[JC455]

Okay, here's the situation:
About 10 years ago I built a 455 +.030, 1971 #96 heads, HO Racing's HC02w/Rhoads lifters, Muncie M21 4 spd, 3.55:1 geared 76 T/A. It was a pretty good STREET car.
Time marchs on...marriage,kids,F##king crap gas/prices...
I have a 68 LeMans-455+.030, 4Xheads, stock cam(?- It was rebuilt to "stock" specs when I pulled it from a 73 Grandville),yada yada yada. I've managed to keep it from pinging on 89 (but I'm not sure it isn't doing the inaudible thing). This thing "should" run on 87- the compression should be way below 8.7:1.
I think I'm gonna build an old school low compression STREET engine using the short block, but changing the cam and using big chambered heads(something that will keep the compression around 8.4 or so).
I decided to go with this level of compression after thinking about how gnarly the 455 HO/SD's were (this also ballparked my cam specs).
Now, the reason for my post- I need to know the flow #'s for the HO & SD heads. I think if I can duplicate the numbers on a D port large chamber head, I should be able to get similar performance and run on crap gas.
Am I nuts? Has anyone tried this? Does anyone have the flow specs???
I posted this on the "RACE" section because I figured it would run 8's @ 200 mph (hahahaha).
No seriously, I figured some of the more experienced people might have the flow specs.
Thanks for any help/suggestions!


------------------
John

[JC455]

Okay, here's the situation:
About 10 years ago I built a 455 +.030, 1971 #96 heads, HO Racing's HC02w/Rhoads lifters, Muncie M21 4 spd, 3.55:1 geared 76 T/A. It was a pretty good STREET car.
Time marchs on...marriage,kids,F##king crap gas/prices...
I have a 68 LeMans-455+.030, 4Xheads, stock cam(?- It was rebuilt to "stock" specs when I pulled it from a 73 Grandville),yada yada yada. I've managed to keep it from pinging on 89 (but I'm not sure it isn't doing the inaudible thing). This thing "should" run on 87- the compression should be way below 8.7:1.
I think I'm gonna build an old school low compression STREET engine using the short block, but changing the cam and using big chambered heads(something that will keep the compression around 8.4 or so).
I decided to go with this level of compression after thinking about how gnarly the 455 HO/SD's were (this also ballparked my cam specs).
Now, the reason for my post- I need to know the flow #'s for the HO & SD heads. I think if I can duplicate the numbers on a D port large chamber head, I should be able to get similar performance and run on crap gas.
Am I nuts? Has anyone tried this? Does anyone have the flow specs???
I posted this on the "RACE" section because I figured it would run 8's @ 200 mph (hahahaha).
No seriously, I figured some of the more experienced people might have the flow specs.
Thanks for any help/suggestions!


------------------
John

[T Hutchinson]

John, I dont have specs handy for flow at all lifts but off the top of my head I remember the 455 HO units are about 10-15 cfm better than D-ports or about 210 @25". The SD units are comparable to a RA IV or 220-225 CFM. If your accustmd to flow nmbrs at 28" just add 10-15 nmbrs to above figures.

[David Holmberg]

Yes you can make the D-ports flow as well as a stock round port head. In fact they can be made to flow more than the factory head. Normal Ported D-port street heads flow 250 cfm @28. Good luck, David

[This message has been edited by David Holmberg (edited 06-24-2000).]

[Rocky Rotella]

This may stir up some controversy, but it wouldn't be nothing new to this board [img]/infopop/emoticons/icon_wink.gif[/img] I was in the midst of wanting to enhance my 455's performance in my 76 T/A without sacrificing factory appearance. With cost in mind, I was planning on spending some serious cash for some desirable Pontiac round port heads. I thought 197, 7F6 or 16 would be what I want. I figured who better to ask than Nunzi or Pete McCarthy.

On two separate occasions, I asked both which heads would be best suited for hard running street 455. I assumed that the SD head would be the most logical choice, but to my surprise, both said stay away. They both said that the SD ports are too large to keep a constant velocity in the port and that to take advantage of the port size, compression, camshaft and rpm capabilities must all be increased. Once all those factors have been met for optimum performance, the exhaust port must be extensively modified to match the flow of the intake port. Keep in mind, both said the heads are great performance heads, but for a low revving 455, flow is not that good.

