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#1
01-20-2010, 08:36 AM
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Re: 1970 Camaro L78 Heads
The biggest difference between those two heads is that the the exhaust valve diameters are larger on the #291 (1.88 Diam.) The #840 still had the 1.72 exhaust valves. Now somebody enlighten me as to what kind of seat is on the spark plug of the 1969 #840 heads. I thought that 1970 #291's used a short-reach, tapered seat. I've heard of several late-1969 L78 cars using a #291 cylinder head on one side and an #840 head on the other. That points towards the #840 head being phased out even before the 1969 model year was over so I would think that ALL 1970 L78 and LS6 engines used the #291's. Especially the late introduced 1970.5 Camaros.
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1962 Biscayne O-21669 MKIV/M-22 1962 Bel Air Sport Coupe 409/1,000 
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#2
01-20-2010, 04:20 PM
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Re: 1970 Camaro L78 Heads
I agree with you Mark. I have seen a lot of June of 1969 built 291 heads. That means some of the late '69 cars could have gotten 291's when they ran out of the 840's.
That's a good question. If each head took a different plug, you would have to get 2 sets of plugs.  Kurt
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#3
01-20-2010, 04:22 PM
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Re: 1970 Camaro L78 Heads
I have 1 840 head that takes the newer plugs? Would that be for that NOVA application with the mixed heads?
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