GC 2 LITER TC TWIN-CAM PREP FOR LADA

Road-race engines and ancillaries - general discussion
Guy Croft
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GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Wed May 02, 2012 4:00 pm

Documenting the build of a GC engine for Ian (badlyworntoy) whose fantastic car is featured in 'Readers' Cars'


GC
Attachments
IN_crankcase after prelim clean.JPG
core plugs stripped out and block just scrubbed with Jizer and hot washed to make it slightly more 'user-friendly' to handle..
IN_crankcase after prelim clean.JPG (121.75 KiB) Viewed 4113 times
IN_crankcase after prelim clean (1).JPG
see how even that cleaning withour even decarbonising transforms a crankcase formerly lathered in sldge, carbon and sh*t
IN_crankcase after prelim clean (1).JPG (128.14 KiB) Viewed 4113 times
IN_head assoc parts cleanup.JPG
scrubbing and dressing various bits and pieces for the head assy. This slavish work takes hours and hours and is variously referred to in my pricelist as "head and camboxes decarbonise, deburr and clean to build-ready"....
IN_head assoc parts cleanup.JPG (145.64 KiB) Viewed 4113 times
IMG_5163.JPG
after clean and beadblast with Honite grade 13 the original ex valves get crack-tested and then reground/stem polished/tip dressed. The last op is done right at the end just before assembly of the cylinder head as the valve tip almost invarriably needs to be adjusted to aid shimming.
IMG_5163.JPG (97.05 KiB) Viewed 4113 times
IN_head prep_post decarb & beadblast.JPG
after 24hrs decarbonising and cleaning as indicated the head is coming 'back to life'..
IN_head prep_post decarb & beadblast.JPG (146.21 KiB) Viewed 4113 times
IN_head prep_erosion cyl 4 as usual.JPG
the usual erosion one sees on the single carb models in chamber 4 and a plug thread that will need an insert
IN_head prep_erosion cyl 4 as usual.JPG (147.69 KiB) Viewed 4113 times
IN_head prep_20 deg top cut starting worst chamber.JPG
..nothing I have not dealt with a hundred times. The erosion has undercut the ex insert (which I will retain) so we start with a simple 20 deg cut with Neway to drop the top of the insert down about 1mm. I have left the old guides in at this time specifically to do this op.
IN_head prep_20 deg top cut starting worst chamber.JPG (123.02 KiB) Viewed 4113 times
IN_head prep_copying the top cut onto the other chambers.JPG
now we try and reproduce the 20 deg top cut onto the other ex seat inserts
IN_head prep_copying the top cut onto the other chambers.JPG (120.39 KiB) Viewed 4113 times
IN_head prep_dressing chambers.JPG
now we set to work with ATABand and split fork tools to dress the chamber. These tools don't really impact on the seat insert and the 45 deg contact face will get done later
IN_head prep_dressing chambers.JPG (121.44 KiB) Viewed 4113 times
IN_head prep_dresing chambers (1).JPG
all 4 chambers pretty-well ready now. I am not interested in the inlet side especially since I am going to machine the head for Trojan inserts and larger (43.5mm) inlet valves
IN_head prep_dresing chambers (1).JPG (124.78 KiB) Viewed 4113 times
IMG_5162.JPG
a bunch of 'allocated' parts incl race springs, guides, pulleys, race spring seats..
IMG_5162.JPG (114.34 KiB) Viewed 4113 times
IMG_5165.JPG
and race head bolts with special washers. When we get the go-ahead' on a unit we always allocate as much as possible straightways and mark up the client's estimate accordingly and email to him (albeit that I have not yet even finished Ian's yet....!)
IMG_5165.JPG (159.45 KiB) Viewed 4113 times
IN_head prep_all over deburr & chamfer.JPG
all over deburr to the head. I must admit after working in F1 with at Brian Hart's famous Essex works I adopted a much more detailed approach to this op..
IN_head prep_all over deburr & chamfer.JPG (127.79 KiB) Viewed 4109 times
IMG_5184.JPG
head gasflowed and race guides fitted
IMG_5184.JPG (124.77 KiB) Viewed 4109 times
IMG_5186.JPG
view down the ex ports. The rough manifold faces will get stoned and then linished to true up and 'pretty' them.
IMG_5186.JPG (93.4 KiB) Viewed 4109 times
IMG_5187.JPG
and the inlets. The gold-colored crud on the guides is the copper anti-seize that I use during pressing to prevent pickup.
IMG_5187.JPG (93.31 KiB) Viewed 4109 times
IMG_5194.JPG
ex valves reground on my new machine supplied by, well, Fondera. Nice Oxfordshire-based firm specialising in the world's very finest engine reconditioning machines, whom I've known for 20 years.
IMG_5194.JPG (108.16 KiB) Viewed 4109 times
IMG_5193.JPG
the OE valves I carry have a rather thick head which can upset piston to valve clearance and isn't needed anyway so here grinding the 45 deg contact face much wider. The other benefit is it gives me a lot more space for the 30 deg back-grind that will go on after lapping
IMG_5193.JPG (100.53 KiB) Viewed 4109 times
IMG_5196.JPG
here (at left) is the modified inlet valve
IMG_5196.JPG (83.87 KiB) Viewed 4109 times
IMG_5180.JPG
various housings etc after decarbonising
IMG_5180.JPG (147.23 KiB) Viewed 4109 times
IMG_5191.JPG
and the next step - various housings after Jizer scrub, beadblast, deburr, chamfer, dress with stone for flatness. One must be careful regarding what IS and what is NOT blasted by the way, easy to render some parts unuseable. The rule is if you cannot fully clean the part free of media - you do NOT blast it. These parts now ready for hot-wash and then they get marked up in a covered tray 'RTB' - ready to build. The next time they come out is to be fitted. Some parts get painted - eg: block end plate and some areas of the tensioner bracket. But that will be a light spray with Simoniz acrylic and no more than that.
IMG_5191.JPG (193.04 KiB) Viewed 4109 times
IMG_5181.JPG
Here the crankcase has been heavily wire-brushed outdoors on a sunny day to remove 99% of corrosion and it's been very thoroughly washed in Jizer. All oil galleries have been brushed out with 'gun brushes' and various internal features 'stoned' free of high spots and polished
IMG_5181.JPG (144.5 KiB) Viewed 4109 times
IMG_5190.JPG
crankcase after some prelim dressing, thru the hot wash again, now hot and ready for deck crack test and then rebore and reface. When this block is finally finished (in about a week) it will look like NEW.
IMG_5190.JPG (159.09 KiB) Viewed 4109 times
IMG_5176.JPG
the dye is applied with the block hot - it opens any cracks. After an hour or so the block is jet-washed with cold water, dried and developer applied. This stuff is either French chalk or very like it and it will lift dye out of a crack. No cracks here. This looks like a good donor item and hopefully clean up at 84.50 or 85mm bore.
IMG_5176.JPG (114.71 KiB) Viewed 4109 times
IMG_5183.JPG
crank unplugged and drilling out the hard (magnetic) sludge that accumulates in the 4 oil galleries. ALL cross-drilled cranks require this treatment on overhaul or certainly after grind. Not that you can grind the 2 liter Fiat crank though. Not without wrecking its hardness and oil-retention anyhow. We had to strip 2 engines to get one good crank which shows (if you have the least imagination) how balls-aching and tiresome this kind of work can really be. Ian and his friend Jackie came down with the second unit and spent the best part of a Saturday at GCRE while this was in process and it was a real pleasure to have them at the works.
IMG_5183.JPG (126 KiB) Viewed 4109 times
IMG_5174.JPG
Hello Beautiful: Cunningham rods - part of Ian Nixon's allocated parts.
IMG_5174.JPG (103.4 KiB) Viewed 4109 times

