So i'm a flathead guy and havn't worked on a sbc in about 40 years. I find myself putting together a 61' 283 for my 39 deluxe coupe.The block was bored 40 over,im running orig power pac heads with a mild cam.Here is the question, the felpro gasket set came with the thin steel headgaskets.I want to be able to run this on regular gas so i don't want the compression to be too high.Should i run the thin gaskets or get something thicker to reduce compression? I'm sure this discussed elswhere at length but i'm old and don't work well with the search function. Any help from all you sbc guru's out there is most appreciated. Thanks,Bob
First you need to know how far down in the bore the pistons are at TDC then we could help with the gasket choice.
Replacement pistons generally sit lower in the hole. Check how far down the hole the piston is at tdc. You just may find the steels are the way to go. Also small bore head gaskets are super hard to find. Everything today in head gaskets available will pretty much drop compression more than you’d like.
Might drop it about 0.4 compression ratio points. But they're not high compression engines, so I'd use the thin gasket and see if there's an issue, first.
Your 283 was factory rated at 9.25:1, and probably wasn't even that in reality. I don't think that you'll have a problem with steel shim gaskets.
Use the steel shim head gaskets. using the thick over the counter head gaskets will destroy the quench area, and can cause more problems than they solve. bad quench will make it run like a dog and can cause detonation issues. This isn't as much of a problem (but it still is a problem) on a larger small block like a 350, but with the 283, the smaller motor is more sensitive to changes like gasket thickness and compression ratios. use the thin gaskets, i can crank the timing back on the 283 in my 39 and run 87 octane with 10.3 to 1 compression, you will be fine.
You also need to know the chamber size of the heads you're using. It's impossible to give you good response without all the details.
I have a .020 350 SBC and and am running heads off a crate engine. I used parts store Felpro blue gaskets and the car runs great. That sucker will "pull the wheels" (with a good jack and a tire iron ). Seriously though, the car runs great. I prefer the thick (or at least thicker than steel shim) replacement gaskets as I feel they are more capable of allowing the block and heads to mate better. Who knows how much warpage an old block and an old set of heads has (obviously both can be decked but, if you're cheaper than doggie doo like someone my wife knows ... ). What's my quench? I dunno. What's my compression ratio? Ahhhhh ... say what? What time do I need to be in line for the next round of NHRA Super Stock? Yeah ... no, just a street car that runs just fine on cheapo gas and has enough balls to get me in trouble
My 283 has felpro 7733 sh-1. Spray with copper coat before installing. This was recommended by the shop that built my motor.
Jail, in 1961 there were 2 common 283’s the 2 barrel had 170 hp and the 4 barrel with 230. They did not share a common head as the compression ratios were different. I will not go into the high performance offerings in 1961. From my memory the 2 barrel head had a smooth flat 1/2”x 1-1/2” surface on each end of the head and the 4 barrel had the same with a single triangle located on top of the rectangle. In not a cast #’s guy so I’ll go with the easy external casting differences. Your description of “power pack” heads indicates your heads should have the triangle. Rebuilder pistons were designed and manufactured to be slightly lower in the bore to keep the compression identical to the original allowing for the over bore. If your heads have the triangle they were originally 9.25 to 1 compression. The non triangle were 8.5 to 1. Originally all the SBC of that era used the shim style head gasket. If your engine is not assemble from miscellaneous parts but one of the original ones in 1961 the above information may help you decide on which style gasket to use. Good luck.
Jason has very good points! Actual dynamic compression will be less than your "static/ mechanical" 9.5:1? Compression. So you're okay. Just use 2 or 3 light costs of KW copper spray (NAPA) both sides and you good with that steel shim gasket. Make sure you check for cracks in those ancient heads!
The thicker Felpro rebuilder gaskets are made with you zero decking the block into consideration, figure your quench area and use whatever gasket will get you closest to .040 quench
How does an engine builder deal with virtually a complete lack of quench when running a dished piston? Where is the quench in a true hemi engine? Asking for a drunk neighbor who came to my door naked
Usually a dished piston has quench...but a flat top piston that's sitting down in the hole a ways, doesn't have any. How to deal with it? Use better gas
lack of squish on a wedge head makes for a longer combustion burn with more total timing needed..extra time wasted for the burn equals less power. I have built tight squish engines and they make better street engines. Supercharged engines generally don't need squish and some Hemis do but many don't
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