Lq4 build some ? And advice needed
10-04-2010, 04:18 PM
#1
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Apr 2008
Location: Clinton, Ok
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
Lq4 build some ? And advice needed Ok well I got a free lq4 block a while back but it had a busted rod and piston (block checks ok) now I'm plannin on a decent street car that runs in the 11s.
My questions are
1. I have several 5.3 rods lying about, are they the same as the 6.0s?
2. I'm having to bore .030 and needing pistons but not needing forged(hyper possibly)something like these?http://www.summitracing.com/parts/STL-H1129CT-75MM/ just to go on the stock rod with no mods
3. I'm using 243 heads that are ported&polished, I'm lookin for around 11:1 compression what pistons(^) or milling on the heads should I do.
I'm also looking (hopefully) for 500whp but E.T more than anything when I do run it. I'm running a 3000 stall. Also cam thoughts would be a help if you have suggestions. Thanks.
My questions are
1. I have several 5.3 rods lying about, are they the same as the 6.0s?
2. I'm having to bore .030 and needing pistons but not needing forged(hyper possibly)something like these?http://www.summitracing.com/parts/STL-H1129CT-75MM/ just to go on the stock rod with no mods
3. I'm using 243 heads that are ported&polished, I'm lookin for around 11:1 compression what pistons(^) or milling on the heads should I do.
I'm also looking (hopefully) for 500whp but E.T more than anything when I do run it. I'm running a 3000 stall. Also cam thoughts would be a help if you have suggestions. Thanks.
10-05-2010, 12:07 PM
#3
Those pistons are intended for LQ9 and LS2. LS2 was 10.9:1 with 243 heads. Figure in your over bore, you'll be at 11.0:1 with no head milling.
LM7 rods are the same as LQ4 rods, assuming both are in the same range of years. Later rods got beefed up. Just take one of each to your local automotive machine shop. The shop manager should be an older guy, graying hair, well practiced at seeing significant differences in similar parts.
LM7 rods are the same as LQ4 rods, assuming both are in the same range of years. Later rods got beefed up. Just take one of each to your local automotive machine shop. The shop manager should be an older guy, graying hair, well practiced at seeing significant differences in similar parts.
10-05-2010, 04:47 PM
#4
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Apr 2008
Location: Clinton, Ok
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
So those pistons won't work on a lq4 rod? If not can you point me to some proper 1s? I thought the only differences where the wrist pins(floating on ls2 and press on lq4?) which those say press in?
10-05-2010, 05:17 PM
#5
Correct, however, it's not a problem.
First, there are no alternatives for pistons. Second, most SpeedPro hypers allow you to do pressed or floating. If these require float, then it's still not a problem. It's simply a matter of drilling a small oiling hole in the exact center of the very tip of the small end, then adding a slight chamfer to each hole. Then the shop will hone the small end so the pin can float. No bronze bushing required, which is good, since modifying non-float-intended rods to take bushings tends to weaken the small ends too much for high rpm use.
I've done this drill-and-hone mod hundreds of times, and driven same myself for better than 70K miles.
Plus, even if the drill-and-hone is necessary, it's still less $ than buying any other pistons.
If the pistons include pin locks, then the d&h is an option. Your machinist can determine if it's necessary.
First, there are no alternatives for pistons. Second, most SpeedPro hypers allow you to do pressed or floating. If these require float, then it's still not a problem. It's simply a matter of drilling a small oiling hole in the exact center of the very tip of the small end, then adding a slight chamfer to each hole. Then the shop will hone the small end so the pin can float. No bronze bushing required, which is good, since modifying non-float-intended rods to take bushings tends to weaken the small ends too much for high rpm use.
I've done this drill-and-hone mod hundreds of times, and driven same myself for better than 70K miles.
Plus, even if the drill-and-hone is necessary, it's still less $ than buying any other pistons.
If the pistons include pin locks, then the d&h is an option. Your machinist can determine if it's necessary.
10-05-2010, 05:36 PM
#6
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Apr 2008
Location: Clinton, Ok
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
Ok so these will work fine, just a tad bit of basic machining if any at all. also the wrist pin is 0.943 not a .945? they need to be a .945 dont they?
Last edited by velox65; 10-05-2010 at 05:48 PM.
10-05-2010, 05:54 PM
#7
I think the actual spec, which is metric, is more like .9437, and this wouldn't be the first time that SpeedPro rounded down. Look at their LS1 pistons. Stock bore is 3.89764, which should be 3.898, but they list 3.897. I could look it up if I was at my own place, but not here.
Trending Topics
10-05-2010, 06:54 PM
#8
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Apr 2008
Location: Clinton, Ok
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
I'm just saying because on another piston from summit(same brand just non flat top) shows to use the .945. So thats whats confusing me on that.
10-06-2010, 02:25 PM
#9
TECH Apprentice
Thread Starter
iTrader: (9)
Join Date: Apr 2008
Location: Clinton, Ok
Posts: 367
Likes: 0
Received 0 Likes
on
0 Posts
Ok well I think I'm gonna go with stock type dish on a .030 overbore using a gm mls gasket what would be my cr? Also what's the dish on a lq4 piston?
