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#61
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Went and found some of those answers via search. Goal was 425'ish HP - Pump Gas Quote:
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wound up with 475+ HP @ 6000rpm with Hyd Roller Cam Last edited by Baron Von Zeppelin; 09-26-2018 at 01:52 AM. |
#62
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4" vs 3.75" crank
So this is a quick model on Performance Trends Engine Analyzer. I used a .030" over 350 with kre small valve heads that flow 260cfm, headers, single plane intake, Holley 750cfm, 10.5:1scr and SD Performance's Old Faithful cam.
One run is with the 3.75" crank and the other is with a 4" crank.....You can guess which is which!
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Karl |
#63
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Karl, I’ve seen dozens of these computer models on engine performance proven highly inaccurate by real world results. Don’t put much faith in them.
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“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
#64
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Well of course a computer simulation would not be exactly the same as "real world" results! Hell, "real world" results aren't the same every time. It will give a general idea and a visual representation to show the general difference between two engine with only the crank stroke being changed.
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Karl |
#65
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I've posted this info before. But some, or most, probably don't remember it. I bought a '69 Tempest, which had been built for NHRA Stock class racing. The guys who built it later sold it to a Chevy guy. He tried to do some bracket racing with it. But he wound it up too tight & broke a cast rod.
He then had another 350 shortblock rebuilt, & put the #48 heads back on it. He gave me the dyno sheets from the engine build. It made 434hp. He said the car ran mid 12's. Don't know what cam he used. It had an alum intake & Holley carb when I first saw it. But, he gave me the Q-jet that was on it when he bought it. Never made it to the track. Our local track didn't open at all in 2010, so I sold the roller. But, the engine sounded good. I still have that shortblock, at another guys shop. I may one day take a closer look & see what cam it has. Will also see if the TRW L2339F030 pistons are still usable. For all I know, rust may have ruined it beyond repair. There was a flood at the shop a few years back. |
#66
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1.25 HP to CI is a good rule of thumb for a good HP street pump gas pontiac engine in my experience.Tom
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#67
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I had a 70 Lemans once with a stock 350 in it. One day a stud decided to break so I put a set of #62 heads on it along with a stock Q-jet and iron intake. The cam was stock and it was also std bore, block was fly cut from the factory. I had 2 1/2" dual exhaust with dronemasters on it along with a 3.23 ratio gear. I felt like I added 100 HP to the car, it really scooted after those mods. I had to run premium after that but it was worth it.
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“Nothing in the world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan Press On! has solved and always will solve the problems of the human race.” ― Calvin Coolidge |
#68
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"...a 70 Lemans...with a stock 350...block was fly cut from the factory..."
That's interesting. A small valve 350 had chamfers from the factory ? Were they on both sides, for both intake & exhaust valves ? Does anybody know exactly which 350 blocks had no chamfers, 1 chamfer, 2 chamfers ? |
#69
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Pic of 1970 350 that had #11 original heads now has #48 heads
A short block is primarily and air pump nothing magical All else equal modest changes in pump volume shift around what RPMs the power is made
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A man who falls for everything stands for nothing. Last edited by Formulas; 12-17-2023 at 10:11 AM. |
#70
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Did you get the heads too ? or get a decent look at them ? [no concern about rule book - just interested if they were worked or not] I might would eventually actually do this imaginary 350/0.060 with some DIY-Worked #670's and medium zone hyd. flat tappet cam if my nephew winds up with a 66 GTO. I could donate a 350 and pair of #670's to the cause. |
#71
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Precisely, Tom. A ..030 over 350 yields 359 cubic inches. 359 x 1.25 = 448.75 hp. That would be more than enough power, especially in a light car such as a G body LeMans or Grand Prix to shock the 400/455 guys. Like Tom, I like to think outside the box. Imagine a .060 over 350 with a 3” 4.00 stroke crank, LS based pistons with either KRE or E heads with 72cc chambers. 389 cubic inches x 1.25 =486 hp. That would rival the power produced by many street 455s and 428s
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“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
#72
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I seriously considered building a 350 but eventually decided on a 455. My plan was .030 over 350, 4.25 crank, 7k3 heads milled to mid 80s cc, 6.800 bbc rods. 407ci with 9.5 comp. I think it's a great performance upgrade for stock looking matching number builds. I don't think the 350 makes sense for an all out performance build
