boat vs car engine
12-04-2003 | 01:54 PM
#13
MarineKinetics
Joined: Oct 2002
Posts: 942
Likes: 5
From: Rochester, NY
Crazyhorse,
JMHO but .022 top gap seems "snug" for a forced induction marine engine. Thats .0048" gap per inch cylinder bore. These numbers are from JE installation guidelines.
High-Perf. Street-Strip Bore x .0045"
Street Moderate Turbo/Nitrous Bore x .0050"
Late Model Stock Bore x .0050"
Circle Track / Drag Race Bore x .0055"
Nitrous Race Only Bore x .0070"
Blown Race Only Bore x .0060"
Bob
JMHO but .022 top gap seems "snug" for a forced induction marine engine. Thats .0048" gap per inch cylinder bore. These numbers are from JE installation guidelines.
High-Perf. Street-Strip Bore x .0045"
Street Moderate Turbo/Nitrous Bore x .0050"
Late Model Stock Bore x .0050"
Circle Track / Drag Race Bore x .0055"
Nitrous Race Only Bore x .0070"
Blown Race Only Bore x .0060"
Bob
12-13-2003 | 09:15 PM
#14
Registered
Joined: Feb 2002
Posts: 1,296
Likes: 1
From: LaPorte IN.
end gap on my 598" project??
So in my case with a 4.600 bore JE pistons naturally aspirated would it be smart to use their recommendation for Street Moderate Turbo / Nitrous and set the top ring at bore X .005" (.023) and the second ring at bore X .0055" (.025")? Is that still slightly to tight on top? It sure would be nice if JE would list some marine applications on their end gap table. I guess us boaters are still only a small percentage of the racer industry. Thanka for the opinions in advance!!
Craig
Craig
12-13-2003 | 10:33 PM
#16
Platinum Member
Joined: Sep 2001
Posts: 5,769
Likes: 150
From: tn
Puder,
Ring heat closes the end gap.
Cylinder sleeve heat opens the bores which opens end gap.
Problem is, the ring heat is transferred to the cylinder liner and it is then absorbed into the cooling water.
While lack of coolant will indeed allow the liners to get hot and grow, the rings heat more quickly than the liners, and the gap closes. If the gap completely closes, the rings try to lock up in the bore. At a minimum, this scores the cylinder walls. At worst, the rings try to seize up and while there is plenty of piston meat to push the rings UP the bore, when the piston tries to some DOWN, it rips the top of the piston off (usually partially, not completely which allows the ring to peel out and lose tension). New parts will be required...
Ring heat closes the end gap.
Cylinder sleeve heat opens the bores which opens end gap.
Problem is, the ring heat is transferred to the cylinder liner and it is then absorbed into the cooling water.
While lack of coolant will indeed allow the liners to get hot and grow, the rings heat more quickly than the liners, and the gap closes. If the gap completely closes, the rings try to lock up in the bore. At a minimum, this scores the cylinder walls. At worst, the rings try to seize up and while there is plenty of piston meat to push the rings UP the bore, when the piston tries to some DOWN, it rips the top of the piston off (usually partially, not completely which allows the ring to peel out and lose tension). New parts will be required...
12-14-2003 | 02:26 PM
#17
Registered
Joined: Jan 2001
Posts: 3,140
Likes: 0
From: Holland MI
F-31, the new school of thought on a larger 2nd-ring gap concerns the ability of air passage through that gap. If the second ring has a tighter gap than the top ring it causes a restriction in the airflow between the top and second ring, reducing the sealing effect of the top ring. Pressure differential is what causes ring sealing. The greater the pressure differential, the greater the sealing effect.
12-14-2003 | 05:35 PM
#18
Platinum Member
Joined: Dec 2002
Posts: 15,270
Likes: 21
From: Burlington, VT
This is the answer Back4More gave in another tread about the difference between automotive crate engines and marine, I thought it was pretty good and clear.
The thread;
http://www.offshoreonly.com/forums/s...threadid=61488
The thread;
http://www.offshoreonly.com/forums/s...threadid=61488
Originally posted by Back4More
Blocks run colder and pistons run hotter....and with a blower on top even hotter. More clearance between piston and cylinder...ring ends get more clearance too Blower pistons are a must with that much power expected out of it...and a high quality set of rings too.
More clearance in the rod bearings for oil flow to remove heat from the bearings. Re balancing the rotating assy...If its anything like the ZZ502 it will rattle it's self to death in no time.
If your looking for a 1000hp blower motor you better plunk down the cash for top of the line internals...not to mention a beefy aftermarket block...There is no such thing as a cheap marine blower motor making 700+hp.
I not slamming this bad assed crate motor, but it is not for powerboats...I read alot about people blowing up the 502s running them at the track. I know nothing about detailed marine engine building but learned a bit while having mine built.
Oh, and we did'nt even talk cams and valve train yet....
Blocks run colder and pistons run hotter....and with a blower on top even hotter. More clearance between piston and cylinder...ring ends get more clearance too Blower pistons are a must with that much power expected out of it...and a high quality set of rings too.
More clearance in the rod bearings for oil flow to remove heat from the bearings. Re balancing the rotating assy...If its anything like the ZZ502 it will rattle it's self to death in no time.
If your looking for a 1000hp blower motor you better plunk down the cash for top of the line internals...not to mention a beefy aftermarket block...There is no such thing as a cheap marine blower motor making 700+hp.
I not slamming this bad assed crate motor, but it is not for powerboats...I read alot about people blowing up the 502s running them at the track. I know nothing about detailed marine engine building but learned a bit while having mine built.
Oh, and we did'nt even talk cams and valve train yet....
