Quote:
Originally Posted by Father Of Giants
Interesting, I thought that a worn out overflow spring/deformed plastic bushings would cause issues.
Greazer's overflow valve springs are indeed a direct upgrade correct?
|
No. The older MW IP's on the 616/617 and earlier engines had the pressure in the fuel rack regulated by the spring on the overflow valve. The spring operated a ball bearing that stopped flow through the OFV when pressure was too low.
The 60x engines use a different setup and a different lift pump. The lift pump can supply significantly more fuel than the IP can consume. Pressure in the fuel rack is regulated by the drilled orifice in the OFV, the lift pump moves a given volume against that orifice and pressure is a result. When pressure gets too high, the piston in the lift pump "floats" and pumps no more fuel. The plastic piece that warps and deforms is only there to serve as a check valve. The purpose is primarily to prevent air ingress when the engine is stopped, not to regulate fuel pressure. The spring is extremely weak, you can blow throw the valve with no effort. A warped or failed plastic check valve piece may cause some rough starts, but it won't affect power delivery or fuel pressure in the rack.
Greazzer's modded OFV will work on the 601/2/3 IP's without modification (I ran one on my SDL). Not sure about the 604/5/6. Be aware that priming the air out of the system is a major undertaking with the 61x style OFV fitted. The 60x fuel system has no primer handle and is designed for the air to be simply pushed out through the drilled orifice OFV.