kjr442

Just trying to gain a little knowledge here, so I am asking for some input on heads. If this has been covered already please just provide a link for me.

Starting with Big block 455 heads, and with what I am sure will be the best factory head, is the F head. What is next inline? Then the same with small block, sticking with 350 heads. I guess the W31 head is first? But I do not know the number for the W31 head is it 8 ?

pogo69

i think the d is the best in regards of the smallest combustion chamber. c heads are probably the most common for high performance...and there were a lot of those made

Octania

"Best" depends on your goals and budget.

Performance and compression generally go hand in hand, but for street driven pump gas you may not want to MAXIMIZE compression.

In no particular order:

Real D, F or H heads are probably best suited to restoring or maintaining a real W30. The extra cost or value of the casting will be best spent there, as oppose to on an F85 or Cutlass or 442 non-W-Car.

Then we have the fairly common C casting. Some are BV- mainly Toronado or perhaps H/O
A's have the 1965-only rocker stud thing. May or may not have A.I.R. bumps in the xst port.
B's have no rotators. Mainly Toronado will be Big Valve, perhaps 442/W30
E/G/Ga are equipped with at least some rotators for longer valve life. Toro E's should be BV, but BV G and Ga's are very rare in my experience.
J's have rotators and work great for many applications. Have never heard of a Big Valve J head unless the local machinist did it.
K's should be Big Valve and have rotators. Accepted W30 replacement castings for broken or missing D/F/H.

All the BB heads with the possible exception of D's should have pretty much the same chamber size.

#5 heads should be used on the '68 Ram Rod and '69 W31, then #6 castings on the '70 W31. In these cases, larger 2.00" std-issue-BB type Intake Valves, if I am not mistaken.

kjr442

For this comparison , I am primarily looking for the " best " as in factory performance, straight off the assembly line, then on down to the worst for both the 455 and 350.

oldsmobiledave

I agree with most of what you wrote above & would like to add.....



Every Toro built in 1971 has G heads with big valves. The Toro reverted to small valve Ga heads in 1972. So to me big valve G heads are not rare but will agree that they are less common than the small valve G heads.


Ks only have big valves and easily match the flow numbers of the infamous C heads that most think are the best BBO heads.


#4 1967 SBO heads are the only SBO head with 64 cc chambers from factory. Also they are predominantly from 39 deg bank angle engines (a few have been documented to have come from 45 deg bank angle engines). All other SBO heads from 1964-1972 inclusive will have 68-69 cc chambers.

dnmfranco

True everywhere I read state C heads best flowing on bench tests.

kjr442

Very interesting so far.

67 Cutlass Freak

All of the D,F, & H heads are extremely rare and command a premium price for the hardcore numbers matching restorers. With enough grinding, any of our cast iron heads can be made to flow as good or better than any other letter head. Check out this thread I started about "Home Porting Techniques". It is very long, but packed with useful information. In it you will find a link to FAQ about our cast iron heads, reference charts from Mondello's Technical reference manual showing detailed information about SB/ BB heads, head flow information spreadsheet, and a ton of other stuff that might make your head spin-
https://classicoldsmobile.com/forums...echniques.html

Here's a thread about aftermarket cylinder head options-
https://classicoldsmobile.com/forums...cast-iron.html

oldolds88

ks= more than 1 k head

bv= big valve

kjr442

Now you can see why I need to learn more about the olds heads. Lol

kjr442

Thank you, I'm sure this will keep busy for a while.

edzolz

I am glad you see the #4 heads get the recognization they deserve. IMHO, they are better than the #5's because they have the capability of being changed to the larger valves just like the 5's and give the better compression ratio needed for performance.

joe_padavano

And yet, if that were true, why would Olds go through the expese to cast up D, F, and H heads for the W-30 motors? To REDUCE performance and increase cost?

Sorry, but all these published tests are typically flow on ONE head, or even worse, ONE set of ports on ONE head. Nowhere is there a test with a large enough sample size to be statistically meaningful given factory production tolerances (and for that matter, flow bench performance variability...).

The fact remains that with the exception of J heads, all other BBO heads with the same size valves probably flow within 5% or so of each other. None are close to aftermarket heads.

madmax442

In Bill Travatos book he states the A head as being the best flowing in stock form and that all heads except J heads are very comparable.

joe_padavano

Back to my prior comments - based on a sample size of HOW MANY? How big was the difference from other heads? Was it within the measurement tolerances of the flow bench, or the casting tolerances of the various heads?

lemoldsnut

I think Joe makes some very good points. What was really tested. a head or two or a port or two?

It is my understanding that most of the bbo heads as Joe has stated flow well. Not to aftermarket flow standards but well. It also makes sense that C heads would be the head of choice to make into what ever you want in a bbo head as they were used for the most years and therefore would be the most available.

The heads from a 67 330 having a tighter combustion chamber does make sense to be one of choice when building a small block. I have never built one for power sake only for daily use.

I think lots of people spend too much on building a motor that will produce huge power when the factory builds are very good power wise. Lets face it, most of us use our car to cruise and just drive around not go full tilt racing. So with that in mind factory specs work very well.


Just my opinion.

I always say " It is your car build it how you want"

Larry

madmax442

I'm sure Bill has done more than a head or two or a port or two to be able to make the statements he has!

joe_padavano

Again, the question is, what was the sample size for each type of Olds head? It takes a lot more than one of each to build a statistically valid set of data.

kjr442

I pulled apart a 70 engine today that has 56,000 on it. This one is a two bbl with #6 heads, such a shame, as this car was not stored properly, and the engine is stuck. The top of the heads look like new, as did most of the top end. I think I will save the heads for a future build.

Run to Rund

The AIR lump might hurt a bit. The recessed exhaust flange in the center hurts, as does having both center exhaust ports going to the heat riser. The lower intake roof to make room for the deeper spring pockets with valve rotators probably hurts a little, but it is a lot easier to find good high tension valve springs for specific applications with the longer spring installed height.


Beyond that, I agree that port flows from A through K are similar. Over the decades I have found that the right camshaft makes a lot more difference. Look at the unported NHRA stockers that run in the 10s.