I'm not finding any 3-7/8 specific steel shim head gaskets listed on Summit. Parts number ??? One of these is for a 348 and one for a 265 Gaskets & Seals Head Gaskets 1959 CHEVROLET IMPALA Gaskets & Seals - Free Shipping on Orders Over $99 at Summit Racing
Doing the math got me a .173 cc difference in volume between the two gasket dimensions. For the .03:1 difference in compression ratio that makes, you would have to maximize your chassis to the N th degree for it to show up.
I've just been thinking about this same topic and like X-cpe working through the changes in compression ratio using different components. I was working up building a 283 bored .040" to 3.915", 58CC 305 heads, 4-valve relief flat top pistons .020" down the bore, and a .015" steel shim head gasket. Based on my theoretical build, using a compression ratio calculator and making only one change from a 3.935" bore head gasket (283 +.060") to a 4.100" bore "350" gasket only changed the compression ratio by 0.034. My plan is to go with a steel shim .015, 4.100" bore head gasket and just not worry about the compression ratio being only 8.807:1 rather than 8.841:1. Gasket thickness would affect the CR much more drastically. Lynn
I calculated the volume for each diameter (in centimeters) using a compressed gasket thickness of .015" (.038cm), then subtracted the smaller volume from the larger one. That's why the answer is in cc and not square cm.
For what it's worth, the "dead space" caused by an oversize gasket hole increases unburned hydrocarbon emissions. I like parts to fit properly, including gaskets. That's why I ordered a few brands of gaskets from Rockauto when they're cheap, in order to find ones with a smaller hole size, then ordered my lifetime supply.. That's for a different engine, though, so not specifically useful for a 283.
Waking up this old thread. I need to get a gasket for my mostly stock, iron-headed 283. It's been a long time since I've bought one, and when I did I think I just bought what the counter guy handed me, and it wasn't for a SBC. This time around I looked on the net and there are so many choices from Fel-pro, let alone other companies, that I'm totally confused. I didn't have any machine work done. Any recommendations? What type and what thickness should I get? Thanks.
So true about the squish/quench....When it gets over about .050 the advantages are lost, like a faster burn with better detonation resistence and more power due to less total timing needed.....040 is a good number for an SBC
so looking for help as i am putting together a 1967 283 motor bored 30 over. Using power pack heads 8884520 that I think are 60CC by what I found on the net. running a 3 duece carb on top. So what head gasket should I be going for the heads .All the part houses want to sell me the generic sbc gasket that is really more for a 350 with a 4.125 bore and are kinda thick . I have seen articles on here talking about using something closer to the 3.9 bore and thinner like .15 thick. Thoughts 10105117 maybe or SCE511961. The heads have not been milled ,
There is a company called Olsen’s Gaskets located in Washington state. I would call them to see if the can make, yes, make the correct head gasket for a 283 Chevrolet.
Great thread! I have a early small journal 283 that's machined and ready to put together when I need it. I bought the Fel Pro gasket set for it over 12 years ago so I'll have to see if its a generic 350 set or specific to the 283 and what the the thickness is. On mine I can't remember if the heads were resurfaced when I had the machine work done, so my question is if the heads were milled .015" or .020", wouldn't that solve the problem?
Gasket thickness needed would be highly dependent on exactly what piston was used, since any increase in gasket thickness will add to quench clearance at TDC and at the same time reduce compression ratio. If you've got a stock spec compression height ("pin height", for a 5.7" connecting rod 283 the stock spec is 1.800") piston in an undecked block, you would need a thin .015-.025" thick gasket to preserve any quench function since the piston is .025" down the bore at TDC per factory spec. If the piston is of the cheaper "rebuilder" style with a reduced pin height, quench and compression ratio disappear fast with each increase in gasket thickness Reducing the chamber volume on the head by milling can recover some of the compression ratio lost to a thick head gasket usage....but it does nothing to fix the increased quench clearance created by the thick gasket. Increased quench is bad in most cases. For example, lets take the same .030" overbored 283 assembly done up both good and bad. Good would be a combination of correct piston pin height, gasket thickness, and block decking amount to achieve .035" quench.....For example 1.800" correct spec flat top piston with 5cc valve relief, block deck cut .005" to get a 9.020" height, 60cc head, and .015" x 4.100" gasket...... results in a nice tight .035" quench for good efficiency, detonation resistance, power, and mileage while reaching 9.16:1 compression . Bad would be a rebuilder piston, no block decking, thick and large bore gasket.... 1.780" height "rebuilder" flat top piston with 5cc reliefs, block uncut at 9.025" stock deck height, 60cc head, and .051" x 4.166" gasket.....results in a terrible quench clearance of .096" and a rotten compression ratio of 7.91:1 that may still have detonation problems despite the low compression ratio because study's have found a distance of .100-.140" is the prime detonation zone. You could mill the head to get the compression back up to match the good example(it would take a pretty heavy cut of about .060" flat milled) but the engine would still have terrible quench, which combined with the higher compression ratio will be even more detonation prone. You have to really mind your component volumes when building these little engines, as every discrepancy has a lot bigger effect than it would on a 350, 383, or 406. Most guys fail to realize that the Sealed Power piston for the 283 is a reduced height "rebuilder" style, starting you out on the wrong foot right from the get-go. I couldn't find any budget friendly offering for the 283 that wasn't a reduced height rebuilder style piston. .
You all are talking a low compression engine, back in the day we ran 12.5 to 1 and it didn't matter. We knew what we had cause that was all that was available, no composition gaskets or cometic's or nothing. We got GM steel shims and they worked fine. Spray them with silver paint, even though they were coated and ran them. Your smogger builds will be fine with composition gaskets. Difference now between a 3-7/8 bore and a 4 inch is nothing . Lippy
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