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  #31 (permalink)  
Old 11-06-2012, 09:55 AM
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Quote:
Originally Posted by Mr. P-Body View Post
After reading through these remarks, I gotta say a couple things.

First, the bore/stroke ratio is of very little importance in building a performance engine today. We used to think it was paramount... it's not. Rod/stroke ratio is far more important for longervity, and as long as the bore is big enough for the intake valve to "work", it WILL make power. The Quad-4 is a good example. The 2.3 version is a larger bore/shorter stroke. The 2.4 is the opposite. The 2.4 will run away and HIDE from the 2.3 (to a much greater "degree" than the slight increase in displacement).

Pontiac installed "48" cylinder heads on MANY '69 350HO engines. Those are 2.11/177 valves. They also used "17" and "47", both "small valve". IMO, these "work" a little better. The shrouding issue is not without some truth.

Making HP and making torque sometimes go "hand in hand". Not always. A 350 Chevy has no trouble at all making 500 HP. A 350 Pontiac (standard bore, it's really 354 CID) will have trouble getting there because the heads don't "work" as well. Can it be "done"? Of course. By the same token, a 350 Chevy has trouble making 450 lb. ft. This is due to the large bore and relatively short stroke. The heads aren't quite as "good" in the low-flow ranges either. The longer stroke and "long" rod in the Pontiac allow it to easily make that kind of torque, and more, usually at lower revs. Camming has a great impact on this, as well.

FWIW

Jim

All true for sure but if you use an ls motor compared to a 23 degree motor in stead of a quad four you get very different results from the engines. Larger bores allow larger valves and make more power.

small block chevy can make 500 tq but they will be making 600 hp when they do it. Pontiac 350 is not going to make 500 of either without some type of power adder.

Are you talking about torque or low end HP. Torque is not associated with rpm it can happen where ever the cam puts it. The amount is based on the VE at that RPM. I would think chevy could be made to make as much tq at 2500 rpm as 350 pontiac. Just got to get the cam to move the ve right to the 2500 mark. Its the high rpm the 350 will fall apart on and that is where chevy motor will be waking up.

But pontiac or chevy can be made to run hard just going to hit limits a lot faster with pontiac and need to spend big bucks to over come them.

Have you seen this:
350 H.O. Engine Build - How To Rebuild A '69 LeMans Small-Block - High Performance Pontiac Magazine

HP pontiac does a build of one and got the 330 hp. The factory rated its engines at with larger valve 48 heads.

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  #32 (permalink)  
Old 11-06-2012, 12:40 PM
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LS engines have smaller bore/stroke ratios than LTs and make more power.

HPP is a magazine, written for entertainment. The very best Pontiac builders are seldom even mentioned in that magazine. Butler Performance gets the most "ink" and for good reason. But I'll bet it wasn't a Butler engine you're talking about...

We often hear "Can't do that with a Pontiac..." I heard once, they can't rev. Well, like every other engine design, if you use good parts, "enough" cylinder head and camshaft, the Pontiac will "rev" with the best of them (of which it may very well be). We shifted Dirty Bird at 9,200 RPM, never had a bearing issue. The only limits are the same as any other. The laws of physics...

PAX

Jim
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  #33 (permalink)  
Old 11-06-2012, 05:41 PM
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Quote:
Originally Posted by Mr. P-Body View Post
LS engines have smaller bore/stroke ratios than LTs and make more power.

HPP is a magazine, written for entertainment. The very best Pontiac builders are seldom even mentioned in that magazine. Butler Performance gets the most "ink" and for good reason. But I'll bet it wasn't a Butler engine you're talking about...

We often hear "Can't do that with a Pontiac..." I heard once, they can't rev. Well, like every other engine design, if you use good parts, "enough" cylinder head and camshaft, the Pontiac will "rev" with the best of them (of which it may very well be). We shifted Dirty Bird at 9,200 RPM, never had a bearing issue. The only limits are the same as any other. The laws of physics...

PAX

Jim
Yep with 350 poncho is small bore so you cant get the big valves and when you do they dont flow well. It can be fix for sure but it will cost alot.

Bulters awesome his **** runs!!

