308 2-V Intake cam differences - Carb vs. Injected

Dave
You might call Giovanni at Autosprint in Chicago. He was recently searching for some carb'd cams for a carb'd car and had run FI cams in the same carb'd car (so the opposite of what you are trying to do). I don't know if his experience will be overly influential, but it did cause him to pull the FI cams out and search for carb'd cams.
Philip

 

The lifts also got reduced on the later ('78-'79) carb and "i" 308 cams I believe (intake reduced from 8.9 mm to 7.7 mm lift and exhaust reduced from 8.3 mm to 7.7 mm lift):

Go to the old site and do a search on "308 euro cam" (and mode, parts of words) and you'll get plenty of homework to read like:

http://www.ferrarichat.com/discus/messages/256120/251131.html

The strict answer to your question is that the K-Jet system will probably work just fine A/F-wise with Euro cams (ignoring the fact that people seem to think it's generally undersized in its 308i embodiment) since it scales fuel feed with air intake (and Euro K-Jet "i" do exist). I believe another practical problem is that the Euro intake cams don't have the distributor drive for the second US distributor so you'd need to deal with that too.

 

I should clarify that those lift numbers are for early US (not Euro/Standard) vs later US. Now that you mention it, I'm not recalling any Euro vs early US cam comparisons, but there might be some info in their respective OMs (at least durations) .

 

Dave,
I downloaded all of the available OMs and extracted the cam specs. Then created tables of cam timings & duration. They're in the thread 91tr referenced below. Look towards the bottom of the thread.

 

I have no first-hand experience on this, so it's hearsay.

I've heard that one of the primary reasons that duration and overlap were reduced on the "i" cars was because "reversion" (the tendency for 'hot rod' cams to spit backwards up the intake system) caused the early injection to screw up and not meter fuel correctly. I have no idea if anyone has tried doing the retrofit to see if it actually works.

I *think* the earliest US cams were the same as the Euro cams. The early US cams work with the 2 distributor setup. Note that in several "Authoratative" sources, such as "Original V8" may contain some errors in this area. In particular, I think there was a misprint in that book.

 

Not sure of the specifics of the cam increase you are contemplating, but you do have to be careful with CIS cars, they can only take mild cams.

This applies to all CIS cars. This is a common issue with CIS Porsche guys, too. On the 70s and 80s 911s, guys want to put in hotter cams, and do so, but are limited in how hot the cam can be. It ends up being only a minor (but supposedly still noticeable) increase.

So if you plan on swapping cams, just be sure that it's going to work with the CIS system.

That being said, if you could figure out a way to get a hotter cam in a 2V and keep the CIS, and get better performance, that would be great!

 

2-valve injected 1980 USA 308i ( ... a model variation, as an aside, which I believe has suffered from an unjustified poor performance reputation within the 308 line),


What leads you to believe the reputation this model variation enjoys is unwarranted? Just curious because when I was searching for a 308/328 thats the only model I was told to avoid by everyone I asked.

 

Gearhead and 4re are quite correct about the Kjet sensitivity to reversion pulsing.

Approaching 1980 Ferrari switched to Bosch K-jetronic, as Porsche had some years earlier, mainly to meet emissions requirements. The Bosch Kjet is PRIMARILY designed for emissions control, NOT for performance. It is a very elegant sophisticated mechanical injection system that is a marvel of fluid dynamic engineering. The amount of fuel going to the always spraying injectors is controlled by the fuel distributor which is really like a giant pressure valve. This valve is operated by the huge airmass sensing plate attached to the fuel distributor. This is where the cam (and airflow) limitations come in.
The problem is cam OVERLAP and timing. You will note that the overlaps of the FI cars are only 26 degrees or so. Euro carbed 308s had 58 degrees overlap to allow for better breathing! This small FI overlap helps to prevent reversion pressure pulses which bobble the airmass plate causing poor performance. Porsche 911s with Kjet 2.7 and 3.0 motors also have this problem.
Perhaps the biggest performance problem with the Kjet system is the RESISTANCE TO FLOW. The air has to take a fairly convuluted path, not to mention get around that big plate, to get to the engine. This air resistance alone costs about 20 horsepower. That combined with the soft cams required by the Kjet is where much of the emissions control power went when combined with ignition timing and exhaust mischief.
Porsche 911 guys have found some more aggressive cams that do not upset the Kjet. Of course, forced induction overcomes both the resistance to flow and mild cams witness the first 911 turbos and the Norwood conversions. These porche profiles are available, but do not know how they compare to the stock Ferrari 244s with 26 overlap. Something that would be easy to try is to RETARD the exhaust cam one screwhole on the timing sprocket. This would add about 4 more degrees of overlap to see if the Kjet would tolerate it. If it does, you may probably feel an hp increase.
Carbs or EFI allow better cams as they can handle the reversion pulses better, and allow for a much less restrictive airflow tract.
I would be way interested (as well as hundreds of others) in your finding a bit more aggressive cam that the Kjet tolerates. Perhaps Pelican Parts can chime in with the Porsche experience.
Well, I hope this a little oversimplified rant helped someone. It's really all about flow.......
best to all
Russ 'of course I could be all wrong' Turner

