1983 SC based race car - need more power!

[jwasbury]

Originally Posted by 3literpwr

Keep engine... Change racing format!!!!

https://www.youtube.com/watch?v=rbLD_xkLefA

^ entertaining video. Looks like fun, but I don't think we do that here in the USA. Closest thing might be a hill climb?

Call into Dawes, left a message. I know they are supporting a PCA race this weekend at Monticello Motor Club, so they probably are a bit busy with preparations.

The goal...minimum, I want to be able to keep up with the fleet of race prepped Caymans on the straights. I had to work very hard to pass this guy on the brakes. Not possible to pull away at corner exit, and for the better driven Caymans, they put such distance on me during the straights I can't make it up in the tighter bits. If I can get a bit more power I think this car will be reasonably competitive in this field and I may be able to show a few more Caymans the rear end of an obsolete air-cooled car I also want to get my hands into another engine. I really enjoyed the build on my 930, itching for a good winter project.

[3literpwr]

We do here in the states...I have been racing with rally america since 2003 and also building a '81 SC for the task...


Home | Rally America
NASA Rally Sport

[DSPTurtle]

Awesome video. I get sympathy pains for that poor gearbox. Motor sounds perfect though… thank god for dry sump oiling. LOL

[jwasbury]

Well...if this car's engine was built for Spec911 - it looks to me like it was a 'cheater' engine.

Cams do not appear to be stock SC - they are stamped Elgin "Super SC" - my research tells me these should be SC330 cams.

Pistons don't appear to be stock CIS parts either - any ideas what I'm looking at here:



I don't think these are CIS pistons.

Leakdown test prior to the tear down had some marginal numbers. I will measure everything and see how it looks, then make some decisions. I still think I can go for some bigger cams, pistons appear to already be higher compression than stock, but how high? I'll get the heads refurbed, twin plugged, and ported.

The rockers appear to be showing strange wear:


As for exhaust...anybody ever seen a set up like this one:


The headers are stepped design. Start at 1 1/2" and increase to 1 5/8"
This set up might be a weak link...and its showing some bad cracks. Last season an entire section blew apart and I had it repaired just to keep things rolling.

[KTL]

I would agree that looks like a cheater engine if it was indeed run in SP911. Definitely not CIS pistons for a stock engine. The deep valve reliefs give that away. I would be those pistons are 9.8:1 compression since the engine is single plug. So they're really not "high" compression. I think the deep valve reliefs can mislead us into thinking they're higher compression than they really are.

Cam followers may show some uneven wear due to using original worn-in rockers against new SC330 cams?

Those headers may have some cracks in them, but they're definitely not a weak link in the engine system. That's the Cox header layout and is a very good equal length system

Supplier for merged 2-1 race exhaust

[Steve@Rennsport]

Those short-tube, stepped headers are optimized for an RPM range that this engine may not see, using SC330 or Super SC cams. Not an effective "marriage".

George's headers would be more appropriate since they have longer primaries.

[jwasbury]

^ so I've got the Cox system...thanks for that info, very helpful. The headers themselves are solid, its the merge collector and 2 into 1 muffler assembly that is cracked and failing. The cracks are quite bad where the bracket that bolts to the engine carrier is welded on to the pipes. I could have it repaired (already had a section replaced last summer that had literally blown to pieces. The material in that section is very thin wall and not the highest quality stainless.

Steve, I am not staying with Super SC cams. I want something bigger to go with higher comp pistons (and I have ITBs, so I can run just about anything). This engine rarely goes below 4k rpm on the track....spends most of its time between 4.5 and 6.5. I try to shift by 7k. Does that info change your assessment of this system or would you still recommend Georges?

[KNIGHTRACE]

This is a great injection, but you can't expect much gain over the stock 180hp with good injection. like 15hp or 20hp maybe. But the 3.0 small port head are not what you want. Best thing to do is buy one of my engine kits, GT3 crank 76.4 mm 98mm Piston and cyl kit some 3.2 heads and special cams for the injection and have yourself a 350hp 3.5 or put the injection on a better motor like a 3.6. both Jeff and Peter are great but this is not brain surgery its about as simple as a stock build.
Hopefully this helps William Knight

[KNIGHTRACE]

The ITB's will not work as well as what you have. COX exhaust is pretty good wouldn't change it. William Knight

[jwasbury]

Hi William - of course my plan is to have heads ported while they are in the shop for rebuild and twin plug machining. Your engine kit sounds interesting, but probably outside of my current budget.

