4.5 performance mods? - PeachParts Mercedes-Benz Forum

Tomguy · #1 01-13-2004, 11:34 PM

Would any of the following increase/decrease the 4.5's performance? Keep in mind, it's eating at me that I have later cams and I want that power back!

-Replacing the later cams to 3.5 (euro) cams
-Replacing the injectors to a 3.5's (blue/green to yellow)
-Replacing the distributor with a 3.5's
-Ignition box from 3.5
-D-jet and/or MAP from a 3.5

Thanks in advance!

psfred · #2 01-14-2004, 11:33 AM

For easy changes, I think the cam swap is about it. Injectors from a 3.5 will give more fuel delivery, but milage is terrible on this car in the first place, and I cannot see needing any more fuel. Black smoke doesn't mean you are producing more power....

The ECU isn't a good replacement, it's different. Doesn't have the full throttle enrichment, for instance.

Find a pair of cams from either a euro 3.5 or early 4.5 (pre '73) and drive it.

For even more power, you could aways find a 6.3 and covert it.....

Peter

Tomguy · #3 01-14-2004, 08:08 PM

Peter: Thanks for the advice. I figured the 3.5's injectors allowed more fuel flow, but I suppose it's true that, on a vehicle which you can so easily change every aspect of the fuel delivery on, why change them?

If I could get a 3.5's cams (~79 "Grey market" 350, 116.982), I would think that they'd be better than the original 4.5 cams, correct? Or would they be in between what I have now and originals, or identical?

I suppose that now, after getting massive throttle response from such changes (manifold cleaning and gaskets tb cleaning/adjustment, vacuum leak repair, etc) I desire even more of that V8 gusto!

psfred · #4 01-14-2004, 08:37 PM

The Euro spec cams will be hotter than any of the US spec cams, I think.

However, you will probably only gain some milage, not noticable power. I haven't floored mine since I put new points in it -- there's always something in front of me these days.

Peter

Tomguy · #5 01-14-2004, 08:43 PM

Peter: I've personally never driven this car when the original cams were on. I was amazed it ran with them in their deteriorated state when I replaced them (no way was I going to drive it with those worn away things - see the attatched image). Therefore, if the newer American cams give worse mileage/HP (HP by 20? What about torque) and Euro 3.5's would be 5HP more than original stock, I might not notice the 5 but I bet the 25 would be detectable. Also, if I get 2-4MPG better... well, that's sure worth it! (I haven't checked my mileage in a while, I filled up ~2wks ago and today was the first time I drove her since).

(Unrelated?) question: Is the allen screw in the MAP just a regular worm screw? The inside of it is becoming a little too stripped-out for my liking.

Tomguy · #6 01-14-2004, 08:45 PM

Oops... apparently I'm not the only one forgetting attachments at least!

psfred · #7 01-14-2004, 09:23 PM

Yeah, sluggish comes to mind.....

Peter

Tomguy · #8 01-16-2004, 03:24 AM

I think I'm going to spring for the 3.5's cams. If I can pick the pair up for like $100 it should be worth it (to me at least!)

Tomguy · #9 01-17-2004, 12:43 AM

One quick question:

I've enclosed a closeup of one of the lobes. Is this an indication of a more agressive design with less wear on the leading and descending edges, or more wear on the tip? The lobes I have now look mostly like the one "good" one in the picture I attached - but is that lobe actually "good" to begin with? (In other words, the ones I have now look more "pointy" but don't have quite that long of an open duration it appears - of course, this would look like it's also less stressful to turn).

At any rate, would these cams be worn or just fine/good/perfect?

psfred · #10 01-17-2004, 10:11 AM

Tom:

The one lobe I can see clearly looks flat to me.

Normally, the tip is fairly sharp, but I've not looked too closesly at mine. On the Volvo, the lobes are quite sharp looking, but show no wear.

A new cam will have a slightly granular appearance on the working surface, and it will be smoothly curved. Flat spots, shiny spots, any evidence at all of ridges or areas with fine parallel "polish marks" indicate wear. The lobes are surface hardened, so when the hard surface is worn away, the softer metal underneath will wear much faster than the remaining hardened material. That gives you the "two steep hills with a wide one in between) effect. I'd not bother with a used cam that show any wear -- it's gonna go pretty fast in use.

Peter

Tomguy · #11 01-17-2004, 11:42 AM

Peter: That's what I was afraid of. I actually noticed it when looking for a part number on the camshaft itself ("116 48" is the only visible marking that may be an MB number). This lobe is for cyl#2 and is the 3rd lobe on the cam itself. I don't recall exactly, but I believe that makes this an intake, correct? (I can go out and look, but it's COLD and I don't want to leave the comfort of this place). It's the only intake lobe which I can actually see clearly. If I asked for a downward view at the top of the lobe, would I be able to see any grooves from wear?

I was hoping that it was because of the more agressive design (green line), it keeps the valves open longer but in order to maintain valve clearance, the top was shortened (otherwise it would follow the red line, causing the valves to crash onto the piston). Granted, I'm no engineer nor am I a mechanic, but these lobes just look "thicker" than the ones I have now. Possibly an easy way to tell would be to ask for the height of the lobe (at the very top) and the width (at the narrowest point) and subtract the two to get total valve clearance.

I'm thinking that I could always get rid of these cams at little loss, if they aren't quite right.

psfred · #12 01-17-2004, 04:09 PM

The red profile is probably more correct. Certainly, the best way to check is to measure the height at the highest point, it should be to spec (in the manual) and the same for all the intakes and exhausts as a group.

The profile will be smooth, and there is no chance a longer cam lobe will cause the piston the hit the valve -- cam should be amost to the "closed" position before the piston gets up that far.

Easy enough to do with a micrometer (english or metric) with adequate reach (needs to be a 1 to 2", I think).

Check for ridges parallel to the cam shaft, too -- if you can feel any around the lobes, the cam is wearing. Fingers can be better than eyes here.

And as I said, shiny tip with some streaks is a sign of wear.

Peter

Tomguy · #13 01-17-2004, 05:21 PM

The more I look at that cam, the less I want to buy it.

Can you tell me what the heights should be for a 3.5, 116.982 engine? And then for a 117.984 engine? I don't have a manual (I assume you mean shop, not owner's!). Thanks in advance!

psfred · #14 01-17-2004, 09:26 PM

Tom:

Can't tell you the height, only that the base is 34mm diameter. You can measure all of them, if any are short, cam is shot.

you want the 46/47 cams, not the standard 52/53 ones if you can get them, they have different overlap.

Peter

Tomguy · #15 01-18-2004, 11:00 AM

Peter: What are you reffering to, the part number? (The part number on my current right cam is 116-051-4901) I assume you mean the 2nd series in the part number (051)? Or are you reffering to height of the lobes?