Semi-Hot engine rebuild

[bullethole]

I'm contemplating taking my spare motor (78 SC) and building it up to a "semi-hot" setup. Reliability is of overall priority for me. Things that I'm looking at

JE 10.5:1 Pistons (current P&C's are great - motor is actually quite fresh)
Lighter Connecting rods (suggestions)
Hotter Cam (suggestions, re-grind the existing cams??)
Knife edge the crank.
Case mods (suggestions)
Light Weight Flywheel (Patrick Motorsports has been recommended)
Crankfire XDI ignition (already on the primary motor).

No dual plug, no head work (other than to have valve guides replaced)

[kenikh]

Originally Posted by bullethole

I'm contemplating taking my spare motor (78 SC) and building it up to a "semi-hot" setup. Reliability is of overall priority for me. Things that I'm looking at

JE 10.5:1 Pistons (current P&C's are great - motor is actually quite fresh)
Lighter Connecting rods (suggestions)
Hotter Cam (suggestions, re-grind the existing cams??)
Knife edge the crank.
Case mods (suggestions)
Light Weight Flywheel (Patrick Motorsports has been recommended)
Crankfire XDI ignition (already on the primary motor).

No dual plug, no head work (other than to have valve guides replaced)

No twin plugs means no 10.5:1 CR - stick with your current P/Cs. Why not twin plug? The machining operation is cheap for the heads and it is a plug and play upgrade for XDi.
Lightweight flywheel isn't worth it for a street motor and makes the car harder to drive
For an SC, no case mods are needed
Knife edging the crank is a waste of money and actualy removed material from the wrong part of the 911 crank
Lighter con-rods, I prefer R&R rods from LN Engineering, but are only needed if you rev the motor high enough that you would port the heads. Since you aren't, I'd just add ARP rod bolts to the stock rods
Cams - if using carbs, I'd say Mod-S/GE40. If retaining the CIS, 964 cams are about as much as you can upgrade

As you can see, there's not much there without changing your spec a bit. My preference for an SC upgrade is:

98mm P/C upgrade and 10.5:1 CR
twin plugs
DC60 cams
Ported and twin plugged heads
R&R rods
46mm PMOs or sell the XDi and go w/ MegaSquirt crankfire w/ EFI, selling the XDi to recooup the costs.

For the costs of your proposed mods above, you could build the above spec and get an easy 275HP.

[snbush67]

These threads have a lot of answers for you:

Shanes 3.2 SS - Recommendations and Advice

Richard's 3.2L total rebuild

Here is my recent build, I stayed with single plug and stock distributor.

High Performance 3.2 Liter Short Stroke
1 Jan 2010 - 17 March 2010

78, 3.0 Liter SC Case
Early SC Heads: Large Port 38mm
Stock Crank : Stroke Leangth 2.772"
Stock Rods

3.2 95mm Cylinders : Bored to 98mm (3.8582")from EBS
98mm J&E Pistons/pins/clips : Compression Ratio 9.5:1: Dome Volume 35.2cc
Gotze Rings : Top, 2nd and Oil : End gaps: .0015mm
GT2-108 Dougherty Racing Cams : Timing set at 3.2mm
High Lift Racing Springs and Retainers : Spring Height : 39.5mm, 110 lbs

PMO Carburetors and Manifolds : 46mm
Venturies: 38
Main: 160
Air: 190
Idle: 55
Idle Air: 130
Emul: F11

Thick flange SSI's
M&K Generation V, 2 in 2 out Muffler

Clewett Racing Wires
MSD 6AL Ignition
MSD Blaster Coil

Chain Housings gasket surface milled .1mm (modified for 3.2 Gaskets)
Rocker Arms resurfaced and reconditioned by C. Garret
Rocker Shafts reconditioned by C. Garret
New Valve stem seals
New Valves : 2E, 3I and 5I
New Oil Return Tubes and gaskets

New 3.2 Chain Housing Gaskets
New Chain Ramps
New Cam Seals and Gaskets
New Exhaust Manifold Gaskets
New Intake Manifold Gaskets

Used 3.2 Cam Bolts and Washers
New 3.2 Pressure Fed Tensioners
Used 3.2 Idler Arms and Sprockets


Shane

[Flieger]

I think your money would be better spent on the twin plug and higher 10:1 compression pistions than on any windage machining- knife edging, mooning, boat-tailing. The components will be stronger as well. Lighter rods like R+R would be nice (If I could work them into my budget, the cost would be worth the "cool" factor which only I will know of.)

