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I dropped off my 317 heads at the machine shop yesterday for a valve job, hot tank, and milling. I haven't yet decided on how much to mill these and my main concern is ptv clearance. The block is a 6.0 lq4 that was decked .010 I believe. Using stock gm gaskets, already ordered 7.4 pushrods and beehive springs. The cam is a summit 8713r1 cam.
Flat tops with stock 317 heads (stock LQ9 setup) will give you 10.1:1.
The .010 decking will raise that to 10.39:1.
Which fuel will you be running?
91 is the highest here in California where I live so I’d like to stick with that.
What’s the highest compression I can go safely on 91? Sounds like I could probably just have the machine shop check them for “true” and I’d still have decent compression with no milling?
Just to be safe, I would not go much higher than what I stated above just in case the 91 ain't quite there.
You can do 87 with 10:1 with the later 5.3 engines pretty easily. I would say not more than 11.5:1 with 91 just to be safe.
Just to be safe, I would not go much higher than what I stated above just in case the 91 ain't quite there.
You can do 87 with 10:1 with the later 5.3 engines pretty easily. I would say not more than 11.5:1 with 91 just to be safe.
So you would stick with no milling (because of the .010 decking)? And with this setup, I would not run into any ptv issues, correct?
Ok, just talked with the machine shop today. I was hoping to bring them the assembled short block so they could measure ptv clearance and determine how much the heads can be milled safely. Unfortunately, they are so busy right now that they can't take on any more work, and there are no other machine shops in my area.
So, now I'm really hoping someone can chime in if they have a similar setup. At this point, I'll mill less than desired if it means I will for sure not have any clearance issues. I just wanted to bump the compression up a little bit, nothing crazy. (Block is decked less than .010). Specs below:
I'm in the Bay Area, Ca. I posted over on performancetrucks.net too and got some good feedback on the topic. Went ahead and told the machine shop to mill .030. This should give me somewhere around 10.5:1 compression I believe (which is good considering we don't have anything higher than 91 octane).
Got my heads back from the machine shop and am currently measuring pushrod length. I used 2 methods: comp cams checker and for the second method, I set the rocker and pushrod to zero lash, then counted the turns it took to snug up the rocker bolt.
Using the pushrod checker, I measured 7.3”.
Using the second method, I measured 7.365”.
In both methods, I accounted for 0.075” of preload on my LS7 lifters. Is this the correct preload I should be using?
So, what length pushrods would I use? I have 7.4s and I’ll be returning those since they’re too long.
I usually shoot for .100 preload on replacement LS7 lifters. I’ve found it’s quieter than .075. Overall plunger travel is around .200 for an LS7 lifter, and I’d rather go deeper than shallower for less noise and better performance.
I usually shoot for .100 preload on replacement LS7 lifters. I’ve found it’s quieter than .075. Overall plunger travel is around .200 for an LS7 lifter, and I’d rather go deeper than shallower for less noise and better performance.
so 7.365 plus an additional .025 of preload (total of .100) will put me right at 7.39.
7.3 plus the additional .025 will put me at 7.325.
could I just toss in the 7.4’s I already have and call it a day or do I need custom length ones?
08-30-2022, 11:43 AM
317 Head Milling - Urgent 
