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  #16 (permalink)  
Old 11-02-2012, 10:07 PM
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Yes but correct me if im wrong 15-20 @ hot idle is low?

See the thing is the machine shop told me he likes to set clearnaces loose for drag racing but i told him i will only use it as a street/drag , im wondering if he did not set the clearances loose and a higher psi would compinsate.....
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  #17 (permalink)  
Old 11-02-2012, 11:09 PM
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Rule of thumb is; 10lbs. for every 1000rpm. You figure it out!

Bill
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Old 11-03-2012, 06:26 AM
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Regular production engine rebuilders and prefer to set the bearing clearances on the loose side because they do not want any "come-backs" due to wiped or spun bearings. That is because the machine shop does not know how the engine is going to be used, no matter what the car owner tells them.

Regular production rebuilt engines will have just enough oil pressure at idle to keep the lifters quiet. Most automobile owners who buy regular production rebuilt engines do not have an oil pressure gauge. The idiot light is caliibrated at the factory to illuminate at 7 lb. at 600 RPM.
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Old 11-03-2012, 09:36 AM
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As Bill and 69 pointed out, those are perfectly normal readings for a 400 Pontiac. Added pressure in the Pontiac is counter-productive as it "heats" the oil more. The big mains in the Pontiac heat the oil enough, thank you... Wayne Hoehns (built the most powerful Buick 231s in the "Busch" days) once told me never put an oil temp guage in a circle track Pontiac or 351 Windsor (both 3" mains). "You don't wanna know..."

What MouseFink says about shops "adding" clearance is sorta true. That is, we allow engines "out the door" with more clearance than factory "tolerances" listed. Partly because of just what he says. Customers don't always end up using the engines for exactly what they say, and we have to "build in" some flexibility. We have SOME customers we "tighten things up" for because we KNOW what they're up to. But it's a common misconception that "tighter is better". As long as there's enough oil to keep the crankshaft "floating", it's all good. "Tighter" will actually add heat to the oil, too.

Aother reason engines are "looser" than original is the parts themeselves. Bearings are now designed such that, when the crank is in the "middle" of the tolerance, clearance will be near the "high lmit". Performance applications typically grind the cranks to the "low limit". That, combined with the "high limit" clearance bearings, an additional .0005-.001" OVER the high limit is seen. This is when oil pressure can degrade at low RPM.

FWIW

Jim
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Old 11-03-2012, 12:37 PM
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My pnocho had 50 pound pressure at idle. 20 is to low for new engine, install the gasket. Careful to get the pump rod square away properly on install.

Larger pump should not be an issue once the new gaskets installed. Melon high volume was all i had. High pressure pumps usally require some machine work on the blocks oil passages.

Always install all the funny gaskets on pontiacs!!! Most important part of poncho build.
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Old 11-03-2012, 04:48 PM
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Thanks for the info guys. I remember him telling me he likes to set clearances loose for drag applications and i told him it would be a street/strip motor.. He line bored it and set the crank and main bearings.
I was going to but when i checked it the clearances were so tight , i just went ahead and dropped the block and crank off to the machine shop that cut the crank. I set up the pistons and rod bearings.

Im thinking he set the clearnaces a lil loose because i said strip.
That would surely explain the pressure.
I ran it today and all is good , once it warms up im showing 20-25 @ hot idle in gear!


Quote:
Originally Posted by hcompton View Post
My pnocho had 50 pound pressure at idle. 20 is to low for new engine, install the gasket. Careful to get the pump rod square away properly on install.

Larger pump should not be an issue once the new gaskets installed. Melon high volume was all i had. High pressure pumps usally require some machine work on the blocks oil passages.

Always install all the funny gaskets on pontiacs!!! Most important part of poncho build.

MY MOTOR HAS 50-60PSI IN PARK , ONCE I DROP IT INTO DRIVE WITH THE MOTOR @190 DEGREES IS WHEN THE PRESSURE DROPS TO 20LBS....
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Old 11-03-2012, 05:22 PM
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I have a couple questions also while i have you Poncho guys here.

1) should i order the copper gasket? Its only $6 and butler claims its much better...

2) what should i set idel at? I have it around 1000rpms in park but once in drive it drops to about 800rpm. Anything less and it wants to stall...


3) I have a edelbroclk 750 catb how would u suggest is the best way to set the air fuel mixture?
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Old 11-05-2012, 07:34 AM
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No need for a copper gasket. Never (REPEAT: NEVER) had an oil pump gasket fail. Yes, install the gasket.

Oil pressure readings given are perfectly normal for a Pontiac.

We don't use E-carbs, so I can't help there. We use Q-Jets or AED Holleys.

Jim
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Old 11-05-2012, 08:31 AM
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Quote:
Originally Posted by oneluv1979 View Post
2) what should i set idel at? I have it around 1000rpms in park but once in drive it drops to about 800rpm. Anything less and it wants to stall...
The problem is in the way the timing and distributor is set up.

The cam you have requires a good amount of initial timing. I'd start w/about 18-20 degrees initial and set the mechanical advance to give the rest, which would be somewhere around 16-18 degrees to give a total (initial plus mechanical) of 34 to 36 degrees. Be prepared to use a bit more initial if needed, and to remove the amount you added to the initial from the mechanical to keep the total where it should be.

Depending on the type of distributor you have, this can mean changing bushings (MSD) or modifying the mechanical advance itself (GM HEI).

You can use a vacuum advance, too. You might find it better to use ported vacuum for the vacuum advance when using a large amount of initial timing. Limit the vacuum advance can to give 10-12 degrees of added timing under high vacuum conditions. Do this by using an adjustable vacuum advance can or by using a simple limiter plate that you can buy or make yourself.

More info can be found here. The article was written w/the GM HEI in mind but the timing info is basically universal.

Quote:
3) I have a edelbroclk 750 catb how would u suggest is the best way to set the air fuel mixture?
You can use a vacuum gauge to set the idle mixture screws to give the highest reading (keep the screws within 1/4 turn of each other). Or set them to give the highest idle speed.

It's important that the transfer slot not be over exposed before trying to set the idle mixture screws, else you'll never get it set up right. More on the carb's transition circuit can be found here.

Good luck.
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Old 11-05-2012, 12:47 PM
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Quote:
Originally Posted by oneluv1979 View Post
I have a couple questions also while i have you Poncho guys here.

1) should i order the copper gasket? Its only $6 and butler claims its much better...

2) what should i set idel at? I have it around 1000rpms in park but once in drive it drops to about 800rpm. Anything less and it wants to stall...


3) I have a edelbroclk 750 catb how would u suggest is the best way to set the air fuel mixture?

for number 3 you trying to set the idle a/f or wot. Idle is set with the screw in front of the carb. WOT is set with new jets. part throttle is handled with needle valves they can be adjusted and replace with different types. Edelbrock has lots of good info on there site.

800 is stock for most ponchos in gear but may need more with large cam and stall.

No felpro gaskets no need to buy copper for stock pressure pump.

My poncho would hold 50 psi when hot at idle. even after the engine was shut off for hours still read 50 on the guage. Maybe mine was too much but the stock 455 ho had the same pressure. so 20 seems low even in gear and hot. But maybe its ok not an expert on oil pressures. I got a feeling you need that gasket.
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