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TX512 03-02-2010 09:15 AM

Need Help Deciding!!!!!
 
I have a set of vortec heads in the box with rockers, rpm air gap intake, 1406 carb, and also have a comp xe262 flat tappet cam with lifters new in the box.

given the two options would YOU (both 350 short blocks costing the same price)

A. buy a vortec shortblock throw on the vrtc heads, intake, and carb

or

B. buy a later flat tappet short block and install the xe262 and lifters with the vrtc heads, intake, and carb

I am currently have a engine in the shop but need something temporary. THANKS

TX512 03-02-2010 12:11 PM

come on this is multiple choice, not an essay LOL :D

oldbogie 03-02-2010 01:38 PM

Quote:

Originally Posted by TX512
I have a set of vortec heads in the box with rockers, rpm air gap intake, 1406 carb, and also have a comp xe262 flat tappet cam with lifters new in the box.

given the two options would YOU (both 350 short blocks costing the same price)

A. buy a vortec shortblock throw on the vrtc heads, intake, and carb

or

B. buy a later flat tappet short block and install the xe262 and lifters with the vrtc heads, intake, and carb

I am currently have a engine in the shop but need something temporary. THANKS

Buy the Vortec block and put the XE 262 in it. That way when or if the 262 craps out with what passes as modern oil, you can switch back to a roller.

Running a FT in the roller block only requires the FT timing set. Leave the thrust plate off. GM did this in 95 with the Vortec block under Swirl Port heads and with a flat tappet cam. Be sure to use 7.8 inch push rods with this.

Bogie

TX512 03-03-2010 05:41 PM

interesting. can you elaborate... thanks

oldbogie 03-03-2010 06:28 PM

Quote:

Originally Posted by TX512
interesting. can you elaborate... thanks

The OEMs switched to roller cams in the mid 1980's because the EPA wanted ZDDP (Zinc Dialkyl Dithio Phosphate) out of oil because it contaminates catalytic converters making them less efficient across time.

The manufacturers understood from their own long term reliability analysis projects that ZDDP is a very useful chemical in oil. It provides what engineers call Boundary Lubrication. It does this by embedding itself into the pores and forms a layer a couple molecules deep on the metals it contacts. If your old enough to remember the TEXACO ads of 40 years ago where they drove a NYC taxi around Manhattan for a day with no oil in it, that's how tough this stuff is.

In our particular case of flat tappet cams, in modern OHV engines the forces are much greater on the valve train parts than the old flat heads. It was found in automotive engines of the 1950s, as it was in WW II aircraft engines, that as loading and speed on these parts went up, so did wear when additive free oil was used. This is because the interface of lobe and lifter doesn't form a wedge of oil between them like shaft journals and bearings do. So part life expectancy in modern engines became tied to ZDDP. Other chemistry has been tried such as Molybdenum Disulfide. It's great stuff and will fill many of the same purposes as ZDDP. But there's a Catch 22. Moly just loves itself, you can grind this stuff into the finest powder possible, mix it with oil and pour it into your engine. But, each molecule immediately starts hunting other molecules just like it. They start to gang up with each other and before you know it, the gang is big enough to get caught in the oil filters drag net. So little by little and faster and faster it goes away.

The OEMs realizing there was no inexpensive option to keeping warranty claims to a minimum all went to roller cams. The hidden lesson here is that of all the better materials cams and lifters could be made from, of all the high-tech processes that could be brought to bear against the problem, the most cost effective solution was to go roller. That says a lot about the problem.

So getting to my recommendation of going with the Vortec block is that we today have a very high failure rate with flat tappet cams, it doesn't take a lot of nosing around in this form to discover that. The additional benefit is that the Vortec block can be run with a flat tappet cam or a OEM roller. A factory roller is lot less expensive to but into a factory roller prepped block than an aftermarket roller into a flat tappet block. The flat tappet block does not accept a factory roller conversion without a lot of effort and expense and is hardly worth attempting against the cost of an aftermarket roller. I mean its done but in the end you save a hundred bucks or less and own a what is often a kludged mix of parts that doesn't function well.

There are many ZDDP additives sold in the aftermarket, so far none seem to have the long term qualities that used to be found in the oil formulations of the major petrol companies. I suspect that from a chemistry stand point, that there's something else missing that was used to enhance, correct, or control ZDDP that the big oil company's either kept proprietary or there is another chemical the EPA had removed that performed the functions I sighted.

Bogie

TX512 03-04-2010 07:31 AM

so basically your saying modern oil sucks.

oldbogie 03-04-2010 08:44 AM

Quote:

Originally Posted by TX512
so basically your saying modern oil sucks.

In regard to flat tappet cams yes, but in many other ways it is so much better. The molecules are stronger, they take a lot more heat before breaking down, they provide better lubrication with less viscosity so drag from running the oil pump and resistance inside the bearings is reduced which provides more power on the end of the crankshaft, they make a lot less sludge than old oils.

But these new formulation oils don't work as well in the flat tappet interface. For production engines we're now 25 years away from starting down this path of replacing FTs with rollers, if it wasn't for the nearly 1 billion flat tappet SBC's that were produced over nearly 50 years, most of which are still out there, this wouldn't be a problem. But the engine persists and so does its flat tappet cam, but technology has marched on, in case you haven't come up against a stock LS7 yet, if you do you'll find it takes a damn well built Gen I to keep close.

Bogie

TX512 03-04-2010 09:06 AM

ok. i got the short block on the stand going to start tear down tonight. I'll decide what i'm gonna soon. thanks for all the info Bogie. I may have some questions later


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