rod knock

[evildky]

well my junkyard motor is already showing signs of fatigue, I have a rod knocking for a split second at cold start, so I figure I may as well slap together a new short block, and maybe get some custom forged pistons, my question is would I be ill advised to use flat tops? I was playing with the engine calculator and flat tops with the P90 yield an 8 to 1 with the 2mm gasket ? this sounds like safe boost compression to me? and the extra compression should help the turbo spool up a bit quicker ? no? anyone try this or at least have more understanding to explain to me why or why not ?

[Guest bastaad525]

you can definately do it. A couple guys run higher compression motors and it works okay. And as far as acceptible compression for any turbo setup goes... it really comes down to your fuel and spark management more than anything. I've seen or read of guys running 10psi or more of boost on 10:1 or greater compression engines w/o problems, but they're running high end fuel control like TEC or some other system. Most newer factory turbo motors are in the 8 to 9:1 range. For the moderate increase in compression you are talking about from dishtops to flattops, you should be able to get away with it on the stock EFI with maybe a little help, depending how much boost you want to run. A good I/C is very important. Extra fuel will most likely be necessary to keep it safe as well, think bigger injectors or more fuel pressure if you dont have one or the other already. And possibly a boost-timing-retard device. It can definately be pulled off safely w/o too much in the way of add-ons, and off boost throttle response, as well as spoolup, and torque will all be noticeably improved.

[Guest Cronic]

Do you really need the turbo to spool any faster?? I generally love high boost, and low compression. However, 8:1 is certainly boost friendly.