badlyworntoy

Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by badlyworntoy » Wed May 02, 2012 10:09 pm

Thanks for publishing the build in this sort of format Guy, it makes understanding it all and referencing things far simpler without the need for all the finer detail. Its also the first time (I think) we've seen all the stages of just one particular engine catalogued rather than bits of several, its going to be very interesting to see how it develops over the next few weeks.
One point of confusion to note though....where the heck did you get the sunny day from?

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Fri May 04, 2012 3:47 pm

Moving along..
Attachments
IMG_5207.JPG
selective honing - especially important if overhauled-valves are being used. This is an 8mm Flexhone.
IMG_5207.JPG (124.08 KiB) Viewed 4034 times
IMG_5208.JPG
exhaust valves all fitting very nicely now, just drop under their own weight. This is a lot more tricky than it looks - imperfections on the stem or distortion of the tip can easily fool you into thinking that the guide bore is too tight. Moreover after fitting, the tightest section of the guide is always in the middle and it takes a fair bit of skill and sometimes specially adapted short hones to correct at that region only.
IMG_5208.JPG (139.25 KiB) Viewed 4034 times
IMG_5206.JPG
New inlet all done too and ready now for big valve conversion that side
IMG_5206.JPG (126.43 KiB) Viewed 4034 times
IMG_5211.JPG
set at left is ready for lap, the one being measured has just had a 45deg grind to 'clean'.
IMG_5211.JPG (121.87 KiB) Viewed 4034 times
IMG_5209.JPG
sharpt 70 deg throat grind to pull the contact face to 1.75-2mm wide..
IMG_5209.JPG (115.9 KiB) Viewed 4034 times
IMG_5216.JPG
now lapping and this one is 'good to go'...
IMG_5216.JPG (114.69 KiB) Viewed 4034 times
IMG_5212.JPG
note how the outer diameter of the contact face is EXACTLY at valve diameter (which it never is on production engines, begging the question 'why not use smaller valves?')
IMG_5212.JPG (112.48 KiB) Viewed 4034 times
IMG_5218.JPG
Giving the ports a final cleanup. Next op new inlet seats..
IMG_5218.JPG (124.54 KiB) Viewed 4034 times

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Thu May 24, 2012 9:05 am

on with crankcase prep ..

