engine specs. Will it be drivable?

[degreeoff1]

Here goes.......

Engine----2.4 with S+ cams (base circle cut on 1 cam) and 2.2 "S" P&C's Heads ported to "S" specs.

Carbs----40 IDS webers with 38mm chokes (I think this is too big)

Ignition--- Electromotive crankfire

All of the above in a 914 with stock gears....Anyone care to chime in on this config and tell me where I will run into trouble? I am working with parts from different engine's (basket case). A local Guru is telling me that the cams are no good because the base circle is cut and the valve Geomerty will be wrong, also he is saying that the rockers would ALL have to be replaced due to cams being out of a diff engine and the wear pattern will kill them.... and he thinks the torque and power will be in the unusable range....I want 7K rpm min

I will be using this car for track/AX and street.....a toy though

Thank you guy's in advance.

Josh

The car will be about 1900 lbs

[degreeoff1]

bumpster

[jluetjen]

Josh;
Basically you've got a high-CR 2.4S with carbs. The higher CR ratio will help with flexibility, but the carbs will lose you some flexibility compared to the factory's MFI system. Having the 914's "wide" set of ratios won't help matters much since you'll be geared for a 151 mph top speed at a 7000 RPM redline. Cruising at 65 mph in top gear will have the engine turning 3000 RPM which will hardly be cracking the throttle. I'm guessing that it will be making about as much HP at that engine speed as my 2.0E. Certainly driveable for highway use, but for track use you'll be hard pressed to ever use top gear. With most east coast tracks, if you're pulling a 135 MPH top speed, you're doing pretty well.

You'll need one of the engine builders or Camgrinder to chime in (check over on the Engine Rebuilding BBS) regarding your cam situation. If you've cut one cam undersized, but not the other, this will result in different geometry. This will mean that your engine will have slightly different performance on each bank. Will this work? Sure -- as a "battlefield fix". Is it optimal? No. Having an engine that is lopsided like that will introduce stresses as a result of the engine being out of balance. Is it a successful strategy for building a high-performance engine that also has a long life? Most likely not.

BTW, if I were you, I would get the rockers refurbed prior to using the "new" cams. It doesn't cost that much, and by all accounts, failure to do so will wear a set of cams prematurely. Once again, maybe Camgrinder can give you a real world example.

[2.7RACER]

Josh,
Your instincts are correct about the 38mm venturi in 40mm Webers. 34mm for your engine will work much better. 32mm if just for the street.
Regarding your cams, I would verify that both cams are the same grind. That is intake opens and closes with the same duration 268 degrees @ 1.0mm lift and 0.10mm gap.
The "S" cams intake opens at 38 degrees BTDC and closes at 50 degrees ABDC. Same 1.0mm and 0.10mm gap.
You'll need a degree wheel to check this.
If both cams are running the same profile the motor will run fine.
Yes the rocker adjusting screw on one side will be set a little longer than the other side, but the valves and engine will see the same timing and lift.
Don't let anyone scare you into thinking otherwise.
Absolutely check the rockers, they are over thirty years old.
Working with a basket of parts to make a motor can be a real challenge, matching pistons and cylinders is especially important.
Keep us advised on your progress. Should be fun, enjoy.

[svandamme]

Originally posted by jluetjen
Basically you've got a high-CR 2.4S with carbs.

I'm guessing that it will be making about as much HP at that engine speed as my 2.0E.

ehm

if it's basically a 2.4 high CR S ,
then why would it only put out the power of a 2.0 E ?


loose something with carbs , but not 30 HP , right?

the 2.4S with 2.2S pistons , wouldn't that be closer to 190 HP then to 160??

[camgrinder]

IT depends on how small the base circle is. Hard to see a change if say, 1mm is removed. If 2mm 's are removed you can see a small change in the lobe center angle and a slight reduction in duration. If the camshaft grinder is sharp, there are ways to make up for this when its ground.
If your worried, I can inspect them, "Cam DR" them (at the valve) and let you know what you have.
Your "guru" is right on the rocker arms. If you have used stuff, it better all go back together the same way it was taken apart. If not you have a good chance for a failure.

[jluetjen]

Originally posted by svandamme
ehm

if it's basically a 2.4 high CR S ,
then why would it only put out the power of a 2.0 E ?


loose something with carbs , but not 30 HP , right?

the 2.4S with 2.2S pistons , wouldn't that be closer to 190 HP then to 160??

svandamme; Relax. Did you notice that I said "at that speed" -- specifically 3000 RPM. At that engine speed an E puts out more torque then a comparably sized S. Check the factory dyno sheets. Once an S gets on-cam, it will certainly outpower an E, let alone a smaller capacity E.

BTW, I agree on the carb venturi sizing. Everyone using carbs on a 2.4 that I've seen is using 32 mm venturi for milder tunes, and 34 mm venturi for more top end power at the expense torque lower down.

[degreeoff1]

Thanks all for your input,

I am sorry I was not here to respond. I have been out in Vegas for a week.

Cam grinder.....what if the cams and rockers are NOT matched and no way to get a "matched set?? will I need to use a "new set of rockers" or will a refurb job do the trick.

The cams are used but I believe check out. I will send them off to you if you give me some info as to where.

I just don't want to spend all the time and $ on a rebuild (my 1st) to have a silly thing ruin it for me. The carbs chokes are easy to switch right?? never done that before....

151 mph top speed eh?? that would be fun......:-)

Thanks

Josh

[svandamme]

if you use old rockers on a new cam, or on a used cam , new to those rockers
it'll wear out the cam prematurely, cause they allready have a wear pattern


this is why you have to keep the rockers numbered if you take apart the valvetrain, it's not a good idea to switch rockers from one cam lobe to another

rockers can be refurbished though , although i'm not sure if that's cost effective, they are still available new , and for me , it wasn't worth the hastle trying to find a shop to do it, sending the rockers, etc etc, and then worrying if it would be done properly...i used new ones on my new cam...

[degreeoff1]

Ya its a delema for me the cams are used as are the rockers (-1 new) and they are all from diff engines...hmph

wonder if I should just get new cams and rockers....$$$$$$$$$

[YTNUKLR]

New rockers are $$$$$$$$$...have yours refurbed (camgrinder, above, or most Porsche machine shops can do this), about half the cost of new (several hundred $).

Best
Scott

[svandamme]

i got 12 new complete rockers for 432 euro's (524 USD)


no cam grinder in Netherlands, and shipping to and from the us wasn't worth it , the price difference after shipping, import taxes , and so on would have made it more expensive if anything

[camgrinder]

Using mis-matched rockers and cams is risky. Its best to redo the cams and the rockers.
I sent you a PM.