Pete McCarthy further stated that the SD head was not a torque producing head. He said if it wasn't for the 455 having so much torque producing ability, the SD motor would have suffered greatly. He also stated that Pontiac engineers knew this and started factory installing 3 angle valve jobs, on the exhaust seat only, to increase off the seat performance. McCarthy and Nunzi both told me that the Edelbrock head was patterned more off the SD head rather than the RA IV that they claim. McCarthy considers a stock SD head a great disappointment.

When I asked both for their choice of what I should look for, both gave me the same answer, "455HO head milled .060" What was strange is McCarthy recommended the 7F6 where as Nunzi prefers the 197. When I asked for reasoning as to their choice, I got the following answers: McCarthy said the 7F6 is made to run on low compression and has a specially designed combustion chamber in relationship to spark plug area. He said that the "bump" can be ground out of the exhaust port and they will flow perfect for the stree 455. Nunzi prefers the 197 because "you can-a get more for less", meaning that you can get more flow with less work not having to grind the bump. Nunzi says he prefers the 197 over the 7F6 because it is basically a 614 with more cc.

As I discussed more and more with these two Pontiac builders, I realized how true there findings are. High flow numbers are not always the greatest factor. There is a optimum number, but its how much it flows in the low range. I had the oportunity to discuss this with Jim Hand and he feels the same way they do. When you get into high flow numbers, there is a price to pay and that is low lift flow. As I was told by some of the best, I forward this thought on to you; Any head may flow a high number at .550" lift,. but think of how long it is at that point. It reaches .50", .100", .200", .300", .400" and .500" twice a cam revolution. Higher flow numbers at those points are where the power is made.

I hope I have explained this so that I have not confused anyone. I am just relaying what I have been told by a few of who I consider some of the best in the Pontiac world. If anyone needs any clarification, let me know. Rocky

[David Holmberg]

Rocky, I agree with you on the SD heads. But it was my thinking that he wanted to run D-ports and just get them to flow as well as a round port head. With proper porting a d-port can surpass a stock round port head and still have very good low lift flow needed for good street manners. Any Pontiac head shop will be able to do this for you. In fact "The Dude" ran a 8.4 400 motor with a hyd cam in his TA, 3600lbs in the 12.70's in full street trim. The motor spec's are posted on his web site.

[JC455]

David's right. I'm not after the highest flowing head, I want a head that flows as well as a factory HO/SD in a D port config.
I really only have experience with the HO head- one of my buddies had a 71 HO/auto w/ an L-88 convertor- man did this thing run good!
I figured if I had someone port the heads for max flow, they'd screw my low lift numbers up. Since most of the operating time is spent at low RPM's, I just want a really great performing D port that can run on camel wizz gas. I already have the headers/performer intake and an Edelbrock 750 performer carb (although I may put the Edelbrock on my 455/4spd 'bird and use the Firebird's Q-Jet on the LeMans- it's REALLY hard to beat a Q-Jet for gas mileage).
Well, with that being said, does anyone have a recommendation for a head casting?
Does anyone know if/where head flow numbers are printed (did Pete McCarthy ever post factory flow numbers in his book)?
Thanks-

------------------
John

[Maurice Hood]

John, Have you checked with SD performance? They sell all kinds of D-port heads set up most anyway you want them....Maurice

musclecarsonline.com/SDPerformance/

[Rocky Rotella]

Sorry guys, I forgot to mention about the d-ports. I ran against a time constraint and had to wrap it up quicker than I had hoped.
I did notice you were refering to the d-port heads. I do realize that a properly set-up d-port can match the flow of a round port. I chose to switch because of the rarity factor of the round port heads. I'm not sure where you are located but I'd contact Jim Hand about doing some port work. He is very knowledgable with the d-port head and is very good at extracting high low lift numbers.

When I spoke to Jim about a week ago, he did mention that he thinks the SD Perf 6X heads are a bargain. For $995 ready to bolt on, they are definately worth the price. These are ported and all new hardware. I'd suggest giving this idea serious thought.

[Triggerman]

JC, about 5 or 6 issues ago, HPP had an article on the SD motor they are covering a buildup on. With the head info, it gave flow specs for the full range of lift. I will pull out my back issues and post what is in the article.

