[ta man]

Originally Posted by Formulajones

It gets outrun by crate motors these days so yeah it's an outdated recipe.

Not saying it doesn't work but it's not super fast anymore

It is an example of a fast HFT cam street car absolutely . Jim's car was not just the engine it was an evolution of testing over the years. Anybody can buy an engine with more power but will struggle to run the same times. Through Jim's testing many street car parts and theories still apply. Good flowing exhaust,x pipes,carb spacers,testing parts,matching parts to intended rpm range,clutch fans,cool air induction,efficient torque converters, traction etc and testing testing testing

[HWYSTR455]

Originally Posted by besserspat

I have a 360P in my 73 bird, it was the OP that got the original 350P rebuilt by CVS machine shop.... ...

Uh-oh. That may be a big factor here...


.

[besserspat]

Originally Posted by HWYSTR455

Uh-oh. That may be a big factor here...


.

That must be a cheeky comment... lol

Personally, I didn't even know who they were, but the engine, has CVS stamped all over the head and block. Maybe you know more bout them ?

I had to google it to find out who it was lol. Bought the 73 in Palm springs CA back in 2010. I think CVS machine shop was based in AZ or Texas I dont remember tbh.

The thing runs well thats all I can say.

Peter.

[HWYSTR455]

Sorry, got them mixed up with CVM!


.

[chiphead]

I thought CVMS in Virginia had closed, as the owner was in poor health last I heard?

Maybe we need calibrated to what sort of cars the OP is familiar with? A P350 isn't a world beater, but it's no slouch either.

[HWYSTR455]

I heard something about his health too, not sure I buy it, the walls were closing in on him. He did close the biz, at least under the previous name. Heard someone was going to buy the biz, not sure about that either.

Jim is still on FB posting, and he still owes me an engine. But I'm not going there on this forum....

No doubt P350s can run decent, have seen a number of them that do, and have done one myself. Same stroke as a 400 just a smaller bore. There's been builds that were testing limits, and some of those were supposedly making pretty big numbers, comparable to larger engines. Thing is, it costs as much if not more than doing a similar 400 or 455.

Here's one that's not 'big' power but still a contender:

https://www.hotrod.com/how-to/hppp-1...o-engine-build

Ken's 462HP 350 build:

https://www.hotrod.com/how-to/hppp-0...c-engine-build

And this one, 672HP:

https://www.hotrod.com/how-to/672hp-pontiac-350s

But not sure I buy it all, no real 'data'.


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[Squidward]

The links you provided were things I read back when I put mine together. My 350 was a built short block with forged rods/pistons, with plans on doing a single turbo in my 72 Lemans. But engine problems in the Firebird made me change direction to keep that car operable.

So I used the 350 HO as an inspiration, but wanted a more modern cam. Paul Carter recommended the Voodoo cams from his experience and conversations with Harold Brookshire, and I have been satisfied with that choice.

What I have seen here on PY has been wildly different views on what defines a street engine. Engines that do 13 or 14 second quarter miles times, while pretty hot back in the 60's and 70's, make some people yawn with boredom now. I'm more of the boring guy these days, I got tired of chasing every tenth of a second.

I fully support tree-fiddy's.

[Squidward]

https://share.google/images/vKvbiY6oDrOBWSkDJ

[ericwoo]

I am not very familiar with leak down tests and wasn't sure if new car shops would know whats best for my unique build older car so I did a thorough test.

I was not aware of how long to wait to record the % lost or what is considered okay with these pontiac engines for blow by. The cylinders never stop leaking air which is unlike newer cars I seen shown in Youtube videos. Not sure if this blow by is just how these older engines are designed, but please let me know.


Anyway, I decided to record the % leak at the 2 min mark and 5 min mark since they slowly leak continuously as shown below:

I warmed the car up in idle for around 10-15 mins and put 100 psi in each cylinder.

Driver Side Cylinders leak down test

• RECORDED at 2 mins & 5 mins
• Cyl #1: 28% & 52%
• Cyl #3: 12%, stopped recording because it was pulling too strong & seems good
• Cyl #5: 30% & 46%
• Cyl #7: 28% & 47%

Passenger Side Cylinders leak down test

• RECORDED at 2 mins & 5 mins
• Cyl #2: 28% & 45%
• Cyl #4: 28%, 49%
• Cyl #6: 22% & 40%
• Cyl #8: 25% & 48%

Are these numbers looking okay?

[Schurkey]

Huh?

Plug the leakdown tester into your cylinder. You have your leakdown numbers in two seconds, not two minutes. The readings probably stay stable as long as the tool is connected. ALL cylinders leak air, new, old, rebuilt. They ALL leak. What is acceptable for indicated leakage depends on the ACTUAL cylinder leakage, plus the construction of the tester...which I tried to warn you about earlier.