 

Need also to say that you canot directly compare 2v cam settings with 4v cam specs.
With 4 valves, a little goes a LONG way.
Where a 2v Daytona ( 80+ hp/liter) has cam durations of 271/264 with 83 degrees overlap, a 4 valve car would barely run on that if at all, even with EFI. For comparison, my notes say that a 355 (over 100 hp/liter = aggressive cam) has an intake duration of 255 and an overlap of 30 or so.
Just be careful all you 4v and 5v guys when comparing cam specs.
best
rt

 

You know, I have had people for years telling me what a lousy car my 81 308 GTSi is. You want to know a secret, it may be slower than the carborated models, but I have never, and I swear never, had a problem with it. It was never recalled, no major oil leaks or consumption problems, it never over heats in stop and go traffic. How many Carb guy's can claim that. Its a great car, I have owned it for 23 years!

 

Flashman,
I don't mean to offend, but what that means is you got a "good one", but unfortunately, history does not seem to bear out that your situation was a common one....

I'd still take your car over a P-car or BMW, any day of the week!

 

Hi Dave, I am currently in the process of having some more hp extracted out of my 82 gtsi. The guy who is taking care of that claims the best way is to increase lift as much as is possible(10.5 mm), increse modestly duration and very modestly overlap.
A minor reversion of flows should be acceptable, since main drawback should be a rougher (richer?) idle. On the other hand (he says) you can really take advantage of higher durations only swapping your pistons for higher CR, but alwys keeping reasonably modest overlap. In the end this shold lead to wider lobe separation, so more top end power at the expenses of powerband, but if you rise CR you shold be able to get to compensate torque losses in the low end.
Custom cams (or regrinding should be the way to go, rather than fitting carbed cams; I guess it shold also be cheaper.
BTW the guy claims that a major work ( cams+ hi-comp pistons + polishing + balancing + exhaust) shold be worth a final 270 hp delivery or more (and a lot of moneY) even keeping original FI. Obviusly chenging to real EFI o mechanic 300 or more wolud be the result.
He used to be chief mechanic at Autodelta with Mr. Chiti and is a well reputed tuner, so I hope (for my own good) the info is reliable.
Cheers
Federico

 

If you stick with the stock 8.8:1 pistons, you are wasting your money replacing the cams for the small gain you will get. To change the lift on the 308 cams, you have to weld the lobes and regrind due to lack of a base circle, the cost is $1340USD from WEB cams for the set + your labour. You wont get a $1300 gain with stock compression. Go all the way, change the pistons, spend the money and be happy with the results or mess with degreeing the stock ones only. From what Ive seen, factory early US cams or Euro cams cost more than regrinding your originals. Im running around 10.5:1 pistons and now Ill do the cams and they will give me the gain they are designed to give and I wont be disapointed.

 

I can't speak for changing cams in a FI car, but have different experience than Paul's suggesting with a carb'd car. First, let me say though, that spending the money and doing pistons, cams, bigger valves etc is not a "sensible" financial investment on a 308. That said, there's a cadre of nut cases, like me, that enjoy the older cars and getting some more "oomph" out of them.

