We only have one grade of petrol and it runs well with it ( 95 octane at coast and 93 at altitude ) . My compression prior to fitting efi was 9,5 and all was well . When I fitted the efi ( and new head ) I kept the compression stock - for a brief moment I considered a turbo so was reluctant to raise compression .
I researched the cam at length and have a very long writeup that I posted at my local club : here it is - hope it helps to make up your mind
Over the last three months I have studied the topic intensely and have stumbled across numerous approaches to modifying the 2F cam for performance .
The 2F with is longer conrod and bigger displacement ( than 3F ) has huge untapped potential . In stock form the 2F has more torque than the 2H ( or any of the era's N/A diesels ) at 1800rpm .
The trick is to retain that torque but wake up the engine so it can run happily on the freeway and in the dunes .
The US approach is to fit a RV cam . In studying what a RV cam is I concluded that RV stands for " Real variable" - every cam grinders' RV cam varies
With
camshafts there are a few variables ( just the basics ):
Duration : the length of time the valve is open ( measured in degrees)
lift : the height the valve gets lifted off the seat
overlap : the amount that both valves are open at the same time
Lobe seperation angle : angle of the inlet / outlet lobes to each other .
All these variables have an influence on each other - changing one will change the other as well
Each variable will gives the engine a particular characteristic and changing it affects the engine .
Eg . Increasing duration = will affect overlap ( most of the time ) , increases lift and will raise the HP at top end at the expense of low down torque.
Overlap is the main thing affecting manifold vacuum .
From the book:
www.4x4books.com/toyown.htm
"Manifold vacuum is crucial in truck pulling power , proper combustion , and fuel economy . In effect an automotive type gasoline engine is a vacuum pump . Your trucks engine operating cycle begins with the vacuum characteristics of the intake stroke . If you plan serious rock crawling and trailer pulling , or want low speed economy and good throttle response , high manifold vacuum will be on top of your priority list."
With all these variables it becomes very tricky if you want to fit a aftermarket cam as it may render the engine unusable for your application .
Lets look at the cams out there :
Stock cam has very low duration and overlap . Gives a engine with decent torque . No need for a lot of overlap as the Compression ratio is very low and the engine can be used with low octane fuel .
Stock 2F
250 duration
duration @ 0.050 = 189
32 degrees overlap
Int 17-53
ex 55-15
valve lift 0.377
L/C 108
3F stock ( it is exactly the same cam as the 2F BUT advanced 5 degrees )
250 duration
duration @ 0.050 = 189
32 overlap
INt 22-48
EX 60-10
valve lift 0.377
Performance
The idea with the performance cam is that with a rebuild the compression gets raised ( one way of increasing HP ) , a branch gets fitted ( to help scavenging / airflow ) , ignition gets improved ( electronic ignition ) etc .
With these changes the cam also needs to be altered . Just fitting a performance cam will render little if the engine is not matched to it . Adding a performance cam in combination with the other modifications will give the required results .
To quote Mark Whatley :
Quote: In an otherwise stock engine you will not notice much power improvement. You'll see a little. In a powerplant with raised compression, increased carburation and intake flow and improved exhaust, it will run like a scalded ape.
The most common perfomance cam in the US market is the RV cam made by Man-a-fre .
Specs of the Man-a-fre cam : RV Cam is 260 deg duration, .420" lift, 42 deg overlap, Lobe Centers @ 109, Clearance INT ..014" EXH .016".
Rainer ,a member of LCCSA living in Namibia fitted this cam in a 3F and had this to say :
Quote: There is definitely a difference, the cam does not lose to much bottom end torque, and it revs nicely up to 4500.
Close variables on it is the Mark Whatley cam .
Mark Whatley himself :
Quote: A
camshaft with a duration at .050 of about 210 to 217 and a lift in the area of .240-245 wil produce a notable improvement in mid range and high rpm power. At the sacrifice of a small amount of peak bottom end power (below 1000 rpm).
This grind has the following specs
Perf 262 grind
Duration intake 262
Duration exhaust 267
Duration @ 0.050 is 217
Intakes opens 24, closes 59
Exhaust opens 62closes 34
58* overlap
cam rise .284 L/C 108 degrees ( gives 0.430" valve lift )
Lash intake .014 exhaust .014
From the book
www.4x4books.com/toyown.htm :
" For the F and 2F inline OHV sixes with the long stroke , its easy to extract serious stump pulling power . A mechanical liefter camshaft of approximately 0.428" gross lift and 260* total duration will work well. Assuming that your 2F has a reasonable compression ratio ( no more than 9,2:1 ) , the idle with this kind of camshaft is smooth , and your engine can develop strong low-end torque plus respectable mid-range ( 2000-3500rpm) HP. Expect this type of camshaft grind to flatten its power abruptly around 4200rpm "
What will this cam give you ?
