924Board.org

[Rich H]

Guys,

not being a frequent user of engine workshops, does this seem expensive to any of you? Seems alot but I have no comparison yet...

full crank regind (-0.30) £115
Glaze bust/hone £40
deck block 4.5mm £115
full engine balance £190

Ta
Rich
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[gohim]

You can't take 4.5mm off the top of the block.

If the machine shop you are looking at says you can, RUNAWAY ! ! ! !

Keep looking for competent shop that knows what they are doing.

The prices that you quoted are for the most part in the extremely range.

[Rich H]

They havent seen the block yet to be fair... More investigation of local shops needed then.

Ta
Rich
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[ideola]

For comparison purposes:

I paid $450 to have my crank welded and offset reground to a stroker. £115 (or the equivalent USD$230) seems on the high side for a simple regrind.

I paid $650 for my block work as follows:
- disassembly (had trouble removing the crank)
- hot tank
- clean cut the deck
- overbore cylinders from stock to 87.5mm
- rough hone the cylinders
- align-hone the mains
- match hone the cylinders to custom pistons

Subsequently, I had the block o-ringed for another $100. I will be taking it back for full balancing of the rotating assembly once I get all of the components in and assembled (just awaiting the Fidanza flywheel at this point). I didn't get a quote on balancing, but £190 sounds a bit on the high side to me.

My work was all performed by Holbrook Racing in Livonia MI. I could have gotten it done for maybe $100-150 less, but based on conversations with those other shops, I just didn't get the "warm & fuzzy" feeling. On the other hand, Holbrook builds sub-7-second cars, and routinely has quarter-million dollar projects scattered about their shop. Simply put, their credentials and the freedom to walk in and ask questions or just chat at any time has been well worth the "premium" price, at least in my situation where I'm attempting to build a maximum effort motor.
_________________
erstwhile owner of just about every 924 variant ever made

[Rich H]

Exactly what I needed, a ball park figure to aim for.

No doubt in the country I'll be paying a bit more but I don't expect to be paying double!

Those quotes were from a race engine shop, I'm going to try a normal engine re-con place when I get the chance. I'm not after anything special particually.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[-nick]

Dan's numbers sound about right - except that balancing can be very expensive. I think I paid ~$600 last time for just balancing the flywheel, crank & pulley, rods, and pistons.

Race shops tend to use more modern equipment and you might end up with a stouter engine. Although even a normal rebuild should get you another 100k+ miles on a relatively stock powered engine. In other words, it usually isn't worth the premium.

By the way- have them gap your pistons rings too. They're a pain to do at home.
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

[Martijnus]

why can't you deck 4,5mm from the block? Is it physically impossible?

I think I know what rich has in mind and I had the same plan for a while...

what damages the block when you take 4.5mm off? will it open up coolant/oil channels? will it severely degrade the structure of the material causing cracks? etc etc? I can't see why you can't do it...

apart from the timing belt issues and knowing that it is not 'smart' to do when it's the only mod... but I guess rich has thought about that too

about the prices.

I've paid 125eur for decking 1mm, decking 4,5mm wouldn't cost much more because it just involves a little more time... most of the time is taken by positioning the block correctly in the deckingmachine/mill/lathe...what's it called....
Balancing the crank with flywheel and pulleys would have set me back 150 eur, didn't do that because there were insufficient funds and I didn't think it was interesting if I didn't add the rods/pistons...which would make it more costly...


Honing has cost me about 30 eur for my bike...times 4 would give 120 eur, but I guess for a car it's not that expensive and hence my simple calculation is pessimistic.

What I know about honing is that it probably takes 15 minutes, so if it's done correctly 40 pounds isn't that extraordinary...

regrinding the crank on the other hand is a time consuming procedure and thus more expensive because it involves lots of measuring, remeasuring, remeasuring and precision machining...

At work there are just a few people who have the skill to regrind a crank....but I can't do it because they haven't tought me and it's not as common as other stuff to regrind a crankshaft...

does the crank need a regrind? wtf happened to it? my crank has been polished and looks like new...does yours have damage? In that case the engine has ran without oil pressure, which causes the pistons/cyls to wear too.... but you've probably noticed that if that's the case.
If the crank has been overheated I'd let it check for straightness (is that the correct term? I've never been tested for straightness but my girl thinks I am )
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[endwrench]

Hmmm, here in the sticks I pay about half those quotes in dollars. I'm sure sevices are a little spendier on that side of the pond but I think I would still shop around. What you are asking to do does not take a "race shop", just find a competent machine shop with some old grizzled guy with years of experience.

Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....

[Mike924]

[Rich H]

Yes Martinjus you are probably correct... 4.5mm is the max I would want to go, I need to look closely at the block and see if anything will cause problems with that. Biggest problem might be waterway break through and loss of stiffness but it depends where it happens. Can always get it welded up.

If it looks ropey then I will go with plan B and skip the heavy decking and go for a 1-2mm instead

Timing belt has been thought about and I have an adjustable cam gear now, which I can combine with a tooth jump if neccesary to get things lined up again I also have a bigger offset tensioner from an Audi something.

The crank is lightly scored, the old mains are down to the copper! That said they are consistantly down to the copper so wear is even, there doesn't appear to be much wear on the journals, just the scoring. The top end of the same engine had serious cam/follower damage.

I suspect that it didn't get regular oil changes, mine does as it leaks... Remember what it means when the leak stops... its run out, so fill it back up!

The main reason for a grind is that I can't get mains at a sensible price and even at £115 is is still cheaper than buying new stds, and given the damage I would prefer the start fresh. With a rebuild it should be good for 50k+ miles anyway... more than enough time to save for my Audi V8 engine...

I now have a mate who has a mate who runs a local machine shop, should find out next week

Cheers guys

Rich
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[gohim]

Have you considered what cutting 4.5mm off the deck is going to do to the compression ratio?

On a 924 engine, the combustion chamber is in the piston top. Will the valves still clear the pistons, or will you change the non-interference design into an interference engine? I don't remeber how much spacer there is between the piston tops and the block deck. Taking that much off you may have a problem with the pistons, and you may have to cut the piston tops to clearance the cylinder head.

Have you taken the head off to measure and see if what you are considering is even possible?

[Rich H]

I'm not just throwing things together you know

A turbo head has around 21.5cc in its combustion chamber.
The bore is 86.5mm
4.5mm off the top will therefore give a CR of around 10.5:1
The valves in a turbo head ar recessed 5mm too so given slightly enlarged piston reliefs it will remain an non interference engine too.

I already have an inlet and exhaust carved out to fit.

The figures quoted are approximate and need to be refined before you all jump up and down

The only casualty from all of this will be a block and one of my 3 exhaust manifolds, even it it all goes wrong and the 4.5mm causes problems I can drop everything into my current block, skim that a little bit and go for a standard head.

TBH its looking like I might do that anyway as its more likely to work, but I'm not giving up just yet!
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[Martijnus]

[Rich H]

I worrying thing is that was applied to the Tornado F3 jets I used to work on
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec