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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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Discussion Starter #1
Looking for opinions and suggestions with some info that was just discovered while motor was getting tuned at a reputable shop. Slight history on this motor when I bought the car in May 20. 454 PO stated was a fresh rebuild. Unknown gen 454 engine with a large unknown flat tappet cam, cast iron oval port heads, GM HEI dist, shorty headers and 4 bbl carb.
I was able to put a few dozen miles on it after purchase and I knew the carb and timing were off, so it needed to get tuned. For the most part the motor purred like a kitten, smooth no ticks, taps or whine from the block, which indicated to me it is a solid base??
So here is the info from the tuner last night and all things taken into consideration I fully understand that a mechanical motor **** can happen at any time.
What was explained to me is I have a GEN 5 454 (not sure what all that means) had plastic style cam cover and older single spring cast iron heads. Told the car ran smooth as daily driver once they added timing from 14*-18* to get it to smooth out and idle, but the one time 3rd gear to 5k it popped/hesitated and ran crappy.
Was told cyl 1&3 may have a bent or burned valve as comp is now low in those 2 cyls, from either piston to valve contact or even weak springs.
I am just wondering if theres a high probability that old style heads and new gen motors dont really go together and single springs was not a smart install move when camming a motor. Im sure towards the end some people looking to get out from a car, may just put parts that are lying around on to get it going.
Anyway thanks for reading, still contemplating which route to go. I am thinking some model of aluminum heads :O) but have to study my options.
 

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Find a new “tuner”.
 

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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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Discussion Starter #3
Why do you say that?
 

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It ”purred like a kitten” when you took it in and now has 2 cylinders with low compression after only one 5k shift. I’m not buying it.
 

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Gen 5 454 has a limited head application vs the 4 or 6 versions. Did the "tuner" say "plastic timing gear"...or "plastic style cam cover"?

If the former and it was spun to 5k and the timing chain slipped teeth because they were the original nylon covered teeth of a timing gear (read motor would not have been rebuilt with that crap) than valves would have hit pistons and ...well bent valves at a minimum (read pistons likely also)

something not right here on what happened how.

did the tuner give you compression check results on each cyl?
did he use a bore scope in the cyl that are low to "see" wtf it looks like?

Or have the VC been pulled to see if it broke any valve springs?

more 411 needed
 

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I think your tuner is right. Sounds like piston to valve hit. Either valve/piston clearance was not checked properly, bad springs or cam not properly timed. In any case you are going to have to pull the heads and hope damage is minimal. New springs or fly cutting pistons will be next.

Had you ever spun this engine above 5k prior to the tune-up? If so you may have a beef with tuner.
 

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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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178 Posts
Discussion Starter #7
Thanks for the replies. At this point he just called yesterday at the end of the day to give a heads up. He did do a compression and leak down test. I will stop in next week to see what he has. If he didnt use a borescope, I will use mine.
I understood him to say plastic cam cover, had no idea they made plastic coated teeth and who would build a cammed motor using that. Definitely will be getting more info.
No I never spun it to 5k that I know of, the tach was not working.
Wishful thinking would be to pull heads, find out what cam it has and either replace it and go aluminum heads with air gap intake (it has a Performer 2 0 with Q jet mounting flange.

SoCal, where can I find info on Gen 5 and compatible heads?
 

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Plastic capped aluminum cam gear was standard equipment on base Chevy engines. Uses a "silent" link chain instead of a solid steel roller chain so that as the chain stretches the links cut into the plastic gear causing it to fail about 70,000 miles (about when the factory warranty expired).

Gen V and Gen VI used an eight bolt plastic timing cover, over the timing chain. It was used to stop oil leaks in the new Gen V and Gen VI motors that also have cast aluminum valve covers and a one piece rear main seal to stop the steady dripping of oil from the older Mark IV engines. Gen V engines will not run with older Mark IV heads as the coolant passages were redesigned in the newer engine and it results in a huge internal water leak if bolted on (exception is a special fiber head gasket that covers the gaping hole in the block, but it is like putting an aluminum mobile home door door on a submarine: could you really trust it under pressure?).

Head casting numbers will confirm what you have. I suspect you have a 454 pick-up truck engine with "peanut port" round intake runners instead of the older and larger oval port intake runners off of a Mark IV engine. Gen V used a flat tappet hydraulic cam and the Gen VI had a hydraulic roller cam with a redesigned block (taller lifter bores to hold a roller cam and the bosses in the intake valley to bolt down the retainer spring). Easy indicator of block generation is to look for a mechanical fuel pump. If it has one it is either a Mark IV on an older two piece rear main seal engine (1965-'90), or a newer Gen VI (1996-'04) as the Gen V didn't have a place to even bolt on a mechanical pump as they were all TBI electronic fuel injected that used a low pressure electric fuel pump in the gas tank.

Big Dave
 

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original older motors used nylon covered teeth on the top timing gear so the engines would run quieter. Over age that nylon would degrade/break causing timing chain to slip which typically resulted in bent valves. Your motor is supposedly rebuilt so it should not have that as anyone puts in steel gears for timing sets. Your note about seller saying the engine was rebuilt...

IDK what your guy means by "plastic cam cover"...maybe someone who knows the 454 BB can comment on what that is unless your guy is referring to a composite timing cover, maybe even a 2 piece one so you don't have to remove (drop) oil pan to change cam

You noted but the one time 3rd gear to 5k it popped/hesitated and ran crappy. I take that to mean the motor was spun to 5k rpm and that's when "something" happened.

