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1964-1990 Miscellaneous Topics


Miscellaneous Topics

Best Flowing Head

It has also been said that all Olds BB or SB heads as a group will flow within 5% of each other. Unless you are turning over 6500 rpm, your heads probably won't be the limiting factor.

Best Flowing BB Head

The '67-69 C (#394548) heads are reputed to flow the best. Pretty much goes without saying that big-valve heads ought to flow better than comparable units with smaller valves. Bigger valves may diminish low-rpm performance and throttle response.

All Olds big block heads have the same mounting holes, port sizes, etc., and thus are interchangeable. Even the combustion chambers are equal at 80cc, plus or minus a little. Olds achieved different compression ratios by using pistons with different size dishes in the top. Some W-30 heads were rumored to have been factory-milled for a smaller combustion chamber. When in doubt, measure (CC the head).

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 ]

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.

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.

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.

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 ¼ 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.

Octane Boosters

A note for people that use leaded aditives for their fuel.

  1. It will destroy the useful aspects of the catalitic converter.
  2. When leaded additives were commonplace in the refineries, the people that handled the lead material did so with extreme caution, and took extensive precautions.
  3. It is considered a poison with extreme toxicity.
  4. If you use this material, wear thick rubber gloves, good eye protection and a respirator face masks at a very minimum. Do not come into physical contact at all.

Remember when gasoline was 'red.' The red was an aniline dye added for anti-knock (relative octaine boost) purposes. It too is harmful to C.C.s.

I don't have a problem with my 10.25:1 455 in the Cutlass (back when I mixed 92 unleaded with 89 leaded), and even now I don't have a problem running my '69 Toro's 10.25:1 455 on 92 or 93 octane unleaded.

I did have a problem with part-throttle pinging, and even backing the timing way down was not enough to cure it. I bought an adjustable Crane vacuum advance unit, followed the tuning advice (it also includes springs and a vacuum advance limiter), and have no pinging on even the hottest of days lugging it up a hill at part throttle, with the initial advance set at the factory 8' BTDC. It seemed that the problem was the excessive vacuum advance under part-throttle load; with the Crane kit, I could tune the spark curve to reduce the advance under those conditions, but keep it at just under pinging in all other places. Highly recommended.

I have mine set at the factory 12' initial advance with 34'-36' total on my 455 with 10.5:1. I don't have any pinging or knocking at any rpm or load. I am using straight pump unleaded Chevron Super Supreme 94 Octane gas. It is the only gas station in Canada that has a 94 Octane fuel. If I use a 92 or 91 Octane then I do get pinging. I have all the stock components under the hood (for now). I did purchase a MSD Adjustabe timing control (I have yet to install it) to use so that when I do travel to areas that don't have 94 Octane gas, then I can just turn the little dial and retard the timing by up to 15'. I have seen it work and would also highly recommended them (ie. either the Crane or MSD system).

Most of the time I go out to the local airport, purchase about 10 gallons of av-gas, and run a 2:20 (2gal av-gas:20 gal super unleaded), and my 10.25:1 350 runs fine at just about any timing setting.

VP Racing Fuel says that octane does not matter as much as the blend of the fuel does. It is all a matter of how well an engine can burn the fuel. They sell a leaded and un-leaded racing gas for stock engines, they sell gas for NHRA Pro Stock racers, and everthing in between. If you tried to run their highest grade stuff in your street car, it most likely would not run at all. Your stock engine does not make enough compression.

I used to run a 50-50 mix of unleaded premium and VP Red (the lowest grade of leaded) in my Fairlane with great results. I have also ran brand X racing fuel with the same mix ratio in my Olds with great results. I thought I had Sunoco 260 in the tank again, just like the old days. I have a friend that runs 3-4 gallons of racing gas with a tank full of premium in his GTOs. He reports smoother running and driveability. I would seek out a racing fuel supplier and shy away from aviation fuel. VP is headquartered in Dallas, Texas and has bulk plants all over the U.S.

When I tried Lead Supreme 130 I found that I could put my timing almost anywhere I wanted it. LS 130 uses the same additives the oil companies used in the good old days. This includes tetraethyl and toulene. One ounce per gal. will raise 93 octane gas to 95 octane. You can custom blend to your own octane needs.

