Lacking power

[porschedavid]

Looking for some technical advice.

1986 Porsche 928 s2 (1986.5 model)

Seems to lack power when accelerating,When accelerating hard at high revs seems to hesitate or feels like its missing.Thanks

[harborman]

It would be helpful to know the maintenance on the car. How are the filters? Is it driven daily? Anything done recently? Rotors and caps? Mileage? Ignition work?

[porschedavid]

118000.miles,
in the last 8 months i have rebuilt engine all new bearings,heads sent off and had new valves,new cap,arm,leads.new filters all round,spark plugs,new belts,recondition gearbox,fuel pump and filter,new breather pipes,

[harborman]

Originally Posted by porschedavid

118000.miles,
in the last 8 months i have rebuilt engine all new bearings,heads sent off and had new valves,new cap,arm,leads.new filters all round,spark plugs,new belts,recondition gearbox,fuel pump and filter,new breather pipes,

My first question, did it ever run correctly after all the work was done? It sounds like a timing issue possibly. Are the cam gears aligned properly? Just some suggestions. Maybe MrMerlin has some ideas for you.

[JK McDonald]

Hey David - Do you know the maintenance history of your car ? 118 K miles on an 86 928 engine doesn't seem to be enough mileage to require a rebuild unless there are extenuating circumstances. Has it had a hard life? I've seen lots of 928's (both twin and 4 cam motors) with 200k miles still running strong.

If you have checked all the basic timing and mechanical stuff, perhaps you are feeling a slight miss from a fuel delivery or injector issue ? Perhaps there is a minor collapse or restriction in the exhaust plumbing.

Good Luck and keep us posted - Michael

[porschedavid]

When i got car it had lot of end play,Flex plate pushed the thrust bearing into block

[harborman]

Originally Posted by porschedavid

When i got car it had lot of end play,Flex plate pushed the thrust bearing into block

Did you do a compression test after the heads were put back on? Maybe you have some manifold leaks, fuel delivery issue, fuel injectors? Good luck on finding the problem.

[Mrmerlin]

did you verify the block was still good IE the #3 main bearing web was not cracked?
Pull the dipstick drip the oil onto a black piece of card board see if you find lots of metallic .

Who did the machine work?
do you have wisdom on rebuilding a 928 engine.
Did you index the cam pulleys?

[porschedavid]

I got another block as mine was cracked after the thrust bearing went,heads i sent away to a good machine shop to get reconditioned,This is second engine rebuild i have done,first was my porsche 911 3.2 carrera which is still going strong.what do you mean by indexing cams?

[Mrmerlin]

did you get new lifters?
Did you clean the oil cooler prior to running the new engine?
if your old engine suffered thrust failure then the lifters from that engine were filled with metal,
if they got used in your new build then its sure they are flooding that metal into your new build.

did you pull the dipstick as asked?.

Porken makes a 32Valver adjustment tool to center your cam pulley to the cam instead of pulling the cam cover off to use a dial indicator.

[harborman]

Originally Posted by Mrmerlin

did you get new lifters?
Did you clean the oil cooler prior to running the new engine?
if your old engine suffered thrust failure then the lifters from that engine were filled with metal,
if they got used in your new build then its sure they are flooding that metal into your new build.

did you pull the dipstick as asked?.

Porken makes a 32Valver adjustment tool to center your cam pulley to the cam instead of pulling the cam cover off to use a dial indicator.

As I mentioned, MRMerlin is one real expert on here. Not sure if he can clean the old lifters of if he installed new ones. I know old ones have to go back in same order as taken out. More things to think about.