[Mark Weymouth]

Your welcome and I understand how hard it can be to wrap your mind around the numbers these cars are producing. With the exception of a person or two who come up to me each year and say I used to go faster in mine back in the day and I never even touched anything...

70 RA III you are correct that the biggest gain likely comes from the exhaust if your motor is already well tuned. The next half is split between the motor and chassis/track prep.

To give a good example an early HO that was dyno'd was Dan's original T-37 motor. It had a +.030 over bore and no other machining or changes from factory spec. It used all factory GM parts. It was well built and tuned. Ultimately it pulled 370 on the dyno with about 500 lb-ft of tq. We have now pushed these same motors with the knowledge we have gained to just over 400 hp and just over 530 tq. Ten hp equates to about one tenth on the track in our racing. BTW with our conservative dynoing method 370 is a good number let alone 400.

Take your RA III for instance. The exact same rebuild was done to it and it made 370 hp also and 455 tq. We now have these motors making so far north of that it is incredible. This latest motor we are doing will hopeful push the 440 hp barrier. We have already pushed to the 430 hp mark with one that had just 10.8:1 compression and A body manifolds. We have also pushed over the 500 lb-ft mark when using the 068 cam. The 744 cam gives tq up to get hp and rev but can only be used on '69 4spd cars. The 068 cam has taken us over 420 hp in well prep trim. RA III's respond even better than HO's do.

RA II/IV's are big improvers also. The same +.030 over bore with all else remaning as the factory built with GM parts took us to 390 hp and 440 tq. My Judge which leaves a point of compression on the table pulled 446 and 488. The T/A motor was even higher with lot's of compression to give still and a smaller bore than the Judge hitting 455 hp. We saw some items on the Judges motor we thought would improve it and they did but we had never intended the T/A motor for racing and did not max items. When the numbers came back we smiled and ran it down the track. It has the matching numbers block so it likely will not come out to play often but it has been out twice at test and tunes and proved to be a strong runner.

Ultimately I think 465 hp could be done in a maxed to the nth degree 1970 RA IV as they seem to carry about 10-15 hp advantage on the '69's. Their heads flow a bit better from what we have tested and they are allowed more compression.

In the case of the RA III and RA IV I would suggest that the motor can be made to equal a great exhaust setup for improvement but would also be harmed more by a poor exhaust. On a HO and SD the exhaust has a bit more value then the engine.

We have played with exhuast combo's on the dyno and it is imperfect at best but take a Gardner Show exhaust vs. a highly thought out X system and depending on motor you could see in the neighbor hood of 50+ hp improvement depending on which motor combo you have. On a RA IV even more.

We did a full test on an L79 Corvette and tested factory 2.5" manifolds, 2.0" later L-79 manifolds, NOS large and small side pipes, and NOS under car exhaust and 2.5" under car exhaust. We built couplers so we could test all the big and small combo's together. The best combo was the small manifolds and big under car exhaust. Next best small manifolds and small under car. This is why I say it is imperfect the big/big side exhaust was third and one might have thought it to be a player or any combo of big/big. Every car truly has its own desires and it takes time and testing to find it.

I am glad people have enjoyed this conversation. If any of you find yourself at the races (this year Martin in June, Stanton in Sept, or Virginia in October) or Woodward Cruise look me up I would love to say hello and put a face to the names and thanks for the venue to exhange thoughts and ideas. Everyone here seems so much nicer and kinder than some other boards. It is a joy to see people treating each other with high regard.

Mark

[OVERULD]

The 455 H.O.........Yeah, I got one! And I'm lovin' it!!!


Thanks Mark for validating yet again, why I had to have a GTO with this motor and a 4-speed. I noted in the HPP article that the M20/M21 seem to be the preferred 4-speed models. I have the M22 and I'm running the original GM 12-bolt with 3.31:1 gears because my car is an AC car. How do you think this combo would perform...Can you elaborate on that just a little?

(I've got original numbers matching block, stock crank, pistons, rods, stock 197 heads, intake, 7041273 carb, stock 068 cam, R.A.R.E. 2.25" exhaust manifolds, no H or X pipe, stock distributor with Pertronix coil and points replacement.)