To raise the octane 1 point (of course I am speaking of R+M/2 method) from 93 to 94 one gallon of LS 130 will yield 214 gals of treated gas. This will really only protect valves and CRs of 9.5:1. To raise octane 2 points add 1 ounce per gallon this will make 129 gals. to get 4 points add 4 ounces per gallon this will make 32.5 gals. For racin' 1 gallon of LS 130 to 9 gals of super unleaded will raise octane 8 points.

One gallon of LS 130 is about $18.00 less S/H.

Product Comments
104+ Good stuff. Car pings a little 90% effective.
Bartyls Lead additive and Octane booster. 80% effective
Snap Octane booster. Save your money.
Trick Octane booster. Haven't tried it yet.
Stp Octane booster. 75% effective.
[ Thanks to Bob Barry, Nick DiGiovanni, Stephen Hoover, Cliff Feiler, Dave Wyatt, Danny, Chris Sparks for this information

Head Porting

Do any head porting before you do the valve job; one nick of the valve seat (and if you work from that side of the port, you will nick the seat) and you've got to do it over anyway.

If you are really concerned with maximizing flow, just follow the standard porting techniques for Olds heads (remove E.G.R. or A.I.R. bump, teardrop the valve guide, port-match the intake and exhaust ports and manifolds).

The Olds head can gain about 80% of its total potential flow by matching ports on intake and exhaust side (yes grind out those headers), removing E.G.R. hump in the exhaust port, clean up of the bowl area behind the valve seat, and tear dropping, or at least narrowing the valve guides. The metal around the valve guide is round from the factory, and you grind it so that it is shaped more like a teardrop, with the skinny end pointing away from the valve.

The intake runner of the head should stay rough to help the fuel atomization. Smoothing the surfaces til they are smooth and shiny will cause fuel puddling and reduce atomization.

When looking at an Olds head exhaust port you will notice the EGR hump on the roof of the port just inside (header side). This hump when ground out so that its flush with the surrounding area will net a gain of approx 30% on the exhaust flow. Also blend it into the roof of the port. There is also a kind of depression next to the AIR boss (it wasn't used for EGR, though it may unintentionally have had that effect) that you will need to blend in to the rest of the port roof as well.

To port match, you scribe the outline of the port from the gasket on the surface of both the head and the manifold, and then grind the entire port up and out to that point.

Just short of all out porting is to have the heads bowl ported to a distance of about 1" just down from the valve seat and blended into the port runners the basic idea is to try to get the bowl area to about 75% of the valve diameter.

This one mod alone will increase power better than any dual pattern camshaft would (when you attribute the increase to the dual pattern and not the camshaft profile). Larger valves can be cut into any head. Unless your cam is really wild, however, and you're turning 6000+rpm, just removing the EGR bumps, tear dropping the valve guides and smoothing out the transition from the valve seat to the port will be sufficient. No sense in trying to increase port volume or such.

Make sure that the shop you take the heads to will actually do a three angle valve job.

Have the intake and exhaust valves back cut on the back side of the valve (called back cutting the valve). Also try to have the back sides of the valves polished or smoothed out.

Have the center exhaust port divider welded up and then milled flush with the rest of the exhaust gasket seating surface.

Needless to say, you should also completely wash out the head after porting it; metal particles and shavings will be everywhere after your porting job!

Any further porting should be left to someone with more experience, as flow can be just as easily reduced as increased.

Mondello offers an entire kit (~$70), with the cartridge rolls and the carbide burrs you would need. You can pick up seperate pieces if you run out, but the whole package will end up costing more if purchased seperately. Go with the Mondello kit, unless you find a good cheaper source for everything.

The carbide burrs are like rotary files on the end of a shank, and you use them to remove material; they come in a few different shapes, such as round and almond-shaped, as well as triangular. I found myself using the round one most often (wore it out, in fact, on one set of heads).

The cartridge rolls are just strips of sandpaper rolled-up like a jelly roll, which screw on to the end of a shank; as you use up the abrasive, that bit of the roll breaks loose, revealing new abrasive underneath (I didn't know this, and got concerned when bits of these things started flying off the tool at 22,000rpm!) They don't really remove much material, and you'd go through a lot of them if you tried to port a head with them alone. You use them for final polishing and blending, and perhaps to even out the surface.

[ Thanks to Chris Witt, Tom Lentz, Robert Whitaker, Mark Prince, Chris Urban, Cliff Feiler, Danny, Bob Barry, Tony, others for this information ]

Manifold 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.

