[PurelyGTO68]

I was looking through one of my old books written by the guys at H-O Racing Specialties and found some flow graphs and section views that compared various Pontiac cylinder head types.

I had always thought the 'magic' with the round port heads is in the exhaust port just because that is easily identified as being different. However, now that I look at them a little more carefully....the intake ports are quite different then the D port heads. The flow graph shows the round exhaust port flows about the same as the D port head and when I compare the two....the port is only round right at the exit. The rest of the port appears about the same (at least when I compare my RAII heads to a pair of 670 heads that I have available....).

So, it appears the magic is in the intake ports instead. Does this sound correct? If so, I wonder if the stock cast intake manifold is able to flow enough to meet the demands of the RAII and RAIV heads. Any thoughts on this?

If the flow chart is correct, there appears to be a sharp drop in flow around the .460 lift mark (except for the 73 455 SD heads....those things just keep on flowing as lift increases....). Any theories as to why this occurs? Just trying to learn a bit more about the RAII and RAIV engines.

Thanks

[PurelyGTO68]

I think I figured out why I was so confused. My mistake was assuming the RAII and RAIV heads were the same or at least very similar. I got to see the differences when a buddy stopped by to pick up some RAIV heads that I was holding for him.

In reality, it appears the intake ports on the RAII are about the same as intake ports on standard D port heads from the same era (we have a set of 48 heads to use for comparison...).

The exhaust ports on the II and IV appear about the same as each other from what we could tell. However, when both round port heads are compared to the 48 D port head...it looked like the floor and roof of the exhaust port is higher...which may improve flow by helping to maintain velocity while the exhaust gasses are making the turn.

So now I think I better understand the various characteristics of the heads in question and can see why the RAII combo is said to perform so well. I still am missing some data to properly analyse but it appears the engineers achieved a very good intake to exhaust flow ratio with the RAII compared to the performance D port heads of the same era. Furthermore, the flow graphs available to me appear to show the flow characteristics are satisfactory up to about .470 lift at the valve....after that then the limitations of stock ports appear to be reached. If so, then it just goes to show how smart and knowledgeable the Pontiac engineers were when they developed the 9794041 camshaft. I might further theorize that adding 1.65 rockers to a RAII engine wouldn't show any measurable gain in performance. Of course, I am just theorizing.....actual track or dyno tests would validate or disprove my suspicions.

I am sure all this has been discussed and tested before but I am just thinking it through for myself since it helps me comprehend things better.

[Bet Winner]

And H-O Racing designed camshafts around this lift number. I believe the lift of the one I used in 1980--the old HC-02 I think was .465 and .469. (It is amazing what you can remember from your youth.)

[PurelyGTO68]

Originally Posted by Bet Winner

And H-O Racing designed camshafts around this lift number. I believe the lift of the one I used in 1980--the old HC-02 I think was .465 and .469. (It is amazing what you can remember from your youth.)

I really liked the H-O Racing cams.....they were the best that I've ever tried so I tried to use them whenever possible. I still have a few of their old catalogs so I'll look and see what the HC-02 specs were. I used HC-01 cam in my 1970 RA III engine with 3.73 gears and a 2300 stall converter and it performed quite well. I have a new old stock HC-03 cam that I am thinking of using in my upcoming RAII build. It's pretty much identical to a 041 cam but with .030" more lift. However, based on the data I am seeing....it may not benefit me that much so I might just stick with the stock cam and see how it runs. Jury still out on that one....

So, at the moment I am leaning towards the thought that the magic is in the 041 cam and the RAII heads have a perfect intake/exhaust flow ratio to make full use of the camshaft's potential.

I am not sure where the engineers were going with the RA IV design. Looks like they improved the intake port quite a bit by raising it up higher, which is fine but then they didn't do anything with the exhaust or cam to match so it kinda seems like a half finished project. Perhaps it was a matter of addressing one problem at a time and they wanted to maximize the air charge potential. If so, then that explains why they came up with the aluminum intake and removable cross over because a cooler charge is more dense.

I wonder how close Pontiac came to the thermal limits with the RA IV set up? A denser charge will quickly expose any cooling deficiencies that may exist in the system. I know it wasn't possible to order the 1968 Ram Air engines with A/C......was the RA IV available with A/C? If so, does anyone know if those cars were easily overheated?

[PurelyGTO68]

I checked my H-O catalogs....
It looks like the 068k was an exact duplicate grind as Pontiac's 9779068 cam
The HC-01 was similar but with a little more lift on the exhaust lobes to help out on that end.

The 041k appears to be an exact duplicate of Pontiac's 9794041 cam.
The HC-02 does the same thing as the HC-01....little more help on the exhaust lobes.
The HC-03 is a high lift version of the 041 with more lift on both intake and exhaust.

I would agree with the earlier suggestion....it appears the H-O cams were very much influenced by the original Pontiac grinds

[Bet Winner]

The RAIV was not available with A/C.