Not talking about the bore stroke ratio. I do not get involed in that argument its all bull not supported by the math everything you get you have to give up on the return trip up the cylinder. I have never seen any big numbers from it. And the 3 hp you might get is expensive.

Link was for ref. Just cause it was same type build with some numbers to go by. If you looking for the hard charging 400hp you can get from a 400 mild build. Its not going to happen with the 350. It will still run good im sure. Just not like a larger engine is going to or a chevy with the same money put into it.

I do agree everyone says pontiacs wont spin. My machine shop guaranteed me 6500 rpm on my 455's stock rotating ***. After he balance and shot peaned the rods. It did it no problem. He did say 7100 will smoke it. It didnt. I did have to put bearings in it after a year or so. Wasnt taking any chances and one was failing but wasnt showing any signs of it until i took it apart.
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Old 11-07-2012, 06:00 AM
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Unlike 350 Chevrolet engines, most give up on the 350 Pontiac engines and go to the 455, if a good one can still be found. A 455 engine's forte is torque and does not have to be spun into the stratosphere to win races.

A late friend of mine had a '66 GTO with a 455 engine, stock H-O camshaft, headers, Q-jet, and 3.36:1 "freeway-flyer" rear gear. With some good bite, his GTO was turning in the mid-13's consistently with closed exhaust.
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Old 11-07-2012, 07:46 AM
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The trend is to go to the "stroker". The 455 block isn't as physically strong as the 400 block. 400 blocks are much more "plentiful". The best place for 455s today is the collector crowd.

You were "lucky" with the 455 and cast rods "living". That's the weakest point in the Pontiac. Change the rods and it's every bit as tough as any other engine, maybe tougher than most.

Jim
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  #36 (permalink)  
Old 11-07-2012, 09:14 AM
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The 1963-1979 cast nodular iron Pontiac rods are strong enough for 7,000 RPM in a 400 and 6,000 RPM in a 455, if prepared correctly. The 1973-1979 cast rods are better than the 1963-1972 rods because GM eliminated the cam oiling spit hole in the rod cap parting line starting in 1973. The lack of the spit-hole forces more oil and increases pressure on the rod bearing where it is needed most. Rod twist must be checked for all rods and the side clearances should be opened up .010" for the 1973-1979 rods to maintain flow across the rod bearing. The old regular production 1961-1962 389 forged "rubber" rods and the 1963 421 H.O. forged "rubber" rods were low carbon forgings for low RPM. Many many people think they are the rods to use and they are cheap. I am sure not many people don't buy that myth anymore after finding bent rods.

The problem with all stock rods is the stock rod bolts. The stock rod bolts must be replaced with ARP bolts, and the rods resized if the engine is going to be anything but a grocery-getter. The scenario is that the stock rod bolt stretches at high RPM on the piston return stroke, the rod pin bore goes out of round, the rod bearing spins out, the rod seizes on the crank for an instant, the rod snaps just below the pin-eye and takes the engine with it. Then the cast iron rod gets the blame for the weak rod bolts.

Another problem with stock rods is improper torquing and over-torquing the stock rod bolts by amateur engine builders. Being curious, I put a stock Pontiac rod in a vise and turned the rod bolt with a torque wrench. The stock rod bolt stretched and broke at 65 lb. torque.

Last edited by MouseFink; 11-07-2012 at 09:21 AM.
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  #37 (permalink)  
Old 11-07-2012, 12:00 PM
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Mousefink,

While this is a popular "arguement" among those that would try to reuse the rods, it's simply not true. A cast part (regardless of where it's used) is much more rigid than a forged part. As a result, they will hold their dimensional stability very well right up to the point of failure. It will then fail "without notice". The factory bolts were SPS, like the Chevys.

It simply makes no sense to pay $150 to resize a set of rods, add $65 for new bolts, when you can buy 5140 forgings with BETTER bolts for $250. MANY a Pontiac found its way to the scrap yard with rods hanging out of the pan.

The spurt hole was eliminated to reduce emmissions. It has no effect on oiling the crank. And contrary to popular belief, the oiling system in the Pontiac is quite good.

