Folks:
I have a 1974 302 in a 47 merc truck and it has rail rockers and a Comp Cams 268H cam with matching springs.
It runs good, but I have doubts about the rail rockers. I read recently that they should not be used with high performance cams.
I have thought about putting on roller rockers. Does anyone make a roller tip and roller fulcrum rocker that would work where a rail rocker was? It would need the rail tip.
What do you think?

 

Most likely not, as rail rockers have all the problems you read about, and aftermarket makers will not try to repeat a bad design when they're trying to sell you higher performance parts.

Their biggest problems are putting side loads on the valve stem, which can mess up the stem, and wear out the guide faster. If you use guide plates, (or slotted push rod holes of the older heads), they take the side loads.

High lift cams can cause the tips of the rails to hit the retainer, and in severe cases, loosen it up and drop the valve. You can look for tell-tale traces of a shiny ring on the retainer around the valve stem.

 

Thanks. So a different head would be a better way.
Got any suggestions, stock Ford or aftermarket?

 

The best stock Ford head and the most common in the junk yards is the GT40 or GT40P heads that came on the 1996-1998 Ford Explorers. They can be had for as little as $100 or as much at $500 depending on where you look and what condition their in when you buy them. Ready to bolt on or in need of a rebuild? Add a set of 1.7 RR's and a RV cam and you'll have at least 250 HP.
Personally I would try to find a 1986 or later 5.0L short block and rebuild that as you can then use the much better roller cams and lifters offered by Ford or the aftermarket. The reduced friction alone is good for a measurable amount of horsepower.

 

I have seen the Explorer GT40 heads and also the E7TE heads for sale at reasonable prices.My question is that since I have a good rebuilt flat tappet engine, can these heads be used on it?

 

I would still look for a good roller short block. I've seen many late model 5.0's that still have the cross hatching on the bores even after 100K miles.
If you find one all you may need to do is put in a fresh set of rings and bearings and you should be good for another 100K miles.

Here in the Midwest car bodies will rust away before the engine wears out.

Since the introduction of fuel injection on cars engines just last longer. What happens is that there is no excess fuel being dumped in the engine like a carb can do which washes down the cylinder walls and dilutes the oil causing higher wear. With regular oil changes every 5-6K miles or around 10K is using synthetic oil most any engine should go 150K-200K.

 

You're fine with that cam and rail rockers. No worries there. The 268H has neither a high lift nor overly aggressive ramp rates that would cause problems with using rail rockers.

 

The lack of cylinder bore wear on the roller blocks has more to do with the use of hypereutectic pistons, low tension piston rings and tighter piston to bore clearances than fuel problems. Seen more than a few roller engines that too had mixture problems due to the injectors being subjected to long periods of use with poor gas with no additives to keep em clean. Lots of em have a motley assortment of both rich and lean cylinders when the heads are pulled.