Has anyone looked into advancing the cam timing 3 or 4° to move the torque curve to the left? These engines with their VVT and DOHC obviously wind out nicely but how many actually crank it up to 6800rpm or wherever peak hp actually is to realize it? Might be nice to bring it on a bit sooner?
Just thinking out loud...

 

You should have bought an XJR; more options for hot-rodding than for an NA engine. Mine will be 20 years old in February, has 183K+ miles, and still runs like a bat out of ... wherever. I'm planning on doing the heads, maybe next summer, and putting on a 2.25" exhaust, but no plans to mess with the cam timing. At least for now, anyways. I still have to get back into the catch can thing when I get done with this bathroom remodel that I'm in the middle of.

 

What are the cam specs? Mainly the intake close? I'd like to see it in the low 40s but I'd also like to see some overlap which I highly doubt is the case as they wouldn't be EPA/EU5 compliant. But overlap can be a huge aid when it comes to cylinder fill. Cylinder fill is the name of the game when it comes to power.
It's still fun tweaking an NA engine. If there was a boosted available here I may have bought it but this Sport suits me too..
My catch can/vacuum pump mod will really give your boosted engine a nice bump. Some boosted engines see in excess of 30hp.
Maintaining a 10+ inHg.
Advancing cam timing is more about redistribution of existing.

 

Ajv8 engines specifically were designed not to have valve overlap. Or atleast very minimum amount. VVT is used on cold start to heat cats faster and used at low to mid range. High range rpm they are in certain position only. If I recall correct.

 

Thanks for the info as I'm not real up on VVT except I like it...a lot. No cons, all pros.
I am curious as to to the cam specs tho. Especially IVC.

 

Here is a link to the AJ Engine Course:

https://www.dropbox.com/s/vqpy3bbjzd...e_168.pdf?dl=0

It may answer your questions. Pay particular attention to page 74 of the PDF.

 

Gunner, how many miles are on your car?

Do you know if it’s the original engine?

 

Thanks for the link. I'll check that out.

Original engine. 126,000 miles.
It's really tight for the miles. Good compression. Blowby is very minimal. Doesn't use any oil and runs as smooth as a baby's backside. Can hardly tell it's running at idle.
Not that it didn't run great before, but the CAI, crankcase breather mod and vacuum pump, has Only made it better. More responsive.

 

If you pull the heads off and get a valve job done by the machine shop, including having them do the valve adjustment, new stem seals, mill the heads and install new MLS head gaskets, that’ll be a pretty good bump in power also.

 

Here's a thread for review....https://www.jaguarforums.com/forum/j...project-52518/

 

I bumped the compression up on my Harley pulling the heads and installing .030 head gaskets in place of the stock .050. Put my CCP at 210psi. A bump of 10+psi. Can't safely go much higher for fear of being a ping monster.
I'm not sure I really need a valve job enough to really benefit from one yet. I could lap them and install valve guide seals myself tho. A 5 angle would be nice tho I suppose.
I should do a leakdown test.
I really am impressed with the power of this little 4.0 and all the little mods add up and help more than you think. I'd bet $$$ I've gained a good 10 ponies. The vacuum pump alone does way more than most know. Maintaining a good vacuum in the crankcase of 12 - 14 inHg adds anywhere from 5hp on an NA to 30+hp on a boosted engine.
I had a weeping VVT solenoid seal that instantly ceased to leak. Just serves to show the crankcase pressure the stock setup has especially when under load.
When the pistons aren't fighting against this crankcase pressure on the downstroke and the crank spins freely without the drag of swimming in aerated oil, the power increase is surprising.

Now imagine a good set of cams with good overlap to maximize cylinder fill across a wide rpm range and do away with any other power robbing emissions considerations(Euros are really bad in this dept.), and the power increases dramatically. Of course the exhaust has to play well here too to take advantage of this overlap or it will kill power instead.
I damn near doubled the hp in my air cooled V-twin with a free flowing intake and exhaust with a $270 set of cams with 42° overlap. Fine tuned with a set of .030 head gaskets and an external breather system allowing me a custom AFR map, MAP based custom timing advance map. That's a big bump for roughly $1000 in upgrades.