As some of you know, I put P6 cams in my car. It has more "oomph". Before anyone jumps down my throat with "show me", I have not dynoed it to tell how much but track lap times show the improvement and others that have driven the car and are very familar with the 308/328 models have opined too that it has more to it than stock, or a 328. The lumpy high overlap cams do make the low end performance suffer, and running with big venturis makes the low end pretty intractable. Given I use the car 90% on the track, I am comfortable with the tradeoff.

The support for cams (even with modest compression) and bigger carbs can be seen in Ferrari's performance literature (look at the durations and overlap with the Daytona's [including racing models] and 246s. But as I said above, doing pistons and cams (and carbs/individual throttle bodies) will give you more.

Some of you know Bill Pound. He's forgotten more about competition Ferrari's than I've learned. First, he warned against putting in the P6's - low end performance and financial ROI. Second, he opined that a set of cams will provide the biggest "bang for the buck" (and all told it was not a cheap "upgrade").

Putting in a set of pistons, valves, flowing the heads, doing the headers etc is not an investment for the faint of heart ($10 - 15K?) when done by a good engine builder. That said, it might deliver another, say, 20(?) BHP. Night and day when you are racing. Not enough to warrant the investment on the street or other track use.

So what to do? My 2 cents: If it is your "pride and joy" and working on it is a big part of the ownership experience, you love the model and so on and you have a long term holding interest, spend the money but don't expect much of a return on your $$$. The emotional rewards will be significant. The financial rewards will likely be negative.

If your time horizon is less certain, save the money just drive the car. This is what it was designed for. When the time comes to sell, 355s will be that much more affordable (particularly when the 360 replacement comes out).

OK, I'll get off my soap box. My apologies if I have offended anyone.

 

Dave,

Glad to see this is back in discussion. I think many of us would like to extract some more performance from our injected 2V motors. I know I would. I played around with my cam timing this summer while I was changing belts to try and find out some of the limitations of the factory injection.

I tried the "Ted Gage" suggestion of retiming the cams to as close to the european centers as possible. This caused significant reversion in the intake tract and made the idle pretty bad below 1500 RPM. Part of the reason was engine vacuum had dropped to 10 lbs. However you could definitely feel an increase in power from 3200 RPM +.

I then tried a compromise of Ted's suggestion. I advanced the intake 6 degrees from the factory spec and retarded the exhaust 6 degrees as well. This resulted in a much improved idle and much better engine vacuum at 15 lbs.

Again this was not an effort to find the optimum intake and exhaust opening/closing points, but to test how much overlap the factory injection could handle.

Below are some of the specs that occur with the different timing values.


Cam Calculations - Lobe Center / Duration - Factory Spec

Intake Open = 16 BTDC
Intake Close = 48 ABDC
Exhaust Open = 50 BBDC
Exhaust Close = 14 ATDC

Overlap: 30.00 degrees
Intake Duration: 244.00 degrees
Exhaust Duration: 244.00 degrees
Intake Installed Centerline of 106.00 degrees ATDC.
Exhaust Installed Centerline of 108.00 degrees BTDC.
LSA = 107 Degrees
Cylinder Pressure = 165-170 lbs.
Vacuum at Idle = 18-19 lbs.

----------------------------------------------------------------------

Cam Calculations - Lobe Center / Duration - Ted Gage - Retimed to Euro Spec

Intake Open = 22 BTDC
Intake Close = 42 ABDC
Exhaust Open = 32 BBDC
Exhaust Close = 32 ATDC

Overlap: 54.00 degrees
Intake Duration: 244.00 degrees
Exhaust Duration: 244.00 degrees
Intake Installed Centerline of 100.00 degrees ATDC.
Exhaust Installed Centerline of 90.00 degrees BTDC
LSA= 95 Degrees
Cylinder Pressure = 185-190 lbs.
Vacuum at Idle = 10 lbs.


