much the same as the original 327 heads... with the exception of having hardened valve seats, larger valves and the bolt holes in the front of the head for accessories, says they are late heads. He said that there will not be any loss of compression and will not be a problem unless the engine is overheated.
For my use..I only want to drive the truck normally and it is not meant to be a high performance engine. With that said, I think, since I have never used the engine before, I will not know any difference anyway. I don't want to go to aftermarket heads, so what is the other choice anyway..he said Vortec heads are the ones with issues and would not be a good choice for me.
How many cars and trucks were produced with these heads and how many actually had any issues? I don't even know if that info is available.
Perhaps it is assumed that I want a high performance engine, but I don't. I just want a good solid motor for my truck. I have had several 70's model trucks and cars with 350 engines that ran for many miles with no problems except burning a ton of gas. So, I am going to stick with what I have and hope for the best.
Thanks again, Bob
03-28-2013 02:20 PM
techinspector1 The chamber volume ain't all you have to be worried about cap'n.

Here are some quotes from shop owners.....
---------------------------------------------------------------------------------------

"882's do have hardened seats!. That is one reason they are so crack prone. They were one of the first of the factory hardened seats and before GM induction seat hardening was perfected.

882's are the "Best" of the worst heads. They are the heavy weight casting. As noted, they are crack prone thru the center exhaust seats. They will flow fairly well if the intake side is port matched and the upper part of the exhaust port is blended. Bowl work is also needed, as is the case with most Chevy production heads.

There are actually three series of these castings. One has large clean intake runners and excellent bowl cutting from the factory and 1.94 intakes. Another has terrible intake runners, bowls. seat area. The third is a 1.72 intake, 3/8" stem exhaust valve head that was used on 2bbl. truck/pass car applications. I actually prefer these castings. As, they are seldom cracked and I have to cut them for guides and big intake valves anyway."

--------------------------------------------------------------------------------------

"I willl argue with that one as those OLD heads were produced from 1970 to 1980 and DID NOT HAVE INDUCTION HARDEN SEATS. As most of the 624 castings that are the light weight casting which are prone to crack and have hardened seats. And over the years we have put enough seats in those 882 heads due to the unleaded fuel.

An easy way to tell if those heads have induction hardened seats is to look where the exhaust manifolds bolt on and if they have 7 bolt holes or the pad for the extra bolt hole they will have the factory harden seats which I believe came out in 83 or 85. And as far as I know there were no 882 with that bolt pattern that I have seen. HMMMMMMMMMMM"

--------------------------------------------------------------------------------------

" I have been an automotive machinist and engine builder for the last 21 years and every 882 I've ever seen has hardened exhaust seats. GM began changing engines over to be compatible with unleaded fuel in 1974.

I have fixed more 882 heads than I care to remember. The center two exhaust seats are the most prone to cracking. Personally, I believe this is due to both center exhaust bowls being open to the exhaust crossover. This seems to put a lot more heat in the center of the head.
Also, the 882's were installed on Chevrolet engines from 1974-1980. Before that Chevrolet used the 993, 487, 336 and 997 castings used from 72 to 84 on the lower compression engines."

---------------------------------------------------------------------------------------

OK, back to my personal observations. 882 heads are published at 76 cc's, but I have yet to see a production head that will pour right on the money on all chambers. I'd bet those heads you have are more like ~78 cc's and may vary 1-2 cc's between chambers.

Next is the piston compression height. Stock 327 pistons are 1.675" from the centerline of the wrist pin to the crown. If you're not careful when you choose pistons for a rebuild, you can end up with "rebuilder" pistons, which will be ~0.020" shorter. This puts the piston down in the bore further when the piston is at top dead center and can contribute to detonation because of a lack of tight "squish" if you're running enough static compression ratio.

