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I bought a used "running" LQ4 a few months back for my 1989 C1500 project. Just started tearing it apart last weekend and im not pleased by what i have found so far. my plans originally were to run stock lq4 bottom end with the tick performance SNS stage 3 cam, 243 heads, stock rockers with the trunion upgrade, and the other necessary valvetrain components. As i was taking the #6 piston out, i noticed it had spun a rod bearing.it ground down the crank a good little bit. enough to where my machinist said it is trashed. Also, there was some pretty bad rust in the #1 cylinder wall. i took the block to the machinist to see about honing the cylinders to get the rust out and the cylinders ended up having to be bored out .030". So they are ordering me new pistons to fit the bore. (stock dished style pistons, just bigger) and are putting the on my stock rods for now. also they are checking everything else in the motor to make sure everything else is ok. My main question is, ive been doing some research on 408 stroker builds. what all is required other than the 4.030" bore and the 4" stroke crank?will my stock piston rods work? How much HP will i gain by adding the 4" stroke crank over a stock crank with the bigger bore? now the plans for the build are as follows:
LQ4 block: 4.030" bore
243 heads stock other than port
SNS stage 3 cam
Stock rockers with trunion upgrade
stock style dished pistons
and need to decide on stock size crank or 4" stroke crank.
how much power difference will i get with the 4" crank?
Peak hp will be about the same and will peak a tad sooner, but you will gain more torque down low and midrange. IMO it's not worth it unless you have a HCI that can take advantage of the extra cubes
If you already bought stock pistons, you are SOL - the stroker kit isn't just the crank, it's a crank + corrected length rods + pistons with a different compression height.
Summit has new 3.622" cranks for a few hundred bucks..
If you can get the machinist to swap the pistons for flat-tops and put the engine back together with 243 heads, I hear that will help bump compression & therefore torque a bit vs a stock LQ4 without the expense of a stroker.
If i stayed with the stock crank, I had planned on keeping the dished Pistons and milling the heads a little to bump the CR up a little. I figured with stock lq4 bottom end .030" over, milled and ported 243s and the SNS stage 3 I would be over my goal witch is around 400rwhp. I don't want a race truck. I'm still going to dd it. Just want the extra power when I take it to the track.
I honestly would try to cancel the order on the dished pistons.
I sell a 4.030" bore Wiseco piston with valve reliefs that will work with stock rods and stock stroke crankshafts. The valve reliefs on the pistons will allow you to mill the heads and retain very safe p to v clearance and gain the most compression possible to help raise your HP/TQ figures. That cam loves added compression and will really shine if you go this route.
I would mill the heads .025" and run a .040" Cometic gasket. With the -3cc 4.03" bore Wiseco pistons, 60cc combustion chambers (result of .025" milling) and .040" gasket you will have 11.7:1 compression which will work beautifully with the SNS Stage 3 camshaft.
I honestly would try to cancel the order on the dished pistons.
I sell a 4.030" bore Wiseco piston with valve reliefs that will work with stock rods and stock stroke crankshafts. The valve reliefs on the pistons will allow you to mill the heads and retain very safe p to v clearance and gain the most compression possible to help raise your HP/TQ figures. That cam loves added compression and will really shine if you go this route.
I would mill the heads .025" and run a .040" Cometic gasket. With the -3cc 4.03" bore Wiseco pistons, 60cc combustion chambers (result of .025" milling) and .040" gasket you will have 11.7:1 compression which will work beautifully with the SNS Stage 3 camshaft.
I sell those pistons for 685.00 dollars shipped.
Let me know if you're interested!
Dang. They're already paid for and on the connecting rods. So I'm gonna have to run them.
But what will my estimated CR be with the 4.030 dished Pistons, with stock 243 heads and stock head gasket? Would I be able to safely mill the heads any for more compression with the dished Pistons?
If there are no valve reliefs in the pistons, you really have no room to mill the heads with that camshaft and retain safe p to v clearance.
They have the exact same dish as the stock Pistons. I didn't think I'd be able to mill them unless I fly cut the Pistons. But what would the CR be if I don't mill them?
If you already bought stock pistons, you are SOL - the stroker kit isn't just the crank, it's a crank + corrected length rods + pistons with a different compression height.
Summit has new 3.622" cranks for a few hundred bucks..
If you can get the machinist to swap the pistons for flat-tops and put the engine back together with 243 heads, I hear that will help bump compression & therefore torque a bit vs a stock LQ4 without the expense of a stroker.
that's what I'm doing......030 overbore with ls2 pistons
Now with a lsa supercharger and 2.45 pulley. ...****** ripps
brand new gm lsa unit complete with p.o.s spring isolator, hence the upgrade of the 2.45 pulley, might as well since I'm in there, ..... just beware if you purchase one of these new, it still may have that crap spring plastic isolator, literally lasted about 150mi then that's when I heard the funky noises.........gotta nice solid one now with a griptech 2.45 pulley. ...whatta difference. ...this is on a lq4 that got bored. 030 with flat top ls2 pistons and 64cc ls3 heads , so it's a higher than average compression 370......
Last edited by dawgs74; Mar 29, 2021 at 05:28 PM.
Reason: Auto spell mistake
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LQ4 Build options? 