Blocking Manifold Heat Crossover Passages

I advise against using stainless steel shims to block the manifold heat crossover passages. I used to use my just-removed intake "bathtub" as a source for clean stainless, since anything much thicker would affect the manifold sealing. This works well for an engine that is torn down frequently (once per year). Beyond that, the steel starts to deteriorate (gets warped and thins out). I had one of these plates break up and a dime size hole appeared when a piece broke off. Thankfully, the fragment that came loose slid downward and was trapped harmlessly between the shim and the manifold; could have been quite damaging if it had been ingested.

I saved up my pennies and put about a pound of Mondello's zinc aluminum alloy in each head. Best money I ever spent. I did this myself, with a handy lab furnace at work. You can use a small cast iron skillet to hold the alloy, and one hell of a good potholder to hold the skillet. Helpful hint: install two old (unwanted) exhaust valves in the center ports with springs to hold them tightly shut. I used an 18 inch piece of 2x4 and bolted over the exhaust crossover outlets (where the intake manifold usually is), countersinking the bolt heads to ensure the head would stand on edge in a stable (read SAFE) manner. Next, you should pour the molten metal (in the port outlet where the exhaust manifilod normally goes) at a good pace so that it hardens as one piece and not in layers. A few gentle raps with a rubber mallet, as you pour, by a second person will help displace any air bubbles.

On another set of heads, I did not use the exhaust valves, so I was only able to fill up the ports until the alloy ran out of the exhaust valve pockets. No harm was done to the valve seats. Because the alloy had a pretty high surface tension, I did not get optimal filling of the entire passage. The top of the alloy cooled in a dome shape which was not tightly in contact with the walls of the port.

While the passage was certainly completely blocked, there was not alot of alloy that projected into the port area for optimal porting of the long side of the runner. Of course, a completely blocked passage is bettter than no block at all, and I was able to shape the pockets pretty well with my trusty CP die grinder and assortment of carbide burrs. I recommend filling the passages right up over the valve stems. This will ensure that enought molten material will contact the walls of the passage for smooth porting. This should provide more than enough meat for port work. I would rather have too much since it ports out quickly with the die grinder.

The alloy seems like very durable stuff, but ports with the same ease as cast iron. To date, I have had no problems with durability. On a cool evening, in conjuction with the OAI hood, the car feels massive. After a good highway cruise, you can put your hand on the intake with no discomfort from heat! The car will take longer to warm up and may stumble a bit when you stop at the off ramp after a cruise on the highway. If you want smooth idle all the time, better buy a road turtle with EFI. For the boulevard cruiser, blocking off the passages won't provide as great of a benefit, since normal heat soak will eventually warm the manifold to the same temp as the rest of the engine. It's the passage of air and evaporation of the fuel (i.e. high speed cruising) that cools off the intake. I used to cruise the highways for a while, then get on the boulevard within a few miuntes. Rarely lost!

[ Thanks to Scott Mullen for this information ]

Oversize Valves

Joe Mondello does not advise the use oversize exhaust valves when hardened exhaust valve seats are being installed in a head. The use of 1.71" exhaust valves w/hardened seat inserts and a 2.07" intake can result in intrusion of the hardened seat insert into the intake seat area. I asked him about this because I had already done exactly what was not recommended. After about 20,000 miles, I have had no problems, but a very small portion of my intake seat is very close to the insert. I think the risk is worth it, since I wanted it all (big valves and the durability of hardened seats).

[ Thanks to Scott Mullen for this information ]

Rocker Arm Ratio

All Olds heads use rockers with a 1.6:1 ratio. By a mathematical coincidence, this is also the ratio between movement at the rocker pedestal and the movement of the pushrod. That is, if there is 0.030" clearance under the rocker pedestal with zero valvetrain lash and zero lifter plunger depression, then there will be 0.048" [0.030*1.6] of lifter plunger preload when that rocker is tightened down.

Since the heads are very similar, and the 350 has a large 4.057" bore, you can put the 2.000" valves, and probably even the 2.072" intakes into a SB head, but it'd probably lose some low-end throttle response to gain some high end WOT power.