I think you're doing SOMETHING(s) very wrong. Starting with not calibrating your expectations with a known-good engine of similar bore size; or a Master Orifice. After that, I'm thinking you need to read the instructions that came with your testing equipment.

Provide a link to the leakdown tester you bought.

[ericwoo]

Originally Posted by Schurkey

Huh?

Plug the leakdown tester into your cylinder. You have your leakdown numbers in two seconds, not two minutes. The readings probably stay stable as long as the tool is connected.

I think that may have answered my question that there is a problem with the piston rings and it needs a rebuild. Because the reading does not stablize and it isn't an issue with the leak down tester because I can hear it slowly leaking inside the engine and feel it blowing out the dipstick and valve cover caps

it is a cheap tester but is working www.amazon.com/dp/B0D3LD2MD9

Someone else mentioned the rings could be put upside down. Could that scenario create good compression readings but have a leak down test that doesn't stabilze?

[Schurkey]

Originally Posted by ericwoo

the reading does not stablize and it isn't an issue with the leak down tester because I can hear it slowly leaking inside the engine and feel it blowing out the dipstick and valve cover caps

What air compressor are you connecting this tool to?

If this is a small compressor that can't maintain 100 psi while the cylinder leaks, the leakdown tester won't function properly, and the indicated leakage will increase over time.

[NeighborsComplaint]

As others have said, there is no set duration for a test. It is simply the differential between the pressure supplied vs. the pressure maintained by the cylinder and is accomplished the moment the cylinder is pressurized.

Assuming you remove one plug at a time to test, 10% leak-down would be considered acceptable. 20% or higher indicates problems either in ring seal or valve contact.

Following a "dry" leak-down test, you can pour a small quantity of oil down the cylinder and retest "wet". The oil will improve the sealing of the rings. If the leak-down % improves, the rings are suspect.

Conversely, no improvement can indicate leakage past the valves. This is usually accompanied by the sound or air leakage within the intake and/or exhaust tract.

[Schurkey]

Originally Posted by NeighborsComplaint

As others have said, there is no set duration for a test. It is simply the differential between the pressure supplied vs. the pressure maintained by the cylinder and is accomplished the moment the cylinder is pressurized.

Yes.

It takes (much) longer to find WHERE the pressure is going, (Listen at the throttle body, listen at the exhaust pipe, look in the radiator for bubbles, wave your hand around the spark plug holes of the cylinders next to the one being tested) than to look at the gauge(s) to determine the AMOUNT of leakage.

Originally Posted by NeighborsComplaint

Assuming you remove one plug at a time to test, 10% leak-down would be considered acceptable. 20% or higher indicates problems either in ring seal or valve contact.

No.

1. Removing one plug at a time is poor practice, because you might miss leakage from one cylinder to it's neighbor(s). If you put air in one cylinder, and you get air out of the next cylinder's spark plug hole...you have a badly-damaged casting, or a popped head gasket.

2. As I've said before...you cannot pick a percentage number and say that it's "good" or it's "bad". The indicated results on the gauge depend on the ACTUAL LEAKAGE, AND the construction of the leakdown tester being used. There is no industry-standard, law, or regulation of automotive leakdown testers. "10%" indicated leakage on one leakdown tester may be caused by more leakage than an indicated 20% on another leakdown tester. You cannot compare test results from one leakdown tester to another, different leakdown tester.

You MUST "calibrate your expectations" of the leakdown tester in-use by one of two methods: Either test known-good cylinders of similar bore diameter to the engine you have questions about; or use a Master Orifice.

Originally Posted by NeighborsComplaint

Following a "dry" leak-down test, you can pour a small quantity of oil down the cylinder and retest "wet". The oil will improve the sealing of the rings. If the leak-down % improves, the rings are suspect.

Conversely, no improvement can indicate leakage past the valves. This is usually accompanied by the sound or air leakage within the intake and/or exhaust tract.

No.

"Wet" (oiled-cylinder) tests were said to be valid for cranking compression testing. I quit doing those decades ago, because I could not understand how the oil was supposed to climb uphill to seal the rings on engines with angled cylinder bores--V8s, Slant 6 or Slant 4, horizontally-opposed engines, etc.

"Wet" cranking compression testing may have been valid on upright engines--Inline 4 or 6, "Straight 8". But mostly, the compression numbers go up because adding incompressible oil to the cylinder raises the compression ratio slightly.

Adding oil to a cylinder leakdown test is useless in any case...the oil just blows down the ring gaps, or around leaky rings--and the rings ALWAYS leak. It's just a matter of whether they leak excessively.

[ericwoo]

Originally Posted by Schurkey

What air compressor are you connecting this tool to?

