Thread: heads

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well I would like to bump up my compressin in my sbc 350, I've found a set of 327 heads. these are the casting numbers 3782461. some ppl say that they are very prone to cracking and others say they are great, just curious of your opinions.

The other question I have is, what would I be running for compression, I want to be able to still run good pump gas.

the block has not been decked, it does have flat tops, and as far as I know the heads have not been touched.

any info would be appreciated. Thanks

Well I am not the most expert to answer this but I had a set of "461" heads and eventually sold them and rebuilt the infamous "882" heads for a rebuilt 350. Here is one of many sites that will allow you to estimate the compression ratio:

http://home.tampabay.rr.com/1bking/c...calculator.htm

As I recall, the 461 heads had a 58 cc combustion chamber which will really increase your compression ratio compared to the 76 cc chambers of the 882 heads. For me the C.R. was too high for pump gas although Tech1 will tell you that if you deck the block and keep the quench gap between the top of the piston (flat top) and the bottom of the head surface to between 0.040" to 0.060" you can run up to 10:1 on pump gas. However on a high mileage engine the slop in the pin bosses may be enough that you risk contact between the piston top and the bottom of the head. Standard head gaskets are about 0.039" but other thinner ones are available such as 0.020". The other thing to worry about is that the 327 heads had softer valve seats made to use with leaded gas while the later 350 882 heads have seats for use with unleaded gas. The softer valve seats will recede over time with heavy use, but maybe not very fast just cruising. The seats can be replaced. All in all with decking the block and keeping the quench at about 0.040" (assuming your piston pins are tight) you CAN use the 461 heads, but I went with the cheap and simple treatment of using the 882 heads and paid to have the exhaust ports cleaned up. The 882 heads apparently have reasonable intake ports but poor exhaust ports and several studies with 1.6 ratio rockers on only the exhaust valves and/or an improved exhaust system have shown that the 882 heads need help for the exhaust valves. I will try the 882 heads for a while as planed to only 75 cc and maybe go to aftermarket heads in the future. There are others on this site who can answer this better than I can but that's my 2 cents.

Don Shillady
Retired Scientist/teen rodder

The intake runners are leaps and bounds better in the 461's than in the 882's and will flow WITHOUT any major work, whereas the 882's cannot be flowed on the intake side because they are formed wrong from the factory & are too thin in the castings for the runners to be flowed properly. To do this you would have to build up the steel inside the runners & re-direct your port angles, a major undertaking even for the most diligent machinest. Most take the easy way out and just open up the exhaust side in an attempt to get some kind of balance of flow.
The 461's are going to make more power if you can get them to run on pump gas without ping, and you will have to have the seats hardened, and I had to change up to a Cloyes hex-adjust timing chain in order to dial in the curve enough to get rid of predetonation. By working between the dist. curve & the timing at the cam I am able to run 92 octane without ping.
I pulled my 882's off to try a set of "prepped" 461's & I just gave away the 882's.

I'd say they are prone to cracking, mostly in the intake seat area. I have had at least 3 of them crack there. Get a set of world products heads they are cheap and they don't crack, and flow well also.

Thanks guys for the info, The fellow only wants $300 canadian for theses heads, but they are bare, I would replace everything anyways. I'm just worried about being able to run pump gas, just because in the summer it is my daily driver. ahh decisions, decisions, I might be better off mbuying a set of performer heads or something similar, because it sounds like it will be around the same price when its all said and done.

10:1 is as high as you want to go for 91-94 octane isn't it?
The quench area what is that?
If anyone has any good recomendations as to what I should run, it would be appreciated. I don't have very much money, it took me 7 yrs to get my s-10 to wherer it is right now, so it doesn't really matter to me if anything is a major brand name. thanks.

Too many good aftermarket heads on the market to be spending hundreds on old heads that will bump the compression way beyond pump gas range. I have a set of those 461's that were free but instead I built some 441's off of a 400 small block and ran them for years with no pinging at all. That's the difference between 62-64cc's and about 76 cc's. When I inquired about installing hardened seats and porting on these old heads, my machinist told that it wasn't worth it considering all the choices. I just bought a set of Dart Iron Eagles; 72cc's, 2.02/1.60 valves, 180cc intake ports. Can't wait to run them along with the new cam; Comp Cams XE274H. Compare these to World Products S/R Torquers. If that's too rich for you, maybe we can work out a deal on my old 441's.

Good suggestions on heads from everyone. Both Dart and World products make an excellent flowing iron street head and they are assembled and ready to run at a fair price. Also don't forget the GM Vortec heads. They are the best as cast flowing iron head GM ever made but they do require a Vortec bolt pattern intake.

I just finished a port and polish job on a pair of '72 smogger heads for my 355 engine project. Why? Because I had never done this before and it was a lot of fun. They had also been cleaned and magged before I started working on them. I left the intakes unpolished but port matched them. The chambers and exhaust ports look like mirrors. There are several good online sites that will guide you through the process.

Anyway, after all this work I still had to take them to the shop for a 3 angle valve job, all new valves (stock type), exhaust guides, better than stock springs and seals and .020 off the surface to arrive at 9.3 cr with a .020 compressed head gasket and flat top Silv-O-Lites .044 in the hole.

Bottom line is that all this work is costing me US$400. on a pair of heads I already owned. Don't pay $300. Canadian for a pair of bare heads that are going to need everything (assuming they mag ok) and then put another US$300. in them. Buy new for less and be done with it. Let some restorer that needs the numbers on those 461s mess with them.

Tom

No offense taken. I thought about taking the block back to be decked more but I just didn't. I figured that with the cr at a reasonable level and with the chambers polished there wouldn't be any place to create a hot spot to cause detonation. I plan on easing over the edges of the chambers when I get the heads back to remove the sharp edge from surfacing.

What you are saying makes good sence. Something to pay attention to on my next one. Thanks for the tip.

Tom

quick question...461 X heads by any chance, we used to try to find them, the X changes the heads...lmk.