1977 454 Quadrajet Secendary issue, pop back fire rough running.

[Jeff K]

 Secondary's:
  About 7 years ago, I bought the best car I ever owned, a 69 el Camino SS396. I'm retiring with this one...  It's worn in (like me) and it has a 1977 454 truck motor with a 400 Turbo and 2.73s out back. 
 
 This motor runs real strong. This Quadrajet has never given me one lick of trouble. Over the winter it started backfiring or running rough when the secendarys are opened. With them disconnected, it runs perfectly just on the primary cercuit. The vacuum gauge needle goes to 6 or 7 when floored then comes right back up at throttle release.

It has the original HEI distributor. I disconnected the vacuum advance and run 18 initial with 30 mechanical all in by 3000. It runs best like this. I use Sams Club, Boron or Esso 87 octane. The 781 heads are suppose yield only 8.0 or 8.50 compression, I very rairly ever heard a full throttle ping. The pinging goes away after flooring it a few times. I'm thinking this must clean the chambers out and lower the compression. It's city driven.

Yesterday, I pulled the secendary hanger (J) and it was bent.. One rod (DN) - Passenger side, was almost a half inch higher then the other, I think I did this installing a lock nut on the air cleaner stud.  When I open the secendarys it makes a wierd popping sound, I think its running lean. I tried to straighten the hanger out but it still is rough but better..

The carb came with the engine. The engine came from a brand new truck that was demolished with a few thousand miles. The prevous owner bought the car with several others from Texas in a package deal. It didn't have an engine or transmission. He had this 454 and th-400 sitting in his garage for decades. He kept it oiled and removed the rockers to save the valve springs.

Should I get new rods and a new hanger?

Thank you..

[Cliff Ruggles]

Without the VA you are missing some timing at light engine load so it's likely going to "load up" the combustion chambers and piston tops. 

IF the engine doesn't like the VA hooked up it's simply adding too much timing and you need to modify the existing VA or get one that only adds about 10-14 degrees.  This will help your engine run better everyplace.

As far as problems at WOT on the secondaries I would start by installing one of my rebuild kits, and correctly repair or replace the secondary hanger.  There is a new secondary plastic cam and spring in the kit.  The springs are always weak from being would up nearly 50 years and the plastic cams shrink, crack, wear down and get loose on the shaft which can have a HUGE impact on full throttle performance just like you are seeing......

https://cliffshighperformance.com/product/quadrajet-rebuild-kit-sr

[Kenth]

HEI distributors rarely or never receive the service that is necessary, (they do not have points that need to be checked occasionally.)
Check that the weights can move easily and are not rusted or binding.

[Jeff K]

 I'm thinking the popping issue comes from number five cylinder is loosing its exhaust lobe. I've been using Mobil 1 5W-30 along with a Wix or K&N oil filter for years without issue.
Then, a week after pouring a quart of Shaler Rislone oil additive into this engine, it starts popping up out of the carburetor..

[Jeff K]

The first half of the last post didn't come through.

I decided to pull the valve covers and sure enough the popping issue is comming from number five cylinder, it's loosing its exhaust lobe.

I've been using Mobil 1 5W-30 along with a Wix or K&N oil filter for years without issue.
Then, a week after pouring a quart of Shaler Rislone oil additive into this engine, it starts popping up out of the carburetor..

So time for a new cam. I'll start looking at the Crower line up since I have always had good luck with there stuff..
I'm going to see if Pontiac lifters made by Johnson would fit the 454 block. I have a bunch of Johnson lifters from the seventies.

[Cliff Ruggles]

Here's my pic for the camshaft:

https://www.summitracing.com/parts/sum-1301/make/chevrolet

USA made and works well in the later "low" compression 454's.  Second choice would be the GM Marine big block cam which is basically a duplicate of the 396/325hp cam.  Very close specs to the Summit cam above on a 115LSA.....

https://www.summitracing.com/parts/mel-22216

Either of these cams have gentle lobes and easy on the lifters plus don't need a butt-load of spring pressure......

[Jeff K]

 Thank you Cliff....

[Cliff Ruggles]

You are most welcome.

You can also take the path that most others take with these things.  Order a Comp XE or Tump-Ya-Mautha cam, install their cheap Chinese lifters on it, "battleship" valve springs to keep things in check, and heavy locks/retainers.   

Of course you'll knock half the lobes off of it in six months but it sure will sound good when you idle thru the next Dairy Queen Car Cruise!........LOL.....

[Jeff K]

I can't believe people are still drinking the Cool Aid!! There's power in advertising.

I miss those videos of that German kid frying those 14" Bias Ply snow tires off his Firebird because he had an XE cam..

[Jeff K]

I'm having a lot of fun being retired and playing around with this 69 el Camino..

I'm thinking about the Melling 22216 Marine cam. I was going to buy Crower hyd lifters with the cool face or try to find some 60s-70s vintage NOS hyd lifters.

Rhoads also sells there lifters before modification. I'm thinking they inspect them making sure they have a good batch before modifying them with there famous bleed channel..

[Cliff Ruggles]

Absolutely and for sure you must run good USA made lifters or the cam just isn't going to make  it.  Cam failure is directly related to using cheap offshore tappets.  It's greatly accelerated by running WAY too much spring pressure combined with ultra-quick lobe profiles.

All the other stuff we read about like not having trace metals in the oil and improper break-in procedures, for example aren't the root cause of the issues.

A very good practice to get into is to paint a white line on the top of your pushrods that will be visible when the valve covers are removed.  Once you are done running the engine in after the cam install remove the covers and start it up so you can see the white lines.  Make sure to have it idling as slow as possible to minimize the mess. 

They should all be spinning nicely.  If you have any that aren't spinning might as well pull it right back down and throw that cam out because it's doomed.......

[Jeff K]

Thank you so much! I will mark the push rods. So far everything looked clean. I put about 40,000 miles on it so far.

I'm going with one of those cams you spec'd. You know more about engines, cams then anybody I know.

Does anybody sell good hyd lifters anymore?

The motor came from a brand new demolished 1978 C-50 work truck that the previous owner picked up in a tow deal back in 1978. When he saw the brand new 454 he bartered it from the insurance company for the price of the tow. Took it apart and stashed it in oil a few decades..

[Cliff Ruggles]

Good luck with finding good lifters.  The best will come from Hylift Johnson if you can find them.....

[Jeff K]

Crower has some interesting flat lifters. I wish they would explain what they did ...

https://crower.com/lifters.html?cat=414

[77cruiser]

Top quality stuff here.

http://jonescams.com/