TCCoA Forums banner

1 - 14 of 14 Posts

·
Registered
Joined
·
7,758 Posts
Discussion Starter #1
I know this isn’t MN12 related, but I thought I would share my “progress”. :D

My truck has pissed me off for the last time with no power and pinging with 8:1 compression and timing set to 4 degrees BTDC!!! (Cranking pressures are 190 psi!) I’ve tried everything from double head gaskets, to racing fuel and it pings!! I’m 99% sure the cam is ground wrong and building way too much cylinder pressure and causing the detonation.

Anyway, Off with it’s heads!! I’m going back to one head gasket and changing the cam to a new cam. Disregard the horribly dirty engine compartment, I’ll clean it tomorrow so nothing goes in the engine. (Yes, I did cover everything tonight though… :D )

Anyway, this is the 472 (460 punched .060 over) with ported (very ported!!) D4VE heads, 2.19 intake and 1.71 exhaust (stock 351C-4V valves) and 1.73 roller rockers (stock is 1.73, just not roller). :D





(Oh, and this combination with the current cam and the timing set very low would not even spin the tires on dry pavement…. :redmad: )

All I know is that the new cam and raised CR had better friggin’ fix this problem. :D
 

·
Registered
Joined
·
199 Posts
Dude, I bet I could put my fist in those intake ports, lol. Sorry I have no input to your problem, good luck.
 

·
Administrator
Joined
·
14,208 Posts
Well since it pissed you off when you get it back together you can just drop it off at my house. ;)
 

·
Slacks 12 months a year, TCCoAAC Member
Joined
·
2,530 Posts
Sounds like you might have a bad distribuator.Even though you have it re-tarded in timing when you rev it up it is not advancing or advancing to far and that would cause it to ping and have no power.
Just a thought,
Chris
 

·
Registered
Joined
·
2,638 Posts
Those are high RPM heads with those huge intake ports. That's probably why you can't spin a tire. With ports like that, I would think that you need forged internals, dual 4bbl intake and maybe a high stall converter.
 

·
Registered
Joined
·
7,758 Posts
Discussion Starter #6
The reason I can't smoke the tires is because the timing is set so low that I have no power. If is set the timing where it should be, I can roast the tires, but at the same time rattling like a diesel!! :mad:

And I have a low gear set C6 tranny with a higher stall converter. (And 2.75 gears with a very tight posi, yes... 2.75 :beek: :leftright )

The previous engine with the same heads, intake, exhaust, compression, blah, blah, blah (and tapping wrist pin) would run on regular and roast the 31 x 10.5's all day long. And keep in mind that a truck has zero weight over the rear tires. Even a 302 should at least slightly spin these tires.

When I dropped this engine in, all I did was a short block swap.

Anyway, in the 7 years I've been fighting this problem, I have done the following: ( :redmad: )
Replaced the Comp 9000 mechanical advance with a vacuum advance distributor (No change except better gas mileage :D )
Installed two head gaskets to lower the compression by about 1 point (I thought maybe I had miscalculated the CR) (No change except slightly less power)
Installed a new harmonic balancer (maybe the marks were off) (No change)
Installed 3.50 gears to try to get to a higher power band (I went back to the 2.75's when the 3.50's did NOTHING!!)
Installed the low gear set in the C6 (NO CHANGE!!! Still pinged at all rpm’s and load!!)
Installed a new carburetor (three times!!) (750 vac sec, w/secondary metering block, and adjustable secondary spring assembly) (No change, except better gas mileage)
Opened the exhaust as much a possible (dual 3” )(Sounds better…. :leftright )
Verified the CR when I installed the 2 head gaskets. It should now be at about 8.25:1
Ran 104 octane fuel (It REALLY liked that fuel and I was able to set the timing “slightly” higher)(Hmmmm sounds like a CR problem doesn’t it?!?! )
Used colder plugs (No change)

These reasons, and the fact the cranking pressures are 190 psi leads me to think the cam is wrong. (And the fact that it was a used cam that a guy sold me VERY cheaply… ) :leftright

I have tried EVERYTHING I can think of to fix this pinging problem and everything has been changed except the cam.

Oh, the only good thing about this truck is that I’m getting about 12 to 15 mpg out of it. :D Normally, with the other engine I was only getting 10 mpg (but that was with 3.50 gears).

Keep in mind, this problem is pinging, not lack of power. The lack of power is due to the timing being set so low to keep it from pinging.

Oh, and I have a new 472 in the shop that will have the forged internals (this current engine has hyper’s in it) and all the goodies… in addition to a roots blower once I fab the intake. (I have the blower, just not the intake.) I think that will take care of my lack of power. :rofl: :rofl:

Now, just to install some disc brakes somewhere on this truck… drums on all 4 corners make for “interesting” stopping… :rofl: :rofl:
 

·
Geek w/Gearhead Complex
Joined
·
2,299 Posts
94 Daily Driven 4.6L said:
Oh, and I have a new 472 in the shop that will have the forged internals (this current engine has hyper’s in it) and all the goodies… in addition to a roots blower once I fab the intake. (I have the blower, just not the intake.) I think that will take care of my lack of power. :rofl: :rofl:
that still won't fix the problem with ...well :D
 

·
Registered
Joined
·
1,544 Posts
This is a little beyond my experience but could the crank/cam not be timed right? Missed by one tooth on the chains? I had a similar problem with an OHC v6 and it turned out I'd missed the timimg belt by one tooth.... or maybe three.
 

·
Registered
Joined
·
7,758 Posts
Discussion Starter #10
Actually that is a good thought and I had already checked it. Usually if cam timing is off, you will have no power, but usually not pinging.

But in any case, when I did the last head gasket swap I also replaced a leaking front main seal and while I was there, I checked to make sure the cam was installed "straight up". It was. But that isn't to say that the crank keyway isn't retarded a few degrees.

Somewhere in the back of my mind something whispers... either the crank keyways were retarded in the early 70's to try to meet emissions... or was it the cam, or the OEM timing sprockets!!! Grrrrr, that information must have been "deleted" when some brain cells were, um, uh, "removed".... :rofl:

This cam WILL get degreed in before I button everything up!!! :thumbsup:
 

·
Johnny Five is Alive, TCCoAAC Member
Joined
·
1,614 Posts
How many miles on those heads? they sure do have some black intake ports, You sure your not dumping to much fuel down its throat ?
 

·
Registered
Joined
·
7,758 Posts
Discussion Starter #12
Oh yeah, I'm sure it was running rich. Even though I had it adjusted for pretty good gas mileage It was still running rich with the timing set to 4. :leftright

There's probably only about 15 - 20K miles on this engine. It just never ran right from day one. (And you have to remember that a carb'd engine is a lot harder to get the mixture right through all rpm ranges... I hate carbs!! Give me EFI any day of the week!!)
 

·
Registered
Joined
·
7,758 Posts
Discussion Starter #14
Nope, flat tops with the "medium" combustion chamber heads (D3VE). :D

If I calculated it right, I should have been in the ballpark of 9.25:1. :D

Anyway, I just pulled the cam and a lobe was rounded off. The eighth lobe (from the front) was wiped!!! (Someone want to look that up and tell me which valve on which cylinder that lobe opens? I didn't pay any attention to when I was pulling out the lifters… and I’m not in the mood to research it… :leftright ). Anyway, the valve was barely opening. :redmad:

I'll bet I wiped the valve the first day I fired the engine. :mad:

Oh well, at least the new cam has all good lobes… :D
 
1 - 14 of 14 Posts
Top