Originally Posted by KNIGHTRACE

This is a great injection, but you can't expect much gain over the stock 180hp with good injection. like 15hp or 20hp maybe. But the 3.0 small port head are not what you want. Best thing to do is buy one of my engine kits, GT3 crank 76.4 mm 98mm Piston and cyl kit some 3.2 heads and special cams for the injection and have yourself a 350hp 3.5 or put the injection on a better motor like a 3.6. both Jeff and Peter are great but this is not brain surgery its about as simple as a stock build.
Hopefully this helps William Knight

[KNIGHTRACE]

Jacob,
Please don't let someone try and hand port the heads, Just switch to a better head, a real CNC custom port job is $1500, its cheeper to just get 3.2 heads and sell those for $500. Your motor needs displacement and cams I sell the Elgin cam designed for that injection. but you need to look at it this way you can put a 964 or GT3 crank in it sell the 3.0 crank, just use a good 95mm Mahle custom piston and you will have a 3.3 that goes from 200hp present to 340 hp and not out lots of money. I am just trying to help you but please don't think I am going to port and add like a 993 super sport grind and be happy because you are going to be very disappointed.

[jwasbury]

Originally Posted by KTL

I would be those pistons are 9.8:1 compression since the engine is single plug. So they're really not "high" compression. I think the deep valve reliefs can mislead us into thinking they're higher compression than they really are.

Further disassembly has revealed that the pistons are JEs. So I took some measurements last night. I will re measure to verify the findings, but it actually looks like the dome volume on these pistons are in line with 10.5:1 compression ratio. This engine was single plug...no signs of detonation that I can see. I have to go back and look at the ECU and see what kind of ignition timing this thing was set for. Seems like an odd combo of parts thus far - great ITB induction, Motec EFI, "Super SC" CIS cams, single plug and 10.5:1 piston.

Rods are Pauter, which is nice.

[KTL]

Nice find on the pistons. Those look like JE's version of the Max Moritz wedge/asymmetric piston with deeper valve reliefs to account for the increased dome volume/higher compression. Do the pistons have a JE part number on them? Usually it's under the pin boss, not the cast-in numbers under the crown.

Get the pistons cleaned of carbon buildup to check for detonation. It looks like this

3.4 Mahle 98mm 9.8 CR - dual ignition needed?

Nice find on the rods too. If you want to have them reconditioned, I would strongly suggest sending them to Pauter. Brian will take care of you. Fair cost, great communication, turnaround time is good. Main reason for sending them to Pauter is they've got the pin bushings in hand, which aren't the same as typical Porsche bushings.

[Jeff Alton]

Who built the original cheater motor?

[carslutt]

dang..... someone put money into that "stock" overhaul ha ha....

[jwasbury]

Originally Posted by Jeff Alton

Who built the original cheater motor?

Supposedly the engine was built at Kelly Moss motorsports, but honestly at this point, who knows. The induction and EFI tuning was done by Rothsport. The fellow who I bought the car from never actually ran it in Spec911, so while this is a 'cheater' motor, the guy himself wasn't. But he would have been had he actually campaigned the car in the class.

The engine was supposedly "fresh" - the pistons and rods certainly look like they are fresh, and there is other evidence that case was split and resealed recently. The rockers and rocker shafts look anything but fresh...

Pistons have thus far measured up ok. I have to check cylinders, but they look fine. I am going to pull the rods and check the rod bearings. Otherwise I think this thing is going back together with the same P&Cs. From my few discussions with Rothsport, they said the engine was "leaving a lot on the table" Hopefully new cams, some headwork and twin plug and retune of ECU will wake it up nicely. It wasn't slouchy at all, just not ready to drag race against the Caymans.

Still need to decide whether to go new on the exhaust, or find someone who can competently repair the Cox system.

[KTL]

Also looks like the head studs are all the std. smooth/partial thread dilavar studs? I'd think about using something other than those for the rebuild. They don't show leakage from the pictures you provided but I suspect eventually you will get leakage. Awhile back the popular idea for some builders was to use all dilavar (and we're not talking best of dilavar- the all-thread style used on the 993 twin turbo) and I don't think long term results are good. My previous engine build circa 2005 revealed all 24 were smooth dilavars and it was leaking badly from the heads and cylinders. Not pure dripping sort of leaking. But lots of weeping.

Have you decided on a cam yet? Just curious what you're thinking. We've used the WebCam 120/104 with good results. You can use a cam of that type (narrower lobe separation/overlap) due to the individual throttle bodies. I suspect that the SC330 cam with wide lobe separation was holding the engine back quite a bit, given that it's a cam that is designed to add some pep to the stock engine configuration. Note how the SC330 is listed (1/2 way down the page) = 1 step up from the stock cam for a stock engine

http://www.elgincams.com/c-por2.html

New cams will make up your mind for you in terms of what to do with the rockers- recondition

I would guess you can get some good money for the Cox system if repaired and sold to the right buyer. You could probably get a new basic exhaust like the George's headers for "free" if you get a good price for the Cox setup

[jwasbury]

Based on conversation with John Dougherty, I'm going for a GT2 Evo profile with a tighter lobe separation than the spec (108 IIRC). He seemed to like them for my application, rev range, and compression ratio goals. Rockers and shafts are at John's for reconditioning.

So what is collective wisdom on the a Cox 2 into 1. Is that set up more suited to a motor that will be spun to higher than normal rpm?