----------------------------------------------------------------------

Cam Calculations - Lobe Center / Duration - JB Spec

Intake Open = 22 BTDC
Intake Close = 42 ABDC
Exhaust Open = 44 BBDC
Exhaust Close = 20 ATDC



Overlap: 42.00 degrees
Intake Duration: 244.00 degrees
Exhaust Duration: 244.00 degrees
Intake Installed Centerline of 100.00 degrees ATDC.
Exhaust Installed Centerline of 102.00 degrees BTDC.
LSA = 101 Degrees
Cylinder Pressure = 175-180 lbs.
Vacuum at Idle = 15 lbs.


What this tells me is we can probably get away with some more overlap and duration as long as the LSA remains wide, somewhere between 110-112 degrees.

Additionally more valve lift will really help. As Steve mentioned the lift was reduced on the later cams, so we know we can probably add more lift without hitting the pistons, and certainly with aftermarket pistons the valve reliefs can be tailored for more aggressive lift. How much will be up to the cam grinders to determine how much they can provide without the lifter bouncing off the cam lobe. Modern techniques should allow a pretty decent amount.

Sorry for the long post.

 

Not offended at all ama1010 but you left stock compression, put in P6 cams and hurt the torque/performance and all around driveability of the car. Not what I would call a good result and thats what I said would happen. 8.8:1 compression and long duration and big overlap dont make a good performing car (for the street) and the bulk of the people here dont drive their car at 8K rpm on a track like you rather than on a road. If I put in P6 cams with stock compression, I would hang myself because of the disapointment and all the money spent. I want to see dyno numbers, especially torque values. My opinion is you made an error choosing those cams but thats just my opinion. The fact remains there is very little to be gained by changing cams in a stock 308 engine and they arent cheap so why bother? Do the engine right, with the right combination of parts so they all work together and perform the way they should. Hope I didnt offend anyone.

 

Paul
No offense taken either. I think we'll agree to disagree. If you are ever down in Chicago when the weather is good, shoot me an email and come and drive the car.

 

I would like to drive the car and Ive been very tempted to go nuts on my cam selection but Ive made that mistake before on other cars (muscle cars from the 70's and 5.0 mustangs) and had regrets. I want a lumpy sound but I want to retain or improve torque and they usually dont go hand in hand especially on a 178CID engine that is torque challenged to begin with. Im sure your combination works well on the track and would work better with higher compression but not as well on the street. The thought of P6 cams makes me all warm and fuzzy inside but they just wont work in my application and most other 308 owners as well. I believe the ferrari engine designers loose sleep over the small details like cam choices and they put alot of thought into the selection to give the best all around performance results so its very difficult to improve on the design by slamming in a set of monster cams like they never thought of it. 308 engines are not cheap to build and my quest for more power will be in an injected and blown version (in the future)because you can expect only so much from a tiny engine, carbed or injected.

 

"my quest for more power will be in an injected and blown version"

Me too

I've seen an awful lot of dyno runs with al sorts of combinations. Here's my very humble opinion. I believe that P6 cams with stock compression make more hp, if I had to guess, I say 20 hp. I also believe the torque is up a little above about 4000 rpm and carries out further, probably 5500-6000 before it starts to drop. It will be great at the track and fine on the street if you tend to keep the rpm up. But I would also guess that below 3000 rpm the engine will be down about 20 ft-lbs on the torque. Some people would hate that, other will never evn notice it. The torque curve will have a step in it similar to what you see on a turbo engine, but not as steep or pronounced. Increasing the compression by about 2-3 full points will pull the bottom back up and yield a nice smooth curve, but will cost you about $4k in parts if you do the work yourself.

So, on a carb car, cams are the biggest bang for the buck, particularly the late cars, but there are so trade-offs. On an injected car, cams arew probably still the best return, but spending the $3k for an EFI or carb convertion at the same time as the cams will move the power up or above the carb guys.

 

$4K is a tad high, my custom pistons cost me $1700cdn, I did the work myself and my guess is it ran me around another $1k for the rest of the stuff I needed. Ive run my car against an early euro 308 with the same mods as mine but he had the good cams and I had no trouble keeping on his a$$. So much for the euro cams.

 

"$4K is a tad high"
It is high if all you do is pistons. I figured bearings, seals, gaskets while it's apart. Fluids, hoses, belts, all adds up, but the service done at the same time.