Quote:
Originally posted by cashizslick
Ls Vtec is a bad idea, you would be better off getting a regular B18C1. Ls Vtec is an unreliable setup, because when the Vtec head is mated to the Non-Vtec block, the R:S of the engine is significantly lowered.
|
If a ls/vtec or crv/vtec is built right it can be pretty reliable but it all depends on the quality of the parts you use, the measures taken in the buildup, and the competence of the builder. If you just slap a VTEC head on a B20 bottom end, don't be surprised if the engine does not last. In order to have a reliable B20 VTEC, there are a few things that need to be done:
1. Upgrade pistons and rods. Stronger and lighter units are needed to withstand higher RPMs. Also, the pistons need larger valve cutouts to accommodate 33mm VTEC intake valves (non-VTEC intake valves are 31mm).
2. Add oil squirters. These are present on VTEC engines but not non-VTEC engines. They help cool pistons and improve cylinder lubrication. These are important when it comes to improving engine longevity at high revs.
3. Upgrade to a GSR oil pump. Because you now have oil squirters, the VTEC mechanism, and better cam oiling, you need to be able to feed it. Upgrade your pump, as non-VTEC pumps are not up to the job.
4. Resleeve the block to withstand the higher rpm's or boost that the b20 block is not used to.
As for rod ratio, consider that the B18C5 really does not have a great rod ratio. Like the GSR, it is only 1.58:1. A stock LS or B20 bottom end has a rod ratio that is 1.54:1. This can be improved to 1.58:1 by using a B18C crank. This destrokes the engine by about 50cc. But you will still have over 1900cc displacement - quite a bit more than a B18C5. A B17A crank will give you a 1.74:1 rod ratio. This would be very reliable and GREAT for turbo use. But it will lower displacement to only 1.8 liters. A B16A crank will give you an even better 1.85:1 rod ratio but will lower displacement to 1.7 liters. For allmotor use, I would stick with either the stock B20 crank or go with a B18C crank. If the engine is built competently with good quality internals and the required upgrades, there is no reason why it shouldn't be reliable. B16 and B17 cranks destroke the engine to the point that alot of the advantages of going B20 are negated. I would use one of these combinations for forced induction only. Not that they couldn't be used allmotor. There would just be little point.