Pinning Liners in a 4.6

Quote:

---

Originally Posted by pibby

i get confused when this topic comes up. i've got a 4.6 in a disco and if my eyes don't deceive me i would say there is a step at the bottom of the cylinder wall which the bottom of the liner sits on. i know the motor was bought new to put into the vehicle.

so in this instance i can't see how a liner can slip. maybe the original factory motors didn't have this lip?

maybe it needs to be distinguished which type of motor is being talked about other than the cc?

---

I would say your 4.6 block is not standard.

I just checked my bare 4.6 block that has standard liners (two slipped) and there is no lip at the bottom.

I also checked the 4.6 engine I am building out of a 4.0 block. It had top hat liners. The first obvious difference is that the top hat liners have thicker walls and as such to fit them - as well as the top hat machining the block has been machined to fit the larger outside diameter liner so there is a lip at the bottom at the sides of the block - however this goes down a good cm lower than the bottom of the liner - I guess if this machining did not go so far down it could be used to stop the lining slipping - but if you go to this trouble the Top Hatting is the way to go.

Has your engine actually been top hatted and what you can see is the machining for the thicker liner and your machinist has not taken the block machining as far down as was done on my block.

Certainly a standard block does not have the lip at the bottom of the liners - just held by the press fit.

Garry

So long as the cylinder liner isn't clamped down by the cylinder head and gasket, the liner only stays put due to friction. Once the stock liner loosens for whatever reason it can move enough to make a distinctive rattling noise. The reasons for the liner coming loose are multiple but the fact is ALL the bigger bore blocks have less cast aluminium around the liners than is desirable. The 3.5 block was very good in its stock form but ALL the 3.9/4.0/4.6 blocks are at higher risk. Some of these blocks (especially late in production) are even weaker due to the sand casting cores moving during the casting process, making them riskier to use than the best blocks. I believe this is why the 4.0 got the less well cast ones in preference to the 4.6 getting the better ones.

One of the reasons why people remember the good ones is because of course they are the ones that are still going. In the past if a 4.6 cracked a block and loosened a liner the engine was frequently driven to destruction by an ignorant owner and either replaced or the vehicle was scrapped. You couldn't tell from the mess left behind as to what died first. Nowadays the vehicles being very second hand the costs have to be weighed more carefully.

........

Not on the stripped down block I have.

I will try to get as much info on why this 4.6l was taken out of service if it was due to vehicle write off it may be worth it, if it was engine failure then ill probably steer clear and go back to my original Plan of using the 3.5l

Quote:

---

Originally Posted by Kevin B

I will try to get as much info on why this 4.6l was taken out of service if it was due to vehicle write off it may be worth it, if it was engine failure then ill probably steer clear and go back to my original Plan of using the 3.5l

---

But with the exception of the liner cost - about $800 the cost of rebuilding a 4.6 vs 3.5 will be the same - it will certainly cost a lot more than the $800 difference to get the 3.5 to perform any where like the 4.6.

In either case though it is expensive and if you want to take a risk buy a used engine as it will be a lot cheaper.

Garry

Lets hope this is not a Stoopid question, correct me if i am wrong but it is my understanding that all Blocks from 3.5 to 4.6 were made from same cast then just bored to size taking int account the last post about the best being used for 4.6 and the ones that ere not got made into 3.9 or 4.0, so here it the stupid question, can you not get a 3.5 block and bore it out fit top hat liners and make it a 4.6 ? or am i missing something..

Quote:

---

Originally Posted by garrycol

But with the exception of the liner cost - about $800 the cost of rebuilding a 4.6 vs 3.5 will be the same - it will certainly cost a lot more than the $800 difference to get the 3.5 to perform any where like the 4.6.

In either case though it is expensive and if you want to take a risk buy a used engine as it will be a lot cheaper.

Garry

---

i didnt really intend to try make a 3.5 perform like a 4.6 my original intention was just a motor freshen up then got to talking to my mate and he suggested a 4.6, before that i hadn't even thought about it. you are correct though the cost would be the same and if i could get liners for say 800 he can fit them so the cost of labor there would be a saving as well and i would have a better motor, of course then i would have to look at the EFI system as well course i was just going to use the original flapper on the rebuilt 3.5 unless it can still be used on a bigger engine, Decisions Decisions....

.......

don't intend to go that way at all, was just curios and you answered my question, thanks.

........

My '86 Rangie was bored and stroked to 4.6 litres in about 1988 by John E Davis Motorworks. It had Chev valves and a Haltech EFI ECU.

If you end up using the 3500, be aware that boring it will cause the liners to slip; so you will need to have it fitted with top-hat liners anyway!

I found out the hard way when I had my P6 3500 re-bored,

Cheers Charlie