78 3.0 race motor, what to build

[jhelgesen]

If you had a big port 3.0 sitting in your garage with nothing better to do, and it happened to be sitting next to your DE/race car, what would you think of building it into?

Assuming you did all the assembly yourself and had built a few motors in the past, but do not have an unlimited budget, what would you do to make it the hot track ticket?

[shbop]

signing-up.......

[sww914]

I'm hoping for a response here, too. I'll be in the same boat soon.

[YTNUKLR]

It depends on how far you're going...

affordable, hot 3.0: good P/C w/ JE pistons, 9.5:1 single plug (on pump gas), DC40, DC60 or similar cams, weber 46 IDAs, leave it as a 3.0L. ARP studs, ARP rod bolts if you're running it hard. weber 40s will work OK, but you are not going to be breathing really well above 6k. 46s if you really plan to haul on this motor; you can bore out 40s to 46.

More money: upgrade to 3.2L Short-stroke; 98mm pistons/cylinders and chamfer the heads for the larger cylinders. Probably want to port the heads out larger for a true race engine. Hotter cams, DC60 or DC80, even.

More money: MFI or EFI on individual throttles, twin plug the distributor ($2k), twin plug the heads, titanium valve spring retainers and race springs, shuffle pin the case, knife edge the crankshaft, moon the cylinders, etc. Of course bump compression up if running twin plug.

[Facey]

well
is it purely a de/track car, and are u trying to fit in a certain category?

if not, then a low boost, low lag turbo is your cheapest big ticket power...stick with CIS or change to efi if you have the budget. MUST swtich to some lower CR pistons and raceware or equilvent head studs. And since its a turbo motor you won't have to wind it out...therefor it should last longer, expecially if your not greedy with boost (many are).


but.... otherwise, budget depending 3-3.5L, single - dual plug, cis-carbs/mfi-efi,.... those are all the budget decisions.

the musts are:
good head studs
good rod bolts (these are the weak point for revs)
reasonable balance
good cooling

ya ytnulkr hit most of the common naturaller breather mods...

[jhelgesen]

Okay, if I scratch off the twin plugging, what could I expect from a hot 3.0 w/ carbs, or a 3.2 short stroke w/carbs. I also still have the box-o-megasquirt and boxster intake sitting on the shelf.

[YTNUKLR]

Depending on cams and compression, 250 easily, maybe 300+. The boxster intake is not going to allow a really hot cam, so your motor will be torquey, but not as powerful as a carb'd motor. If you used megasquirt and individual throttle bodies, you could do very well making a lot of power efficiently (TWM throttles, Jenveys, etc)

[jhelgesen]

Okay, now this is getting fun.....

For a 3.0, the list would be new pistons, carbs (46's or 40's?) hot cams, headers, rod bolts and stuff. I would guess some work would be done to the heads, would it require the fancy valve springs etc.

For the 3.2, would be p&c's, plus the stuff listed above, and more extensive head work.

Which works better on pump gas, or am I being to tight wanting to stick to 2.50 a gallon vs 6.

[JohnJL]

What a timely thread. I have almost the same ingredients (spare 3.0, spare 2.7, 2 spare CIS intakes, a built megasquirt, spare MSD ignition, spare 3.0 9.3CR factory set, spare 3.0 9.8CR set, SSI's, spare weber 40's, spare SC cams, spare GE20 cams, 2 spare SC dizzys) but my goal is different...I am just about to undertake the same decision for my 1971 daily driver.

Here are my thoughts...

Single-plug on SC dizzy triggering MSD box and coil
3.0 mahle 9.8CR p/c
GE60 cams
2.7 heads 46/40 I/EX ports
Weber IDA40's (flow lower volume at full open but higher velocity/more torque at 25-75% throttle)
3.0 crank
Supertech/ARP/Raceware studs and hardware
I think that looks like a good use of spare parts vs. expenses. Any suggestions?

***sorry for the hijack, but I'd like to hear how guidance differs when the basic materials are the same but the goals are different.

[jhelgesen]

Wouldn't consider it a hijack......I'd like to hear about it too.

I figure 3.2 p&c's would be a few grand, so what pistons would I use to bump up compression in the 3.0 cylinders and use carbs, and how high can it go on pump gas?

[ChrisBennet]

The very first thing on the list would be stiffer valve springs. They won't make you go faster but it might keep you from going home on a trailer if you miss a shift.
-Chris

[cstreit]

Well if you don't want to twin plug you're limited to 98mm to be safe... But if you're willing to spend a few thou. on P's & C's, why not spend a little more on twin-plugging? Then you can get to the real potential of the engine..

