Added 15 to 20 HP to my 1977 450 SLC - Page 2 - PeachParts Mercedes-Benz Forum

Graham · #16 10-30-2017, 09:19 PM

By the way, my unmodified US spec 72 107 4.5L Djet (with recommended standard copper core plugs! Platinum not recommended for these engines) could do 0-60 in ~9sec on a good day ! No emissions stuff to slow her down

Getting mixture right was key. Now not quite that good, because tuned for economy.

Sounds like you must have seen this site

Mercedes Benz 107 SL SLC Roadster Information Horsepower Page

Tony H · #17 10-30-2017, 11:13 PM

Car is in storage but I can find a pic on the net

Tony H · #18 10-30-2017, 11:24 PM

Here's a few pics I found(not my car)

breastroker · #19 10-31-2017, 12:07 AM

I do like that site, has better information than many. Especially about the Bosch Platinum Super-4 spark plugs.

I sure would like to know where all this anti platinum plug information comes from. An engine is just an air pump that sucks, squeezes, bangs and blows. It doesn't care if the spark plugs are copper core, platinum or some other exotic metal. As long as the gap is correct for the coil and the advance is correct, the plug doesn't need to be copper core. I think this needs to be but to bed. Heck the correct Champion spark plugs aren't made any more. So NO ONE is using the correct plugs!

I can say my engine loves the Bosch Platinum Super-4 spark plugs. Better idling, smoother acceleration and seems to have more power. I highly recommend them.

The K&N air filter isn't recommended for the later Mercedes that use the hot wire for air flow measurement by these early 450s like the extra airflow.

Your engine is rated almost 50 HP more than the later 450s and has more torque in fact as much as the 560SLs. The specs call for a 10.5 sec 0-60 but I think that was understated, like the American engines that were rated at 360 HP but would actually do 450HP. Your can is lighter with more HP and torque, 9 seconds seems reasonable.

breastroker · #20 10-31-2017, 12:22 AM

That web site talks at modifying the throttle body by enlarging it. The throttle body isn't the restriction everything is sized for at least 250 HP, except the air cleaner and the lower plenum of the intake manifold.

But the air filter housings up to 1980 used those tiny holes, normally those holes are used to straighten air flow. But in this case they restrict air flow by 40 to 45%. So when Mercedes went to larger air cleaner snorkels and finally to dual snorkels (5HP more in the 560SEC) they opened up the holes many times larger and with much less restriction.

In my opinion they didn't go far enough. The dual snorkels have both air streams meeting behind the air cleaner at the rear of the housing. There is zero air flow from there into the engine! Nothing but turbulence, They should have put curved dividers to rout the air flow on each side forward into the front portion of the air cleaner assembly.

One thing people should know is to rotated the air filter one quarter turn every 5 thousand miles, as there is zero air going in from the rear area, so that is clean.

Graham · #21 10-31-2017, 10:09 AM

Quote:

Originally Posted by breastroker

I
Your engine is rated almost 50 HP more than the later 450s

Wish that was true

Actually the 72/73 NA 107 was rated at 192HP and the 1979 at 182HP (SAE Net). There are some misleading numbers for the 72 because the method of rating engines changed during that model year (SAE Net vs SAE Gross). This shows up in this link - 72 and 73 NA 107s are essentially same car but HP ratings shown are different.

The way my 45 year old car is driven these days, don't need much HP anyway

Quote:

SAE gross power

Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower, because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a stock test engine, generally running with few belt-driven accessories and sometimes fitted with long tube (test headers) in lieu of the OEM exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic.

SAE net power

In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.

Graham · #22 10-31-2017, 10:21 AM

Quote:

Originally Posted by Tony H

Here's a few pics I found(not my car)

Different rad it seems - no separate overflow/expansion tank.

breastroker · #23 10-31-2017, 07:55 PM

It took me 3 days to get Photobucket to load these photos

I have been able to push the overflow tank one inch closer to the wheel well, but that might not be enough.

