3.000 € Budget / Rookie / DIY 3.0 rebuild - successful

[buster73]

Needed a spare engine to run my car while the the original 2.4 engine is out for a full rebuild.
Starting point was a “reasonably priced” SC engine (1980 Euro 930/09, 188 hp, big port) from a Porsche wrecker. Being a freshly retired mechanical engineer, one target was to do most of the job myself and to gain experience for the planned 2.4 project. I worked on a wide range of modern and classic cars for the last 40 years, tackling all kind of jobs including some engine work, but had never dared a full engine rebuild (except the model airplane engines of my childhood ).

Targets:
Having fun and accept the challenge.
Get reliable spare engine within a reasonable budget.
Engine suitable to be converted back to CIS for potential future resale.
Gain experience for next 2.4 project.

Individual jobs:
Rebuild 3.0 engine.
Convert engine to Weber carbs (parts from 2.4).
Convert to early style exhaust with SSI (parts from 2.4).
Install 55 A alternator and fan/housing (parts from 2.4).
Add complete external oil cooling system to car.
Prepare exhaust for O2-sensors.
Install new 123 ignition distributor with Bosch 3-pin CDI.
Program distributor with 930/10 ignition curve.

To cut the story short I'm glad to report that break-in of the engine has been completed and it runs strong and without leaks. All-in-all I spend just shy of 3.000 € (ca. 3.600 USD) on parts incl. the new distributor and not counting the additional jobs such as oil cooler system and of course without expense for tools and my own labor. Probably could have saved 500 € by reusing valves, piston rings and some other components that were still within spec.

Engine was missing some parts (distributor, fan...) and has not been running for quite a while. No history other than the engine was sitting in a Porsche workshop for many years and of course no warranty whatsoever. Anyway price was right and prices for used engines seems to keep going up all the time. Positive surprise was to find high compression 9.8:1 pistons, installed together with all the CIS components from a 930/10 engine. Strange was to find cylinder heads modified with 935-style flame-rings instead of the stock CE-rings.

Luckily engine turned out to be in good shape without any unexpected damage. Mahle Nikasil P&C fully within spec and main and rod bearings only showing minor wear. Just the IMS-bearings were showing significant wear marks. Exhaust valves were rusty (from bad storage) and covered with a thick layer of carbon deposits. After cleaning all valves probably could have been reused, but decided to use a new set of TRW valves anyway. Valve guides were worn beyond acceptable limits, so a full top end rebuild was necessary.

Guess without Wayne's book and the invaluable resource from this forum, I would have not been able to complete this challenge. Many thanks to everyone for all contributions. It remains a complex job and I can only recommend it as a DIY project if you are fully committed and willing to spend many hours in your workshop plus plenty of time doing research and preparation. Of course you also need a suitable workshop and a good set of tools. I now also have a better understanding for the prices charged by professional engine builders.

[buster73]

Engine as received from wrecker:





Final assembly:



Back in car:

[buster73]

Modifications from stock:
Mahle 9.8:1 compression pistons (95L70) (by PO)
Cylinder heads modified with 935-style “flame ring”seals (by PO).
Carrera chain tensioners (by PO).
Standard steel cylinder head studs (replace 12 Dilavar studs).
Viton o-rings for case through-bolts.
RSR seals for rocker shafts.
Weber carbs (from 2.4, with 34mm venturis+jetting for 3.0).
PMO fuel pressure regulator (from 2.4).
PMO inlet ports (from 2.4, widened and matched to carbs and big port cylinder heads).
6 mm phenolic insulator spacers between cylinder head and inlet (DIY).
K&N air filter (from 2.4).
Seine heat shields for cylinder heads.
Backdated SSI-exhaust 1 3/8“ (from 2.4).
Modified with O2/AFR sensor adapter (Bosch LSU 4.9) for left and right bank.
Stock Dansk muffler (from 2.4).
Programmable 123 ignition distributor (USB).
Clewett Engineering ignition leads.
3-pin Bosch CDI with black Bosch coil (from 2.4).


New parts:
All gaskets and seals.
Inlet and exhaust valves (TRW).
Valve guides, standard size.
Main bearings 1 to 7, standard size (Glyco).
Rod bearings, standard size (Glyco).
Intermediate shaft bearings (Glyco).
Piston rings (Mahle for 9.8:1, 204 hp).
2x Chains (IWIS).
Chain ramps.
Rod bolts and nuts.
Flywheel bolts.
Clutch pilot bearing.
Oil pressure regulator springs.
Oil pressure regulator caps.
Oil return tubes.
Chain tensioner oil lines.
Cam oil restrictor fittings.
Oil pressure sensor (10bar/140 psi to match 2.4 gauge).
Oil pressure switch.
Oil temp. sensor.
Oil cooler hoses.
New front oil cooler (73-style trombone).
Oil cooler feed and return lines (reconditioned used parts).
External oil cooler temperature regulator (reconditioned used part).