[bullethole]

I guess I should have been clearer here. this is for a race motor, so lighter flywheel would be a benefit. Anyone have a ballpark cost of dual plugging heads, I know the XDI setup is easy, just another set of coil packs and a connector for the unused wiring (XDI is already installed and operational) on the harness. I don't want to stick with the stock pistons, as i believe in 78, the compression is 8.5:1. I know I can go 9.8:1 with a single plug setup. I belive that the 78 has the larger ports than the later US spec SC's

What about cam's. Someone suggested the 964 cam grind. What is better, new cam shafts, or having the existing ones re-ground.

My reason for considering knifeedge on the crank was to decrease rotating mass, it seems that this is not a good idea, and would weaken the crank. The same rational for connecting rods was where I was going, but I'm not sure how much weight savings going with non stock con rods would buy me.

It seems that I could cut my list to
Light Flywheel
Cam Grind
Higher Compression Pistons
Dual Plug on heads

[lindy 911]

What class are you planning to race in? I think the rules are going to dictate what you can do. If you are just building a "race motor" for a track car think about this;

1. Raceware or ARP rod bolts for sure.
2. JE 10.5 : 1 shelf pistons
3. Used Weber or PMO 46 mm carbs
4. GE-60 or GE-80 cams
5. Stock '78 heads with race retainers and springs, twin plug.
6. Spin it to about 7,500 rpm and make about 275 hp. If you rev any higher you'll need to look into better oiling of the bottom end and stronger rods.

I have this combination with the GE-60 cams in a "street" motor and it rips. It's all I can handle for the street. Runs great and hits really hard at about 4,000 rpm to 7,500.

Lindy

[bullethole]

I'll be GT5S in PCA. so all the modifications are legal.

[jpnovak]

I thought GT5 was limited to 2.2l.

A 3.0 would be a GT3 car. Even then you would build the class limit 3.4.

Unless you use the performance index. In this case... What does the car weigh? You need to target 110HP/l. This puts you in a DC80 -DC100 cam and high rpms. Much more work needed to support these numbers on the motor.

[bullethole]

using the performance index. at 2708lbs my car fits just into GT5S for a 3.0L motor
Allowed 110HP/l of displacement.

[bullethole]

Note, I'm not trying to build a GT5S class leader (i suck, and no amount of hp is going to fix that problem), there is no way I'm going to be able to throw the money at it to get to the 110hp/l mark. JE pistons being illegal for stock class put me in GT class (my current motor has 9.5:1 JE's, because it was cheaper to reuse the good cylinders than to buy a whole new set of euro P/C's for the rebuild), and adding 40lbs put me into GT5S, so that’s where I'm landing at this point..

Yes, I know there are a lot of "cheater" motors in stock classes (including things like carillo rods, significant cam changes)(I know of one builder who has his own "custom grind" that is used on a bunch of stock motors).

Honestly, PCA should not care about what Piston's I have in the motor, just that the compression ratio meets spec (really, how significantly different is a 9.8:1 factory euro piston compared to a JE of the same ratio). IMO, the NASA model of Dyno and HP/Weight driving the class is a much fairer system to classify cars than the PCA model. And it does IMO mitigate some of the cheater factor. But this digresses from the thread, since this is not the place to discuss the pitfalls of PCA racing.

Yes, I could lighten the car, and go into GT4S, or i could just go back to Prepared stock. which would still allow a lighter flywheel, crankfire ignition etc.. but I'm digressing.