[66geeto]

I knew more people would check out the thread if I named it that, but my question is, the pontiac motor is one of the best designs for the time period and can still kick the hell out of alot of current engine designs. I hear claims that the bottom end is the weakest point in the pontiacs, which is logical considering the weight of the rotating assembly compared to newer engines. What is the biggest thing holding our engines back from hitting high rpms without contacting evey muscle i have in nervous anticipation for the big bang. so.....
A) drag guys, what is the first mod to a bottom end/ rotating assembly to prepare for high rmps.
and B) what is the first thing to break due to winding the engine to high.

[PONTIAC DUDE]

Only issues i ever had were cracking up the webbing.

Made and currently making over 950hp or more depending on which calculator ya use, low 9's with a possible 8.90 thrown in, with a factory block 400, cast 455 crank, and 8.5-1 compression 270 cfm iron heads in a 3450lb street car.
Shift at 6800, thru the traps at 7400.

Rotating mass, billet caps, filling, paying attention to detail, etc are the keys.

[flamedabone]

The thickness of the main webbing could have used some more thought...

Here is a shot of my daily driver high 12 second car. This kind of damage is not typical, but not exactly rare either...

-Abone.

[455-4+1]

So thats what a later "thin" block looks like !!

Sorry to see that

Do you have a new block and if so how does it compare in the main area ?

[Steve Barcak]

To answer your question from another perspective-
You asked- What is the biggest thing holding our engines back from hitting high rpms without contacting evey muscle i have in nervous anticipation for the big bang. so.....

what do you call 'high rpms'? Most Pontiacs are limited by head flow. This is changing somewhat with all the new heads out in recent years but, if you are running iron heads that is the biggest thing holding you back. Pontiacs like mid range and often make more power and go quicker when shifted earlier as opposed to later at higher rpm.
Guys learned years ago that most Pontiacs went quicker with 3.90 or 4.10 gears than with 4.88 or 5.13s. They also learned even if your motor was made to spin over 7,000 it didn;t always go quicker that way. This was in part due to the heads.
There are few reasons these days to even build a high rpm Pontiac unless you are building for a certain class or just want to. You may be surprised at how modest most of the fast Pontiacs are spinning at the track. Ask around.

To answer your question better, elaborate as to what you call 'high rpms'.
If you are talking aftemarket heads or power adders there are different answers.
Some complain about main webbing and I have suggested early blocks for years but look the other way. Early blocks have the thickest main webs and the full length rib that reinforces the block further. Pontiac engineering purposley removed this rib and material out of production blocks starting in 1961 to reduce weight. The blocks had been over engineered. don;t take my word for it, take a look at one and see for yourself.

Steve Barcak www.pontiacheaven.org

[66geeto]

well i'm just jealous of the newer technology of the LS1 and engines like that where my buddies shift at 6700-7000. It just seems like more fun. I do realize that poncho motors put out twice the torque that other motors do at low rpms. I guess I was just curious as to the weak link in the bottom end.
Steve, you say the heads are the biggest hold back, is that with flow or valve float or what. I am running Iorn heads but will probably eventually go to edelbrock aluminum heads (mine are ported). I would assume that at that high of rpms a close chambered head like a 093 would do a pretty sh$$ty job of keeping things organized. I have newer heads that are open chambered. My engine is already together and I really don't plan on changing much besides maybe heads, i was just looking for a way to explain to my friends why my poncho will always beat all, no matter how high you wind up a late model engine, and also how a pontiac block could be modified to handle 6700-7000 rpm without problems. All your info has been super helpful in solving my curiosity.

[SWEETJUDGE]

I did not read all this & will probably hear it all. WIEGHT IS A KEY FACTOR in a rotaing assembly. BALANCING & BLUE PRINTING A MUST Im sure racers know which blocks have a higher NICKLE CONTENT for strength & Durability. Saw your pix & webbing looks thin, DID it ever DETONATE? Im sure racers also sonic check the blocks weakest looking parts & areas. The weakest links ive found with pontiacs are NON FLOWING HEADS, 4 head bolts per cylinder, lifterbore cracks at 800 plus HP, CAST RODS are garbage. CROSS DRILLING cranks a MUST on a racer. Keep in mind the pontiac doesnt have the best bore stroke ratios either. we have small bores & big strokes. There is also a lot of valve shrouding with the cylinder walls aswell. YOU NEED 300 CFM just stay in the game with head flow. I have a set of E heads for sale NEW still in boxes, when your ready.
my 462 a 455 .030 over has cast crank, eagle H beams, TRW forged pistons, Stock 71 455 HO round port heads. I spinn her at 6900 rpm. AND drive locally around town.
REMEBER an engine is an AIR PUMP thats all it is. AIR must get in & burnt air MUST get out. Some other manufacturers just do it better. LOOK at any current race car today. FORD, Chevy, MOPAR they arent corporate motors anymore. THEY ARE all based off the big block chevy, except the HEMI. but they are not chevy motors. Merlin blocks or donovan meant to handle the abuse of racing & 2000 plus horsepower. Try that with your typical pontiac & there will be a lot of parts on the ground.

[Tom Vaught]

Prep and Engine specs have a lot to do with the answer.

Marty P raced a Traditional Pontiac block for THREE YEARS at HIGH BOOST and never hurt anything. Don't say impossible to do. By the way the engine was about 1600+ hp.

Tom V.

[slowbird]

If you want rpm like a LS1 build a 400. Ours turns 6500 all the time and we drive it everywhere on the street. No main issues at all so far with 15,000 miles on it.

[rzrektd]

What year block is that flamedabone?