The last thing I'll mention is the piston deck height. This is the dimension from the crown of the piston to the block deck where the heads bolt on. Stock production blocks were produced with a block deck height of ~9.025", so that when the stack of parts, 1.675" for the piston, 5.700" for the rod and 1.625" for the crankshaft radius were installed in the block, they totalled 9.000" in a 9.025" block. This left 0.025" piston deck height. When the motor was assembled at the factory with a shim head gasket ~0.022" thickness, the squish (piston crown to underside of cylinder head with the gasket in place) was ~0.047", which allowed the piston crown to "squish" the air/fuel mixture that was above the crown, across the chamber in a "jetting" action. This turbulent action homogenized the entire mixture, eliminating lean and rich spots in the chamber and allowing the mixture to be burned completely and smoothly for a very efficient burn. Many fellows have found that they can operate on a cheaper fuel grade without detonation when the squish is engineered properly on the build. Anyway, if the block is 9.025" and a rebuilder piston was used, then the piston deck height is ~0.045". Now, if you add a composition gasket (~0.040"), the squish is ~0.085" and is ineffective. I'm not saying your motor will detonate. At your current SCR, the motor is a long way from being detonation sensitive.

Anyway, long story short, I agree with Mr. Peabody that you are probably in the 8.0:1 to 8.5:1 range of static compression ratio. This SCR will support only a very short camshaft, usually the first one on the list of any cam grinder's catalog. Too much cam combined with a low SCR will make a very soggy motor and you'll be an unhappy camper.

Here's an example of a "rebuilder" piston. Remember I said that a stock 327 piston is 1.675" compression height? Look at the specs on this piston.....
http://www.summitracing.com/parts/sl...make/chevrolet

Here's an example of a cam that I might use in your motor....
Crane Cams part number 113971
Brute low end torque, smooth idle, daily usage, fuel economy, 1600-2200 cruise RPM, 7.75 to 8.75 compression ratio advised. (50 state legal, pre-computer, C.A.R.B. E.O. D-225-18)
Grind number H-248-2
Operating rpm's 800-4600
Duration @0.050" tappet lift 192/204, duration @advertised 248/260. Lobe separation angle 112, valve lift 0.400"/0.427".
03-28-2013 07:47 AM
captainbob
Quote:
Originally Posted by Mr. P-Body View Post
What IS the casting number? That will make all the difference. There are SOME "small chamber" 350 heads. The vast majority from the '70s/'80s are "large chamber". Large chamber heads will give a very poor "low compression" ratio. With flat-top pistons, you're looking at around 8:1 with 76 CC chambers on the 327. Also, the vast majority of 350 heads have 1.94" intake valves, the same part number as those found in most 327 heads. Determining WHICH 350 head you have will tell the tale.

Jim
Now, I'm worried..the casting number is 333882 and N 75 near.
Appreciate the help.
03-28-2013 07:29 AM
Mr. P-Body What IS the casting number? That will make all the difference. There are SOME "small chamber" 350 heads. The vast majority from the '70s/'80s are "large chamber". Large chamber heads will give a very poor "low compression" ratio. With flat-top pistons, you're looking at around 8:1 with 76 CC chambers on the 327. Also, the vast majority of 350 heads have 1.94" intake valves, the same part number as those found in most 327 heads. Determining WHICH 350 head you have will tell the tale.

Jim
03-28-2013 06:40 AM
captainbob
Almost stock 327 built for my 47 International Pickup

For all the unimportant reasons I chose a 327 to install in my 47 International build. I have a question about heads. When I got it back from the rebuild shop, I started assembling the important things on the block, like the polished alum alternator, ps pump, ac compressor, intake and Edlebrock 600cfm carb. After I found tdc and installed the Mallory distributor, I tried to install the spark plugs I bought for the 69 Camaro 327 engine I am working on...no fit. I pulled the valve covers and got the casting number to search on Google. I found out that I have 350 heads from the 70-80's. The only difference I could find was that they have slightly larger intake valves than the stock 327 from 69. The only change to the 327 is a stage 1 cam addition and the 4 bbl carb & intake.
Is there any advantage to having these heads over the stock 69 327 ones?

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