Higher compression ratio needs the longer duration and overlap to bleed off the extra pressure . Extra lift and duration will mean a lot more power in the high rpm range - but a bit of low end power is lost . The bigger overlap will increase scavenging effect as the inertia of the airflow draws air out of the chamber .
So if you want to have a 2F that can handle the dunes and be a great freeway car ( good throttle response between 2200 - 3500rpm ) then this is for you .
Torque is King
Downey ( not operational any more ) in the US had two cams to offer :
1. Torquer cam : 214 duration @ 0.050
2. HP cam : 224 duration @ 0.050
The HP cam has a huge duration and I would never consider something like that as you would need to really rev the engine to get any HP out of it .
The torquer cam apparently gave great torque and still could rev up to 3000rpm comfortably . In the absense of other specs I cannot analise it properly and since the company went bust it does not really matter but it was a cam worth fitting IMO .
After numerous e-mails between me and Jim Chenoweth I came to the conclusion that if you want a real "torquer" cam you should keep the overlap low , keep the duration as close to stock as possible .
A lot of the "torquer" cams out there do give torque but you have to go up in the rev range to achieve the promised torque . ( some claim the RV cam by Man-a-fre to be a real torquer but you get that torque from 2200 rpm onwards - too late IMO ) . The stock 2F has peak torque at only 1800rpm .
So if you want a torquer stay with stock or go for the MC803 cam . It is a Melling aftermarket cam ( apparently of better metal than OEM ) and is identical to stock but its LSA is 112* and not 108* . This
camshaft will however fall flat on its face at 3000rpm .
A real crawler but not great in the dunes .
Melling 803
camshaft : ( as per their technical dept )
MC803 duration @.050 int. 189, exh. 189
Valve lift .379int. .379exh.
Lobe centers 112deg. int. 112deg exh.
Compromise
The challenge is to get a cam that will give you the low down torque of the stock 2F but still rev up to 4000rpm for that occational sortie in the dunes and to make it a pleasant DD on the freeway.
The answer ( for me ) I have discovered lies in a cam that Delta in the US grinds .
Perf 250 S grind
Duration intake 250
Duration exhaust 254
Intakes opens 17, closes 53
Exhaust opens 60 closes 14
cam rise .255 L/C 108 degrees ( eq valve lift of 0.383)
Lash intake .014 exhaust .014
This cam is very similar to stock . The intake timing is similar to a 2F cam , the exh timing is similar to 3F cam . The duration at 0.050 = 215* ( compared to stock that is 189* ) . The overlap is practically the same as stock ( 31 vs 32 ) .
The duration @0.050" is slightly lower than the 262 RV
camshaft but advertised duration is a lot lower . Thus the valve will lift quickly and close quickly as it does in OEM . The low overlap will also mean that vacuum in the manifold remains high .
This cam will thus give the same torque features of a stock 2F but due to the longer duration @ 0.050 is will rev comfortably above 3000rpm .
Jim's concern was that this cam will require premium gas due to the low overlap in the high compression engine ( in the US premium petrol of octane above 91 is 20cents / liter more expensive ). He himself uses a MC803 cam in his 4,5l overbore 2F with 8.8:1 compression . In SA and Europe the regular octane is 95 thus making it usable in SA .
He says :
Quote: It is a good choice, especially with your higher compression and good gas. Should run strong, and not fall on it's face at 3000rpm. Delta cams in the US answered my question to them :
Quote: correct, your engine will be creating the torque rather than your foot to the floor and relying on momentum.
Here are more cams options that I found on the net .
Isky cams in California offer these grinds
Isky Z99+E3 grind
258 duration
42* overlap
INT 21-57
ex 57-21
lift 425
Isky z99-005 grind
260 duration
50 * overlap
Int 25-55
ex 55-25
lift 406
Crow cams in Australia
Adv duration 266
duration @0.050 is 208
int 24 - 62
ex 64 - 22
L/C110*
valve lift 0.420
46* overlap
I struggled a lot to get decent info on the net . The problem is that aftermarket cams are usually made for "racers" or " dragsters" , not for off road 4x4 cars . Guys usually seek HP and look for a rough idle to sound cool . I wanted a slow car that does not run above 4000rpm - these guys usually start at 4000rpm .
I found a site that is dedicated to inline 6 cylinder cars like the 2F and they have a lot of valuable info that is easily understood by a appy like me :
www.classicinlines.com...ectCam.asp
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