928 - Engine Seized
05-31-2009, 02:33 AM
#16
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In the process of putting things back together and noticed I had a piston with a bad ring. The mechanic said you could either get new rings or what he suggested was boring out the cylinder to the newer 100mm pistons which he said he has plenty off. They came off several 944s. What do you guys think. Stick with what I've got and put new rings or go along with the mechanics advise...
05-31-2009, 10:13 AM
#17
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boring the block isnt usually something that you do if the bores in your engine are good I re ring the pistons.
Also check the pistons in question for a broken land
Also check the pistons in question for a broken land
05-31-2009, 04:56 PM
#18
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show us pictures of the block bores. If they need cleaning up, it might be worth going 100mm, but probably easier to just fix the one hole. I have a set of 1 size overbore if that is all it takes to fix the one hole and re-ring the rest. however, he better have experience with the Silicon aluminum boring process.(critical) I mean, GOOD experience. if not junk the block and just replace it with a 5 liter bottomend.
re-ring that, and install it. that is what we SHOULD Have done with scot's . It was fun building it up with all disparate parts, but much cheaper with a proven, stock, good shape, 5 liter 85 bottom end. just notch the pistons for the 2 valves, and re-assemble with new rings and bearings. DONE. a bunch more power, brand new motor and no risk that the shop screwed up the bore and silicon process job.
(priceless)
used 5 liter blocks are found for 1 to 1.5K $. boring the block, buying pistons, balancing the parts, can cost more in labor than the entire new(used) 5 liter block. Ask me how I know. Ive done it a few times!
mk
re-ring that, and install it. that is what we SHOULD Have done with scot's . It was fun building it up with all disparate parts, but much cheaper with a proven, stock, good shape, 5 liter 85 bottom end. just notch the pistons for the 2 valves, and re-assemble with new rings and bearings. DONE. a bunch more power, brand new motor and no risk that the shop screwed up the bore and silicon process job.
(priceless)used 5 liter blocks are found for 1 to 1.5K $. boring the block, buying pistons, balancing the parts, can cost more in labor than the entire new(used) 5 liter block. Ask me how I know.
Ive done it a few times!mk
06-02-2009, 02:49 AM
#19
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Sorry guys but my internet service was down yesterday...
We're in the process of cleaning out the engine right now...Checked out the block bores and they look good. Tested a new ring in there and it looked tight.
Got new head gaskets (manufactured here at a local factory !), got a new set of rings...
What we're using from a second engine (4.5 928 and not 4.7) I have is the crank along with its main bearings, the con rods also along with their bearings and the oil pump cause it looks better than the one I have...Everything is staying in its original place !
The pistons are the original ones since they are indeed 97mm and the second engine are 95mm...and nothing else changes.
I could order main bearings and con rod bearings from the States and wait till they get here...but since the crank is not going to be machine at all shouldnt they just fit exactly like they were before ?
We're in the process of cleaning out the engine right now...Checked out the block bores and they look good. Tested a new ring in there and it looked tight.
Got new head gaskets (manufactured here at a local factory !), got a new set of rings...
What we're using from a second engine (4.5 928 and not 4.7) I have is the crank along with its main bearings, the con rods also along with their bearings and the oil pump cause it looks better than the one I have...Everything is staying in its original place !
The pistons are the original ones since they are indeed 97mm and the second engine are 95mm...and nothing else changes.
I could order main bearings and con rod bearings from the States and wait till they get here...but since the crank is not going to be machine at all shouldnt they just fit exactly like they were before ?
06-02-2009, 02:38 PM
#20
Rennlist Member
If I understand what you are doing correctly, you will want to balance the 4.7 pistons to the 4.5 crank and rods. Is that what you are going to do, mix and match cranks and pistons and rods with the 4.5 stuff?
also, i dont like the 4.5 cranks very much as they have the much smaller oiling holes for the rod bearings. I would find a good used 4.7 crank and use it, or fix /use the one you have.
mk
also, i dont like the 4.5 cranks very much as they have the much smaller oiling holes for the rod bearings. I would find a good used 4.7 crank and use it, or fix /use the one you have.
mk
Sorry guys but my internet service was down yesterday...
We're in the process of cleaning out the engine right now...Checked out the block bores and they look good. Tested a new ring in there and it looked tight.
Got new head gaskets (manufactured here at a local factory !), got a new set of rings...
What we're using from a second engine (4.5 928 and not 4.7) I have is the crank along with its main bearings, the con rods also along with their bearings and the oil pump cause it looks better than the one I have...Everything is staying in its original place !
The pistons are the original ones since they are indeed 97mm and the second engine are 95mm...and nothing else changes.
I could order main bearings and con rod bearings from the States and wait till they get here...but since the crank is not going to be machine at all shouldnt they just fit exactly like they were before ?
We're in the process of cleaning out the engine right now...Checked out the block bores and they look good. Tested a new ring in there and it looked tight.
Got new head gaskets (manufactured here at a local factory !), got a new set of rings...
What we're using from a second engine (4.5 928 and not 4.7) I have is the crank along with its main bearings, the con rods also along with their bearings and the oil pump cause it looks better than the one I have...Everything is staying in its original place !
The pistons are the original ones since they are indeed 97mm and the second engine are 95mm...and nothing else changes.
I could order main bearings and con rod bearings from the States and wait till they get here...but since the crank is not going to be machine at all shouldnt they just fit exactly like they were before ?
06-02-2009, 05:08 PM
#21
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Mark: Exactly what you said use the the 4.7 pistons with the 4.5 crank and rods. Not sure what you mean by balance. I think the mechanic is just gonna put them together. Problem is that parts are not readily available here and lucky for me I had a spare 4.5 engine. What do you recommend I do given the conditions...
06-02-2009, 05:29 PM
#22
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So, why cant you just put new rings and bearing on the existing rods and crank?was the crank damaged? Pistons seem like the are ok as you are going to re-use them. I think someone should chime in here, but I think if you go to the 4.5 rods and crank, they are not balanced for the 4.7 liter crank. You might have to have it balanced. However, It might be ok.
I would be more concerned with the oiling holes of the 4.5 liter crank being smaller. But, if the 4.7 crank is damaged, and its all you got, it should be fine.
mk
I would be more concerned with the oiling holes of the 4.5 liter crank being smaller. But, if the 4.7 crank is damaged, and its all you got, it should be fine.
mk
Mark: Exactly what you said use the the 4.7 pistons with the 4.5 crank and rods. Not sure what you mean by balance. I think the mechanic is just gonna put them together. Problem is that parts are not readily available here and lucky for me I had a spare 4.5 engine. What do you recommend I do given the conditions...
06-03-2009, 03:37 AM
#23
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Yeah actually the 4.7 crank is damaged so thats my only option since we have very limited parts. I'm still not sure what you mean by balance ? What we will basically do is use the 4.5 crank and rods along with their respective bearings in the same position they were in. That is each rod will sit on the crank were it was originally seated and in the same cylinder bore. And same goes for the pistons. Anything else I need to do....