[Ken K]

When you decide which heads you want to use let me know. I have lots of different D port heads. I just had a set redone last week. It cost $350.00 to have a set redone with new stainless valves, new bronz guides, new springs and retainers.

[Triggerman]

HPP, Feb, 2000 issue. Casting #16 with a 3 angle valve job and gasket matched.
.100 I=87 E=n/a
.200 I=149 E=112
.300 I=217 E=146
.400 I=240 E=166
.500 I=250 E=177
Says testing was performed on a Superflow 110 at 10" H2O and converted to 28" H2O.
Lexan radiused air inlet guide was used.
Hope this helps. TM

[Tim Corcoran]

I think that the 6X/455 combo is hard to beat. With a little work (bowl work, minor porting and improved valve seats) the 6X heads will out flow a stock round ports no problem. Also with little or no milling the 6x head will give you an optimum C/R for pump gas. Yes Dave of SD performance has great cylinder head packages and he does top notch work.

Tim Corcoran

[critter]

Interesting discussion. I have #16 SD heads on my car. I understand the issues here. Jim Butler brought them to my attention as well. The SD heads need porting, more cam and milling to take advantage of their maximum potential. I didn't do any of it. Why? I was building a street motor. I'm running low 13's and still fighting a fuel delivery problem (yeah, I know, get the electric pump). Would I spend the money for SD heads for a street motor? No. I'd buy ported 6X-4s. I did it because my car is 74SD and a I was trying to be as "original" as I could and still have a driver. Besides, I wanted to keept he door open for a EFI system or nitrous. Lets see, 8.4:1, EFI, turbo...

[JC455]

Everybody,
A big THANKS for all the responses. TM- your the man, dude. I forgot all about that article. Thanks for all the suggestions from everyone.


------------------
John

[Skip Fix]

One of the local Texas Pontiac racers runs a 455 SD heads with a small Ross dome to get closer to 9:1, Performer RPM, small tube Hedmans, Comp 242@ 0.050 cam and 3.55 gears in a 64 GTO and runs 11.80s in the 95 degree Texas heat. Look for the car in a future HPP.

I've flowed a bunch of different heads on my home meade flow bench some ported some stock Ds and HOs and RAIVS. You can get ported Ds to flow what stock round ports flow no problem. But just put a pocket porting on some round ports and you leave the Ds in the dust. EVEN in the low lift range. Friends stock 197s flow better than his ported 72 HOs(ported by a knowledgeable Pontiac porter). RAIVs leave them both esp if you put a flat intake valve in them. That stock 71 HO head also flowed as good as some SD Performance 6Xs we flowed the same day.

Done correctly you don't kill all the low lift flow with porting and the rounds have the same as a ported D.

When it comes to port size and velocity I disagree with Pete. Shoot the new Fast Burn small block Chevy has a 215cc intake port, Vortec almost that big for a 350 ci motor. Tell me a long stroke fast piston speed 455 is not going to make more "suck" on the port and pick up velocity! These SBC motors peak at 6000 rpm so not high rpm motors either.
These SBC are put on their crate motor.

11.80s and drive it to the track, sorry I'll vote for round ports any day. Throw some good rods in it and it can turn to 6000 without worry(my old worked cast ones did in a RAIV 455 too.)

[Tim Corcoran]

Here are the flow numbers for the #16 heads that are on my 65 LeMans, and the 6X heads on my 67 LeMans. These numbers are @28 in. H20 and were flowed by Dave Bisschop on his Super Flow 600.

#16
Intakes
.100=69.0
.200=136.6
.300=196.5
.400=246.0
.500=282.5
.550=290.6

Exhaust
.100=54.5
.200=112.0
.300=143.6
.400=170.6
.500=189.2
.600=201.2

Although these numbers might not be all that impressive I think they are a tad more flow than a stock round port.

The 6X heads have more in them with a little more work.

6X
Intakes
.100=75.4
.200=138.5
.300=182.4
.400=221.7
.500=256.2
.600=271.3

Exhaust
.100=63.7
.200=116.3
.300=148.8
.400=176.2
.500=190.6
.600=198.9

Tim Corcoran

[This message has been edited by Tim Corcoran (edited 07-04-2000).]

[Dave Kovar]

How well would the #12 Ram Air III heads work with some mild clean up and port matching on a 455??