Guest diesel_jim Posted July 12, 2006 Share Posted July 12, 2006 I started stripping and rebuilding a 300Tdi i got "cheap" the other day. cheap coz the bloke had got it sandblasted. just as it stood. so sand everywhere! anyhoo, the head gasket is missing. looking through RAVE it says how to get a magnetic DTI and measure the protrusion of no.1 piston @ TDC etc etc. is there a "quick" way.... can one just use the middle thickness gasket and be done with it? or is this a real crucial thing? (hmmm... thinner gasker=higher comression ratio.... power?) Any engine building guru's on here? Also, the injectors are stuck like **** to a blanket in the cylinder head. they're knackered anyway, so damage to get them out doesn't matter, but i don't want to damage the head. i've left them overnight with them swimming in WD40 and tried a blowlamp today to heat the surrounding area, but no joy. I've got oxy, but don't want to cause any damage to the head. would oxy damage it? (assuming i didn't try blowing a hole through it!! ) possobly a slide hammer might "break" the rust thats holding them in place. cheers guys! Quote Link to comment Share on other sites More sharing options...
white90 Posted July 12, 2006 Share Posted July 12, 2006 Oxy will result in a new head a slide hammer will have them out in seconds a DTI is cheap the base cost me more still only £30ish then you can have the right gasket Quote Link to comment Share on other sites More sharing options...
Les Henson Posted July 12, 2006 Share Posted July 12, 2006 The abrasive grit they use nowadays will be oxide particles or maybe pearl beads, and even a tiny amount left in the engine will wreck it very quickly. I doubt you could put enough strain on the injectors to damage the head. The engineering firm where I get my heads skimmed would remove them for a few quid in the hand. They replaced the studs in my turbo for £20. I would suggest no heat as I think the alloy expands more than steel, so the hot alloy would grip even harder. You can get those super freezing sprays that are supposed to be the best way of removing seized items. I would use the thickest head gasket - you won't notice the difference in performance. I do this quite often to most makes of car - especially if the head has been skimmed, or the gasket thickness can't be determined. Grit blasting abrasive - nasty stuff to engines, I'd be very worried about that Jim. The engineers I use are behind the Bulldog pub out park North - Kerry engineering is it? Les. Quote Link to comment Share on other sites More sharing options...
Disco_Dunk Posted July 12, 2006 Share Posted July 12, 2006 Jim..... I can't help with any of the answers, but I thought I'd add a few thoughts I've had on the same subject (and I'll be interested to hear from the experts, too!!) I had the head off my 300tdi a little while ago....... the existing gasket had no holes (it didn't even have the tab that has the holes in it), so I decided to go through the 'proper' process to find out what gasket it SHOULD have....... not sure if it was my measuring, or what, but I ended up needing the thickest gasket. Ever since the re-fit, though the motor's been a tad low on 'oomph!' and I've been investigating possible causes. I'd thought about the gasket thickness, and wondered about doing a compression test. Unfortunately there are no 'correct' compression figures available to compare with, so a compression test will only really tell you if you've got a blown gasket Various threads on various forums suggested that it makes no difference, and I think there was mention of a possible urban myth that the RAC (or similar) always fitted the thickest gasket to be on the safe side My only remining thought is whether it's all a red-herring and the rubber piston 'cap thingy' just takes up any additional, or reduced space in the cylinder....... sorry if this makes things even more unclear - hopefully a diesel guru will answer all our confusion!! Dunk I started stripping and rebuilding a 300Tdi i got "cheap" the other day.cheap coz the bloke had got it sandblasted. just as it stood. so sand everywhere! anyhoo, the head gasket is missing. looking through RAVE it says how to get a magnetic DTI and measure the protrusion of no.1 piston @ TDC etc etc. is there a "quick" way.... can one just use the middle thickness gasket and be done with it? or is this a real crucial thing? (hmmm... thinner gasker=higher comression ratio.... power?) Any engine building guru's on here? Also, the injectors are stuck like **** to a blanket in the cylinder head. they're knackered anyway, so damage to get them out doesn't matter, but i don't want to damage the head. i've left them overnight with them swimming in WD40 and tried a blowlamp today to heat the surrounding area, but no joy. I've got oxy, but don't want to cause any damage to the head. would oxy damage it? (assuming i didn't try blowing a hole through it!! ) possobly a slide hammer might "break" the rust thats holding them in place. cheers guys! Quote Link to comment Share on other sites More sharing options...
