bkingdon

I am confused and need help.

I thought all 5 litre blocks would be the same, but comparing the PETs I see differences. The crankshaft and bearings carry the same part numbers but rods, pistons and rings show different numbers. Why is this?

Can an 87 short block be replaced with an 86 block?

Why do I ask? My 87 has TBF and I am exploring all affordable options.

This project is driving me to

Brian.

Vilhuer

'85-86 32V has smaller valves than '87-95. Valve reliefs at piston tops is at least one reason for different piston part number. Its also possible '85-86 pistons have different compression height than '87-91. This would mean conrods need to be different lenght also as block compression height and crank is same. Rings, don't know. One other difference are actual blocks. '85-86 has mounting points for intake while same points are on the way when S4 intake is used.

You should be able to use '85-86 block as long as you remove those mounting points and block is same tolerance group as you S4 block. What else is involved depends on what pistons you use.

GlenL

It's the pistons that are different. There are subtle differences in cranks over the years as well. There are variations in connecting rods too but, except for the 5.4l engines, are the same basic dimensions.

For your car with TBF you only need to replace the block. It'd be nice to get an assembled short block so look for one with the same engine model number. (e.g., M28/01)

Using just the block means re-using your pistons which, as V points out, means matching pistons to cylinders. This has it's own options and perils. The tolerance groups are not exact (that's why they're "groups") and with wear the holes get bigger and the pistons get smaller. The groups are done on 0.01mm increments which is awfully small. What you;d likely need to do is trial fit the pistons you have to the block you get and be prepared to source extra pistons to go with the holes that don't find a mate.

I'm frankly not clear on what differences an S4 block has compared to and earlier 5l block. Anyone?

Stan.Shaw@Excell.Net

I just heard of an '89 GT motor with computers available for $6k, so probably not affordable (my opinion it is over priced).

John Speake

Make sure the earlier block has the possibility to mount the knock sensors used with your '87.....also make sure that the flywheel assembly from your 87 will fit - others can advise...

Vilhuer

Knock sensor mounting is most likely easy since they can be mounted to as early block as '83 ROW S using existing holes and plugs.

UKKid35

With that much metal in the oil would you be able to flush the lifters, or would they have to go too?

Also I think only the 87 block has oil squirters.

Vilhuer

And only first xxx of them, not all. xxx between 400 and 700 I believe.

UKKid35

Like this one then:

Vilhuer

I'm not sure if engine numbers for '87 started from 00001 or 00501 for example. So its possible largest number is higher than 007xx for example. In any case some '87 blocks have them while many others do not.

mark kibort

The Holbert S4 engine is 00004.

Mk

Vilhuer

So at least prototypes were done with low numbers. Does it have squirters or have you been that deep yet?

GregBBRD

The starter motor mount is different for an '85/'86 engine. The '87-on starter mount will not fit. The '85/'86 starter mount will not clear the flywheel from the '87 engine. The '85/'86 flywheels don't have the tooth sprocket needed to tell the fuel injection what is happening. This pretty much "paints you into the corner". There is a way around it....but it does get pretty complex. I think the averge guy would be happier using a '87-on engine in an '87-on vehicle.

The combustion chamber is about 20cc bigger in an '85/'86 engine, so the piston has a different design to make up the difference. I took apart a stroker engine recently (from another place) that only ran 50 miles before the pistons galled the bores and ruined the block. The builder needed to go back to basic autoshop 101 and forget about building engines. He used a piston design for the '87-on heads with the '85/'86 heads.....not much compression. Combine what with an early (narrow) thrust bearing and rod bearing that were not champhered for the radius on the crankshaft and you begin to get the idea.

greg brown

greg brown

GlenL

I think that everything past the oil filter is OK.

The screen over the pick-up will stop big chunks. I'd flush the oil cooler and lines as a precaution and take a hard look at the oil pump if that's to be re-used.

mark kibort

I would think the 85 bock for the 87 heads would be an easy way for a quick 1 point of compression.

my issue with scots car is using the older blocks ('82 euro) with a newer 84US crank. there was some clearance issues, but i basically dremmeled them away. how much clearance is close with these types of mods. it started out jamming the crank to a stop, just in the initial "seeing if it all fit " type spinning. I have about a 50 thou clearance most taken from a corner area of a counterweigth on the crank. think that will be ok??

Mk