Machining and mechanical work:
Through-bolt holes chamfered in RH engine case (DIY).
Rocker shaft holes chamfered for RSR seals (DIY).
Valve guides installed and reamed to spec (DIY).
Valve seats re-cut (DIY).
Valves and valve seats grinded (DIY).
Pistons and rods balanced to +/- 2grams (DIY).
Flywheel resurfaced (machine shop).

[Mixed76]

Cool project, thanks for sharing!

Please tell more about:

Rocker shaft holes chamfered for RSR seals (DIY).

Valve guides installed and reamed to spec (DIY).

Valve seats re-cut (DIY).

Valves and valve seats grinded (DIY).

These seem to require specialized equipment and some precision; how did you do it yourself?

Sent from my Nokia 7.1 using Tapatalk

[buster73]

Initially I was planning to have the heads done by a pro machine shop. Unfortunately the shop closed down in the middle of the Covid pandemic and I was happy to get my heads back before they might declare chapter 11 (which luckily did not happen after all). Anyway I needed the heads be ready in order to keep my timeline, so decided to do the job myself. You can find several detailed threads on these type of jobs in this forum. Here a short description of what I did:

Removing the old guides:
Tap a 10mm thread to the spring side, drill the center from the other side (just shy of the threaded area). Screw a bolt to the threaded side and use a suitable drift to hammer out the guide from combustion chamber side to spring side. No big deal just cover the head with a rag in case you miss the drift and risk damaging the head with the hammer. Important: Measure guide holes in the heads to decide if you can use standard size guides or need over-sized ones.

Installing new guides:
I first built a wooden support to hold the heads in place (must be really solid and hard wood to take the beating). Then the heads are heated to ca. 150°C to 200°C (300 to 400°F). Kitchen oven is fine but heads better be clean before). I place the head in the cold oven and heat slowly from room temperature to reduce risk of warping. Wait at least 30 min to allow the heads to heat up all the way. The guides are put into the freezer (as cold as possible, dry ice even better). Then you have to be fast to hammer the cold guides into the hot head (everything prepared and of course you need thick gloves). Be careful to press guides to the right depth. Then I put the heads back to the oven and let them cool down slowly.

Reaming the guides:
You just need a suitable reamer (Size 9H7 should be correct for new valves) to ream the guides to the correct size. Helpful to have a bore measuring tool (bore gauge) but with some experience you can feel when valve stem has just the right play/wiggle and moves up and down just right.

Re-cutting the valve seats:
Probably not always necessary but should be good practice to make sure valves are well centered in guide and seat. I used a manual Neway style cutter and on most valves it only took some minor cutting to do the job. Just one guide had to be redone after I realized the bore was too much off-center (guide had to be exchanged with a new one – learned my lesson to better check guides before you install them).

Grinding valve and seats:
You just need a basic rubber valve grinding tool and fine grinding paste. To check I use a black marker pen to paint the valve seating surface and turn the valve in the seat. You want to see a 360° metallic line on valve and seat not too far from the edge of the valve seat. Once you think its o.k., verify seal by putting water to the inside of the combustion chamber and watch if seat is water tight. If not good, you might have to go back to the cutting procedure and start a new loop.

Rocker shaft holes chamfered for RSR seals:
As advised by others in this forum, you should chamfer the rocker shaft holes to avoid cutting the seals during installation. Just used a small manual chamfer tool (small enough to be squeezed into the cam housings) paired with a set of 3/8“ extensions to reach all rocker holes from on side of the cam housings. Of course you should think ahead from which side you will insert the rocker shafts into the cam housings during final assembly.

As said you will find plenty of detailed information on these jobs in this forum. Special tools required are reamer, Neway cutter and measuring tools but you might borrow them from a friend. However - if you have never used a reamer or cutter - you probably don't want to practice with you valuable 911 heads. Looks easy but still takes some experience and routine to do things right. I recommend to get a set of old VW heads for training purposes.




Chamfer tool:

[Mixed76]

Thanks much for the detailed explanations.

Maybe I need to expand my thinking.

