69 tripower power valve

[John M.]

This car is a 69 435 tripower that I was having some detonation problems with using 93 octane. I have it back together with a thicker SS head gasket but it dies shortly after startup. I switched the center carb off another car and it seems to run pretty good. I took the "faulty" carb apart and everything inside looks good, clean, correct jets, good gaskets, etc. The float level was OK on the engine. I'm hoping it's a faulty power valve.
What is the power valve vacuum value for this carb, this engine? Could it be dumping too much fuel and causing the engine to die?
Thanks

[Ken A.]

Re: 69 tripower power valve

Yes, a backfire will blow out the PV on any Holley. Use a #65 for your app and install a blow out prevention kit (basically a checkball & spring) that Holley sells and also use only Holley parts.

[John M.]

Re: 69 tripower power valve

Ken,
Just wanted to let you know that it was the power valve. I have a bag of them but for $8 got a new one and a Mr Gasket anti blowout thing.
The Mr gasket thing is junk, shoulda listened to you about Holley only.
Anyway the BB is running and I'm happy.
Thanks,
John

[Ken A.]

Re: 69 tripower power valve

Good to hear a quick success story. The bag of valves can be tested, but I would pitch any of them above a 65. They are stamped on the edge of one of the flats. Testing is done by mouth & that's another story.

[Clem Z.]

Re: 69 tripower power valve

Good to hear a quick success story. The bag of valves can be tested, but I would pitch any of them above a 65. They are stamped on the edge of one of the flats. Testing is done by mouth & that's another story.

the new holley PV are stamped on the face not the flats on the side. PS some are very hard to read.

[John M.]

Re: 69 tripower power valve

Ken and Clem,
The problem is not quite solved as I had thought. Upon restarting the next day the engine went back to it's stalling, just not quite as quickly. So I kept it running by increasing the RPMs. There was gas coming out of the main jets, sort of splashing out when it was at about 1500RPM ( like when power valve cuts in) but when it got warm the gas stopped and it would idle. Aha, a vacuum leak somewhere that got sealed off when things warmed up. But where? Checked PCV valve, intake gasket by sealing off PCV and checking for vacuum through valve cover, nothing. I removed the carbs and checked the base gaskets and they all look like they are getting squeezed. The carb base plates are flat. Before this, last week, I checked cylinder compression, all around 175.
This engine ran very well before I took it out to clean up the car, suspension, etc. I also changed the head gaskets to a thicker Cometic to try to lower the compression ratio a bit because of detonation on 93 pump gas.
I'm going nuts.
John

[Clem Z.]

Re: 69 tripower power valve

Ken and Clem,
The problem is not quite solved as I had thought. Upon restarting the next day the engine went back to it's stalling, just not quite as quickly. So I kept it running by increasing the RPMs. There was gas coming out of the main jets, sort of splashing out when it was at about 1500RPM ( like when power valve cuts in) but when it got warm the gas stopped and it would idle. Aha, a vacuum leak somewhere that got sealed off when things warmed up. But where? Checked PCV valve, intake gasket by sealing off PCV and checking for vacuum through valve cover, nothing. I removed the carbs and checked the base gaskets and they all look like they are getting squeezed. The carb base plates are flat. Before this, last week, I checked cylinder compression, all around 175.
This engine ran very well before I took it out to clean up the car, suspension, etc. I also changed the head gaskets to a thicker Cometic to try to lower the compression ratio a bit because of detonation on 93 pump gas.
I'm going nuts.
John

check the metering body and the main body were they meet to see if either or both are warped by using a straight edge. also check the main body where it meets the throttle body for warpage

[Ken A.]

Re: 69 tripower power valve

Ken and Clem,
The problem is not quite solved as I had thought. Upon restarting the next day the engine went back to it's stalling, just not quite as quickly. So I kept it running by increasing the RPMs. There was gas coming out of the main jets, sort of splashing out when it was at about 1500RPM ( like when power valve cuts in) but when it got warm the gas stopped and it would idle. Aha, a vacuum leak somewhere that got sealed off when things warmed up. But where? Checked PCV valve, intake gasket by sealing off PCV and checking for vacuum through valve cover, nothing. I removed the carbs and checked the base gaskets and they all look like they are getting squeezed. The carb base plates are flat. Before this, last week, I checked cylinder compression, all around 175.
This engine ran very well before I took it out to clean up the car, suspension, etc. I also changed the head gaskets to a thicker Cometic to try to lower the compression ratio a bit because of detonation on 93 pump gas.
I'm going nuts.
John

Every time it backfires it usually blows out the PV. Also make sure you use the right HOLLEY PV gaket and it didn't slip when tightened down. You did use a BOX wrench to tighten it, right? THE PCV has nothing to do with the carbs. Sounds like a internal FUEL leak. Make sure you use Holley gaskets, they fix a lot of errors.

[John M.]

Re: 69 tripower power valve

Thanks Ken,
What I meant about the PCV was I was trying to detect a vacuum leak into the engine by sealing off the PCV valve and the ports in the valve covers but got no vacuum. No backfires since the last PV was installed. I think the fuel is spilling because there's not enough vacuum to keep the power valve closed. Then, when the engine warmed up the spilling stopped and it ran a little better. I think theres a vacuum leak somewhere causing this. I also noted some pulsing in the tube and on the gage when I was checking manifold vacuum. I don't have a leakdown tester but would it help to diagnose this? The compression was the same in all cylinders with engine warm and all plugs out.
John

[Ken A.]

Re: 69 tripower power valve

L-71's do not produce much vacuum in tip top shape. Search for intake leaks and carb base leaks and/or PB leaks. Use the WD-40 method (squirt around suspected leaks and listen for a change in engine speed. OR, you have too much idle causing air bleeds to seep. Set idle and air mixture screws at 800 RPM with 12 degrees initial timing & total 36-38 degrees. Are you SURE you installed a NEW Holley # 65 PV?

[John M.]

Re: 69 tripower power valve

Thanks Ken,
I ordered the PV from JEGS and it came in a Holley package with gasket so yes, I believe so. I'll report on the WD40 next week, after Carlisle.
John

[Paul J.]

Re: 69 tripower power valve

Thanks Ken,
I ordered the PV from JEGS and it came in a Holley package with gasket so yes, I believe so. I'll report on the WD40 next week, after Carlisle.
John

John, you can also find a vacuum leak with a cheap propane torch. Much less messy than WD-40.

Paul

[John M.]

Re: 69 tripower power valve

Thanks Paul,
I'll be trying these things Monday after Carlisle.
John

[Ken A.]

Re: 69 tripower power valve

That is the preferred method, but you better know what you're doing or you'll have a bang up accident!

[John M.]

Re: 69 tripower power valve

Thanks,
I'll be careful