[620 dude]

I have a set of 3973493 cyl.heads that I got about 10yrs ago.they have double valve springs threaded rocker studs w/pushrod guide plates.
My question is what SBC do they fit. Are they worth using?I have a stock
rebuild 350 truck short block I was thinking about using them on just because I go the block w/o heads.

[geezer69]

they came from a 72-76 400.1.94 intake 1.50 exhaust.76 cc.

[gizmo-1948]

My source indicates these heads were used on the Passenger, Chevelle and the Monte Carlo 400" engine from 73 thru 76. Nothing special and probably the light duty castings. Be sure to have them checked for cracks prior to using them.

[620 dude]

so do you think the double valve springs would be to much for a stock hyd
camshaft ? and do I need special headgskts to cover those small holes between cylinders on the heads?

[DoubleVision]

Yes double springs will be too much for a stock cam. You should be able to remove the inner spring and just use the outers for a stock cam application. Your question about "what sbc do they fit" is somewhat confusing since all generation 1 heads will interchange.
Some years ago, the EPA forced the oil companies to remove many anti wear agents in motor oils such as zinc. Since all cars roll off the line with roller cams that have far less friction, engines using flat tappets weren`t considered and many have fallen victim. This is why when you run a flat tappet, be it stock or not, you must use oil or a oil additive that has ZDDP. Valvoline in there racing oil line still has the needed additives. No, there`s no worry about the steam holes and the gaskets. You can use a regular head gasket without worry. However, from a performance stand point the 493`s aren`t the hot tip. The large 76cc chambers have rather poor combustion characteristics.

[cobalt327]

Originally Posted by 620 dude

so do you think the double valve springs would be to much for a stock hyd
camshaft ? and do I need special headgskts to cover those small holes between cylinders on the heads?

Use a head gasket made for the 350 SBC not the 400. Ignore the holes in the heads from this point on- they will be plugged by the 350 gasket.

Another option to what has been offered is to replace the dual springs w/stock-type springs that have an inner damper.

These springs are 1.25" diameter w/an installed height of 1.7". This means using different retainers, in all probability. The stock set-up also uses a steel "umbrella" under the retainer to shield the stem from excess oil and a single O-ring oil "seal" on the valve stem. You may find the seals on it now won't fit if you use the stock-type single spring w/damper, this depends on what seals are used and what was done to the guide boss to allow the seals and springs to fit. It might be a good idea to replace the oil seals anyway after they've sat around dry for all these years.

This is a lot of trouble to go to unless you have an old set of heads to pirate the parts from, but will give you what you need to have stable springs. The only problem I see w/just using the outers of the dual springs, is you really don't know what you have for spring tension w/them.

An alternative would be to haul one outer down and have it checked for pressure.

Or I worry too much.

But in any event, those heads are a poor choice from a performance standpoint, as has been said. A much better alternative (unless you're on a shoestring budget), is to hook up w/a pair of Vortec heads and an intake to match. This change alone is worth something like 25-30 HP over stock.

They will require self-aligning rockers- like they come with stock. If you got a stock set of Vortec heads w/the rockers included, it would be be a bolt-on affair if using a cam with 0.450" lift or less.

[620 dude]

Hey guys thanks for the input it's very informative and you know your stuff.I guess what I'll do now is start researching this new Vortec head technology. Is there one set that I should shoot for since it's going to be a driver?

[DoubleVision]

I would get a set of RHS Vortec heads. They flow better than stock vortecs, plus the guides are already clearanced. Best of all, they are much heavier casted. Use a small RV cam with them, a set of headers, a good intake and carb, tune it right and it`ll shock you with the power it`ll make plus it`ll get good mileage.