Ptv and push rods
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From: Louisiana
Ptv and push rods Gen 3 5.3
gen 4 cross top pistops
243 heads port polished and milled .030
7.4 x .080 wall pushrods
head gasket .050
cam 218/224. 553/.553 110+0
So it was mentioned to me that I need to check my ptv and pushrods length but I wanted to ask if you guys think I will be ok or do I need shorter pushrods or a different cam. I've been running this setup but just recently did the port, polish and mill work
gen 4 cross top pistops
243 heads port polished and milled .030
7.4 x .080 wall pushrods
head gasket .050
cam 218/224. 553/.553 110+0
So it was mentioned to me that I need to check my ptv and pushrods length but I wanted to ask if you guys think I will be ok or do I need shorter pushrods or a different cam. I've been running this setup but just recently did the port, polish and mill work
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Pushrod length does not affect PTV.
That being said, now that the upper valvetrain is now .030 closer to the cam, the lifters still should be within their stroke.
But having 7.375 (commonly available length) pushrods would put things closer to spec.
That being said, now that the upper valvetrain is now .030 closer to the cam, the lifters still should be within their stroke.
But having 7.375 (commonly available length) pushrods would put things closer to spec.
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From: Louisiana
Last edited by Tommy42088; Mar 9, 2023 at 06:34 PM.
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It's kind of a pain to measure for piston to valve clearance. You know what's more of a pain? Rebuilding your engine because someone on LS1Tech made an educated guess and said "Yeah man, you'll be good to go!" and you smacked every valve on start up. Don't cut corners when building an engine. Get a couple of old lifters and disassemble them, stack washers under the inner piston until all the slack has been removed and you can reassemble them. Get a pair of checker springs for the valves. Put some modeling clay on top of the piston ( not Playdoh, it has memory and will spring back slightly when compressed ). Install your checker lifters on cylinder #1. Install your head with a used head gasket. Install checker springs on cylinder #1, along with your pushrods ( the correct ones, 7.375 ). Roll the engine over a couple of times. Remove the head and carefully cut the clay directly through the center of the imprints made by each valve ( top to bottom of the deck, not front to back ). Best to use a plastic razor blade so you don't gouge your piston. Take a pair of calipers and use the depth portion to measure the clay thickness. That's your PTV. That's actually the quick and dirty way to do it, in my opinion. With that said, you're probably unlikely to run into PTV issues with that small of a cam, but the tight(er) LSA warrants checking for sure.
As mentioned, you will probably be fine on PTV with that size of cam and a factory thickness HG. If you have a dial indicator and a degree wheel, you can be a little more detailed on your measurement. But the clay works just fine for a quick job
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Wow that seems kind of hard to do but I'll give it a shot. I didn't realize milling a head 30 thousands over would give me such a headache but I appreciate the input and I'll get the correct pushrods ordered.
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From: Grand Rapids, Michigan
.030 is a pretty large amount, in reality. Anytime you are significantly altering specs it's better to check it and be sure than not check it and have a failure that could have been prevented. That said, since I knew my LS3 was bone stock internally, I had no qualms about installing a BTR Stage 4 LS3 cam without checking PTV. However, when I build my LH6 turbo engine, I'm most definitely going to be checking everything because the block will be decked, the heads milled, and I'll have aftermarket pistons. Even though the cam will be smaller, it's too much of a risk.
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From: Louisiana
.030 is a pretty large amount, in reality. Anytime you are significantly altering specs it's better to check it and be sure than not check it and have a failure that could have been prevented. That said, since I knew my LS3 was bone stock internally, I had no qualms about installing a BTR Stage 4 LS3 cam without checking PTV. However, when I build my LH6 turbo engine, I'm most definitely going to be checking everything because the block will be decked, the heads milled, and I'll have aftermarket pistons. Even though the cam will be smaller, it's too much of a risk.
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Verdad Gallardo Joined: Apr 2006
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From: Grand Rapids, Michigan
Popping off a couple of valve springs is cake. The tools are pretty cheap, I got mine from BTR. As long as you reinstall everything just as it was removed, you should be fine. I understand you had no issues with the setup previously, but my guess is you never measured PTV then either? What if, for some reason, you had .020 PTV before and it ran great, zero problems. Then you mill your heads .030. You won't be happy with that outcome. If you had measured it before and had, say, .080, you could be pretty sure that you won't have issues with the milled heads. In reference to the machine shop telling you if you'll have problems or not, they can't possibly know where your valves will be located in reference to piston position with any given cam. They'd be no better at guesstimating the outcome than any of us on here. I'm not saying this to berate you for just wanting to toss it together, but I've been on here for 17 years and have seen the results of people just assembling without measuring. I've even scored deals on cylinder heads after someone bent all their valves on startup. It can happen. Is it likely with your cam? Probably not. Is it better to measure anyway? Yes.
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Popping off a couple of valve springs is cake. The tools are pretty cheap, I got mine from BTR. As long as you reinstall everything just as it was removed, you should be fine. I understand you had no issues with the setup previously, but my guess is you never measured PTV then either? What if, for some reason, you had .020 PTV before and it ran great, zero problems. Then you mill your heads .030. You won't be happy with that outcome. If you had measured it before and had, say, .080, you could be pretty sure that you won't have issues with the milled heads. In reference to the machine shop telling you if you'll have problems or not, they can't possibly know where your valves will be located in reference to piston position with any given cam. They'd be no better at guesstimating the outcome than any of us on here. I'm not saying this to berate you for just wanting to toss it together, but I've been on here for 17 years and have seen the results of people just assembling without measuring. I've even scored deals on cylinder heads after someone bent all their valves on startup. It can happen. Is it likely with your cam? Probably not. Is it better to measure anyway? Yes.
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From: Grand Rapids, Michigan
You can test it like that, just be absolutely certain you've stacked enough washers in your checker lifters so there is ZERO slack. Any clearance there will be multiplied 1.7 times due to the rocker ratio, and could give you a false sense of security.
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so when you say put the washers you mean to take apart the bottom of the litfter and put the washers under the lifter and then install the tray? I'm kinda confused on what you mean woth the washer thing. I searched on youtube and didnt see anyone doing the washer thing
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The best, and quickest way is to ditch the clay, get a decent dial indicator and some light tension checker springs. Mount the indicator parallel to the valve stem. As the piston approaches TDC, you simply move/push the valve open farther than the cam lift can, and check the indicator travel for the distance it takes to stop, which happens when it contacts the piston. If the travel you create by pushing the valve open is greater than the lift of the cam by, oh, .100", you should be fine. You're trying to mimic the lift of the cam. Basically lifting the valve open farther than the cam will ever do. Let's say you have a .600" lift cam. Start checking travel about 10°-15° before maximum lift, and check it thru maximum lift, then until youre 10°-15° after maximum lift. If you push it farther open by that .100", or more, you're good to go. No clay needed. If you use very weak checking springs, you won't need a special lifter.
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You guys have given me alot of different options and I'll definitely give one of them a shot, the heads are still at the machine shop but when they get back I'll give it a try and I'll post an update.