Greg Reimer
Well Known Member
I just today learned about the existence of a 69 300 horse 350 with a casting number ending in 041 X. Anybody know about these?
date code on 461 heads
- Thread starter denson1932
- Start date
I read something years ago,that the X typically meant that those castings had a larger than normal internal port volume than non X versions.I dont remember what it was in and whether or not the author had factory documentation to support that or if it was simply his speculation.It also said that there were X versions of several different castings including non camel hump types and I think there was a list or chart of them.It also seems like he had reason for them but I don't remember it.
cliff-1972
Well Known Member
When I bought my 64 in 1986 it had a 68 350 in it.The heads were 461X on it. I imagine the 461X’s were removed from the original 300 hp 327 and put on the 350.They did have 1.94/1.50 int/exh valves but I ported them and installed 2.02/1.60.They really woke the 357 up from the 186’s that were on it.Wish I would have keep that engine.
Greg Reimer
Well Known Member
In the very different world of class racing, Stock and Super Stock in particular, very stringent rules regarding what was allowable and what was illegal have been in place practically since this sport's inception. Some heads just seem to work better than others, after all, they are mass produced castings, so variations are an inevitable occurrence. Fudging on the rules resulted in NHRA issuing a set of specs for intake and exhaust ports as to the number of CC's the port could hold. Practically no head right out of the box is any where near the maximum port volumes so some racers get a bunch of heads of a given alllowed number for the combination they are running, and they found quite a bit of variance. The best two heads were set aside for the car's best motor, the heads then were rated as to how they flowed, whereby the racer would keep the best few sets and would sell off the rest. One thing that can cause variations in port volume is what valves are used.Some tend to be a bit thinner than others, they might have a different profile than others, even though they are all perfectly allowable valves for that application. It's a time consuming process matching and mixing parts to get the desired results. One thing that used to happen a lot was acid porting the heads, using acid to etch the ports oversize. This was hard to detect, but a trained eye could spot it. If the heads were a bit oversize and were checked, they would hold more cc's of fluid than the spec. One way this was compensated for was to surface the intake gasket side of the head. That was a good way to lose excess port volume, but the logical extreme resulted in compromising the valve cover bolt holes.NHRA then came out with a rule amendment stating that no portion of the valve cover bolt holes could be penetrating the intake gasket surface. How about if you race a Ford FE motor? Also, it can take up to .050" to get a block's deck height down to the minimum spec for deck height, and as much as .080" or so off the deck surfaces of the heads in order to get the combustion chamber volume where it belongs. After all this gets done and all the specs check out, the push rods can be up to .125" too long. Custom length push rods from the aftermarket are the answers here. Push rod length can be pretty critical here, here's one more thing to consider. Getting the engine up to a long block now means that the intake manifold is too wide.Finding a machine shop that can face off the front, rear, and side intake gasket surfaces is essential here. As you can see, building an optimal motor is quite a job. Another thing that can bite you is what happens when the distributor bottoms out into the oil pump drive shaft before it seats into the mount on the intake manifold. Decking all this stuff makes the total height of the motor shorter so here's another one for the books. Somebody makes a distributor spacer to take up some of this excess length. Does it ever end?
Same things get checked on crank stroke and weight. Lots of differences in the stroke and weight of the stocker stuff.