Ironically, it was the use of pcv valves and the slight vacuum they create that first brought this benefit of crankcase vacuum to light and race engines started running mechanical pumps. The electric one I'm running is ideal for a street engine.
Throw in cleaner, cooler air in the combustion chamber calling for more fuel and restored octane levels from the use of the catch can and it all adds up.
I'd like to play with bumping the ignition advance up now. Far less likely to ping without the carbon buildup and hot, oily air robbing octane levels. Advance can be a power bump and make for a cooler running engine.
You'd probably $h!+ if you saw the timing I'm running on my air cooled V-twin.

 

Interesting observation on the VE of cylinders 7 and 8. I've also considered looking at the throttle body as a choke point. I'm sure cams would be a huge improvement but short of aftermarket availability, isn't going to be very cost effective. All the advancing/retarding of the cam timing I've mentioned does is move existing power left or right.
I've got to read more there and of the link above.

 

Valve overlap isn't everything. Overlap has it's disadvantages witch are easily bad.

 

I acquired my 98’ XJR with 234k miles back in 14’. My intentions were to fix the car up a bit and sell it. At idle, the engine made such little vacuum that the supercharger bypass stayed closed at all times. I pulled the heads to replace the original fiber type head gaskets with the later, thinner mls head gaskets. I pulled all 32 valves and replaced all the exhaust valves (with better used ones) because the pitting was too deep to lap out. I also replaced all the valve springs & stem seals with new ones. I spent a VERY long time painstakingly lapping all the valves, reassembled the valves, flipped the heads upside down and filled the combustion chamber with mineral spirits and saw that most of the leakage was coming out of the exhaust ports after all that work. I did more lapping again and got one of the heads to not have any leakage. I took the other head to the machine shop and had them cut the valves and seats. When that got done, I then had another project all on its own..... adjusting the valve clearance which took a long time. Do yourself a huge favor and DO NOT attempt this on your own unless you just love wasting weeks of time. Just take the heads to the machine shop and pay the hefty price to have the pros do it right the first time.

My daughter now owns the car and it has 266k miles on the original nikasil engine. The car runs very strong for its age/mileage.

 

Such as? A lumpy idle associated with muscle cars? I guess if you like to sit on your porch and listen to a nice smooth idle...then overlap might not be so good. Personally, I like a lumpy idle.
The only really bad thing about overlap is emissions which is of no concern to me. Emissions are the ONLY reason you don't see cams with overlap in stock form anymore. It's also why one of the first things we Harley owners do, right behind replacing the EPA compliant exhaust is replace tbe EPA compliant cams and EPA compliant breathers.
There is nothing about EPA compliance that's good for an ICE. Only bad. And it's more bad than most realize or care to admit. It's damaging bad.
Like I said, the exhaust plays a HUGE part in power and the benefits of overlap tho. With the right exhaust,the benefits are HUGE!. The benefit of having the exhaust from one cylinder draw the next intake charge in for the next is undeniable. With the stock, EPA compliant exhaust however, you'd end up with a **** ton of reversion.

I gained over 35hp and 12ft.lbs of peak torque in my Softail with nothing but a $270 set of cams with 42° overlap. This was on a Harley that's 67hp in stock form. Of course the exhaust was replaced as well.

 

Yes I do undestand why people like lumpy idle. I do like it my self too. But you must have noticed how modern engines do have clearly more power in NA form without any big cams. Same goes with ignition timing. More modern cylinder head designs doesn't need 30-50deg of ignition timing to make power at wot. EPA and others has done it's job that it was kinda designed. I do not love new stuff at all. Way too complicated where you only need one switch. I dont know from harleys much but comparing engines what were clearly strangled to meet emissions to the engines that were designed from the scratch in the epa emissions time is not right. People has bought stainless tube exhaust manifolds and highflow cats to ajv8 engines. No massive hp gains. In R form slightly more I think ? More flowing cats was the thing here.

Making engine running lumpy at low speed and possible getting way more difficult driveability down low rpm where gearbox keeps rpm usually is not right way to me atleast. With older engines you can bend this thinking especially with manual gearbox. I have done it many times too. I don't want to continue this "debate" more.

 

The engines I'm comparing to were designed in this era too. They still benefit from bigger cams with overlap and as much timing as it'll take without pinging.
The stock crankcase breathers make them more prone to pinging with the carbon buildup and lowered octane levels tho.