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I want to put a L28 with my E31 but i need to know what to do to get the maximum horsepower out of it. LIke bigger 280 vavles port and polish??? Tell me whats the best way? also whats the best Block? flat top or dished. i don't want to high of compression. As much so it still runs on 93 or94 pump gas.
thanks alot
matt
 

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> I want to put a L28 with my E31 but i need
> to know what to do to get the maximum
> horsepower out of it. LIke bigger 280 vavles
> port and polish??? Tell me whats the best
> way? also whats the best Block? flat top or
> dished. i don't want to high of compression.
> As much so it still runs on 93 or94 pump
> gas.
> thanks alot
> matt

Bolting a E31 on a flattop L28 and stock gasket will give you 10.2:1 10.5:1 is about the limit on pump gas.
Bolting a E31 on a dished L28 and stock gasket will give you 8.5:1 This is quite low for a N/A engine.
All else being equal, the 10.2 c.r. is going to offer way better performance. The best block to use is the F54 turbo block and some flattop pistons (from an earlier ZX L28). It has extra internal webbing for the higher pressures encountered from the turbo. All L series blocks are the same height. All the pistons on L24/L26/L28 are at 0 deck height. Rod lenghts are different for the L24 and L26/L28. The L24 rod is 133mm and the L28 is 130.5mm.

If you're going to be rebuilding the head, then go ahead and install the larger valves. The larger valves arent' really going to make much of a difference, however, unless you have a cam and exhaust designed for higher flows. But, don't go out and buy a high lift/duration cam unless the head can flow that much air. No sense in doing one mod without doing the complimentary mod on the other part. Unshrouding the intake valve always helps.
 

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> Bolting a E31 on a flattop L28 and stock
> gasket will give you 10.2:1 10.5:1 is about
> the limit on pump gas.
> Bolting a E31 on a dished L28 and stock
> gasket will give you 8.5:1 This is quite low
> for a N/A engine.
> All else being equal, the 10.2 c.r. is going
> to offer way better performance. The best
> block to use is the F54 turbo block and some
> flattop pistons (from an earlier ZX L28). It
> has extra internal webbing for the higher
> pressures encountered from the turbo. All L
> series blocks are the same height. All the
> pistons on L24/L26/L28 are at 0 deck height.
> Rod lenghts are different for the L24 and
> L26/L28. The L24 rod is 133mm and the L28 is
> 130.5mm.

> If you're going to be rebuilding the head,
> then go ahead and install the larger valves.
> The larger valves arent' really going to
> make much of a difference, however, unless
> you have a cam and exhaust designed for
> higher flows. But, don't go out and buy a
> high lift/duration cam unless the head can
> flow that much air. No sense in doing one
> mod without doing the complimentary mod on
> the other part. Unshrouding the intake valve
> always helps.
Any non-turbo F54 block will have flat top pistons. Look for an '81- '83 non-turbo (with the P79 head). This is the F54 you want. The F54 is not really a turbo block, it was used in all '81-'83 ZX's, only the turbo engines had the dished pistons.
 
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