gared69
Sep 28th, 04, 9:03 PM
A friend I know wants to sell me his Double Hump Heads for 150.00 for the set. He had them on his car for about 3 months and got some new heads.My current Heads are 882 76 cc heads.If I buy the heads will I see any real improvement in my car?What if I install the Double Hump Heads and drop my cam down to a XE268? Also what if I keep the current cam (XE284) and install the Double Hump Heads will I see any improvement? What type of compression will I have? (Flat Tops 4 relief ).Thanks in advance
gared69
Sep 28th, 04, 9:13 PM
Also the Double hump heads have 202 160 valves in them.
Pat Kelley
Sep 28th, 04, 9:20 PM
I think you will see a marked improvement. 64cc should put your CR about 10.2. The 268 is a bit small for that CR and could cause detonation. A 276 is about the smallest you'd want to use. The 284 you have will work fine, much better than with the 882 heads.
When you get the heads off, measure the deck. Stock is .025". If it's that, I suggest using a .015" head gasket for a .040" quench. If it's less, try to find a gasket to give you between .035" and .040" piston to head clearence (quench). If it's more use the .015" gaske and take what you get.
75c10
Sep 28th, 04, 10:33 PM
Pat, what do you mean by measure the deck?. What part is that?. Please Forgive my ignorance. gared69, I don't mean to hi-jack your post but I always wanted to know this. Thanks
baddbob71
Sep 28th, 04, 11:04 PM
bring a piston to exact top dead center and measure the clearance from the top of th piston to the engine's deck (top of the cylinder) This measurement added to the thickness of the head gasket used is the amount of piston to head clearance you have. .038 of an inch is ideal. Most pistons are .020 from the deck surface and if a composition gasket of .045 -.050 is used you'd end up with .065 - .070 for piston to head clearance which would be far from the ideal .038 figure. Steel shim head gaskets are available with thicknesses of .015-.018 to help achieve the right clearance. GM used steel shim, and factory gaskets are still available. Composition gaskets are also available in different thicknesses. Many people have the block zero decked by a machine shop and choose a gasket with around .038 to use.