Compression too high
Road Captain
Joined: Feb 2014
Posts: 607
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From: Arizona
Impact 560. It's a 2003 Sportster.
The new motor has Hammer's 100hp package. It has everything listed here in Hammers sample invoice.
The new motor has Hammer's 100hp package. It has everything listed here in Hammers sample invoice.
At 11.00:1 it's showing a 190psi cranking pressure
Edit: also showing the HP @101 with the 11.00:1
Last edited by snatchcat; Jan 26, 2025 at 11:33 AM.
Grand HDF Member
Joined: Nov 2012
Posts: 4,994
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From: Newport,TN area
pistons, 10.5 cr, and 61 CC Chamber.....
T.
Road Captain
Joined: Feb 2014
Posts: 607
Likes: 243
From: Arizona
I agree with whoever said "something isn't right"
Grand HDF Member
Joined: Nov 2012
Posts: 4,994
Likes: 2,081
From: Newport,TN area
Is it "off by one tooth" ?
good luck,
T.
Road Captain
Joined: Feb 2014
Posts: 607
Likes: 243
From: Arizona
Can You be off a whole tooth without hurting something? It's been a good 25 years since I cut new key ways to move Sportster cam timing around. I don't have that great a recall anymore haha. Everything is a new adventure now
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HDF Community Team
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From: Santa Ana, CA
Thread Starter
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HDF Community Team
Joined: Aug 2019
Posts: 1,843
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From: Santa Ana, CA
Last edited by OCSpringer; Jan 26, 2025 at 12:56 PM.
Road Captain
Joined: Mar 2009
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10.5:1 with the 48 degree IVC of the IMPACT 560 cams, the 3.600 bore x 3.813 stroke of the 1275, and the 6.926 rod of the XL, works out to 198.5psi, at 64 degrees and sea level.
Keep in mind that this is not the first 100hp package HP has ever sold. That package was very carefully designed and tested more than 12 years ago, it's an enormously popular package, and they've got literally hundreds of happy customers running that package in all corners of the globe. The package is well proven. An issue like this is an anomaly, not some fundamental design issue.
There's a reason behind it, it just has to be found. And that ain't always easy. Like I said, if it was mine, I'd start by taking a close look at the cam timing. That's an easy mistake to make and this is the exact symptom it causes.
If all the marks are right, I'd check to make sure the pinion key hasn't sheared and allowed the pinion gear to move. This is something else that'll screw up the cam timing.
And I'd make sure all the lifter preloads are correct. A short pushrod will pull back the IVC and raise compression, although it'll also make a racket. So if the valve train is quiet, this is unlikely.
I'd also double check the compression tester against another one.
I haven't spoken with HAMMER Dan about this. But my guess is that he's already double checked all the records he keeps on all the builds. He keeps every detail of all work that goes through the shop. It's kind of a drastic action to start sending parts back for verification of measurements that have already been done. But I have no doubt he's perfectly willing to do that.
Keep in mind that this is not the first 100hp package HP has ever sold. That package was very carefully designed and tested more than 12 years ago, it's an enormously popular package, and they've got literally hundreds of happy customers running that package in all corners of the globe. The package is well proven. An issue like this is an anomaly, not some fundamental design issue.
There's a reason behind it, it just has to be found. And that ain't always easy. Like I said, if it was mine, I'd start by taking a close look at the cam timing. That's an easy mistake to make and this is the exact symptom it causes.
If all the marks are right, I'd check to make sure the pinion key hasn't sheared and allowed the pinion gear to move. This is something else that'll screw up the cam timing.
And I'd make sure all the lifter preloads are correct. A short pushrod will pull back the IVC and raise compression, although it'll also make a racket. So if the valve train is quiet, this is unlikely.
I'd also double check the compression tester against another one.
I haven't spoken with HAMMER Dan about this. But my guess is that he's already double checked all the records he keeps on all the builds. He keeps every detail of all work that goes through the shop. It's kind of a drastic action to start sending parts back for verification of measurements that have already been done. But I have no doubt he's perfectly willing to do that.
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Road Captain
Joined: Mar 2009
Posts: 654
Likes: 734
Did you happen to take a pic of the top of the piston, or the underside (where you'll find the part number) for that matter? It's always possible there was human error in pulling the correct pistons off the shelf.
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HDF Community Team
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From: Santa Ana, CA
Last edited by OCSpringer; Jan 26, 2025 at 01:18 PM.