Jon White Posted July 12, 2006 Share Posted July 12, 2006 If you're only measuing the hegith of the piston when at TDC above the block cant you just use a vernier? Or am I missing summat - I dont understand these diesely things........ Jon Quote Link to comment Share on other sites More sharing options...
Les Henson Posted July 12, 2006 Share Posted July 12, 2006 I have a DTi if you need to borrow one Jim, no mag base though, but you could probably make something suitable. Les. Quote Link to comment Share on other sites More sharing options...
western Posted July 12, 2006 Share Posted July 12, 2006 Just use the thickest gasket, the one with no holes, I added a reply earlier this week with a list of protrusion ranges they cover. info mentioned above 0 hole gasket is the thickest, then 3, 2, 1 as the thinnest 0 = 0.81 to 0.90 for 300Tdi only IIRC 3 = 0.71 to 0.80 2 = 0.61 to 0.70 1 = 0.50 to 0.60 all mm chose depending on piston crown protursion above the block face. Quote Link to comment Share on other sites More sharing options...
Guest diesel_jim Posted July 12, 2006 Share Posted July 12, 2006 Thanks all. thickest gasket it is then, i reckon. maybe #3. I used a slide hammer before on my current 300. think i'll go for that route again. Thanks for the offer of the DTI Les, i've got one as well, although like yours, with no base think that'll be on my shopping list next! as well as a slide hammer. I know the engineers.... quite near Ashcroft & Allens? anyone know a good source for a slide hammer? As a side note, i put into use last night, my engine cradle (one of those thigs that bolt to the rear face of the block, and you can rotate the engine through 360 degrees)... great bit of kit! i bought it with my engine crane from a chap on one of the forums, clarke stuff i think it is. beefy as you like! the engine cradle can carry 1000lb, and it's just at the right working height! Quote Link to comment Share on other sites More sharing options...
Ajlorton Posted July 12, 2006 Share Posted July 12, 2006 I have a dial gauge + mag base if you want to borrow also. Let me know. Quote Link to comment Share on other sites More sharing options...
Guest diesel_jim Posted July 12, 2006 Share Posted July 12, 2006 Thanks Ant. I had a reply from Richard Turner on the ORRP forum, his idea was good.... put a straight edge across the tops of the pistons, and with feeler guages, measure the gap underneath. but he said, the measurement doesn't have to be super accurate anyway. B) Quote Link to comment Share on other sites More sharing options...
dirtydiesel Posted July 12, 2006 Share Posted July 12, 2006 If the injectors are properly seized in you may be as well buying a new head. I had one seized in my 300 i tried every thing eventually i slide hammererd it in half. at this point i gave up and let my local machineist have it he could only machine so far through it because of two hardened inserts in the injector, i them sent it off and had the inserts spark eroded out, then back to my engineer to have the rest of it machined out. Total cost £280. Sickening as a new head is only £250, but head has been worked on, so i just had to fork out. Quote Link to comment Share on other sites More sharing options...
Tonk Posted July 13, 2006 Share Posted July 13, 2006 if the engine has been blasted and u're going for a complete rebuild then have the lot chemically cleaned, bout 30 quid normally to get a block done, well worth the pennies imho Quote Link to comment Share on other sites More sharing options...
02GF74 Posted July 13, 2006 Share Posted July 13, 2006 put a straight edge across the tops of the pistons, and with feeler guages, measure the gap underneath. I was gonn say that, assuming the pistons have flat tops and most usually are. about these injectors - are they a push fit or screwed in? (sounds like push) also from the previous stuff, I gather head is steel/iron and injector bodies alloy? stick head in deep freeze, then make a press using angle iron and fat bolts to press them out? Quote Link to comment Share on other sites More sharing options...
white90 Posted July 13, 2006 Share Posted July 13, 2006 no the head is alloy and the injectors are steel Quote Link to comment Share on other sites More sharing options...
Bush65 Posted July 13, 2006 Share Posted July 13, 2006 The comment about higher compression ratio = more power is totally wrong for a turbo engine. With forced induction, a lower compression ratio increases the amount of oxygen in the cylinder (at BDC there is more volume for air to be pushed into), which can allow more fuel to be burned. I suspect that the issue with gasket thickness is possibly to do with piston to valve clearance, but more likely to do with "squish" as the piston approaches TDC and how that benefits combustion. Quote Link to comment Share on other sites More sharing options...
Guest diesel_jim Posted July 13, 2006 Share Posted July 13, 2006 I bought a slide hammer today, so i'll weld up the adaptor and get them out tonight. Actually, i'll take some piccies and do a tech article on it (to help the chap on the 200tdi injector thread) Quote Link to comment Share on other sites More sharing options...
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