If this is a small compressor that can't maintain 100 psi while the cylinder leaks, the leakdown tester won't function properly, and the indicated leakage will increase over time.

Ok, I just made a post and deleted it because I just tried a 3rd time and realized something must have been done wrong.

This 3rd time, I got the compressor up to its max of around 150 psi, then turned up the max exit pressure but only showed around 120 psi.

I calibrated the gauge to 100 psi as instructions show, then tested and cylinder #1 showed around 8-10%.

I assume that should be good for a healthy engine. Regardless, I am happy to figure this out and get a stabilized pressure reading.

Another thing I realized, that even though the exit pressure was maintained 120 psi on the gauge, my old compressor has an pressure release valve that leaks to turn off the compressor when it is at its max pressure. I taped the valve temporarily to ensure it doesnt leak. Not sure if that was causing my leak down test to not get a stabilized reading or if it is because I turned the exit pressure to max.

I am thinking my engine is healthy and may check the transmission next.

[67Lemons]

Have you checked every cylinder? You should do that before you move on to the transmission.

[Schurkey]

Originally Posted by ericwoo

I calibrated the gauge to 100 psi as instructions show, then tested and cylinder #1 showed around 8-10%.

I assume that should be good for a healthy engine.

WHERE is the leakage? My standard--not shared by the entire world--is that ANY leakage past the intake or exhaust valve(s) is unacceptable. ANY leakage into the cooling system is unacceptable. ANY leakage into an adjacent cylinder is unacceptable.

The ONLY acceptable leakage is past the rings, and then only within limits.

And without experience with known-good engines of the same bore size, or a Master Orifice, you have no idea if 8--10 percent leakage is acceptable. You can GUESS that it's acceptable. It is PROBABLY acceptable. But you don't know for sure.

And--as said--you still have seven more cylinders to test.

Originally Posted by ericwoo

Regardless, I am happy to figure this out and get a stabilized pressure reading.

Agreed.

Originally Posted by ericwoo

I am thinking my engine is healthy and may check the transmission next.

A failed torque converter stator one-way clutch could produce poor low-speed performance while not affecting higher-speed performance. But that doesn't really match your symptoms.

I suspect you still have "engine" issues, and you've not answered my questions about ignition timing and fuel mixture that I posted quite a while ago.

[ericwoo]

Just wanted to post an update in case anyone was curious. I finally ran it down the 1/4 mile track a handful of times.

The best time I did was a 14.1 seconds which is better than I expected. I think I am just used to a more street friendly camshaft instead of a hot cam because driving it on the streets almost doesn't feel much better than stock. I may actually switch the cam out for something like the 068 at some point.

Between having little experience as a driver, the tires not gripping well at start and a weird issue with losing power the last couple hundred feet, I think this little 350 is capable to at least be in the high 13s.

Not sure why but it stops pulling around 90 mph. My original thought was the 2004r transmission might have been pulling up air instead of fluid which is an issue I hear about. I did realize it was slightly low. However, now I am thinking it might be a carb or fuel delivery issue at high speeds.

I found a local listing for a holley 670 street avenger for a good price which I may pick up this weekend before running it again. Would that be sufficient for my engine? Summarizing everyone's suggestions (shown below), I am partially leaning toward the Qjet also because it has small primaries for low rpm but I do not know a whole lot about these.

Also, how would I calculate the jet sizes to put in? Just trial and error with a O2 sensor installed?

Summary of your helpful suggestions: though too many options now has me wondering what is best.

• Holley 650 DP
• 3310 750 with tuned secondaries to come in later.
• Q-jet rebuilt by Cliff Ruggles
• Recalibrated 1976 or later 800 CFM Quadrajet. The 800 will only feed the engine what it needs
• Use a conversion kit to convert the 4160 to a 4150 so you can jet the secondary side.. Go back to mid-range secondary vacuum spring
• Qjet or a Edelbrock 750 AVS2, or a tuned 750 double pumper

[Squidward]

Glad you updated! Was wondering how things turned out.

Your performance is very similar to what I have seen in my setup.

I have also had the "nose over" at the track. I chased after it with a pusher electric pump back at the tank. I also tried to make sure my tank was half full or more. First gen tanks have the pickup at the front part of the tank, so I always wondered if the launch caused fuel to pool up at the back of the tank. Data logging with an afr meter might determine if that is happening.

[Jay S]

It may nose over at 90 because the 600 vac is only jetted for 280 to 320 HP, creating a lean condition limiting top end power.. A fuel pressure gauge would tell for sure. If you get a bigger carburetor the stock fuel system can quickly turn into the next hurdle though.. Especially at a race track.

I would try a properly tuned 800 qjet.