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75 Malibu Digger build

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Post by Digger Thu Jun 17, 2021 11:37 pm

I’m new to using forums, let me know if this is place to post new topic.

I recently said Hi in the intro section.

So my first step on this 75 Malibu was to install a 454 motor and seems I have a mystery already.

Motor is in. It was advertised as rebuilt 454 that had a long list of upgrades and rated 450hp. I have zero knowledge of who built motor or if they broke it in properly. It was a “deal”. Headers on it and beautiful Flowmaster.

Runs like crap. A local shop did the install and I think they were over their heads.

Upon tuning, too much noise from valve covers triggered a stop and investigate. The main nuts on rockers were all loose and one completely off.

Comp Cam 924-16 springs I think as I have a box with this part number. I also have inside this box a set of install instructions that underline 85000-16

Cam is Comp Cam hydraulic flat tappet. 11.246.3 extreme energy
552/555 lift
230 / 236 0.050
1800-6000

Mechanic put new nuts on, tightened them 1/2 turn.

I have no idea why nuts came off. Mistake? Lazy? Or some pressure forcing them off?

Investigating further. Instructions say remove inner spring for break in and only tighten 1/8 turn.

Getting it home it ran poorly and my first worry is motor damage. Looking further one lead was off and the carb vacuum line goes to nowhere. (Plugged off)

Removing valve covers it has two types of springs

One spring has an inner and an outer spring. Outer spring is round while inner is flat. Perhaps this is a damper?

The springs further away from Center all have the dual spring. The springs all closer to center of motor have single springs.

What do I have? What should I have?

Can anybody help with this mystery?

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Post by bracketchev1221 Fri Jun 18, 2021 6:52 am

Well the 924 spring IS a double spring so you should see 2 coils AND a damper. From what I remember the 924-16 is recommended by comp for a lot of these cams, though they are a little weak on higher rpm control but that does not seem to be your issue. Assuming you have stamped steel rockers I'm guessing they are normal lock nuts. I have seen replacement nuts not have enough crimp on them and back off. Now that is not saying that the mechanic didn't do something wrong. I don't know him from anybody. First things I would rule out is IF the springs are installed right. And then move on to the wires and vacuum leaks.
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Post by Digger Fri Jun 18, 2021 11:48 am

Thank you for your help.

I can confirm it looks like old (used) nuts were on and that’s why they backed off. New nuts are on now.

Comp Cams tech stated 1/8 turn vs 1/2 turn should make little difference when tightening nuts. Hmmm, but okay.

My theory is that the engine builder put the old nuts on for break in, then intended on switching to new nuts for long term.

Still very unusual that 1/2 the springs have the inner spring removed and half do not. This looks very intentional so I’m wondering if it is a shortcut of some sort. Less work later?

I’m hoping to get time today to drain the oil and have a look. Fingers crossed. Then I think I have no choice but to purchase a new set of springs so I will know exactly what is in there.

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Post by Digger Fri Jun 18, 2021 12:14 pm

ONly other think I can think of is the builder is trying to hide a flat lifter and but single springs on one side to allow that side to work easier, an attempt to make Cam work and hide the problem.

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Post by REVINKEVIN / Mr. 600+HP Fri Jun 18, 2021 1:01 pm

Hey. It wouldn’t be a bad idea to take the intake off and check out each lifter. Check your pushrods and make sure that they are straight. For sure get the correct spring kit. How sure are you that the cam is really the cam that’s in your engine? Post pictures of what you find. In this day and age with the oil that we have it’s easy to wipe out solid flat tappet lifters during break in. You need some oil with a zinc additive. Pull the lifters out one by one. Inspect it and put it right back in the bore that you removed it from. You got this man.
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Post by Digger Fri Jun 18, 2021 1:47 pm

Haha, no I don’t got this lol, but appreciate the support! My plan was to pay the experts so I could turn the key and drive out. Focus my efforts on suspension and body which is within my skill set.

I think I will inspect oil for metal and do a compression test. There are some other issues, they never got carb vacuum set up, instead just plugging the line, that can’t be right and vacuum could be affecting entire fuel delivery.

I will focus on body and take a breath before diving back into motor. I’ll see if I can upload some photos.

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Post by Digger Sat Jun 19, 2021 7:13 pm

75 Malibu Digger build 9ce8c510

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Post by Digger Sat Jun 19, 2021 7:14 pm

75 Malibu Digger build 478fff10

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Post by Digger Sat Jun 19, 2021 7:21 pm

75 Malibu Digger build 8c12db10

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Post by REVINKEVIN / Mr. 600+HP Sat Jun 19, 2021 7:53 pm

That looks pretty solid. Can you post a couple of pictures from the front and the back? Post a picture of the 454. You have a good car to work on. Let’s get this thing back on the road.
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Post by Digger Mon Jun 21, 2021 2:29 am

This picture shows two valve springs, one single coil and one single with damper. Singles are consistent on all exhaust valves. Single damper on all intake. Neither spear to be the Comp Cam 924-16. I found zero springs where the manufacturer suggests two separate spring types. However, informally the odd builder out there feels they know more and put in two different weight of springs. General consensus seems to be “Why?” But also they should not directly hurt engine.

