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Old 07-30-2006, 08:56 PM
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olds #5 head

i was struggling trying to put this olds 350 rocket engine together, at the moment funds are low but i need a good set of heads, eddelbrock has a 455 head but its way out of my budget, i can get and rebuild one of the following, a #5 or #7 head for this project, is the #5 better then the #7, and how do they rate with the eddelbrock head? i'll be using a eddelbrock rpm intake. thanks...

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Old 07-30-2006, 10:05 PM
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do a search on this forum for 403 Olds, there will nbe Olds 350 head info

your talking 350 Olds #5 & #7 heads correct ? I bought a set of 350 #5 Olds heads (mine #5s are for a Olds 403) that need rebuild including harden seats for $50 look on here for info & parts (http://www.realoldspower.com)

(LOTS OF OLDS INFO HERE, ALL ENGINES SIZES AND YRS http://www.442.com/oldsfaq/ofe403.ht...IDEngineDetail)


Best Flowing SB Head
Dick Miller claims that #5 heads flow the best bone stock and untouched.

[ Thanks to Chris Witt, Mark Prince, Chris Urban, Bob Barry for this information ]
Exhaust Crossover Passage
Some W-30 heads have only one center exhaust port open to the intake manifold heat crossover. This is called "blocked heat crossover." If you can stick your finger from the intake heat crossover passage into both valve pocket areas of the center exhaust ports, it's not blocked; if your finger can access only ONE exhaust valve, that is blocked. Blocked is better, for performance. For similar performance gains, more mundane heads can have this crossover blocked with molten metal, etc., or a stainless steel shim can be placed over that heat passage when the intake manifold is installed.

Gasket Thickness
Today's thicker head gaskets [0.045" vs. 0.025"] place the head about 0.020" farther from the cam, which lowers the compression about point and takes that much out of the lifter plunger preload. If you have an engine apart, have the heads milled for the combustion chamber volume that your calculations indicate for the desired compression ratio.

In the case of most Olds heads, the guides feature a spiral cut inside the guide from the factory to aid in stem/guide lubrication. Which provides less material for the knurl to "expand". The bottom line that applies here is that old saying of "Save Money By Doing It Right The First Time".

[ Thanks to Greg Rollin for this information. ]
Hardended Valve Seats
Before 1971, all Oldsmobile street engines require lead. An engine uses lead for valve seat protection and octane boosting. GM states in the 1971 Owner's Manuals that all 1971 GM engines can safely use unleaded fuel. You might want to consider that 100,000 miles on an unopened engine wasn't a common occurance back then.

The lead (actually tetraethyl), when burnt in the combustion process is deposited on the valve seat. This cushions the softer metal of the pre 1971 heads. Without the lead the harder valve slams into the unprotected seat and will cause seat recession. This leads to burnt valves. Heads with soft seats are A - F. Heads with hard seats are G - K. Although some Ks might have the soft seats. I'll have to defer on 350 heads.

While I don't have a GM reference, I do have period magazine articles which refer to the low-lead requirement. It was a federal mandate in 1971 that all cars be able to run on low lead. This is the reason for the across the board compression drop from 10:1 or more to an average of 8.5:1. This compression drop resulted in a real horsepower drop (as opposed to the simultaneous apparent drop when net HP was used vs gross) and, of course, signaled the end of the muscle car era.

To distinguish the hardened valve seat heads from the earlier, non-hardened seat heads, Olds cast a small capital-letter "A" along with the larger casting number/letter. This letter is smaller, and down to the right from the main casting number/letter; hence, it is designated by the lower-case "a", even though it is cast as a capital "A" (also to distinguish it from the later 307's #7A head, where the capital A is the same size as the 7).

Heads with the small "a" designation are guaranteed to be hardened seat heads. Such as Ca, Da, Ga and also Ka and J heads. The J is the exception due to being a smog head from 73-76. Other heads (such as E and F) are rumored to have hard seats, but only your budget, gut feelings, and eventually the heads will know for sure.

I guess since the "A" is more of a revision code, and not really part of the casting number/letter (unlike the 3A, 4A, 5A and 7A heads on the '77 and later cars), the '72 heads are called "#7" heads officially.

Studies made on pre-71 engines showed that unleaded gas normally would not be horrific to your engine unless you were at sustained high rpms, such as drag racing, or using 6.13 gears on the street or something similar. Theoretically, an engine running on no-lead will need a valve job sooner than one running leaded, even under normal driving. But no-one I know of, including myself, have ever run across this no-lead curse.

The lead in fuel helps soften the pounding of the valves against the seat. This is where you would find the damage. More so on the "hot" exhaust side. The valves have a tendency to sink into the head. Although most engines would be succeptible to this sort of wear, Olds heads usually don't suffer this type of wear very often. At least not to the degree some do. Chevies seem very prone to this valve sinking, however, based on the number of junkyard buildups I've read in the car mags.

Heads without hard seats will go about 60,000 miles on unleaded gas. In a car that will see a lot of driving, you will need the hardend seats installed. Valve recession is apparently not a big problem for street-driven cars. Though the lead is gone, there are additives in gasoline today that perform much of the same lubricating function. The only time you absolutely need hard seats are on an engine that is not going to be apart for a longer duration than that. All these shops that insist on hard seats do so because they sell/install them.

Almost any machine shop can install the hardened valve seats. This in conjunction with a 3 angle valve job. Also an octane boost will help. I have only found one octane boost that earns my seal of approval. It is called Lead Supreme 130. It will formulate today's pump gas into yesterday's Rocket fuel. Contact: Stone oil co. area code 912-489-2896. They will ship UPS. 1 ounce of this stuff per gal. can increase octane 2 points.

Use a fuel additive that contains lead if (1) your heads are pre 1971, (2) your compresion ratio exceeds 10.1, (3) you have no catylitic converters, and (4) you rev past 3 grand regularly.

The ~only~ time I have seen any damage to valve & seats were newer (1980's series) Chevrolet 350 engines, with the .375 diameter valve stem sodium filled exhaust valve, as opposed to the 11/32 (.312) std sized valve stems. I used to run into a bit of valve pitting and recessed seats on those "Heavy Duty" heads. Go figure out that engineering!!

A caution about having hardened seats installed. Make sure that they're of the right depth for Oldsmobile heads, as Chevy seats are too deep, and machining for that depth will end up in the water jacket.


ID/ Use Casting
Code Year(s) CID CCs Number Notes

5 '68 - '69 350 64 397742 Excellent candidate for use today.
Good flowing, and high compression.
6 '70 350 64 403859 W-31's had larger 2.000 intakes. '69
7 '71 350 64 409147 W-31's had larger [2.000] valves.
7A '72 350 64 409147 The 'A' is a subscript, like "
tall, to lower right of the '7',
like | 7A.

7A '85 - '90 307 67 0142 This 'A', and the others from 2A to
6A, is a large capital letter equal
in size to, and immediately adjacent
to the 7, like | 7A.
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