Dead cylinder??

bomar76

bomar76

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Re: Dead cylinder??

For the record...this was NOT anything I said...this was a botched quote attempt....

RCSConstruction said:
Quote:
Originally Posted by bomar76

Semi-true...
Plug was fouled, although if not getting fuel, how?

It was sucking oil up past the rings, probably. Might be pretty easy depending on a few factors that if I went into might be construed as disparaging Rapido, and I don't want to do that.
Click to expand...
 
QC

QC

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Re: Dead cylinder??

SuperNova said:
Dodge HEMI with MDS works on this principle to cut FOUR cylinders in such a way as you can't tell it's been done.
Click to expand...
Yeah, you open the exhaust valve during the compression stroke ;)
 
QC

QC

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Re: Dead cylinder??

bomar76 said:
It was sucking oil up past the rings, probably.
Click to expand...
Probably that and the valve guides which is normally burnt, but since 'dere ain't no fire, it just accumulates . . .
 
SuperNova

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Re: Dead cylinder??

QC said:
Yeah, you open the exhaust valve during the compression stroke ;)
Click to expand...
Not true...we actually shut both valves down and close the cylinder completely. The trapped air acts as a spring which the piston compresses over and over. When the piston hits the top of it's stroke and all the air is compressed, the air pressure helps push the piston back down again. This action helps minimize energy loss and make 4 dead cylinders in a v8 engine virtually invisible. Now ask me how we kill 4 cylinders. I will tell you in advance we take out two cylinders in each bank and they are not necessarily front or rear cylinders, some fall in the middle.
--
Stan
 
QC

QC

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Re: Dead cylinder??

Yeah, I understand the stored energy in the compressed gas, but it would seem that you'd get less vibration and less lost energy (heat) by just letting it go . . . Hmmmm. I was concerned I Had that messed up, thanks for straightening me out.

Truck engine retarders (commonly called Jake Brakes) use a similar but opposite strategy, they run the entire compression stroke with the valves closed and then open the exhaust valve at the top to eliminate the "spring" . . . They can develop over 400 "retarding" hp in a 12 liter engine with high tech control available these days.
 
SuperNova

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Re: Dead cylinder??

It's neat the ideas the engineers come up with and how they implement them. I really love what I do-- most of the time:D
 
FreeBeeTony

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Re: Dead cylinder??

You learn something new everyday...........Thanks!
Makes sense now that you explained it..........

"If your intake valve is not opening you can't draw any air in, so the downstroke of the piston just develops a strong suction above it and the upstroke (which would normally be the compression stroke) only serves to alleviate the vacuum it created on the downstroke, thereby creating......NOTHING."
 
R

RCSConstruction

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Re: Dead cylinder??

Just an FYI....
Got the boat back, she sounds great!!! Will take it out this weekend and see if I can pull the rocker stud out....
A word on my motor.
I bought (what was advertised as) a 1996-2000 5.7l VORTEC replacement. Well, it's your standard gm block with vortec heads and hydraulic lifters, no roller cam, no roller lifters. VERY DISAPPOINTED!! I am told Vortec's don't like too much lift on the valves and if this has a RV/performance cam (which I'm told it did when built) that it could be too much for the heads. Possibly the culprit for the pulled stud..
Going to be interesting this summer...
 
MikDee

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Re: Dead cylinder??

FreeBeeTony said:
You learn something new everyday...........Thanks!
Makes sense now that you explained it..........

"If your intake valve is not opening you can't draw any air in, so the downstroke of the piston just develops a strong suction above it and the upstroke (which would normally be the compression stroke) only serves to alleviate the vacuum it created on the downstroke, thereby creating......NOTHING."
Click to expand...

As I said earlier in this thread, I knew exactly the concept Supernova meant, because "I've seen something like this before, a few yrs ago at the marina, it happened to be a big block chevy then, no suction?, no compression?, a dry dead cylinder, just a broken valve spring, a simple fix." Whether the valves are hung open just abit (by a broken valve spring), there's no compression, & vacuum, Or, with both valves locked closed, the vacuum, & compression stroke, cancel each other out.

One more item, I think the rocker studs on the Vortec heads are too big a diameter to use the original old style screw in studs, But maybe they can be pinned in place with roll pins thru the stud, & stud boss, like they used to do years ago as an alternative method. I don't see why at least this last method can't be applied?

Also, IMO, a pulled stud would be because the valves were adjusted too tight!, leaving the press in stud the weakest link in the chain.
 
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TilliamWe

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Re: Dead cylinder??