By the way, I may not have direct questions here, but just sharing my build on this car.

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Post by bracketchev1221 Mon Jun 21, 2021 7:10 am

I would check what Comp recommends for that cam. They usually have a recommended spring and then a BETTER spring for it. I would go with the better spring especially with a big block. 3/8" stem valves are heavy and hard to control. But first thing is get all the springs changed and equal.
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Post by Digger Tue Jun 22, 2021 3:49 am

Yes, they do reccomend the 924-16 spring but I will ask about a step up.

There is more though. As I inspect the valves I do find metal . It looks like casting head aluminum. Tiny chunks. And as I feel may way around the corners a greyish paste forms, likely from aluminum. I’m the head there are oil drain holes. On one side what should be a nicely kidney shaped hole is ragged around the edge, it does not match the other side. This edge looks damaged and perhaps where metal came from. Not good. I don’t know if metal from a cam failure would find its way up here. Plus the metal I found is non metallic.

I will change oil when I get a minute.

Forgot to mention, when I got it home from the shop I found one spark plug wire off at the distributor and the timing vacuum advance hose take off the distributor and plugged.

I have had no time to get after it but I need to fully understand and keep going backwards (compression test, lifter and rod inspection etc) before I can make a plan forward. I’ll see if pics will
Load up today.

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Post by Digger Tue Jun 22, 2021 3:52 am

Two different valve springs

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Post by Digger Tue Jun 22, 2021 3:55 am

Aluminum greyish paste75 Malibu Digger build 2ac04610

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Post by Digger Tue Jun 22, 2021 3:57 am

Valve springs described earlier75 Malibu Digger build 46a7dc10

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Post by Digger Tue Jun 22, 2021 4:05 am

This throws the whole engine build under suspicion.

But hey, on a positive note the new Flowmaster exhaust and 304 headers are looking great!😐75 Malibu Digger build 7189611075 Malibu Digger build 71896110
75 Malibu Digger build Bc65491075 Malibu Digger build 71896110
75 Malibu Digger build Bc65491075 Malibu Digger build 71896110
75 Malibu Digger build Bc654910

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Post by Digger Tue Jun 22, 2021 4:13 am

Well the exhaust is good but maybe not worthy of six pictures. First no pics now too many, Can’t seem to find an edit button.

Anybody find aluminum up top
In their engine like mine? If they came from up top do they end up in oil pan and perhaps stopped in filter? If Cam failure would metal find its way up top?

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Post by bracketchev1221 Tue Jun 22, 2021 7:08 am

The gray paste kinda looks like cam moly paste assembly lube. The head drainback hole, they are just cast that way. From what I can see, it does look like 2 different springs.
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Post by Digger Wed Jun 23, 2021 12:33 am

Thank you for feedback, hopefully you are correct and it’s just a paste. More good news, not a sliver of metal to be found in the drained engine oil.

I think now I can move forward with the motor and more than likely looking at timing issue in regards to no power.

In the meantime I have rust proofed 80% of the underside. Wire brush, rust converter, rust paint.
Still need to dig out rust on passenger side rockers.

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Post by Digger Thu Jun 24, 2021 10:50 pm

Sway bars - I can’t find any used T/A or Impala sway bars around here. I think I will keep the stick one up front for now and install a rear. I assume beefier is better? I have found a 1.5 inch steel anti sway bar comes with instal pieces, bushings etc.

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Post by Digger Thu Jun 24, 2021 11:21 pm

Anybody put in lowering springs?

My rear wheel well sits at 26.5 inches. Springs worn and shocks doing very little.

Front wheel well sits at 28 inches, springs feel
Okay but shocks poor.

I could just do the rear, see how it turns out as far as ride hieght. Or I could do everything all round to even everything out again. I’m considering lowering springs 1.5 inch.

Any problems associated with this?

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Post by Digger Thu Jun 24, 2021 11:23 pm

Is there an edit button?

Above I’m asking any problems encountered putting springs in; or affecting suspension, max tire size negative?

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Post by REVINKEVIN / Mr. 600+HP Thu Jun 24, 2021 11:32 pm

Hey. When you post you will have 4 tabs on the top right of the post. One of them says edit. Click on that and you can edit your post or delete pictures.

By the way, I have all Global West suspension on my car with a big block. I think it sits pretty good. Some guys on here have part numbers for some Moog springs that also lower the car. My shocks are pretty expensive, Viking brand, but just some good stock replacement ones would be a great upgrade. Keep up the good work!

75 Malibu Digger build 5db7f710
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Post by Digger Thu Jun 24, 2021 11:43 pm

Your ride hieght looks great. I prefer the lowered look today over the old muscle car
High in the rear end. Just my preference. So Kevin it the Global West a 2 inch or 1.5 lowering spring? They don’t look too difficult to install but those are famous last words.

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