[ Thanks to Chris Witt, Tom Millard for this information ]

Stainless Steel Valves

From what I have read the cause of seat recesson is that when the exaust valve closes a few molecules of the seat weld themselvs to the valve. When the valve opens these are ripped off the seat and go out with the exaust. Leaded gas helped to prevent this by forming a cushon and lubricating the seat and valve mating area with molecules of lead. S/S valves may help some but I don't think they would prevent it.

Stainless steels have thermal conductivities along the lines of 15 W/m k, versus carbon steels that are aound 60 W/m k. This means that the stainless valve will not conduct nearly as much heat to the valve seat when they are in intimate contact as the carbon steel valve. I know that the exhaust gases will still be rushing by the seat at the same temperatures, but they will not be slamming against the seat, in a way providing a weak sister of a force weld. The continual contact at much elevated temperatures will result in earlier wear. How much, I don't know. Always ask a guy with experience for that kind of info.

The conductivity is much lower in the S/S valve, it will take on less heat than the carbon steel. It will also not give it up as readily. the decreased thermal conductivity causes the stainless steel valve to retain more energy in the form of heat at the stem. This is because the rate of heat transfer to the valve guide is lower. Basically, the S/S valve has higher heat resistant properties and is more resistant to mechanical stresses and strains than the carbon steel valve.

Truck engines (I mean real trucks, not pickups) have used hardned seats for years. Not even leaded fuel will save the cast iron seats when the exaust temp gets high. A truck pulling a heavy load up a steep grade is very hard on seats, as is a motorhome that catches a lot of wind and is heavy too. This is because the throttle is wide open at a low rpm for a long period of time creating very high exaust gas temp. Sometimes the manifolds will turn cherry red. It doesn't take many miles under these conditons to completely destroy a seat.

I have seen very few high performance engines have seat problems even when using older heads. I think that this is because most ot these engines are run with a richer mixture which helps keep the exhaust gas temperature down and they are not run under lugging conditons. Of course they are usually driven less miles so that helps too.

If I am building heads for car that will be hot rodded I offer to put in hard seats if they want. If the vehicle is to get a lot of highway miles and doesn't have the factory induction hardened seats I recomend them. If it is to pull a trailer I insist on them.

[ Thanks to Walter, Paul Brillhart for this information ]

Valve Rotators / Spring Seats

Starting with the E/F heads in 1970 came valve rotators, which required deeper spring seats to be cut. With those heads, you can use valve rotators, or standard retainers and stiffer, longer reach springs suitable for very high lift cams [over 0.600" valve lift]. Shallow spring seats do not allow valve rotators or very high valve lift. Shallow seats can be cut deeper to suit, however. The presense of rotators doesn't necessarily indicate hard exhaust seats.

Valve sizes

Generally speaking, there were two intake valve sizes: standard run of the mill engines used 2.000" valves [which also served as the small blocks' "big valve"], and performance engines used the larger 2.072" intakes. A small, but not negligible, 3.6% difference. Generally speaking, for heads up to and including G, the large valves have a 30 degree face, and the 2.000" valves have a 45 degree face. Almost all heads used 1.625" exhaust valves with a 45 degree face. Notable exception would be the 1972 Ga heads. Aftermarket performance exhaust valves are commonly larger than stock: 1.710" diameter. Any head can be fitted with larger valves, this only requires grinding the seats to match, about $50.

Various valve lengths were used by the factory, with as little as 0.005" difference in length. Generally, the pre-'72 Toronado and 442 engines used the same valves, while more common engines had slightly different length valves of smaller head diameter. When a valve job is done, the valve tip is generally ground a bit, and the valve has moved due to cutting of the seat and face anyway, so what difference 0.005" might have once made is probably lost. The most important thing to check is that when you assemble the engine, you have the recommended 0.050" lifter plunger preload [+/- 0.020" or so].

Intake, Exhaust Port Sizes

SB and BB intake ports are definitely different:

Big Block
 Head    Floor    Roof    Width    Height
  C      0.470"   2.85"   1.37"    2.37"
  G      0.470"   2.85"   1.37"    2.37"

Small Block
 Head    Floor    Roof    Width    Height
   5     0.435"   2.45"   1.30"    2.03"
   8     0.435"   2.45"   1.30"    2.03"

Note: Floor was measured above the block/head surface for all heads.

These measurements were taken with a dial calipers, and there was some variation among ports, up to 1/16" = .060". Head overall height, width, and port position along the length of the head were very nearly the same for all heads.

