Engine rebuild advice

cal csl

cal csl

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Hi guys

I am about to rebuild the engine out of my CSL.
It is a 3.0L and was suffering from high compression, knocking and thus run on. After inspection found that the original block has been heavily machined and the pistons have a 1.3mm deck height.

The crank appears to be stock and unmodified.
The bore is at 1st re bore spec 89.25mm
The pistons are to stock spec 31.8mm
(from top gudgeon pin to flat top of piston) as per blue book.
The stroke measures approx. 80mm

At the moment I see only two options:

Option 1 re bore block to 89.50 mm and have a set of 30mm custom pistons made to suit.

Option 2 Find another 3.0L block that has not had its first rebore and bore it out to 89.25mm to match the existing pistons that are in good condition.

Also thought about putting in a multilayer head gasket but would be way to thick and also shorter custom con rods but way to expensive.

The plan is to put a 300 degree cam in the head to get a bit more excitement out of the engine but open to suggestions on going bigger in the cc department.

Any advice and thoughts on this would be great and most appreciated

thanks

cal
 
First and foremost you need to decide if you want to stay "original" and if so, how original. My own view on this is that the CSL's are getting rarer and that their value remains higher if they are in pretty much original condition. Rebuilt is OK, provided we dont stray too far from the original spec.

Now I know alot of people dont agree, and that's OK, their view is that these cars are generally for weekend use, so why not modify to maximise performance etc etc.

So the "original" option essentially means staying around 3.0 litre, but maybe with a cam, head work, exhaust, say a bit like Richard Batchelor's race car (ask Ian about it)
Your block is then a major problem. If your piston deck height is 1.3mm, this is 0.8 to 1.0mm too high. You can order custom thickness Cometic head gaskets through VAC, but I dont see this as a nice engineering solution, or very long term, as the multilayer gaskets tend to weep after a while.

The problem with a shorter than standard block is that the cam timing becomes excessively retarded, requiring modification of the cam sprocket. The compresion ratio will be quite high, probably 1.0 to 1.5 points higher than standard, but the piston squish will be different, and piston - to valve clearances will be very tight, especially if you go for a high lift cam, then you have to relieve the tops of the pistons, losing compression in the process, not ideal....

So they way I see it you have two reasonable options: 1) find another block, bore it to suit your pistons, change the engine number, and lose that nice "matching numbers" feature, or 2) get a copper head gasket custom made to bring the piston deck height back to normal. Standard head gaskets are 1.5mm, add 1.0mm to allow for the block height, you will still have 0.3mm deck height which would be good. Reuse your pistons, rods, crank, just clean everything up, fit new rings & bearings, a bit of porting around the valve throats, Clive Cams has a nice 300deg grind, away you go. Just remember, more cam means more airflow, = extractors, exhaust, bigger throttle body etc etc. Dont go too big on the cam - use the Schrick 284?

The copper head gasket works well, especially if sealed with Threebond 1211 sealer. I'm leaning towards this option because I reckon you'll have plenty of money to spend on the rest of the car. Let me tell you the engine in my coupe is the original 3.0, standard cam, balanced bottom end, a tiny bit of clean up around the valve throats, standard cast iron exhaust, standard inlet manifold, Wolf ECU, that's it, and it goes well as you know....

The "modified" option involves 3.5 litre engines, in a million different possibilities - second hand / rebuilt standard / rebuilt modified / 3.5 inlet manifolding or orig CSL / Motronic ECU / aftermarket ECU / etc etc how much time and money have you got? Do you want a race car, or something smooth to drive on sunny Sundays with just a bit more grunt because you could?

Hope this all helps!! Good luck !!
 
Hi guys thanks for the info,

Bill,

after some thought I agree that the custom pistons is not the best option. I was aware of that the cam sprocket had to be milled so that it could be adjustable but see what you are saying about the piston tops etc. It will probably end up being a lot of cost and tweaking for not the best outcome.

I will quiz Ian about the copper gaskets as this seems like the easiest and probably cheapest solution.

In regards to cams, the engine was rebuilt back in the day for my dad for race track meets. It has seen minimal use and generally in very good condition. It had a heavy ground cam in it which we changed for a stock cam recentley, I will have to check if the head already has stiffer valve springs etc in it. Ian is an advocate for the 300 degree cam, not to sure which one he uses but will check out clive cams. The schrick 284 seems a popular in between cam.
I was planning on putting a stainless exhuast/headers system (existing one rusted out) but will check to see what other mods might have to be done to run a heavier cam.

I will do some more research and crunch some figures to see which way I want run between the gasket vs new block.

Generally I am about keeping the car stock with only a few adjustments, cam, suspension etc but all within spec. This is not so much from a resale point of view, as I cant see myself parting with the car anytime soon, but more about keeping it classic.

I agree with you and if I was chasing power then i would be dropping a 3.5L in it with an after market computer and using anything the modern day has to offer.

thanks

cal
 
As a thought for you- CoupeKings Stainless exhaust is flat out beautiful in workmanship and wonderful in execution.
 
It sounds like the "best" option is custom pistons. You can have a modified deck height and set the CR to whatever you want, while keeping the rest of the engine as original as you want it. The gaskets do tend to be failure points as the layers delaminate over time, but I have generally seen that more a problem when under boost, rather than NA applications.

