A310 V6 tricky question

Hi Guys

This indeed a very odd question but here I go.

Found out that my engine has been rebuild due to sandblasting damage. After rebuild cams are changed and weber Ida40 3C1 installed. Engine produces 151 HP and 225 Nm with Devil exhaust measured on Dyno when adjusting webers.

I was wondering why and found the engine rebuilder that informed R30 pistons and liners were used.

What I wonder is what the impact of lowering compression from 10,1 to the R30 PRV 9,5 would have on HP output as I feel 150 is on the low side ?

Thanks in advance for hints and help.

Regards

Jan

[stephendell]

On a normally aspirated engine generally lower compression ration = less horsepower

Maybe the small gain from the cams is lost by the small decrease in compression.

But 150bhp is normal for A310 if the engine is new and perfect.

Did you fit triple IDA carbs? Any 3 branch manifold and exhaust?

Thanks for a reply

The history of the car (related to engine ) is :

- The cars was brought to DK by owner DK1
- Engine sandblasted and paited and damaged by use but he never realised it
- Car purchased by owner DK2 ( I am DK3 as 3rd owner in DK)
- Owner experienced low oil pressure but continued driving. Eventually the engine seized as they do with no oil pressure
- Exprienced Alpine owner helped DK2 restore the engine and missed the details of the A310 having different pistons to R30
- DK2 Owner installed the 40 IDA carburettors and special cams with broad and increased torque band
- Probably due to lack of technical abilities it was sold on to me (faulty bakes, bushings, cooling and many other issues)
- I had the engine fully adjusted on a rolling bed and initial figures were 114HP before adjustment

The exhaust and manifold should be a 3 port devil as I can see and is a dual seperate exhaust

I would expect the power output to be closet to 170-175HP based on all the improvements and wonder where the horses has gone ?

I see one options in wrong pistions = lower compression and cams not properly timed but not much I can do here

Regards
Jan

A little late.
Dynos vary from one to another. Is the Hp reading at the wheels or an estimated flywheel Hp involving the roll down slowing to equate the drivetrain losses? The lower compression won't help and usually because of the greater overlap of the "sports" cams, actually require a higher compression ratio to work well. The next thing to look into is the cam timing after being ground, as various cam grinders have made a mess of these for the PRV engines in the past.

Check each cylinder at Top Dead Centre (TDC) on overlap, being when both valves will be partially open. Check the lift on each valve on that cylinder in this position, as they should be approximately the same. Maybe around 2mm, or perhaps more depending on the wildness of the cams. If one valve is open 4mm and the other is closed with clearance, your cam timing is out, possibly because of being incorrectly set in the grinder in the first place. If all are out the same way on the same bank it would be possible to make or purchase a vernier adjustable pulley to right it. If the cam timing was out by a full tooth it would be very likely that valves would be hitting pistons, and if not, power would be much less than you currently have.