Thanks,
BJ

[Lloyd-TX]

Quick question, Mark . . .

Are the R.A.R.E. 2.45" outlet Ram Air / HO / SD exhaust manifolds considered to be legal on the PS engines?

TIA.

[74 SD455 Formula]

Mark,
First of all I would like to say thanks for all of the input.Could you please tell me ( us ) what brand Cam Shaft you use (or recommend ) and what you have done special ( grind ) to them and how there installed ? I am having a HO 455 rebuilt for my 72 GTO and greatly enjoy reading your little articles on these subjects.I was so prepared to put in a Hydrulic roller cam,but after reading alot of the info you are offering I feal like I am wasting my time with over kill.Thanks for any future info you have to offer.

[bird72]

I've read all the pages in this thread last night and today. If I may humbly join this club as a bastard stepchild member... I am looking at a pile of parts, that in the next year will be put in action. Hard to believe I actually got some HO heads after being into Ponchos so many years.... and resigning myself to D port heaven..... so my 72 Formula 400 will continue the non matching number deal, but in a bit better style. I'll use the bottom end I have running now, a 4 bolt 455 (not HO).... but swap the 96 heads for the HO's.

End result:
YC 455 w 4 bolt caps I added
forged rods (undecided type, moderate cost) (have stock rods now)
HO top end
stock valve train
good springs
all balanced of course

(I also have option of leaving bottom end alone, it only has 2000 miles on it although 12 years old!)

above coupled to: 12 bolt 3.55 posi and Turbo 400

My goal is a 5200 rpm and under street motor. Low compression.

I am running a Performer RPM cam now (RA IV similar) and want to de-cam a notch for streetability and manners, and bring it down to a 1000-5200 RPM powerband with maximum torque and HP in that range, which from everything I've read here is HO's forte.

Cam suggestions?

[Jim Robertson]

Mark and company,
Thank you, Thank you, Thank you for the very informative post here...plus the magazine articles. Great info that did not come easy nor cheap.

From one enginehead to another...you are the man!
Jim

[Mark Weymouth]

HO's you gotta love them. Twenty five years ago when I was 16 I picked up my first HO motor and intended to drop it in my first car. In the end I still have my first car and left the numbers motor in. Good thing as my HO T/A now carries that motor while the numbers motor is slumbering its life away. Even as a dumb young kid I figured out that HO's are not just another round port motor but something truly special.

BJ: The M22 carries the same gear ratio's as the M21 and genarically us Pontiac PS guys tend to call them all M21's. Not sure why. Kind of like my cousin who is an original owner of a RA II convert Goat and he always called it a RA IV when I was a kid. Habbit I suppose. I have the stock M22 in my HO. It works great. We have a 3.73 gear and Scott was hitting consistent mid 1.90 sixty foot times this fall with it. That puts him in rare company as only about 20 of the 152 cars at the PS race got below 2.0 short times. He was one of only two non Corvette 4spd cars to do so. Bruno and his RA IV Goat was the other as I recall. I made one pass in the car all weekend and hit a 1.94 short time. The M22 with a 3.73 is an easy car to drive, well relatively easy as the one two shift sometimes can catch you out or point you East West on a North South track which is always less then fun.

Lloyd: You touch on a sticky spot at the PS races. If you cert your car they absolutely are a no no. If you are running at the head of the pack for your type of car and showed up with them we would likely ask you to change them for the following year. We know they have shown up and we have seen them. So far though those cars have not set the world on fire and they have been mostly left alone but a subject of on going conversation how to handle them. Some mid-year Corvette's have the same thing going on. The 1965 and older small blocks have 2.5" outlets for their manifolds and 1966 into the C3's have 2" out lets. Some later guys try sneaking on the older manifolds. Our testing of an L79 with all combo's kind of proved that they were not really an advantage at all or even somewhat. As a tech and racer I would prefer to not see them around for our venue. It makes it easy on us to not have to confront the situation if some one is really laying down the times. Our racing is for fun and not really about who brought the fastest car overall. There was a pecking order to these cars back in the day and it should still be there today. For us HO fans we just so happen to have a rare quantity in that our low compression motor will out run most high compression motors from the brand x guys. Sure is fun to beat a big rep high compression motor with a low compression motor that has a broom stick for a cam.