100 or 102mm pistons and cylinders
46mm Webers
Twin-plug heads
ModS cam, GE60 or the like and stiffer valve springs
ARP Rod bolts and updated head studs (993 or Supertech)

275-300HP reliably...

[jpnovak]

John, I have nearly all the parts to build a similar motor. Let me run down what I have and why. Remember you have to put it all together to work as a system. You don't want to comprimise performance for one bad choice. Since you still need to buy parts let's move on.

First, decide what you want to build based on how you will use it. I don't want to spend the cash for an 8Krpm motor and frankly don't think I will need it. There is a lot of extras involoved with respect to gearing and other items if you want to spin a motor that fast.

Think light car, low torque, low gears = high rpms vs. heavier car, taller gears = more torque = lower rpm

I based my build on an early S motor with a little help. Planned redline will be 7100 but the build should be good for a few hundered more.

My goal is 260HP and more than 200 ft/lbs. (Based on an easily attainable BMEP of 180) The Build:
-base 930/03 RoW 78 3.0
-early heads 39mm intake ports. NO need to port with any cam smaller than a 906. All intake speeds will be around 100m/s at this port diameter with those valve lifts and durations. (Look up John Leutjens posts about cam design and port diameters. TONS of good information about the different cams, their usable rpm range and how that relates to port diameter)
-HP valve springs in heads. Chris said it first... Any thing bigger than an early-E cam will need new springs. The larger valves of the SC head have more mass and therefore more inertia. Stock springs can not keep up with the valve accelerations when using high-lift cams.
-Mod_S cam. Peak HP should be just under 7K rpm. this will have more usable low rpm torque than a *60 cam but run out of revs sooner. With the taller SC gearing I feel it is better to boost the low end torque. Since I don't plan to spin the motor beyond 7300 that extra HP from a 60 cam would be wasted.
-JE 9.5:1 pistons. Have yet to CC but I don't want to twin-plug. That is for another motor.
-MS-II EFI with TWM 3003 ITBs. Traded some carb bodies for the ITBs. They are a bolt on to the weber manifolds. I ported the manifolds to match the heads and ITBs by hand using a rotary file in my drill.
-Stock dist for now (modifed curve) but after break-in will switch to the MS-II box for spark control. I need to learn the fuel tuning before moving to spark.

-most of the rest of the engine is stock. Don't forget the steel headstuds and all the other usual upgrades.

A few more thoughts: WEber 40s will be too small for your track motor. They work fine for a stock internal 3.0 since you run out of HP after 6200 rpm. You will need 46s. I think you will find a set of TWM ITBs for less than the 46 webers/PMOs. You already have the MS to make it all work. Check with Mike Bonkalski at Motomotions. He can get the TWMs. Cams: Once you finalize the induction, decided rpm range and compression ratio call John Dougherty. He can recommend a grind that would have more performance with EFI vs carbs. (For example Changing the degree of overlap with the same lift/duration.)



JohnJL-Your factory 9.8:1 pistons will not clear a 60 cam unless they are RSR or you notch the CIS pistons. Also the 2.7 heads will not fit the 3.0 case. Wrong spigot diameter and head stud spacing.

[shbop]

While on the subject. If he decided to stay single-plug, is there a Mahle set that would allow clearance for GE-40's?

[JohnJL]

Thanks Jamie, and agree with your endorsements of Mike and John.

Be sure to CC your heads...I don't know if they shipped the wrong ones or there were manufacturing tolerances out, but I ordered 9.5JEs but when I checked them they cc'd out to 10.2:1 compression! I ended up going twin-plug EDIS, triggering off a 36-1 wheel and comtrolling spark and fuel with an Adaptronic ECU.

[jhelgesen]

Okay, tonights plan is to start the build spread sheet, guesstimate cost and HP.

[jhelgesen]

Wow, going faster costs a lot. Here is what I have so far. Anyone have more info to add or update. I don't have costs for any machining or inspection yet, or the cost of carbs, etc.

[cstreit]

Originally posted by shbop
While on the subject. If he decided to stay single-plug, is there a Mahle set that would allow clearance for GE-40's?

Sure is... The Mahle RSR piston, but the compression is too high for single plug... A Custom J&E would fit that bill and less expensive than a Mahle...


JH, I noticed that you want to use "stock" cylinders... Do you have Mahle's on it? Or KS? Didn't find that in the thread. You must have Mahle's to use the J&E piston...

[jhelgesen]

Hi Chris, haven't gotten the engine on the stand yet to even look. Anyone know what usually comes on a stock 78sc 3.0?

[Lukesportsman]

John,

Look back a few weeks and there was a thread that discussed this. We were trying to determine a way to determine type with engine assembled. It could have either so you must look. I posted some pictures and there is a visual difference in the Mahle vs KS. Chris gave some good hints and descriptions.