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LR8 Spec diff between 84 and other years by benoitmalenfant
Started on: 08-04-2013 11:24 PM
Replies: 4 (110 views)
Last post by: benoitmalenfant on 08-05-2013 08:57 AM
benoitmalenfant
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Report this Post08-04-2013 11:24 PM Click Here to See the Profile for benoitmalenfantSend a Private Message to benoitmalenfantEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sorry if this has already been covered here, but I tried to search and couldn't find exactly what I wanted.

A member of my local club (doesn't speak english, hence why I'm posting here for him) wants to take the LR8 from his 86 and put it in an 84 he is currently restoring.

We already discussed that the wiring is different, especially the C500.

I was looking at the specs for both years and found the following differences:

1984 pushrods length = 242.316mm or 9.754"
1986 pushrods length = 213.35mm or 8.3996"

BUT! If I look at everything else in the engine specs everything is the same between 84 and 86 (springs, plunger travel, lobe lift, pistons, etc.).

My questions:

1- How is it possible that for longer rods, the 84 has the same specs for everything else (wouldn't longer rods require other parts in the valvetrain to be shorter for same lift?)
2- Would swapping out only the bottom of the 86 and keeping the top from the 84 work? (this would save messing around with the wiring).

Thanks!

------------------
Ben
87 GT / 88 GT
84Indy #1863

[This message has been edited by benoitmalenfant (edited 08-04-2013).]

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Raydar
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Report this Post08-05-2013 06:12 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
The 86 has roller lifters. The 84 (at least the original ones) have regular "flat" hydraulic lifters.

Externally, the engines should be about the same. They both had distributors and the same model (I think) throttle body.
I don't know about sensors, etc.

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Bloozberry
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Report this Post08-05-2013 07:01 AM Click Here to See the Profile for BloozberrySend a Private Message to BloozberryEdit/Delete MessageReply w/QuoteDirect Link to This Post
There were two head designs used in '84 as well. That could certainly have an impact on pushrod length, though I'm not sure it does in this case.

The P22 lists a 1st design (part number 10038231) identifiable by code "Z8F, Z8C, Z8H, Z8J, Z8K, or Z6A" on the timing pointer. It's also identified by the push rod cover requiring a gasket and four round corners. The first design is actually what's listed as the head design used in '85 -'86 as well).

The 2nd design (part number 10120966) is listed as having the code "XJC" located on the bell housing face of the cylinder head and has a push rod cover requiring RTV sealant and flattened lower corners.
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olejoedad
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Report this Post08-05-2013 07:10 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
The wiring is not as big a deal as swapping heads,etc.

The heads on the 84 are different than the 86, they are taller.

Wiring is straight forward, the harness from the 84 will work on the 86, but you will need to use the 84 distributor and coil, or convert the coil / distributor wiring to fit the 86 style coil and ICM.
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benoitmalenfant
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Report this Post08-05-2013 08:57 AM Click Here to See the Profile for benoitmalenfantSend a Private Message to benoitmalenfantEdit/Delete MessageReply w/QuoteDirect Link to This Post
Once again this forum is a gold mine of information.

Thanks for the answers, a + rating for all of you!

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Ben
87 GT / 88 GT
84 Indy #1863

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