454 strange noise

[legomybago]

1985 Quadrajet 454 with HEI.

When I first fire up the beast when cold, there's a strange metallic clunking sound around 300 rpm's until the engine catches and idles at normal speed like 600 rpms and runs like a sewing machine?  Well I've played with the timing to no effect, replaced the module inside the dizzy, plugs and wires have around 7k on them. It sounds like pre-ignition clatter, but like I said, retarding and advancing the dizzy has no effect. I will say ever since we installed the electric fuel pump, sometime after that is when this started happening. I can turn the electric pump off, and it makes no difference. I just changed the oil, found no metal. The sound echo's throughout the engine making it hard to pin point.

Questions:

1) Can a cracked flex plate do this? Rattle at low rpm? A lot of 454's have a balanced flex plate I've read, maybe we lost a weight? The engine has had a mild vibration around 1000 rpms for ever that I've never been able to pin point. Harmonic balancer seemed tight, I rebuilt/replaced all the accesseries on the front of the motor.

2) Could too much fuel pressure over time cause damage to a piston? I've never smelt a rich running condition? We installed the Holley red pump near the rear fuel tank about 5k miles ago, which is supposed to be rated at 7-9 psi. So we didn't install a regulator, the mechanical pump has it's built in return going back to the fuel tank, and I never did test the fuel pressure at the carb...my bad I suppose? W%

3) Is there something in a Chevy HEI ignition system that can cause slow lumpy idle pre ignition condition besides too much timing advance??

I need to pull some spark plugs and inspect, and hopefully when I remove the inspection cover on the front of the tranny, I will be able to see some of the flex plate? We are hitting the 100's with weather, so working on it in the evenings is a slow if even happening thing right now! Beer is cold.

Some ideas would be good from you kind folks...Thanks

[Rickf1985]

Sounds like the symptoms of a cracked flex plate. Or it could be a main bearing knock, you might want to get a mechanical oil pressure gauge and check the pressure at low idle.

[legomybago]

Thanks for info Rick. I should have a mechanical oil gauge on it, your right. After I check the flex plate, I'll come up with a gauge and etc...

[cook elandan]

Just checking....Could the starter cause the noise if it does not return.

[legomybago]

I don't "think" that's what's happening in my case, doesn't sound like a starter catching. But I am going to be looking in that general area really soon. Maybe it is??

[lemortede]

Did you remove the old fuel pump?
I assume that since you replaced it with electric it had gone bad.

[legomybago]

When we first started having vapor lock issues, I replaced the mechanical pump and all the rubber fuel lines on the rig. Made no difference with the vapor lock. I've had a few mechanical pumps "click" when they start making noise on other rigs in the past, but the sound I'm getting is not that.

Lots of good ideas coming...I just got to get to work on it

[M & J]

A hydraulic lifter bleeding off will do it until it pumps back up. Does it do it every time you start it or just when cold? Sorry if you said and I missed it.

[Rickf1985]

The lifter would most likely be accompanied by a miss in that cylinder until it bled down.

[legomybago]

Problem solved!!

[legomybago]

I wasn't sure if my pic was going to load, I already lost a paragraph explaining what I found...

So last night when I got home from work, it was 100* out, but underneath the rig was still kinda cool, and there was a light breeze....so got the front end in the air, pulled the inspection cover of the TH400, and grabbed the torque converter...LOOSE. One of the bolts sheared off, and the other two were really loose! We were just a few short trips away from sitting on the side of the road....I need to drill out the broken bolt and replace. It looks like I'll drop the starter, and have plenty of room to do the job. I fired up the 454 without using the choke, and she sat there at low lumpy idle and purred! Very happy. Thanks for the ideas fello's.....

[Rickf1985]

Do yourself a BIG favor and go to a Grainger or similar and get a set of left handed drill bits. These drill in the opposite direction and you will find that as you drill that bolt it will most likely spin out. They are special short bolts, you can get them from Summit fairly quickly. Use blue lock-tite when installing.

Or if you have a Chevy dealer you can probably get them there.

[Froggy1936]

I Highly recommend the left handed drill bits You will need a reverse able drill motor (recommend an angle drill motor) as they cut wile turning CCW , If you go slow and are lucky the bit will snatch the bolt as it goes thru the end and spin it out ! Be very carefull as the drill bits are very hard and brittle any side force will break them off, Then the world will end for ya ! Frank

[legomybago]

Yep, that's the plan. Left hand drill bits. I have a 90* drill too. I'm going to use RED lock tight!!

[Hahn007]

Yikes....I know what I will be inspecting very soon. I recently found all of the bell housing bolts to be loose, but hadn't thought of checking converter bolts until now.....

[Rickf1985]

I just went to Grainger today to get some stuff for work and checked into replacing my left handed set since a few are broken. OUCH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Has the price gone up on them!!! 232.00 for a 15 piece set! I believe I will be looking around other places.

[Piraterik]

Yep, that's the plan. Left hand drill bits. I have a 90* drill too. I'm going to use RED lock tight!!

Why not try those new Grabit screw extractor sets?  And re-assemble with lock tight?
Why not just a Torque wrench set at the right torque setting. Just saying, since it is the Head of the bolt that holds the flexplate and Torque converter together.  Just as in most Bolt Applications.  (Just a Bugger to get out with Thread lock) if there is a next time. As It Sounded like PO had Transmission work done at some point (ie. loose bell housing bolts as well)  j.m.o.

Craftsman Tools has them for like $25 bucks.  Have you got a good Clicker type torque wrench?.

[Rickf1985]

A Grabbitt may work if the original screw did not have Lock-tite on it or had been removed and replaced. They are more for smaller screws though. As far as the lock-tite do not use the red or you will have a hell of a time if you ever have to get it apart. Generally you have to heat the bolt to over 600 degrees to burn out the lock-tite with the red and that would be tough with the mass of the mounting block on the converter. The blue is what is speced for this type of job, that and the torque wrench.

[Froggy1936]

The L/H Bit asst. is also available @ Harbor Freight   For a seldom used item price is a factor !  Hm? Frank

[legomybago]

I've read on other forums that the Harbor Freight L-hand bits actually work alright...I'll try that route. The only items I like from Harbor Freight are there moving blankets for (laying under rigs), and there orange ratchet straps.

[legomybago]

So I thought I'd cap off this thread. Went to Chevy and bought 3 new torque converter bolts, they have the factory thread locker on them and they are a goofy thread size and length, the broken off bolt in the converter came right out using an easy out after I center drilled it. Was able to use a standard 18v cordless drill with the starter motor was removed. Piece of cake! I actually fixed it around the 4th of July..She's been running good ever since...

[EldoradoBill]

Norseman makes about the best drill bit you will find anywhere, half the price of name brand tools and in fact they make drill bits for the famous S-O brand and the M brands. I use mine professionally day in and day out and have yet to replace one.


Bill