74 SD Formula: We have used several different cams. Wolverine and Melling have both been consistent performers for us. We had a short stint with Lunati cams that came up very poorly for us. We lost two AMC motors and a HO due to cam wipe out. We break all motors in on a stand carefully. No inner valve springs, Brad Penn break in oil or equiv., GM EOS (now discont.) or equiv. cam break in additive. When we are done we change the oil but stay with those items again even on the dyno. We want safety first at the expense of higher numbers. We have traded that combo out at the end of a dyno session once for Brad Penn racing synthetic oil. We got almost 6 hp as I recall. Anyhow the Lunati had great specs for a RA III/HO street motor. Being at the NHRA max lift rule of .424 on both sides but having a touch of extra .050 duration of 220/228. This cam is not legal in our racing but the numbers looked great for street motors. It did make good numbers on the dyno also. But in the end nothing really better then what we now have. I actually grind our own cams often now for Dan, Scott and I. But as myself and them are not really into cam sales we do not readily have them around or sell them. Usually if Dan is doing a motor or possibly Scott they give me a heads up and I have one made. I also help with a few motors a year for freinds beyond my own or brothers. As this is a hobby for me and I am already way to involved in my hobby I have kept them closely held so as to not let it consume me anymore then it has.

With that said when I am doing a non PS or part time racer we look at the engine program as a whole. I have changed center lines to match the project. This can also be done with Comp or Crane. They will sell you their 068 cam for example with your specified centerlines. I did that early on before creating our own cams. The Lunati experience tainted my trust in many companies and at that time we ran into several PS AMC projects and a Boss 302 project that no one made repo cams for. That got the ball going to replicate the originals by using NOS cams as our guide. This long winded dissortation I suppose is to say I might sell a cam here or there on a special basis or I would certianly help you find the correct center lines (lobe seperation) for your project and you could order a Comp or Crane that way. We have tested all manner of center lines and have a pretty solid idea what works best for each motor, compression ratio, trans type and rear gear. It does matter.

Bird 72: A properly set up 068 will give you 5200 rpm. We shift my HO at 5200 and it hangs in pretty tough until 5500. After that it signs off quickly.

Strictly speaking there is not much wiggle room on the cams in PS rules. Lobe seperations being altered is getting more and more attention now. Not good attention. I think that Dan and Bob are likely going to shut that down soon. But for all of you who likely will not or can not come and play with us it makes great sense. You have maxed out your stocker with out altering its nature. Except Lloyd who I know wants to come play with us as soon as possible. A general rule on most any 389/400/421/428/455 a 110 intake 114 exhaust and 112 lobe center line works well. The 350 HO's both '68 small valve and '69 big valve have their own set of rules. The 110/112 combo has great bottom response and will give several hunderd extra revs while not falling off as quickly after it peaks hp. It is a very tolerent setup for ping/gas issues also.

You guys sure have sucked a lot of info out of me!!!

Thanks, Mark

[OVERULD]

Thanks a million Mark! I really want to try to make it to one of your events. Maybe Virginia.

BJ

[Lloyd-TX]

2.25" outlet manifolds it is, then.

Thanks for answering that question, and all the other questions, Mark.

[2manyT/A'S]

GREAT INFO,Mark!

Keep it coming!

This question is not really engine related,but as far as PS tech goes,are urethane body mounts,engine mounts & suspension bushings considered legal?

Can you post some pics of your 71 T/A?

Show us the rest of your HO.

The engine shot in the magazine was COOL. (it's looks so...,er....,well..., stock?

[Mark Weymouth]

I will have to try and remember to post some pictures when I am home. The front sway bar pix in HPP PS Prep School article is of the HO does that count? The rest are mostly from my RA IV T/A, is that a fair substitute? If you envision the blue over spray as white on the bottom side they are the same... Ok I am trying to get away with being lazy.

I have poly graphite bushings in the suspension of my HO. The car only has 30K on it and I left the stock body mounts alone. The car was always stored and they were in perfect shape. You could change them though to poly ones if you choose. Same with the engine mounts. I used fresh motor mounts when the race motor went in.

