3.9 V8 on SUs.How much power?

nickm · Post by **nickm** » Tue Jul 26, 2011 9:41 am

I am planning on putting a 3.9 into my 110 v8.I am keeping the carbs and the engine will be rebuilt to standard specs.How much power can I expect from that set up and will there be much difference to the low comp 3.5 already in?I would leave the 3.5 in but the bottom end is getting a bit noisy.Nick

kiwicar · Post by **kiwicar** » Tue Jul 26, 2011 10:57 am

Hi
I think a standard spec 3.9 is about 168 bhp, get the SUs set up on a rolling road properly and feed them with cold air from outside and you should see the same.
Yes it should go better than a low comp 3.5.
Best regards
Mike

POAH · Post by **POAH** » Tue Jul 26, 2011 8:11 pm

3.9 running lucas gives around 182hp standard.

badger · Post by **badger** » Tue Jul 26, 2011 9:02 pm

Stick in a real Steel Viper Hurricane camshaft, keep the airbox and filter (but feed it with cold air from behind the right headlight) and fit BAC needles in the carbs and it'll fly! Good torque through the range with a power increase from 3000rpm.
Ought to give around 190bhp (or 200 with a little head work) and 220 torques.

nickm · Post by **nickm** » Wed Jul 27, 2011 8:09 am

Would the Viper cam affect fuel consumption much and would the heads need any attention to valve springs, etc or is it a straight swap?

badger · Post by **badger** » Wed Jul 27, 2011 9:20 pm

It's meant to be a straight fit, but I normally buff about 2mm off the top of the guides as I always have the heads off at the same time anyway. Std springs are fine, some fit the -1 coil ones for safety. Pull the heads, fit composite gaskets, replace all the stem seals at the same time then you can buff 2mm off each stem for safety and peace of mind.
A friend that I built an engine of this spec for reports better mpg than the original 3.5, in a G-WAC discovery.

paul c · Post by **paul c** » Tue Aug 02, 2011 7:34 am

The carb 3.9 in my 110 HT has a very noticable increase over my 3.5 hicap, both are autos, and soon both will be 3.9s.

nickm · Post by **nickm** » Tue Aug 02, 2011 9:15 am

Interesting.Can you tell me what jets you have in your SUs?

paul c · Post by **paul c** » Wed Aug 03, 2011 7:24 am

my 3.9 has solex's, they were bought new two years ago, factory set for a 3.5 RR and havent been altered at all. Colortune says the mixture is good so I havent changed anything, just using light oil in the dashpots instead of engine oil.

Karel R.R. & Capri · Post by **Karel R.R. & Capri** » Fri Nov 04, 2011 7:29 am

badger wrote:you can buff 2mm off each stem for safety and peace of mind.

Can you explain what you mean with "buff", I'm having some translation problems

POAH · Post by **POAH** » Fri Nov 04, 2011 9:30 am

Karel R.R. & Capri wrote:
badger wrote:you can buff 2mm off each stem for safety and peace of mind.
Can you explain what you mean with "buff", I'm having some translation problems

badger means he removes 2mm off the stem