No RV cam lifts too much for a set of Vortec heads.
But that is disappointing that it doesn't have a roller cam. Vortec engines don't have roller lifters from the factory, though. So you weren't cheated there.
 
R

RCSConstruction

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Re: Dead cylinder??

TilliamWe said:
Vortec engines don't have roller lifters from the factory, though. So you weren't cheated there.
Click to expand...

Interesting.. Did Volvo penta use roller lifters? The guy measured a pushrod to confirm it was an older style cam and not roller. I figured a roller cam needed roller lifters..
Thanks for the info. I don't feel so bad but I suspect I will pull another stud and have to either swap cams or buy studs and do that....


Is anybody familiar with these spring kits that claim .550 lift without any machining or need for screw-in studs?. Comp cams "beehive" style? That may work??
 
R

RCSConstruction

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Re: Dead cylinder??

MikDee said:
As I said earlier in this thread, I knew exactly the concept Supernova meant, because "I've seen something like this before, a few yrs ago at the marina, it happened to be a big block chevy then, no suction?, no compression?, a dry dead cylinder, just a broken valve spring, a simple fix." Whether the valves are hung open just abit (by a broken valve spring), there's no compression, & vacuum, Or, with both valves locked closed, the vacuum, & compression stroke, cancel each other out.

One more item, I think the rocker studs on the Vortec heads are too big a diameter to use the original old style screw in studs, But maybe they can be pinned in place with roll pins thru the stud, & stud boss, like they used to do years ago as an alternative method. I don't see why at least this last method can't be applied?

Also, IMO, a pulled stud would be because the valves were adjusted too tight!, leaving the press in stud the weakest link in the chain.
Click to expand...

I see screw in stud kits for the vortec. Measure 3/8ths... I dunno, I will find out.

I guess the weakest link in this case was good news for me. The thought of tearing into my motor was making me ill..
Thanks for the info.
 
SuperNova

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Re: Dead cylinder??

I thought all V8 vortec's were roller cam equipped. I think you can buy a set of L31 vortec heads pretty cheap from GM already assembled...under $500 for a pair, I think. Also. another thought on your stud pulling out. If the rockers were adjusted too loose, the hammering action when the valvetrain took up the slack could have worked like a slide hammer at pulling the stud out. If the valve train were too tight, in my experience, it usually bends the pushrod as well as loosening the stud.
--
Stan
 
J

John_S

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Re: Dead cylinder??

RCS,

Very unlikely you have a cam lift problem. You need to find the specs for your RV cam and not make assumptions on "standard" vortec cam. There is no such thing as a Vortec cam.

Marine flat hyd lifter cam has .394 I and .404 E lift.
Marine roller hyd lifter cam has .431 I and .450 E lift

Both make the same hp. The flat has longer duration than roller.

Most SBC torque cams designed to run 5K or less rpms will have higher lift on the exhaust valve to help compensate for restrictive exhaust systems. You indicated flat based lifters and it was an intake stud pulled.
 
R

RCSConstruction

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Re: Dead cylinder??

imported_John_S said:
RCS,

Very unlikely you have a cam lift problem. You need to find the specs for your RV cam and not make assumptions on "standard" vortec cam. There is no such thing as a Vortec cam.

Marine flat hyd lifter cam has .394 I and .404 E lift.
Marine roller hyd lifter cam has .431 I and .450 E lift

Both make the same hp. The flat has longer duration than roller.

Most SBC torque cams designed to run 5K or less rpms will have higher lift on the exhaust valve to help compensate for restrictive exhaust systems. You indicated flat based lifters and it was an intake stud pulled.
Click to expand...

Thanks for the info iJohns. Your input in this thread has been very helpful.
I got my mind made up that if/when I pull another stud, I am taking the heads off and getting them screw-studded, change the cam/pushrods/lifters back to roller and call it done. Already called machine shop. 100.00 if I supply the studs. One day turnaround. Shouldn't be more than a week of downtime.....haha or three weeks or 2 months.. lol:cool:

This will/should keep me going for years to come.
 
J

John_S

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Re: Dead cylinder??

My recommendation is: if the rv cam is the wrong match for your engine/app, just buy one that is. A new flat based hyd cam and lifters will be around $150 vs $600 to convert to roller. (steel cam, roller lifters, push rods, spyder and retainers, timing gear/chain, cam retainer plate, special fuel pump rod or elec fuel pump, and possible distributer gear) For our boat engines, the main advantage of a roller is less cam wear. While that is true, I wonder if the reliability of the roller lifters are less than the flat based. I've seen a few posts on roller lifter problems.
 
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