Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: Jeff K on May 19, 2023, 04:58:46 AM
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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..
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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
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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.
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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..
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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.
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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......
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Thank you Cliff....
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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.....
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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..
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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..
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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.......
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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..
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Good luck with finding good lifters. The best will come from Hylift Johnson if you can find them.....
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Crower has some interesting flat lifters. I wish they would explain what they did ...
https://crower.com/lifters.html?cat=414
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Top quality stuff here.
http://jonescams.com/
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Here's what I'm ready to buy. I want to use the stock 781 head valve spings..
Cam- Melling 22216
https://www.summitracing.com/parts/mel-22216
Lifters- Chevrolet Hard Faced #12371044
https://www.summitracing.com/parts/nal-12371044#overview
Summit Standard Timing Set W/gears
https://www.summitracing.com/parts/sum-g6511
Fel Pro Gasket set.
https://www.summitracing.com/parts/fel-260-1009
Isky Rev Lube.
https://www.summitracing.com/parts/isk-rl-1
Thoughts?
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Looks good as long as the lifters are really hard faced and USA production....
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Thank you so much Cliff!!
By the way, the old 462 is living by you in Lancaster, Ohio.. It has to have close to 100K by now! I almost flipped when the guy who bought it said, " I'm looking for a 60s street rod to take the kids to Dairy Queen in. I knew he was the right guy after hearing that LOL!! ".
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Hey guys will I need new lifters with either the Melling 22216 or the Summit 1301?
I'd like to keep the stock springs and just change lifters and cam.
My engine is a 1978 454 with 336781 heads all stock.
The Melling 22216 cam's specs are;
Duration @50 exhaust 218
Duration @50 intake 214
Lift W/stock 1.70 rocker, exhaust .496
Lift W/stock 1.70 rocker, intake .476
The Summit 1301
Duration @50, exhaust 218
Duration @50, intake 214
Thank you!!!
Lift Exhaust .501
Lift Intake .502
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Sorry for the error, I meant will I need new springs with either cam. I really like the Melling 22216!! I got a lot of good feedback on both. Everybody says as long as the lift is at or under .500 Im good.
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That Melling cam is a pretty close replica of the GM Chevy LS-5 454 and L34 396 cam. Duration at .050 and LSA are the same. Lift on the GM cam was .461 int and .480 exh.
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Thank you Von.
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Well I got a cam and lifters from Melling. There a small chip out of the cams mid bearing lobe. I'm not sure if it matters. I'm not using the lifters. They say made in Mexico on the box, kind of strange for Made in USA parts..
I have a guy on the Chevy forum that makes and sells cams and will sell me a set of USA made lifters. The cam doesn't say Mexico just the lifters.
Thanks for all your help guys.
This is a shame I got to come over here and bother you guys with this cam stuff. But I've bought a few things from Cliff and your the only guys I can trust..
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The cam.
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I wanted to clean this all up.
I took the cam and Mexico lifters to my motorcycle machinest and he looked it all over and said both are fine and the machine work on the cam is actually pretty good.
I still sent it all back and bought the more expensive 22216 Melling cam that was suggested in the first place and $200 lifters from GM. It should be here today and I'm all ready to go..
By the way Melling specs there lift at 1.76 rocker ratio but the 454 Chevy uses 1.70. So I got to drop the 22216 cams lift spec down from;
Intake .476" to .479"
Exhaust ..496" to .479"
Next will be the Quadrajet rebuild and I finally get to spend some money with you guys LOL..
Thank!
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Jeff, I'd be glad to take your money but rest assured I'm happier to know that you are buying the best parts in this industry and will get good results from using them!.....
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Cliff, the Melling 22216 cam is fantastic in my 8:1 454!
It has a slight lope but the vac is around 18". My car now has a mid range!!
I have about 500 miles on it now still taking it easy.
The GM lifters Summit sells seem very well made.
Thanks!
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Good news! I've not found a better cam for one of those engines and it's really easy on the valve train plus doesn't require a lot of spring pressure either. Thanks for the update......