Below is the melted portion of the large 3 inch snorkel. I may have to cut out a section and glue a portion of the extra to it so the snorkel is more front to back instead of pointing outwards.

oldsinner111 · #24 11-01-2017, 05:08 AM

the spark kernel on most new plugs,while powerful,there small.Are older motors will foul them easy. HP gains are more of timing,the cam,changing lift.Cheap way I did mine was to buy used nitrous kit on ebay,$250,125hp wet shot.If my 6 could handle it,a small block v8 will.Just err on the rich side always.Nitrous needs copper plugs too,plat. may break off plugs.

breastroker · #25 11-01-2017, 02:28 PM

Bummer

Quote:

Unfortunately the Mercedes Air Cleaner Intake Hose (560SEC 560SEL) - Genuine Mercedes 1170941982 is not currently available from MB in the US and we have had to remove it from your order as a result

That's the big 3 inch passenger side tube.

Tomguy · #26 11-01-2017, 02:50 PM

Quote:

Originally Posted by oldsinner111

the spark kernel on most new plugs,while powerful,there small.Are older motors will foul them easy.

This is exactly the point. The platinum plugs may run fine for a short time but due to the much lower energy ignition systems they will have fouling issues and under load will cause pinging and even misfires due to weak spark. Spark is around 1/4 the power of modern spark systems - P(W) = I(A) × V(V) and both the amperage and voltage is about half what you get from a modern coil-on-plug setup.

Also for power ratings, the 4.5 had two versions, 8.8:1 compression AND 8.0:1 compression, not to mention the gross to net switchover, I am unsure if we'd ever get actual accurate net power ratings from the earliest 4.5 engines, the 8.8:1 D-Jet in mostly 71 or early 72 vehicles, and apparently only early 72 in the R107 from what I've seen posted or parted (not the 108 or 109). My 4.5 when I put 3.5 heads on it gained top-end power, didn't seem to gain anything low-end, but it pulled harder during those kickdown-to-second acceleration bursts.

Graham · #27 11-01-2017, 04:03 PM

Quote:

Originally Posted by Tomguy

Also for power ratings, the 4.5 had two versions, 8.8:1 compression AND 8.0:1 compression, not to mention the gross to net switchover, I am unsure if we'd ever get actual accurate net power ratings from the earliest 4.5 engines, the 8.8:1 D-Jet in mostly 71 or early 72 vehicles, and apparently only early 72 in the R107 from what I've seen posted or parted (not the 108 or 109). My 4.5 when I put 3.5 heads on it gained top-end power, didn't seem to gain anything low-end, but it pulled harder during those kickdown-to-second acceleration bursts.

I don't believe there was anything but the 8.0:1 Compression ratio in the early M117 Djets installed in NA 108/116 sedans and 107s (72-75) Published HP was either 192 or 195 depending on who you believe for the 72/73 R/C107 models. After 1975, Kjets were also 8.0:1.

In 73-75, there was a Euro/ROW Djet with 8.8:1 CR and later Euro Kjets were also 8.8:1. But other than gray market cars, we didn't get those.

Tomguy · #28 11-01-2017, 06:29 PM

I've seen the 8.8:1 D-Jet 4.5 heads. I have no idea if those were replacement MB parts, grey-market cars, or what - but I've seen them firsthand. I think Tony also had (or has) a set, maybe he can chip in where he got those from.

Tony H · #29 11-01-2017, 09:36 PM

I have a spare set of 3.5 heads and a right K jet head if anyone wants to see pics of the combustion chamber. Ebay is a good place to see pictures of various parts for a quick reference. BTW looking for a pair of K jet 4.5 heads-hopefully in the Carson City/Reno/Sparks area-don't want to pay for shipping.

breastroker · #30 11-03-2017, 05:26 PM

Yesterday I lost a couple of HP, installed two 2.5 inch resonators. Car was just too loud.
Shop had to move the two 2.5 inch catalysts a couple of inches forwards to fit the resonators in.

So I have the factory H manifold, the two 2.5 inch in/out catalysts, two 2.5 inch in/out resonators and finally the Borla dual 2.5 inch" / dual 2.5" muffler.