Alternatively, for a more radical solution, what if you modified the combustion chambers to allow for the additional height? This would let you modify the clearance volume (and therefore the CR) as you see fit with all your original hardware. Depending on how it was done, you could eliminate some squish spaces, too. It would be extremely difficult to modify all the chambers in the exact same way, but it is a potential solution.
 
I think you still have the problem of cam timing - I'm not sure how much of an issue that would be on your motor. Variable cam sprocket solves problem but gets expensive. I had the same problem with a four cyl. block that was decked without my permission. I then had the added challenge of getting the front cover machined to match, not to mention piston height, etc., and decided to scrap the block and start over. I have to think a used block and machining is cheaper than custom pistons.
 
Phemisg said:
I think you still have the problem of cam timing - I'm not sure how much of an issue that would be on your motor. Variable cam sprocket solves problem but gets expensive. I had the same problem with a four cyl. block that was decked without my permission. I then had the added challenge of getting the front cover machined to match, not to mention piston height, etc., and decided to scrap the block and start over. I have to think a used block and machining is cheaper than custom pistons.
Click to expand...

This is just my experience, but in my area, an engine bore and deck, along with the head resurfacing etc. will run at least 1000$. An appropriate M30 block, depending on the completeness of the short block, starts at 500$. A set of custom M30 pistons from Ross or Weisco should be about 1200$ or less, based on other custom BMW piston costs I have seen.
 
As I understand it, the engine is already apart, so incremental requirements are either (a) custom pistons with approprite rings or (b) fresh block and matching front cover, cleaned and bored to match old pistons. The latter route has the advantage of avoiding both the cam timing issues and the challenge of establishing precise specs for custom pistons.

As I recall, any block from Bavaria, CS, 530i and even (if memory serves)528i will do.

The advice I got was that decking the block was to be avoided if at all possible, and if done, the top of the front cover has to done at the same time.
 
Hey Guys,

So been doing some home work as there are a few ways to skin this cat.

In the adding thicker gasket department there are two schools of thought.

Cometic (multilayer) gasket. To have a custom one made is about $650. Ouch if you have to replace it down the track and as bill mentioned they can weep.

Other gasket option is a copper gasket. Have not found someone that could make it as thick as i want it but if i did the engine would still have to be stripped down and sent off to have the o rings machined to stop leaks.

Feel this will be chasing my tail a bit

Can pick up another M30 block for $300. Hoping to find one that can be bored to fit existing pistons but probably going to lash out and get some new ones and up the bore size.

Does anyone have any info on the 3.0 and 3.15 alpina spec engines that were built back in the day.Food for thought hmm
 
Keep in mind that the Alpina engine that Terry and I picked up a few months ago is the early version- turbocharged and parts made of purest unabtanium. You might try Terry and see if he is willing to sell. That engine came from a B7- the fastest 4 door car in the world at the time >}
 
Stroked 3.0

88 would indicate a 3.3 (L) crank resulting in 3.480 . In a hypothetical 3.0CSL with a 3.15 L vs. early 3.0, it should be 84 wchich results in 3.307.
The difference is seriouly close to what you describe. I can see that not taking into account what early hotrodders had to work with can be somewhat unobvious 40 years later. I myself have a odd stroker
(by todays standard) Give or take the diff and you've got a possible stroked 3.1 to 3.3.

And we haven't discussed rod dimensions and possible stock variations nor compression ratios. (drop on a b35 head)

So dropping in the same crank in a new/used block might not be the approach if that's what you had in mind.

Tuners and early engines were restricted by displacement rules for racing/ early block design limitations in the beginning. Most were 10/1, cammed 300deg., heavy cylinder head prep/ larger valves, triples, and exhaust. Oh, and lightening the bottom up to spin higher as the stock crank disenigrated because of harmonics at higher rpms.

P.S. If you do have the 3.3 ( and there were two according to the bluebooks)- pls. document the casting i.d. for others out there.:-D
 
I'd expect you could buy a whole car for $300. But may be more cost effective to buy the block already out and bare. You prob need matching front cover - if your old one was decked along with the old block. It has to match EXACTLY, as does the upper cover need to match the head. Don't ask me how I know.
 
Hi Guys

thanks again for the feedback and thoughts. I will have to check the front cover but it is most likely that it will need to be changed.
Pretty sure the original engine still has the stock 3.0L crank and rods in it.

I have 2800 engine that i pulled out of a cs that we stripped for parts.

Would anyone know if this can be bored out to 89.25?

Pretty sure the stroke and crank are the same as 3.0L but just wondering about the cooling ports etc. Guess best way is to have it sonic tested.
 
2800 Block Variation Question

For some time, 2800 engines have been bored and stroked to 3.2. I believe Korman or Metric mechanic still does or can for those that wish to keep the original block.

The story goes that as a result of racing, the factory engineers relaxed the overbore safety factor. Check around for Grp 2 engine specs for 2800 which was just shy of the piston size you're speaking of.

All the M30 blocks had 100mm bore spacing as far as I'm aware. I guess the tale is that it started with 86 and went as large as 94 as time went on.

But you're right, it's best to sonic test and check for any gross defects.
 
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