Rebuild vs. Remanned

[Joopin]

Heres another issue I just found out about... Reliability of the stroker.
I was talking to a buddy of mine that races motocross, and he said when he strokes the engines in his bikes, the reliability goes down. I guess the life of the engine is shortened. He wasn't sure if it will happen to this engine, but he said since it's my daily driver I should find out if this is a factor to think about. Does anyone know? I may just call a place that sells those stroker kits and ask them too.

 

[ecor]

80 CJ7 Laredo in NJ for sale

Hesco and jakes racing engine both say that the stroked 4.0 is a reliable engine when compete. They say that the only other motor that it compares with when stroked is the 350. Neither of them really seem to experience shortened life span. In motorcycle motors stroking makes an unstable motor more unstable.

 

[Joopin]

Well I just got off the phone with Accurate Power, one of the companies that make a stroker kit. They told me that the only thing that is less "reliable" than the stock 4.0 is that the pistons travel at a longer distance and putting more miles on the rings. BUT he said that this is the exact amount of wear that a 4.2 would get cause the crank is the same which means the stroke is the same. So that being said, I would get the same # of miles from my 4.0 stroker to as a brand new 4.2 258.
He also said that one of the guys there drives a 4.0 stroker everyday, 90 miles to work and his has been fine. Looks like you were right ecor, not that I doubted you!

 

[Snitty]

i dont know how much lift i have, i want to know

what you are basically doing is putting the 258 internals in a 4.0 block, with the technology of a 4.0.... the life should not be any less than it would be with a 258.... though.... a longer stroke does put more stress on the connecting rods and cylinder walls... when one cylinder is pushing down, that will be pushing another cylinder upward.... but since the crank will be out at a greater distance perpendicular to the stroke, it will be pushing more horizontal in the cylinder wall... and with the added power from the 4.0's tech, and the increased displacement from the larger bore... it pushes at this horizontal much more than it does in the 258... still not TOO much of a problem to worry about.

joop... another thing you might think about for more power is getting the block decked... there will be about 1/32 to 1/16 inch left in the block for quech height at TDC from the difference in parts... that means that the piston will no come up ALL the way to the top of the block... which allows one of two things for you... you can get high dome pistons which can fit because of that... or you can deck the block... both for higher compression, which equals more power.... but then.... more power from compression equals more strain on the internal parts....

you can also get higher compression from a thinner head gasket... though... not only does high compression put more strain on the internals... you may also have to run pump gas.... ask your mechanic what he expects the final compression ratio to be.... if it is anything higher than 9.5-10:1.. then you may have to run a higher octane gas... but if your injectors are up to par, then you shouldn't have a problem...

one last thing when dealing with compression... platinum plugs are an enemy to high compression... they are often associated with detonation.. which is bad...

 

[Joopin]

wouldn't "decking the block" be the same as Shaving the head? The pistons are closer and the compression is increased. I don't think I'll be doing any of that on this engine. Maybe if I were racing it... the power increase from the stroker will be more than enough.

Oh and I don't think I've ever bought platnum plugs... so why start now!

 

[skyjeeper]

i actually wasn't aware that the 4.0's don't have a pcv valve ( only dealt with the 4.2's ).

how does that work? i can't see how. if you backfire you're going to pressurize the case.

 

[Snitty]

there are two ports on the 4.0 cover... one for intake of fresh air to the crank, and one for removal of air from the crank... if in good condition, it will allow great ventilation

 

[rubicon]

Hey joopin, check out speedomotive.com. Their price is $675 for the stroker kit. Sounds pretty reasonable. They can also balance it for a
reasonable price. I've used their parts before, with good results.

 

[Joopin]

Thanks rubicon, I'll check it out... thats half the price of the other kits!

 

[redrooster]

You mentioned swapping cams earlier inthe thread. What cam are you going with and why? The reason I ask is that getting too dramatic with the cam can mess up the vacuum of the engine and cause issues with the fuel injection. That was one problem I had when putting GM fuel injection on my 360. The computer kept reading low manifold vacuum which is commonly associated with a radical cam. We had to program two dozen chips before we got it right.
Just thought I would throw that out there.

 

[skyjeeper]

i guess where it's FI you don't reall have to worry about the backfireing as much as a carb. so the pcv valve isn't really necessary.

thanks
derek

 

[Snitty]

you want a cam with a good strong idle... i have a lot of cam recommendations for the amc motors