Jim
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  #38 (permalink)  
Old 11-07-2012, 12:59 PM
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No argument about the old Pontiac forged rods. They are worthless even if you can find one that is not bent.

However, I must take issue about the rod cap spit-hole. The oil spit-hole was mandated by the EPA in an attempt to reduce emissions by reducing oil spray on the cylinder walls and it certainly DOES help rod bearing oiling. It helps rod bearing oiling by re-directing the oil from the spit-hole and across the rod bearings. The re-directed oil flow is more effective if the side clearance of each pair of rods is opened at least .010" (.005" each rod) so the re-directed oil will have a path for escape.

Aftermarket forged steel Pontiac rods are available from $480 to $1,250 for the all-out competition engines and for competition, those rods are the best choice. It is becoming difficult to find a good stock rods. Pontiac engine have not been built since 1978. "Pontiac" engine vital parts are now being built by aftermarket suppliers, blocks, cranks, rods, and heads etc., and they are far from being "Pontiac" engines.

Pontiac powered cars have gone the way of the "Do-Do Bird" and those that remain should be in Barrett -Jackson Auctions.
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  #39 (permalink)  
Old 11-07-2012, 03:52 PM
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I agree with barret jackson coment. I am stunned someone will spend 50k on a 340 dart and not jump at the ponchos big power. My 71 SJ had crazy low center of gravity and very good front to rear balance. It was awesome handler. The guy i got it from had gm heavy duty shocks that are no longer available i think but they were stiff enough to stop the roll all togther and soft enough you dont give up the driving a couch feeling. The car would flat spin not lean and slide. It took great big tires 245 all the way around. 455 ho from the factory and 12 bolt 308 rear it was smoking fast. It had to have more punch stock than any none hemi mopar.

My rebuild engine was a virgin so rods were in good shape. Smoothed over and shot peaned they held up just fine. Even at 472 cubes they were fine. Always had 50 lbs of oil pressure. Hell it had 40 the next morning when i went to start it up and go to work. It started life as a sd or ho cant remeber anymore. Sep it was all i could find even rebuilders did not have any blocks in stock at the time.

I did have to pay a ton of cash for the motor carb to oil pan unmolested stock form was not cheap. But got it from a guy had 4 69 gto covn. He also had a 4 speed judge. No he would not sell them. I offered good money. But he gave one to each of his kids. Maybe that is why barret jackson doesnt have any. No one is selling. I have a friend right now with a gto and lemans 69 and 70 he wont sell either. Rather let em rust...
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  #40 (permalink)  
Old 11-08-2012, 11:15 AM
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I feel totally gypped. I never got to rebuild an engine in physics class!
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Old 11-08-2012, 11:37 AM
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Quote:
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I feel totally gypped. I never got to rebuild an engine in physics class!
Don't feel to bad, Neither did I, I got to balance the rods and pistons though and spend my 2 week expulsion rebuilding the 326. It was still a topic of discussion at our last reunion in 2003.

Ray
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  #42 (permalink)  
Old 11-08-2012, 11:47 AM
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My school wouldnt let me take Automotive.....still sore about that to this day....
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  #43 (permalink)  
Old 11-08-2012, 12:20 PM
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Why not? You should be able to take whatever you want...I know when I went to school (many years ago), some people in the facility considered taking a shop or trade course was for the less academically gifted...I thought it was ridiculous then and I think it's ridiculous now.
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Old 11-08-2012, 12:30 PM
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It is stupid, Long Story Short I was in "Gifted" classes....talked my parents out of it....vowed to never do that to my kids. I just talked to my machine guy and he says go for the Pontiac 350. Bring it down to him so he can check out the block and heads and he wont charge me to teach!
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Old 11-08-2012, 12:59 PM
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Yes it's amazing how some people pigeon hole other people into what they think is right. I know the "jocks" in my high school used to call them "shop dummy's" until several of the guys taking automotive became extremely successful. One owned a GM dealership and the other a large construction company...I loved it and these guys didn't throw it in popular crowds face...they just went on with their business.

Glad to hear your machinist is willing to help you out...That's going to be a major expense avoided.

Good luck and any questions, don't be afraid to ask....You can see there are a lot of opinions.

Ray
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