The 5A heads have the 'std.' older larger regular SB size ports, not the miniscule nostrils that the 2A, 10, 6A, 7A heads have. Port size mismatch occurs with these heads and most factory and all aftermarket intake manifolds. Earlier SB's used rectangular ports, about 1.25 x 2". The 260 and later 307's, starting with the #6A heads, have teeny tiny ports, same width, but height cut down to about equal to width. So, imagine the A/F coming down the intake, all happy in its 2" tall port, when wham 1/3 of it has to STOP or cram into the rest of the space left by the port there in the head.

So, the BB ports are about 3/8" taller, with the difference being at the top of the port. Bottom is virtually the same location. Mind you, the later model engines, like 260, 307, 350's with 3A or 5A heads, etc. may have very different ports.

[ Thanks to Chris Witt for this information ]

Combustion Chambers, CC's, Interchange

From the spreadsheet, we examine what becomes of the compression ratio of a SB Olds if we swap heads from some other SB Olds engine...

A large number of assumptions have been made in the above. Do NOT take this as gospel. First off, the heads' cc numbers are not from personal measurements - subject to typos, etc. Then, since I did not know the exact CRatio for all engines, like the #10 head 260, I assumed about 8.0 or 8.2:1 was a good start. Also assumed that the gasket volume did not change [not very realistic until after they started using the thick gaskets we see today].

With these assumptions, the method was:

CRatio == volume at BDC/ Vol at TDC, by definition.
CV == 'Clearance Volume' = all volume at TDC = head volume + gasket vol.
+ deck clearance vol. + piston dish vol, etc.
PSV == Piston Swept Volume = engine CID / # cylinders.
Vol. at BDC = CV + PSV

Thus, mathematically, CV = (PSV) / (CR-1.0) which gets us the total clearance volume listed in the 5th and 6th columns [ci and cc resp.]

New CV = Old CV - Old head's chamber size + new head's chamber size. EZ!
New CRatio = (PSV/ New CV) + 1.0

Heh, the SB only engine the #8 heads will give a CR over 8.0 is the 403!

Eng  Head  Head Stock *Cyl vol*    New CRatio, w/ head of chamber size: [cc]
CID   ID   cc    CR    ci    cc     57    60    64    67    75    79    83 
330   3    60   9.0   5.16  84.5   9.29  9.00  8.64  8.39  7.79  7.53  7.29
330   4    60   9.0   5.16  84.5   9.29  9.00  8.64  8.39  7.79  7.53  7.29
350   5    64   9.0   5.47  89.6   9.68  9.37  9.00  8.74  8.13  7.85  7.60
350   6    64   9.0   5.47  89.6   9.68  9.37  9.00  8.74  8.13  7.85  7.60
350   7    64   8.2   6.08  99.6   8.74  8.50  8.20  7.99  7.48  7.26  7.05
350   7a   64   8.2   6.08  99.6   8.74  8.50  8.20  7.99  7.48  7.26  7.05
350   8    79   8.0   6.25  102.4  9.91  9.59  9.20  8.93  8.28  8.00  7.74
260   10   57   8.0   4.64  76.1   8.00  7.73  7.41  7.19  6.66  6.43  6.22
260   2A   ??   8.0   4.64  76.1   --can't do it w/o head cc info--
350   3A   75   8.0   6.25  102.4  9.49  9.20  8.84  8.59  8.00  7.74  7.49
403   4A   83   8.2   7.00  114.7  10.3  10.0  9.63  9.37  8.74  8.46  8.20
307   5A   67   8.2   5.33  87.3   9.13  8.83  8.46  8.20  7.60  7.33  7.09
307   7A   64   8.2   5.33  87.3   8.83  8.55  8.20  7.96  7.39  7.14  6.91
             Interchange Head ID:   10    3-4   4-7   5A    3A    8     4A

Hoo-boy, look at that 260 with 403 heads... 6.22 compression ratio!

[ Thanks to Chris Witt for this information ]

Heads 1995 - Present


All aluminum, with 4.0 appearing near the top edge of the head.

ID/                          Casting
Code  Year(s)    CID   CCs   Number   Notes
                             1647501  LH;
                             1647504  RH;

Detailed Listing

Intake, Exhaust Port Sizes

Combustion Chambers, CC's, Interchange

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