Lq4 build
Thread Starter
Teching In
Joined: Sep 2015
Posts: 27
Likes: 0
Lq4 build Lq4 with flat top pistons no valve relief, 6.100 scat rods, stock crankshaft and Eps (PatG) 23x/23x cam. I have a set of used stock 243 heads I brought about 3 years ago for a project but never installed. They will probably see a valve job with new Springs. How much can I mill without fly cutting?
TECH Junkie
Joined: Dec 2012
Posts: 3,612
Likes: 1,324
From: Iowa
No numbers for lift?
It would also be good to know what the piston deck height is. Are they even with the deck? do they stick out of the hole, or stay below? what thickness head gasket. Lots of variables here you're not accounting for.
It would also be good to know what the piston deck height is. Are they even with the deck? do they stick out of the hole, or stay below? what thickness head gasket. Lots of variables here you're not accounting for.
Ok, most 230's cams are going to be fine. A few considerations:
Lower LSA means more overlap, which means higher chances of hitting. Also if there's a lot of advance ground in that makes intake valve more likely to hit. Example is say a 110+4 I'd be worried. 113+2 probably very safe.
23x isn't necessary enough to do calculations. Big diff between 231 and 239.
FWIW, I'm running equivalent to 232/240 112.5+2 without flycut. 041 head gaskets
But I also run aftermarket heads with raised valves.
If you're not sure, install a solid lifter and do the clay test
Lower LSA means more overlap, which means higher chances of hitting. Also if there's a lot of advance ground in that makes intake valve more likely to hit. Example is say a 110+4 I'd be worried. 113+2 probably very safe.
23x isn't necessary enough to do calculations. Big diff between 231 and 239.
FWIW, I'm running equivalent to 232/240 112.5+2 without flycut. 041 head gaskets
But I also run aftermarket heads with raised valves.
If you're not sure, install a solid lifter and do the clay test
Teching In
Joined: May 2020
Posts: 2
Likes: 1
So So maybe it’s been discussed but I am running a completely stock LM7 with 862 heads with Flat top pistons and no reliefs. Cam is a 223/226 .600 and .600. Not sure if it will have interference or not by the time you put timing in or pull timing out. I read what gray z said about TDC but if you add or subtract timing wouldn’t it make a difference too?