Mark

[mmarx]

Mark, as always, great info...I really enjoyed this comment:

"Sure is fun to beat a big rep high compression motor with a low compression motor that has a broom stick for a cam"

That's priceless...

Thanks again,

Mike

[bulletpruf]

Wow, great thread! Think I'm going the PS route with my RAIV 70 GTO. Have almost all of the engine components assembled (need crank, carb, dist), so time to start doing a bit more research...

Thanks,

Scott

[1971WARBIRD]

Originally Posted by bird72

I've read all the pages in this thread last night and today. If I may humbly join this club as a bastard stepchild member... I am looking at a pile of parts, that in the next year will be put in action. Hard to believe I actually got some HO heads after being into Ponchos so many years.... and resigning myself to D port heaven..... so my 72 Formula 400 will continue the non matching number deal, but in a bit better style. I'll use the bottom end I have running now, a 4 bolt 455 (not HO).... but swap the 96 heads for the HO's.

End result:
YC 455 w 4 bolt caps I added
forged rods (undecided type, moderate cost) (have stock rods now)
HO top end
stock valve train
good springs
all balanced of course

(I also have option of leaving bottom end alone, it only has 2000 miles on it although 12 years old!)

above coupled to: 12 bolt 3.55 posi and Turbo 400

My goal is a 5200 rpm and under street motor. Low compression.

I am running a Performer RPM cam now (RA IV similar) and want to de-cam a notch for streetability and manners, and bring it down to a 1000-5200 RPM powerband with maximum torque and HP in that range, which from everything I've read here is HO's forte.

Cam suggestions?

got to thinking,go into (your best pontiac stories)go back to the top of page 3 and see a story(lost in the smoke)one of the reasons i'll always love HO's.if i could keep my foot out of it that car would get 16 mpg on the interstate,or go sideways if i couldn't.

[1971WARBIRD]

Mark.thank you thank you thank you.you are one of the many here that give priceless informantion for free.

[300 H&H]

New member, first post. Own a 72 T/A 455 H.O. 4 speed.....finally found the "Holy grail" here I think! Nothing against super Duties, but the H.O.'s were "First" and at least here they get some due respect. I look forward to this thread. Best reguards Kirk

[threefidee]

Mark, I have several pics of your car and have been trying for a few days to get them on here but am having trouble. I read another post somewhere on this board saying they were also having trouble as I have sized the pics to the size it says to, even a little smaller and still no luck

Jody

[2manyT/A'S]

Welcome to PY Forums,Kirk.
Glad you picked the thread for the fastest STOCK Pontiacs for your FIRST post.

GREAT bunch of guys here & TONS of REALLY GOOD info.

Tell us about your 72 & post some pics for us.

[300 H&H]

Here is a picture of my 72




I've had it since 1977. It is modified some what. Back in the day who would have ever thought they would be worth as much as they seem to be now days. 1Le 12" front disks and spindles, and 79 rear disks in back. It currently has a Doug Nash 5 speed and 3.08's out back. Moroso frame connectors, Vett brake products composite rear springs, Flow Master exhaust, Koni adjustable shocks. Poly graphite bushings ect..
The motor has TRW forged pistons, blue printed and polished stock rods with ARP bolts, zero internal balaced. The heads have had the cross over ports plugged and the cast cross over is deleted (stored) The intake is port matched to the heads. The oil filter housing was removed and there are now 2 remote filters with no by pass, along with a road race type oil pan it holds 9.5 quarts. Removed the fan shroud and now have 2 electric fans to keep it cool. The cam is a comp cams grind of a single pattern and vintage 1980...Lumpier than stock by quite a bit, got the number here somewhere....
I've not really done anything that cann't be undone some other time. But I like it alot the way it is, so probably will stay this way! I know collectors hate this sort of thing but I'm not a seller .... my kids are wanting to know which one will inherit it! Best reguards Kirk

[300 H&H]

Here is another shot of the under hood oil filters, (mounted to the steeing idler arm bolts) and the electric fans(work much better in hot weather)

Best reguards Kirk