Building a GMC 702 V-12
(→Hydraulic Tappets) |
(→Hydraulic Tappets) |
||
| Line 157: | Line 157: | ||
Note the difference in design of the lifter galley over a GM V-8. More to come..... heads next and that is just as interesting, right down to the sodium filled valves. | Note the difference in design of the lifter galley over a GM V-8. More to come..... heads next and that is just as interesting, right down to the sodium filled valves. | ||
| + | One caution on assembly of flat tappet lifters with a new cam lifter assembly. This WIKI is great cause I can share my BS stories so here goes.... When I started my HP addiction in the late 60's the EPA was worried about river's catching on fire from the toxic/flammable stuff floating and also trash on the side of the road. They really did not care what was added to the gas or oil that we used. Well we all now live successfully with unleaded gasoline (though this alcohol craze is killing stuff in storage and robbing HP from our street cars)and... unrealized by me until last year, no more "heavy metal" anti-friction additives in our oil. Not exactley sure when this happened but somewhere after the last flat tappet 350 chevy I built in 1998 (I had switched to roller cams after that, again HP addiction)and up to 2009 they pulled the plug. I was putting together a big block 396 with my son and wanted to run a flat tappet for cost and did not really want a HP monster in his car. I assembled using cam assemble lube (Comp Cams camshaft)and added by Castrol 20-50 oil as I had done so many times before. It was a dual spring matched to the cam and the directions sort of said remove the inner springs on break-in (the 20 minutes between 2000 and 2500 RPM right?)and I thought that was stupid as I had never done that and did not want to spend the extra time on it. So, 20 minutes of running in the garage and we were good to go, at least I thought. Within 15 miles the car started to backfire, I drove it to verify and get a NYS inspection (another BS thing) and within the next 10 miles it would not idle and continued to backfire no matter what I did with the timing. Long story short, by the time I got it back home and pulled a valve cover the heads had up to 1/8 inch of what looked like gray moly past on them. Rockers were all loose and when I pulled the cam EVERY lobe was wiped. The engine had to be completely rebuilt, every bearing, pistons, rebore, crank turned.... expensive lesson. So, get yourself a bottle of MPZ (Magnesium, Phosphorous, Zinc) assembly lube and use liberally on all lifters, cam lobes and lifter bores. The add a break-in additive to your oil. | ||
| + | [[File:MPZ.jpg]] | ||
== Heads or rather Head Ache == | == Heads or rather Head Ache == | ||
Your Privacy Choices