stroker cylinder wear LT4 396
Thread Starter
Registered User
Joined: Oct 2001
Posts: 144
From: overland park, ks usa
stroker cylinder wear LT4 396
I tried this on the LT1 forum, no bites over there...
I have an LTx-398 (4.040" bore x 3.875" stroke). I pulled my head last night because I thought I might have a small head leak...looks ok. However, the cylinder bores, starting about 2" down from the deck, on the upper and lower sides of the bore, are show signs of wear....a 3/4" strip appears to be nearly polished smooth (side load wear?). If I had a lot of miles on the engine I wouldn't be concerned but as I only have about 1,000 miles on it, it got me worried. My engine spec's are in my signiture below and I run about 12 psi of boost. I'm using dyno oil 5w30, mix of race and pump gas (both unleaded...about 96 octane mixed) and a 160 degree thermostat. Is this type of wear normal in a 396 and what could cause it? I'm used to seeing cross-hatching (sp?) in engines w/50k miles on them.
I have an LTx-398 (4.040" bore x 3.875" stroke). I pulled my head last night because I thought I might have a small head leak...looks ok. However, the cylinder bores, starting about 2" down from the deck, on the upper and lower sides of the bore, are show signs of wear....a 3/4" strip appears to be nearly polished smooth (side load wear?). If I had a lot of miles on the engine I wouldn't be concerned but as I only have about 1,000 miles on it, it got me worried. My engine spec's are in my signiture below and I run about 12 psi of boost. I'm using dyno oil 5w30, mix of race and pump gas (both unleaded...about 96 octane mixed) and a 160 degree thermostat. Is this type of wear normal in a 396 and what could cause it? I'm used to seeing cross-hatching (sp?) in engines w/50k miles on them.
West South Central Moderator / Special Guest
Joined: Dec 1998
Posts: 1,650
From: Coppell, TX USA
Sounds like "normal" stroker wear. Welcome 
Anyhow, I would ditch the dino oil and go with a good synthetic. I have also heard good things(wear wise) about "schafers". its a snyth blend
Anyhow, I would ditch the dino oil and go with a good synthetic. I have also heard good things(wear wise) about "schafers". its a snyth blend
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Toughts:
Compression height about 1.06?
How short are the piston skirts?
What piston/cylinder wall clearance did diamond recommend? What did you have?
Any evidence of detonation?
Did you leakdown the engine before taking the head off?
I agree on the synthetic oil.
My $.02
Compression height about 1.06?
How short are the piston skirts?
What piston/cylinder wall clearance did diamond recommend? What did you have?
Any evidence of detonation?
Did you leakdown the engine before taking the head off?
I agree on the synthetic oil.
My $.02
Registered User
Joined: Jan 2001
Posts: 293
From: houston, Tx
All regular engine wear the bores there. We do 2 to 1 rod ratio 358 inch sbcs with 6.125 rods and 3.335 stroke and they all look like that too. So does a regular 350. Wouldn't worry about it too much.
Thread Starter
Registered User
Joined: Oct 2001
Posts: 144
From: overland park, ks usa
Originally posted by OldSStroker
Toughts:
Compression height about 1.06?
1.0725" (0.015" deck height)
How short are the piston skirts?
They're short. However, they are about 0.25" longer than the 28cc JE 383 6" rod pistons I took out...I know, it seems strange to have a 396 6" rod piston w/longer skirts...have photos, can post.
What piston/cylinder wall clearance did diamond recommend? What did you have?
The pistons are barrel shaped at the widest part (the bottom third), they're 0.004" to 0.005"clearance, per manufacture spec.
Any evidence of detonation?
none.
Did you leakdown the engine before taking the head off?
I gapped my rings on the big side...rings are close to the heat source and I plan on bumping up the boost to 17-19 psi once it's broken in....suspect they would leak down pretty quick. however, I did a compression test 130 psi on the two center pistons (3 and 5) and 140 on the outer pistons (1 and 7). The exhasut headers on 3 and 5 would glow red at idle and I could smell antifreeze...figured I had a bad head gasket seal between the two bores (oily fingers when I put it together may have affected the seal??). Also will be using the GM lt4 HP intake gasket on the install...the felpro intake gaskets may have been too small and started leaking (big ports in afr 220s)...possible cause for lean condition in those two cylinders? I was also getting an intake pop on tip-in...vacuum leak?
I agree on the synthetic oil.
Yes, I plan on running mobil-1 5w30...w/3000 changes. Dyno oil was for breakin only.
My $.02
Toughts:
Compression height about 1.06?
1.0725" (0.015" deck height)
How short are the piston skirts?
They're short. However, they are about 0.25" longer than the 28cc JE 383 6" rod pistons I took out...I know, it seems strange to have a 396 6" rod piston w/longer skirts...have photos, can post.
What piston/cylinder wall clearance did diamond recommend? What did you have?
The pistons are barrel shaped at the widest part (the bottom third), they're 0.004" to 0.005"clearance, per manufacture spec.
Any evidence of detonation?
none.
Did you leakdown the engine before taking the head off?
I gapped my rings on the big side...rings are close to the heat source and I plan on bumping up the boost to 17-19 psi once it's broken in....suspect they would leak down pretty quick. however, I did a compression test 130 psi on the two center pistons (3 and 5) and 140 on the outer pistons (1 and 7). The exhasut headers on 3 and 5 would glow red at idle and I could smell antifreeze...figured I had a bad head gasket seal between the two bores (oily fingers when I put it together may have affected the seal??). Also will be using the GM lt4 HP intake gasket on the install...the felpro intake gaskets may have been too small and started leaking (big ports in afr 220s)...possible cause for lean condition in those two cylinders? I was also getting an intake pop on tip-in...vacuum leak?
I agree on the synthetic oil.
Yes, I plan on running mobil-1 5w30...w/3000 changes. Dyno oil was for breakin only.
My $.02
Thread Starter
Registered User
Joined: Oct 2001
Posts: 144
From: overland park, ks usa
Originally posted by KCFormula
I wonder if your excess ring gap along with your running rich for "break in" is causing wash down of your cylinder walls?
I would put the small pulley on it and let 'er eat!
I wonder if your excess ring gap along with your running rich for "break in" is causing wash down of your cylinder walls?
I would put the small pulley on it and let 'er eat!
will you be in town this weekend? as for ring washout, i'm not running that rich...14.5:1 below 2000 rpm. got to love those widebands.
ct
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