spode134

I,ve been running my 79 2 valve for a season and a half and am on my second used engine.... first one started running on water and gas on#4 cyl. The car is reasonably fast about even with a AS class mustang or camaro. In between clutch, fuel delivery and overheating issues as long as this motor holds together it's pretty sorted, handles ok and is fast enough to put a grin on my face most times.
I have available a 89 4 valve for a good price and am having a tough time deciding if its worth the time and money to switch to the 4 valve. I would have to change headers, clutch [donor car was auto] engine wiring and probably remove or modify the roll cag braces that tie to the front shock mounts. I will then have 2 worthless 2 valve lumps and another wreck sitting in the yard. Or... build 1 good motor out of the 78 and 79 with out spending a bundle. I like the simpicity of the 2 valve fuel system and any extra space under the hood is a good thing
DK made a 2 valve go pretty good so I know it can be done but whats more cost effecive?

GlenL

Do you have dyno numbers from your existing engine?

A swap between a stock '79 and a stock '89 will garner about 80 Hp. That'd be nice. Don't overlook the cost of the LH brain and wiring it into the car.

You could also look into supercharging the engine for more power. Or going to a bigger block (5L) under your intake and heads. Or going to a Euro S CIS engine.

One thing to consider is what the engine swap would do to your race class. Would you be bumped up to a class where the the new performance would be better or worse than where you are now?

spode134

With DOT tires the car is ITE legal my second class is SPO which is unlimited, in both classes there is considerably faster cars than mine.
What I,m not clear on is if i switch flywheels can i use the twin disc, what's involved with the computer wiring, will my fuel pumps work and the shock tower braces clearing the intake.[see pic]

hacker-pschorr

I have an 88S4 motor waiting for something. I've decided to drop the shortblock into my 79 track car with the stock heads - Euro S intake / TB / ignition and fuel system. This will be supercharged to a goal of 400rwhp. Based on what we've learned by supercharging my stock 81 US, 400 will not be very hard to reach.

What is the average HP output from an 85-86 shortblock with Euro top end? Doesn't that end up being around 12:1 compression?

Imo000

I think the HP output would be about the same as a stock early 32V ~290FWHP.

Best and least expensive solution would be to use the S4 shotblock and bolt the exisiting top end. Unless you really need an extra 40hp I would keep the original engine untill it needs a rebuild. Sounds like you already have a well sorted out track car. Enjoy it for a bit longer.

GlenL

Lemme see here...

Eyeballing, the S4 intake is fairly narrow so I think it'd go.

The fuel pumps are different with the CIS cars having a higher pressure (IIRC!)

Not sure about the wiring problems.

Swap the flywheel and the twin disc clutch will work just fine. The engine will not as the crank sensor is on the flywheel starter gear. His has been discussed and I suggest a search but the solution involves mounting the later gear to the early intermediate plate.

"5L Euro hybrid" engine has produced around 300 at the wheels. The stock Euros are 300 BHP and with more displacement and a higher CR they pop up to around 340-350 BHP. I recall the CR was in the low 11s.

I generally agree with Imo; run what you've got until it requires attention. On that topic, what oiling system mods do you have?

Dennis Wilson

If you run mostly short courses, switching to 4 valve will sacrafice the low end torque of the CIS engines. IMHO the ideal engine in this situation is, as mentioned earlier, the euro CIS setup.

Dennis

mark kibort

torque is of no real issue . remember, this is a performance race car discussion. we all shift at the lowest rpm of 3700rpm. (any lower, and you are not driving the race car correctly!)
so that said, most all S4s or euro 5 liters, run max torque near 4000rpm
the peak values could be different, but usually both torque and hp numbers are numerically the same. the curves are close to the same. Actually, the 2 valve hp vs the 4 valve hp shows that the 4 valve hp can peak near 6000rpm,where the 2 valver seems to be closer to 5700rpm.

bottom line, because the 2valve 5 liter runs near 300rwhp. (290ish with a very restrictive Ljet AFM!!!!), and you would expect to get slightly more of an equivilant GT cam'ed S4 engine!!

I think the best combination would be the 85 shortblock with S4 heads and GT cams. (higher compression)

so, i would forget about an S4 engine conversion. too much work. just find an 85 short bock, 84 euro 2 valve intake stuff and put that together.
its about 10:1 compression. (48cc heads, 8cc '85 pistons with 2 valve cuts)

think about it, an S4 conversion means clutch mods, both brains, wiriing, power steering and alternator mounts, fuel injection connection and a host of other unknowns. (i dont know, has anyone done this before?)

What i do know and other do know, is that you already have the twin disc set up that works. you bolt on the 5 litre bottom end and find the big valve heads, cams and intake from an 82 euro.

Mk

mark kibort

If you want, i can provide a practically brand new 5 liter short bock with 2 valve cut 4 valve 85 pistons, 84 crank, stock rods, all professioally balanced, new rings, and bearings, for about $3k.
The good news on this conversion is that it is made from a 4.7 euro block, so all the stuff fits on to it with no changes. the block is at the machine shop right now. Just say the word.

since you already have CIS, stay with a 5 liter 85 block with euro top end.
300rwhp should be expected which is near 360BHP . not bad for all stock 928 components.

mk

Dennis Wilson

MK,

I appologize for my ignorance but I thought you matched your shift pattern to your peak torque curve. Since the CIS cams have about the same lift but longer duration than the 4 valve cams it would seem that you would shift at a lower rpm.

Dennis

SharkSkin

Nope, peak HP is what you want. Curve below is from a '78, but the 300HP euros have about the same shape curve -- it just goes higher. For racing, the ideal section of the power band is the RPM range that has the peak in the middle. Using the first chart below, the HP peak is about 5300RPM. Using the last chart below, there is about a 1500RPM drop between gears near redline.

Rough cocktail-napkin calculation would then be as follows: Split the 1500RPM drop. That's 750 RPM. Working from a 5300 RPM peak, add 750 RPM -- that's a 6050RPM shift point, which would drop you to (5300-750) or 4550 RPM for the next gear. Plot these points on the first chart and you will see how it maximises HP. A common misconception is that you should shift at peak HP... doing so is less than optimal!

sublimate

Mark, I'm interested in this shortblock.
You said (in an earlier post, I think) that this would have a 10:1 compression ratio?
Is there a different piston I can use to lower this somewhat for forced induction?

mark kibort

sure, we could use the S4 pistons. (vs the 85) for near the same price of the pistons.

PM me and we can talk about the details.

MK

mark kibort

Dave is right on the money.
a summary of 10 pages of debate, would be
acceleration = power/(mass x velocity)

what this means, is acceleration , at any vehicle speed, is proportioal to power.
Thats why, as Dave has shown, you shift at such an engine speed, as to optimize the hp you put to the wheels. Engine torque values are relatively meaningless, although they can indicate a flater hp curve .

Mk

DK

Hey D!
32v and a 16v 5.0 hybrid are both good choices. You should also look into a supercharger. It is allowed in ITE and SPO. As I recall... 79 euro does not have the 2/7 oiling problem, and CR is around 9.5:1, right?

I remain skeptical on CIS for turbo or CIS cars, and yes, Porsche used CIS for 911 turbo cars. I'd go with a programmable EFI - which is good for a ton of engine and car options.