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#73
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"...ridge reamer and ring compressor? Do they have tools like that?" |
#74
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#75
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http://forums.maxperformanceinc.com/...17&postcount=8
From the info posted in that thread, it appears that we MIGHT could say that MOST '68-'74 350's had double chamfers. Has anybody here seen a '68-'74 350 block with none or only 1 ? One guy posted that he knows of 1 block that didn't have any. So, has anybody else seen one from ANY year that had none or 1 ? If so, do you know what year or at least the casting number. "... I believe the chamfers were there to unshroud the valves, not for valve deck clearance since Pontiac used a flattop no valve relief piston in the 350 that would have hit the valve before the valve hit the deck. The unshrouding may not have been needed in the later blocks with deep chamber heads and eliminated when the casting changed in 1975-76..." I'm trying to think about this. Ya'll help me here. When the valves are fully open, the pistons are not at TDC, therefore would logically hit the deck(if any part of the valve would contact the block on the way down) before they could possibly hit the pistons. I assume the valve reliefs are need mostly for larger, longer duration cams, which might have the valves open a bit more at TDC or very near TDC. I suppose that's why engines with really big, long duration cams need deeper reliefs. I think the no relief pistons began in '74. All '74 350 heads had small intake & exhaust valves, and the deeper chambers, actually slightly larger than the 6x-4 head chambers used in the last 350's. At least that's what this Wallace info says. The biggest cam used that year was an 066, in the GTO. All others were smaller. http://wallaceracing.com/head1.htm But, a guy posted that he had a '74 that had both chamfers. The 6x-4 heads had 2.11 intake valves. So, did the '75-'77 350's have just 1 chamfer ? I have a '77, but haven't pulled the heads yet. A Pontiac friend told me that what he did was to bolt the head to be used, to the bare block, then turn it over an look down into the cylinder, to see which valves might hit the block, and exactly where, then grind the chamfers there, if needed. The pic below is of a block with only 1 chamfer. But, I don't know what year or casting number. Last edited by ponyakr; 09-27-2018 at 02:59 AM. |
#76
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OK, here's some more pics I have listed as 350 blocks.
(1) Only 1 chamfer. Appears to be for the intake valve. (2) I have this listed as a '70 block. But it don't have all 5 motor mount bolt holes drilled. Does anybody know which '70-'74 blocks didn't have all 5 holes drilled ? (3) Lookin from the bottom of a cylinder, with a small valve head bolted on. (4) With a big valve head bolted on. Don't know if the big valves would actually hit the block or not, if dropped. Anybody know ? Anyhow, it's easy to tell why the blocks had double chamfers for big valve heads. Don't have a pic of a block with no chamfers. Anybody have one ? Last edited by ponyakr; 09-27-2018 at 03:39 AM. |
#77
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Wow, here is a 500810 block, which would have had 6x-4 heads, with 2.11 intakes & 1.66 exhausts. But the chamfers are on the exhaust valve side of the cylinders. That blows my theory out of the water.
https://www.partrequest.com/auto-par...k-252260646166 And, to complicate matters even further. Here's a 350 said to also be a 500810, which has double chamfers. I realize that chamfers could have been added somewhere along the way. https://www.partrequest.com/auto-par...0-253442524678 So, from what I've seen, I really can't say FOR SURE, which blocks had how many chamfers. I reckin everybody who plans a 350 build will just have to examine the block he plans to use, to see how many it has, and add or enlarge chamfers as needed. More chamfer info: http://psp.aquacomp.net/topic.asp?TOPIC_ID=1035 http://psp.aquacomp.net/topic.asp?TOPIC_ID=9903 http://transamcountry.com/community/...?topic=41573.0 http://www.pontiaczone.com/forum/arc...p?t-21173.html Last edited by ponyakr; 09-27-2018 at 05:02 AM. |
#78
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Reference thread: http://forums.maxperformanceinc.com/...d.php?t=770414 So... With that being said, I think small valve heads could support significant lift in a 350, or at least heads with no larger than 2.11/1.66 valves. But definitely check valve to bore clearance on a 350, as well as valve to piston clearance. And I would guess that smaller valves would have less shrouding/better flow? I have a set of 7H1's and a set of 47's. I might put those on my 69 350 HO block and see how the valves fit with the bore. 7H1's are weird: 1.96/1.77. 47's are 1.96/1.66.
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"...ridge reamer and ring compressor? Do they have tools like that?" Last edited by Squidward; 09-27-2018 at 05:06 AM. |
#79
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Thanks for that info. Great pic !
What was the bore size ? |
#80
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40 over, so 3.915.
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"...ridge reamer and ring compressor? Do they have tools like that?" |
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