Mortec seems to be gone. I pulled my heads from the 35 because I had a coolant leak when its sat for a few months. It would stumble on start up and pushed smoke out of the left pipe till warmed up. Heads are off and the left bank looks to have a crack on number 5. Looks to have rotted through the casting on the water ports next to the spark plug area. These are the casting numbers that I have Right Bank 3998891 Left Bank 458642 This is the one that is cracked and has water jackets leaks into the cylinder. Both heads have GM 72 cast right in the center of them in the valve train area. I just want to get another set of rebuilt comparable heads. Nothing radical or expensive. Its just a driver. Just looking for what years I need for another set of iron heads. Or casting numbers that I can give over the phone to a supplier to order them. There is a local guy advertising a set of Power Pack Heads that are rebuilt. I was wondering if these would be an option? The casting number on them are 377492. Thanks to all in advance.
Also wondering if I will need to get another set of new push rods and rockers if I go with a set of new heads. The casting number on the block is 3970010. It would ne nice to just get a crate motor for it and be done with it. But everyone around here wants at least 2G's for one. Is there a 1-800 Long Block that any one would recommend thats not going to be 2G's. That you have actually used and would stand by. Once again,Thanks in advance.
The 492's are not the old school power pack heads from the 50's... Those heads were released in the early 70's as over the counter performance angle plug racing heads. I'd buy them and bolt them on my 302, 327, or 350 motor if I had one...
Let's do it this way so we will all be on the same wave length. What engine do you have and what is it's present size? --- (Actual bore and stroke sorta thing is all here)... I say this because a 307 SB engine and smaller can run powerpack heads fine up until the 265/283/287/292/301/302/306 engines get way up in horsepower!! And I'm talking BIG, up to 10,000 rpm HP here!!! Then think hard about installing 1.94"/1.50"/2.02"/1.60" valve MODERN double-hump type heads on the 283/292 with a .450" lift cam or lower. And this is because there MAY be a chance of a big valve head operated by a higher lift cam smacking the top of the cylinder lip... Otherwise, the 301/302/306/327 engines can use big valve heads and high lift cams from hell fine!! Notice 4.00" bore here is all...... pdq67 PS., the hopped up .020" overbore 283 that I finally got that was my Nephew's had a good set of big valve -291 heads on it along with a TRW PN TP-146 hy-cam that was like a 308/244, 108/108, .430" lift or so(???)..... Again, notice the low lift because of the smaller 283" engines bore is all.
Back again, my pair of '56, 265, -306 trough sparkplug heads are down around 118 to 120 CC intake port size. Real Power Pack heads come in somewhere around 137 or so cc intake port size. I like to think of them being the later big triangle heads even tho the earlier heads did not have the triangle on them, but I think just two thin columns, but it's been years and years? Now my virgin -461 real so-called big valve "fuelie heads" come in at 160.0 and 160.+ cc intake port size and with a chamber of right at 66.0 to 66.+ cc's. (Measured)... This is due to the medium valve heads needing GM's "plunge-cut" that they used to unshroud the larger intake valves so they would **** better. Otherwise, medium valve heads with just big valve's installed, won't **** as good AND this is a FACT!! pdq67
Mor-Tec ain't gone ,,there's a ton of their web sites out there ,,check this SB Chevy Head I D page ,,might help ,, http://www.fastnuf.com/Headguide.html
A bit of hunting shows 3998991 307, 350, 75cc, 72-73, 73 had hard seats 458642 350-400, 67-70, I didn't find a 377492 but found 3774692 283, 60-61 Corvette 3774692 283, 58-64 P***, Power Pack From here: http://www.kendrick-auto.com/chevrolet_head_casting_number_re.htm Unless you are sticking this engine in rod and want the old non drilled heads for the "look' I'd p***. I don't think they are what you want for a daily driver. No bolt holes for the accessories you engine might have and unless they have been worked on they don't have hardened valve seats for today's cruddy gas. If it were me, I'd pick up a pair of mid 70's 350 heads, have them done at a reputable shop and be done with it. I used to work in an exchange cylinder head shop at one time and I don't care for most exchange heads from a lot of places due to the way they process the heads and valves.
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