Rebuild 3.9 Rover V8 power loss after 3000 rpm
Discussion
Hi Guys
I have done a rebuild on a 3.9 Rover V8 that I bought but the engine struggled to idle and overheated but was insanely fast for a 3.9 rover v8 in a td5 body,top speed of 162km/h was achieved(bit scary though). It had a piper 285 cam,0.020'' pistons,edelbrock 500 carb,performance headers,the works.
I decided to do a rebuild and take everything back to standard size because the 285 cam was damaged,pistons was bad and so the list continues.
Fitted Standard 3.9 cam,re sleeved block for std pistons,stromberg carbs ex.Now,the car idle well,doesn't over heat and runs smooth but I loose high end torque when 3000 rpm is reach. I takes forever to get to 100km/h.
It pulls great in 1st,2nd and if you thump it a bit in 3rd it feels like the engine is leveling out. It just don't feel right. I know they are not renowned for their top speed but 100km/h is below standard. What can the problem be? Should the engine still produce power at above 3000 rpm for a standard 3.9 carb engine?
I have done a rebuild on a 3.9 Rover V8 that I bought but the engine struggled to idle and overheated but was insanely fast for a 3.9 rover v8 in a td5 body,top speed of 162km/h was achieved(bit scary though). It had a piper 285 cam,0.020'' pistons,edelbrock 500 carb,performance headers,the works.
I decided to do a rebuild and take everything back to standard size because the 285 cam was damaged,pistons was bad and so the list continues.
Fitted Standard 3.9 cam,re sleeved block for std pistons,stromberg carbs ex.Now,the car idle well,doesn't over heat and runs smooth but I loose high end torque when 3000 rpm is reach. I takes forever to get to 100km/h.
It pulls great in 1st,2nd and if you thump it a bit in 3rd it feels like the engine is leveling out. It just don't feel right. I know they are not renowned for their top speed but 100km/h is below standard. What can the problem be? Should the engine still produce power at above 3000 rpm for a standard 3.9 carb engine?
Assuming ignition timing and carburettors set up correctly:
Running lean? - pull spark plugs and check colour of tips
Diaphragms split? - remove top and check
Strombergs have far fewer metering needle options than SU, also no diaphragms to split so much more durable.
I originally had carburettors on my 3.9, these were SU HIF6 with BDR needles.
It pulled really well past 4000 rpm, with BBC needles it went even better!
On BDR needles I could get around 20mpg on highway cruise.
Running lean? - pull spark plugs and check colour of tips
Diaphragms split? - remove top and check
Strombergs have far fewer metering needle options than SU, also no diaphragms to split so much more durable.
I originally had carburettors on my 3.9, these were SU HIF6 with BDR needles.
It pulled really well past 4000 rpm, with BBC needles it went even better!
On BDR needles I could get around 20mpg on highway cruise.
Edited by 100SRV on Monday 11th June 10:44
wheelbarrowman said:
I'm not sure how to test it, but would check the vacuum advance is working. This can apparently get a touch sticky resulting in poor performance at higher engine speeds.
Good shout!Remove distributor cap.
Remove vacuum advance hose from carburettor and suck - you should see the distributor plate move as you suck the hose.
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