The gen 5 454 had the small "peanut port" heads that make no power, typically GM truck motors. Edelbrock, AFR, etc make heads for 454 that will match up to a new intake manifold like the Edelbrock Air Gap. Its using the stock intake where there is more a limited head selection using the stock peanut port heads

Buying a car with a supposed "new rebuilt" motor that craps the bed within miles suggests it was not or done poorly. Happened to another guy posting his issue on a "only 1 mile on motor" that had issues. He bought a new crate motor as the cost to rebuild his 454 was not worth it

From this side of the internet we really can't determine what happened to yours other than what you are relaying from someone that may or may not be supplying accurate info

Bore scope will show valve to piston contact/damage. The compression & leak down test shows you have at least 2 bad cylinders, never good. If the bore scope reveals new looking piston tops (read no carbon buildup) and fresh crosshatch on cylinder walls that's is a sign it was recently rebuilt. If you have stock peanut port heads you want to get rid of those. A Gen 6 454 is roller cam, 1 piece RMS which is always a better way to go.

You are going to find out through a closer look and partial tear down how bad the motor is and costs to fix/rebuild. Given its a Gen 5 you then may want to consider a crate motor. Blueprint Engines would be what I recommend, and did but mine is a 355 SB. They offer a few 454 block 496 motors with warranty. Just depends on how thick your wallet is.

EDIT: I see Larger Dave jumped in Op while I was typing this...listen to his advice
 

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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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Discussion Starter #10
Thanks for the replies gentlemen. I am still learning the idiosyncrocies of big block motors. FWIW if the motor is toast I can live with fixing or replacing it. The rest of the car is original sheetmetal, no rust pristine paint job (bondo magnet showed good) etc, so this is fixible.
I kind of suspected it may be a truck engine, I have yet to see the engine numbers but I did get the head casting number and borescope of the lifters. The number is 346238 which I followed up on and it says its a 75-87 oval port open chamber 113cc chamber.
I saw the lifter and confirmed its a flat tappet cam, and judging by the surfaces inside the head and lifter there it looks new. It does have Lunati 1.7 roller rockers (can that be the most valuable part of the motor? lol
You guys are great thanks for all the help.
 

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The last to get a BBC was the 1974 Corvette, last passenger regular production car was a '73 full size. The years you stated (1975-'87) are all three quarter ton or one ton pick-up truck engines as that was the only vehicle to get a BBC installed after 1974. It is a Mark IV two piece block with the old style oval port heads, but made for unleaded gas (case hardened seats, not pressed in steel seats).


Big Dave
 

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It ”purred like a kitten” when you took it in and now has 2 cylinders with low compression after only one 5k shift. I’m not buying it.
So what exactly would the tuner have done to cause a problem ?????? Any different than taking it out on the road or to the drag strip and putting a couple of hard passes on it ????

My bet is that it does not have the right valve springs on it for the cam and a couple of valves ended up tapping the pistons.
 

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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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Discussion Starter #13
Bill, thats kind of what was discussed after the road test. The tuner guy builds race cars, so Im sure his idea of putting his foot in it was a lot more than my version of putting my foot in it.
 

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When you bought the car did you get the receipts for the engine rebuild? Machine work and parts?

1st thing I would have asked for.
 

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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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Discussion Starter #15
No. I asked the guy said the motor was built when he got it. Story goes, his friend was building the car and he bought it bc the friend had to off it due to a divorce. Thaats why he didnt know what cam was in the motor. My thought when looking at the car was, my interpretation of its appearance upon my inspection. I have looked at enough cars that whatever seller is saying basically goes in one ear and out the other, Theres a ton of BS out there. So there were overwhelming indications that the car was an original sheetmetal, no rust, pristine paint job (seller owned the body shop), obvious new powder coated diff, sub frame new headers, Milodon low profile pan. AAW throughout the car. So the obvious signs were there. My goal was to find a car that had as near perfect body and paint, anything mechanical I can do. Which I think I got.
I am going to bring the car home and start looking under the heads to see if theres any damage and go from there.
 

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How much had you driven the car before the tuning incident? And above you stated the car doesn't have a tach so how did the tuner know it was at 5000 rpm it 3rd gear when it went bad?

I'm guessing that if no tach perhaps he over reved the engine and floated the valves causing the damage
 
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That’s the second 454 fried by a tuner this week....

Don
 
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How much had you driven the car before the tuning incident? And above you stated the car doesn't have a tach so how did the tuner know it was at 5000 rpm it 3rd gear when it went bad?

I guessing that if no tach perhaps he over reved the engine and floated the valves causing the damage
That was probably after the 7000 rpm in 2nd. 😄
Sorry BillK couldn’t resist.
 

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68 Camaro SS/RS clone, 454 BB 4 speed, 3.73 Posi, new paint, motor, trans and diff assembly. 2" Drop
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Discussion Starter #19
How much had you driven the car before the tuning incident? And above you stated the car doesn't have a tach so how did the tuner know it was at 5000 rpm it 3rd gear when it went bad?

I'm guessing that if no tach perhaps he over reved the engine and floated the valves causing the damage
Only about 20 miles total. The guy builds and races cars at Bonneville, so if he didnt fix the tach Im sure he drove by feel. Yes the valves could have floated but let me ask this question. If this truck engine is overcammed and with weak valve springs (think he said they were single springs) it wouldnt have taken much to exceed the springs ability right?
 

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Only about 20 miles total. The guy builds and races cars at Bonneville, so if he didnt fix the tach Im sure he drove by feel. Yes the valves could have floated but let me ask this question. If this truck engine is overcammed and with weak valve springs (think he said they were single springs) it wouldnt have taken much to exceed the springs ability right?
It’s possible just not likely at 5k. I agree with SoCal805. You may want to cut your losses on this engine and just get what you want. The car in the pic looks great, more than likely worth the investment. Do your homework on finding an engine. Lots of good options out there. You might want to look at the Chevelle site for engine builders and ideas.
 
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