[Will]

When assessing the weaknesses of the Pontiac bottom end as they were delivered from the factory, the most glaring problem is with the connecting rods. Specifically the bolts that hold them together, not the rods themselves. The next biggest problem rears it's head in the large journal engines - the stock oil pump is not adequate to oil those 3.25" mains at 6K+ RPMs. Too many people bought Pontiacs back in the day, pushed the RPMs to 6K or more and when they tossed a rod or spun a main bearing they just used that as a justification for claiming Pontiacs are weak. After all, the 327 Chubby their brother had would rev to 6500 RPM no problem.

Best way to build a high RPM Pontiac engine is to use a small journal block (3" mains are easier to keep oiled), make some very basic mods to the oiling system and pump to ensure adequate oil delivery, and use the lightest weight reciprocating components you can afford. Forged rods are so affordable these days that it just doesn't make sense not to use them.

[Steve Barcak]

66 GEETO-

If I wasn't clear about heads let me add. I don't consider 6,700-7,000 'high rpms'. Of course it is much higher than a stock engine but that is more of a upper mid rpm engine in the racing world. There is nothing to be jealous about. The Pontiac is more than capable of handling the late model stuff. You just have to build accordingly. I am sure you are aware of the numerous accomplishments in Pontiac performance that many have achieved right on this board. That should be inspiration to you. It can be done.
If your application is natually aspirated the head flow of most iron Pontiac heads is limited and you will not gain hp or ET by building a shortblock to handle high rpm as a result so it is senseless to do so under those circumstances. If you are building something blown the story changes, if you are building with much better heads, the situation changes. Of course, you will need much more gear, etc, etc with your high rpm engine too and reliablility and maintenence is much more. High rpm engines will not have the grunt torque of a stroker engine. In the 60s and 70s many thought about rod to stroke ratios and high rpms for power, since about the 80s to today, more rodders, regardless of brands have gone with longer strokes, more torque and less rpm for street, street/strip and most bracket applications and that is where the Pontiac can really shine. Rod ratios and short strokes are more important in performance based class racing. Everywhere you look, stroker chevs, fords, mopars, etc, etc are 'in' because they make great power and at less rpm and they do it more reliably too. I am talking the aftermarket, hot rod world, not new cars. Aftermarket hot rodding will always have more power when built right than anything made by the new car companies. That is because they have to build cars with warrantees and to pass emissions, government standards, etc, etc. You and other hot rodders do not have all of these restrictions to you can make much more power. Never be intimidated by anything on the showrooms. Not now, not 40 years ago and not 20 years from now. You, the hot rodder can always out build them because you are building for you.. They are building for the masses.
With that said-
If you still really want to build a high rpm Pontiac there are many ways to do it and many have done it. However, most people are cost consious and this is not a cost consious way to make decent hp or ET. Is that more understandable?
I have little problems with the design of the Pontiac V8. Others do. I do not have a problem with the 4 bolts per head design. There are engines making well over 3,000hp with 10 head bolts and they have no problems with head gaskets. The engine Tom mentioned also had 10 head bolts. You need to deal with what you have and make it work. It can be done.
As Slowbird said, you can build a 400 to 6,500 if you like. You can actually build it to spin much , much higher. My 3.75 stroke Pontiac is desinged to spin over 10,000. I haven't had it there yet. I has gone 8,300 plus a few times with no problems. Others, like Pontiac Jack has gone over 9,000 reliably. again however, even though it can be done it is not the cost effective way to make hp or Et unless you are in a class with restrictiona as I am or you just want to do it.
There are other options to rev real high and keep your shortblock costs down. The 370, built in '58 had smaller main size, a 3.5625" stroke, 4.06" bore and a forged crank. They can be had for very reasonable cost too. Any head will bolt to it, many of them can be safely bored .125" too. some have gone more than that.
Let me say more-
judges post says... "Keep in mind the pontiac doesnt have the best bore stroke ratios either. we have small bores & big strokes....."
Well, respectfully, that is not entirely true. Just what kind of bore to stroke ratio do you want? Pontiacs have a fairly high deck at over 10.200". Strokes available as short as 3.25" in production engines and even shorter if you count 303s, etc.
If you are building high rpm and rod/stroke ratio is a concern you have to look beyond the bread and butter 400, 428 and 455. I again must state, there are few real practical reasons for building a high rpm Pontiac other than certain class requirements or just the will to want to do it. It is much cheaper and more practical to build a med rpm engine for et and hp.
.....and, we are just talking about short blocks here. The higher you want to rev the more pricey the valvetrain gets as well as maintenence too. This is why the brakcet racer types avoid these type of engines, they require work and most bracket racers just want to be consistent and go rounds. If you are building for a performance based class, the costs and demands go straight up, higher than most can imagine.
Something to think about.
Steve Barcak www.pontiacheaven.org

[Bad Karma]

Originally Posted by Will

When assessing the weaknesses of the Pontiac bottom end as they were delivered from the factory, the most glaring problem is with the connecting rods. Specifically the bolts that hold them together, not the rods themselves. The next biggest problem rears it's head in the large journal engines - the stock oil pump is not adequate to oil those 3.25" mains at 6K+ RPMs. Too many people bought Pontiacs back in the day, pushed the RPMs to 6K or more and when they tossed a rod or spun a main bearing they just used that as a justification for claiming Pontiacs are weak. After all, the 327 Chubby their brother had would rev to 6500 RPM no problem.

Best way to build a high RPM Pontiac engine is to use a small journal block (3" mains are easier to keep oiled), make some very basic mods to the oiling system and pump to ensure adequate oil delivery, and use the lightest weight reciprocating components you can afford. Forged rods are so affordable these days that it just doesn't make sense not to use them.

I agree 100% will.