Someone talk me out of (or into) this... (F54 combo)

[BrandenZ]

Picked up an F54/P79 L28e longblock from a junkyard recently, sold to me as a "good running motor", and naturally I found this:

 

Using a long machinists square and feeler gauges, the head appears to be warped, between 4-6 thousands of an inch in various spots depending on where the measurement is being taken. At a minimum, the head needs to be resurfaced.

 

The block, however, appears to be spot on. The rod bearings are all in spec, the journal on the crank measures out perfect, as does the cylinder bore.

 

Compression test showed 150-160 across all 6 cylinders, and a leakdown came back with 7%-14%.

 

I've got this lying on the shelf:

 

It's an E88 with the A grind cam (longer duration, lift on intake) that's been hottanked, resurfaced, with L28 intake valves. Measures out to far better than spec with the same square and feeler gauges.

 

I'm extremely tempted to put the P79 on the shelf, and bolt the E88 up to the F54. I've got a 1.25mm felpro headgasket ready to go and believe that'll give me roughly a 10.4:1 compression ratio.

 

The intended use for the car is heavy autox, light track, light street. It'll see _maybe_ 1-2k miles / year, of which 30-40% will be wide open.

 

I'm running dual weber dgvs with plenty of spare jets lying around, a 6-2 square port header (which also better matches the E88 head) and dual exhaust.

 

I'm also running an optical dist with a 12v coil and crane xr700 electronic ignition (used to be alison before they were bought out).

 

All I can find to discourage me are the threads concerning detonation issues. I have zero problems running 93 all day long, and given the low mileage and intended usage of the car, I don't necessarily have any issue with the idea of running around with cans of octane booster ready for each and every fill-up. However, that being said... there isn't a lot of point to all that compression if I have to dial the timing way way back to prevent detonation.

 

 

What do you guys think? Worth the risk to go E88/F54, or should I go the "safe" route and send the P79 head off to the machine shop?

[BluDestiny]

I was running that combo on my 260z with Triple webers and 91 and a far bigger cam. I had no detonation issues. I would try and have your cam reground just a little more aggressive to really liven things up.

[ozconnection]

I was running that combo on my 260z with Triple webers and 91 and a far bigger cam. I had no detonation issues. I would try and have your cam reground just a little more aggressive to really liven things up.

 

He hit the nail on the head when he said "far bigger cam". That's the deal with stock type cams, they're designed to work with low compression engines.

 

It's all to do with valve overlap and dynamic compression.

 

Run the E88 head but put in a cam that is designed to work well with the higher expected compression ratio otherwise your fears will come true.

 

Good luck with it.

[Moltar]

Verify the CC of your combustion chamber on the E88. Some E88s (if from a 1971 Z) actually have the smaller combustion chamber from the E31 head, but have a casting mark for E88.

[madkaw]

Don't know if your e-88 is ready to bolt on or not, but you could lay your head gasket on that head and unshroud those valves which would let it breathe and gain some chamber size to a safer CR.

[roger280zx]

I thought felpro only made a 1.00mm L28 gasket. I would double check since it could drastically increase the likelyhood to detenate.