Guys,

Just hoping for some quick clarity. I have read on here so many times that Pacemakers on a 3.0L sit lower than a 3.5L. Fair enough. Why?

Why does the 3.5 block sit higher than a 3.0L? What structural changes were made to make the 3.5 sit higher than the 3.0 and why was this done???

After having an exhaust guy look at me today like I was retarded when I mentioned that pacemakers sit lower on a 3.0l, I found myself stuck for an actual concrete reason why and I dont think I have ever seen an explanation of WHY on this forum.

Anybody got any facts on this, would be much appreciated.


Mark.

because my mum said so and shes never wrong.

This is only a guess but when they bored and stroked the 3L the block and in the process im guessing they moved the exhaust ports where the manifold sits higher as if they storked it things would get pushed up. if u get what i mean.

Engine 3L gets bored stroked
when stroking u need a taller block or another part onto the block to add the extra height the piston will travel. thus u also move the exhaust ports higher as well.

This would prob get resolved if someone put the exhaust manifold from a 3.5L onto a 3L and then u would see if there is a difference, in the height each sits at, so this would show how the block is sitting.

Pls dont kill me if im wrong im only making a absolute guess.

Tom

Sounds like a pretty plausible guess to me. If the 3.5 block is taller due to the longer stroke, the head therefore sits higher in the car.

I'm with Mark H's "Exhaust Guy"...... I don't reckon there'd be any difference between the cast of a 3L block and head and a 3.5L block and head. Best person to verify this would probably be monjunior.

Boring increases the diameter of the cylinders (i think) - and I'm pretty sure the 3L wasn't bored to make the 3.5L - stroking involves using different crank/conrods to change the distance the pistons move inside the cylinder - thus increasing the displacement volume (or whatever).

When I first heard that the difference between the 3L and the 3.5 was essentially a stroker kit - I expressed my dismay that such a change could yeild a 0.5L difference in capacity to a mate who has alot of contacts in the drag racing world. He confirmed that 0.5L is a pretty standard stroke increase.

6G74 has larger bore and stroke dimensions than the 6G72. Doesn't use the same pistons either.

Still doesn't explain the block or head casts being larger.

Sure it does. If the stroke is longer then it throws further therefore a need for a slightly higher deck height. Heads are pretty much the same. Pistons aren't the same shape and head shape is the same therefore compression ratio remains pretty much the same.

6G74 has larger bore and stroke dimensions than the 6G72. Doesn't use the same pistons either.
IF the 6g72 was mildly bored out and the 6g74 uses a different crank and pistons, then it is feasible that the external dimensions of the block would still be the same even though the engine has a 0.5L greater displacement.

If this is the case, still does'nt answer the original question as to why the pacemakers sit higher on a 3.5L. Afterall, they fit on a 3.0l and 3.5l.

I am guessing at this, but are the engine mounting points or mounts themselves the same on a 6g72 and a 6g74??? :confused:

Mount points are the same.

Mount points are the same.
Are they the same inside the engine bay as well? I mean, could they have been altered to make the engine sit higher??? (its probably pulling at straws but its the best I can think of at the moment hehe)

IF the 6g72 was mildly bored out and the 6g74 uses a different crank and pistons, then it is feasible that the external dimensions of the block would still be the same even though the engine has a 0.5L greater displacement.

I don't know about Magna engines specifically, but two possibilities exist: using a longer stroke crank in the same block as you describe (which is quite possible depending on the block design) or the 3.5 has a taller block to accomodate the extra stroke. Only the latter would explain why the extractors would sit higher on one engine than on the other.

The 3.5 litre block is higher...im not exactly sure how much but i think its an 1 inch or so. heads are the same so consequently if you use the same extractors they will hang lower...i would wager that you should be able to purchase 3l and 3.5 litre extractors to counter this.
If you guys look at the difference between the top alternator brackets on 3 and 3.5l they are different due to the top bracket being bolted to the head. The 3.5l one hangs down further to meet the alternator.

The 3.5 litre block is higher...im not exactly sure how much but i think its an 1 inch or so. heads are the same so consequently if you use the same extractors they will hang lower...i would wager that you should be able to purchase 3l and 3.5 litre extractors to counter this.
If you guys look at the difference between the top alternator brackets on 3 and 3.5l they are different due to the top bracket being bolted to the head. The 3.5l one hangs down further to meet the alternator.

Thanks for verifying that monjunior..... I stand corrected.