Sent from my Nokia 7.1 using Tapatalk

[buster73]

Wanted to give an up-date on the status of my rebuild project. After a long winter break had finally time to complete the break-in phase having completed 1,500 km on the new engine last year already. Drained oil which looked like fresh from the refinery. Re-torqued head bolts with only two bolts moving slightly at 32 Nm. Adjusted valve gap and again very little adjustment needed. After installing the new oil filter and filling up oil, started the engine and immediately realized something was wrong. Engine ran on 4 cylinders only with cylinder 4 and 5 both dead. Spark was strong but obvious no fuel at idle and no combustion. Cleaned all jets without effect. Following Paul Abbotts trouble-shooting guide I suspected a hidden gallery problem, although somewhat unlikely that 2 galleries get blocked at the same time. Anyway took out the carb and drilled hidden gallery plugs as documented by Paul. Gallery of cyl. 4 actually showed some debris but for cyl. 5 nothing suspicious was detectable. After plugging the galleries with cal .177 lead pellets, installed carb again and found #4 now working but #5 still dead. Even fuel supply was there, cylinder obviously was too lean to fire. Only explanation was a vacuum leak. Spraying brake cleaner around the inlet manifold confirmed a leak between inlet manifold and head. After taking off carb and manifold, gaskets seemed to be all fine. Looks like gaskets and the sandwiched phenolic spacer had settled slightly, opening up a small gap between heads and manifold. For next re-build I will add "re-torquing manifold bolts" to my check-list ! Glad to report engine is running great again and with the break-in completed the fun can start. Next step will be fine tuning of the carb jetting.

[zztot]

Curious as to what you did to refinish fan. Did is remove pulley for plating ?
Full explanation would be appreciated.
Looks great.

[buster73]

Originally Posted by zztot

Curious as to what you did to refinish fan. Did is remove pulley for plating ?
Full explanation would be appreciated.
Looks great.

Fan actually was a present from my powder coater in NorCal many years ago. Powder coating went horribly wrong and his customer actually refused to accept (and pay) the fan coating with plenty of bubbles and terrible surface quality. My powder coater promised he will never coat a magnesium part again, after I explained him the fan was cast magnesium and something like "Alien technology". I manually grinded off all the remains of the powder coating (took days, if not weeks of grinding and lots of sanding paper) and then glass bead blasted the surface back to pure magnesium. Then simply coated the surface with WD40, and repeat a quick respray with WD40 as soon as any sign of corrosion appears (whitish build-up). Typically required twice a year. Otherwise no issues with magnesium for me. Sorry, pulley actually is just "fake galvanizing". After glass bead blasting the whole fan unit, I just protected the "naked" steel pulley with some golden paint. Drilling out the rivets and separating the pulley just for galvanizing would have been overkill - IMO. Not to mention the risk to crack the mag casting when resetting the new rivets. Of course this would be the perfect solution for a museum/collector car. You can also buy new galvanized pulleys, but still risk to crack your fan casting during riveting. Hope this helps ?

[PeteKz]

Guenter, nice work. I just looked back at your detailed description and didn't see any mention of cams. Are you using the stock SC cam, or something else? Given the mods that were done to the engine before you bought it, there's a good chance it had something more aggressive in it too.

[buster73]

Originally Posted by PeteKz

Guenter, nice work. I just looked back at your detailed description and didn't see any mention of cams. Are you using the stock SC cam, or something else? Given the mods that were done to the engine before you bought it, there's a good chance it had something more aggressive in it too.

Thanks Pete,

cams are stock SC cams. After realizing engine had been modified before, I checked them to be sure they had not been ground. With the carbs you certainly could use more aggressive cams, but for me this is just a temporary spare engine. Decided better to save efforts and $$ for my coming 2.4 project, which will be more pricey and challenging and where I want to "go all out" including cams etc. Anyway the 3.0 should easily deliver 200 hp which is plenty of fun for an early car .

[mikedsilva]

This is a pretty good build thread. Very impressive. Well done.
Good idea on chamfering the rocker shaft holes.

[buster73]

Originally Posted by mikedsilva

Good idea on chamfering the rocker shaft holes.

Thanks Mike,

just followed the advice from the more experienced builders on this forum. The rocker shaft openings have like razor-sharp edges and I can not imagine to install the RSR seals without cutting them in the process. Guess at least you should round the edges off with some sanding paper, but better to have a beefy chamfer to comfort the seals in place. Must be even more frustrating to have leaking RSR seals instead of just leaking rocker shafts.