I believe Ken Crocie said that the cams changed at some point after I bought mine. Ken purchased H-O from "H & O" (or possibly just from H) so it may not be exactly the same as the HC-02 that I had. I ordered my cam in 79 or 80. I remember the lift numbers well so I thought the lift appears to have been set based upon the head flow.

I'm surprised you still have one of the old cams, but I believe Ken may still be selling them. good luck

[Half-Inch Stud]

P68GTO,

Can you compare your RAII sparkplugs " proudness" to the Ram Air III (and IV) to verify they are indeed kept dry of the Intake fuel charge?

Mine are recessed compared to D-ports & 48's. just didn't get to compare to IVs.

[rexs73gto]

There is another thing you forgot to mention that the RAII only used the 1:55 rockers & the RAIV used the 1:65 rockers. The overall lift of the cams in both were different to. The RAIV total lift was .520 & if I'm correct the total lift for the RAII was in the .480 realm. The RAIV was a better version of the RAII heads. Each step was just a bit better. Although there were some back in the day that didn't like the RAIV cam but loved the RAIII cam. I like the RAIV cam & have used the Crane blue print version in the last 5 $%% & $)) builds. I love the way they work for me. & I use the 1:65 rockers on all of them to.

[PurelyGTO68]

Originally Posted by Half-Inch Stud

P68GTO,

Can you compare your RAII sparkplugs " proudness" to the Ram Air III (and IV) to verify they are indeed kept dry of the Intake fuel charge?

Mine are recessed compared to D-ports & 48's. just didn't get to compare to IVs.

Mine seem like they are hiding as well.
Unfortunately the RA IV heads are in a container heading to Europe (that is where my friend lives...). The set of 48 heads are at my brother's house (they belong to him). I have a set of 670 heads but they are on a WZ block still. I went ahead and took some pics anyway....

The first couple of pics are of 670 heads.
The 3 third pic is the RA II head.
The last 2 pictures show a spark plug screwed into the RA II head. I just pulled a plug of my shelf that would normally be used in my 1970 RAIII engine but this gives you a pretty good idea of how sheltered they are.

I have no idea if I am using the correct plug....I haven't even gotten that far in my research yet....
However, you have me curious now....I am going to try and get over to my brother's house soon so I can see how the same plug looks in those things.

It's funny how strange stuff like this is fascinating to me....

[PurelyGTO68]

Originally Posted by rexs73gto

There is another thing you forgot to mention that the RAII only used the 1:55 rockers & the RAIV used the 1:65 rockers. The overall lift of the cams in both were different to. The RAIV total lift was .520 & if I'm correct the total lift for the RAII was in the .480 realm. The RAIV was a better version of the RAII heads. Each step was just a bit better. Although there were some back in the day that didn't like the RAIV cam but loved the RAIII cam. I like the RAIV cam & have used the Crane blue print version in the last 5 $%% & $)) builds. I love the way they work for me. & I use the 1:65 rockers on all of them to.

Correct. I didn't mention the 1.50 vs 1.65 rockers since I assumed that was common knowledge but it's good that you mention it in case others stumble across this thread later one. To clarify for those that might be new to the hobby.....the RAII and RAIV camshaft are identical. On the RAIV, the overall lift at the valve is greater due to the 1.65 rocker arm ratio.

No doubt the RAIV intake ports flow much better than the stock RAII and other hi po D ports of the same era. I am curious as to why the Pontiac engineers felt they needed that much more flow without also addressing the exhaust port at the same time? Maybe they realized the development of the exhaust port has reached it's zenith and that led them down the patch of developing the RAV? It sorta looks like those exhaust ports should flow quite well...

[PurelyGTO68]

In case anyone is curious...
Here are a couple more pics.
The exhaust ports appear to be rectangular and then go round right at the exit.
I wonder if this was done with the idea that headers would likely be bolted on at the track?

[rexs73gto]

Yes it does come out at a little bit of a rectangle & then go round, but if I'm thinking correct the reason for teat is velocity. The port come out like a trumpet as it opens up to the round port. I would think that would give it some pick up speed when it come out like that. I'm not an engineer but just looking at it I would think that was what the designers were trying to do. Plus if you look into the port it gives you a bunch of room to open it up for more flow. The reason I say this is if you look at the SD head it looks like the RAIV head but opened up more , & then if you look at the heads i have which are the Eldo. alum. head which were designed from both the RAIV heads & the SD heads. My Eldo. alum. heads can flow up to & more then 340 cfm with work & I would bet that the SD heads can be done to do the same. As can the RAIV heads be done almost as much as the others. You have to remember that GM even in 69-70 were still watching the designers close so they didn't go to big on the HP ratings of the engines. Maybe thats why the RAII heads were 1:55 & the RAIV were 1:65 rockers. They were just building up to a certain point for HP but didn't go all the way so they wouldn't get shut down. You never Know?????? But my Eldo. heads are a great set & just bolting them up to a 400 or 455 give you a great boost from the iron heads. Because of there design. I think so. Heres a big what if, what if the Pontiac guys had the alum heads from Eldo. back then. How fast would the 69-70 's been then. WOW !!!!