GC
Attachments
IMG_5241.JPG
1. crank after unplugging followed by 24hrs in decarbonising fluid and Jizer/hot wash. The decarbonising lifts carbonised oil out of the nitrided layer and the color of the forging turns from black to a kindof greeny-grey.
IMG_5241.JPG (116.32 KiB) Viewed 3791 times
IMG_5258.JPG
2. modifying the main journal oilways to improve pickup, first op is fairly brutal as you can see. The sharp edges this generates have to be slavishly radiused and polished..
IMG_5258.JPG (106.79 KiB) Viewed 3791 times
IMG_5259.JPG
3. closeup of the mains after burr reshape. The work needed on the adjacent regions should be pretty obvious..
IMG_5259.JPG (123.33 KiB) Viewed 3791 times
IMG_5260.JPG
4. the radius on the crankpins (big-end journals) varies - in standard form - from virtually none to massive. We want a progressive form here to allow the oil to exit into the bearing region with minimum loss - same principle as gasflowing a cylinder head really..
IMG_5260.JPG (90.17 KiB) Viewed 3791 times
IMG_5261.JPG
5. conical burr is used to give the crankpin oilway a decent form. The tool is not just rammed in - it is worked in an orbit. That gives a smoother finish and allows me to form the taper accurately. If you just force it into the existing 'radius' the final thing can look a real mess..
IMG_5261.JPG (114.39 KiB) Viewed 3791 times
IMG_5262.JPG
6. after roughing all the oilways main and big-end get the second op with this slim tapered burr. Using this I can dress all the sharp corners. I go quite deep into the oilway to get the shallow taper I need. I don't want any sudden transition in shape.
IMG_5262.JPG (95.4 KiB) Viewed 3791 times
IMG_5263.JPG
7. now a tapered abrasive with some spray oil is used to begin the polishing.
IMG_5263.JPG (116.98 KiB) Viewed 3791 times
IMG_5264.JPG
8. here a main oilway by this time. Next comes about 1/2hr of hand polishing with 500 grade Norton abrasive tape and Scotchbrite.
IMG_5264.JPG (100.85 KiB) Viewed 3791 times
IMG_5287.JPG
9. threading out @ 7/16UNC for oil gallery plugs. All cross-drilled cranks must get this treatment. No way can you clean out a cross-drilled crank without unplugging it. And I have done this op to some really difficult cranks - like Alfa Twincam and VW 16v.
IMG_5287.JPG (104.44 KiB) Viewed 3791 times
IMG_5288.JPG
10. the No 1 tap goes in first and it won't go far and must not be forced too hard or it will snap. Here are the no2 and 3 taps, the latter is parallel. They must be sharp - when they go blunt (and mine do..) they feel 'springy' as you thread and that is a sure sign they are about to shear off. Get some new ones! The right tapping oil MUST be used. Occasionally I find a crank where I just cannot tap deep enough and then it's necessary to open out the bottom of the hole (there is a step there) using burrs.
IMG_5288.JPG (111.35 KiB) Viewed 3791 times
IMG_5289.JPG
11. after these ops the crank gets the most thorough clean with airline, Jizer and small brushes to make sure all the debris is out of the oilways and galleries
IMG_5289.JPG (193.28 KiB) Viewed 3791 times
IMG_5290.JPG
12. main bearing caps have been decarbonised, deburred, beadblasted, dressed with a fine stone (to eliminate high spots - ie: make sure they are flat where they should be) and internally polished with a Scotchbrite wheel. One thing we always look for is sharp edges or overhanging debris on the oil feed slot.
IMG_5290.JPG (177.08 KiB) Viewed 3791 times
IMG_5291.JPG
13. crankcase after rebore and parallel honing to size (84.50mm) and deck reface. Now I chamfer all the round holes on the deck incl the bolt holes. Sharp edges are places for cracks to start and around bolts and studs - if you don't chamfer - you get thread 'pull-up' where the top thread becomes distorted and actually rises out of the hole. It is more prevalent on soft materials like aluminum alloy but it can happen in cast-iron too.
IMG_5291.JPG (102.53 KiB) Viewed 3791 times
IMG_5292.JPG
14. coolant galleries and oil drains get deburred..
IMG_5292.JPG (89.41 KiB) Viewed 3791 times
IMG_5293.JPG
15. the bores have a sharp edge which I first relieve very lightly with a tapered burr. This cutter has quite a fine pitch. I split the circular region into 4 'quadrants' - turning the block round and round. If you try and do it any other way you are liable to make the chamfer massive.
IMG_5293.JPG (87.89 KiB) Viewed 3791 times
IMG_5294.JPG
16. next op on the bores is smoothing with 120 grade abrasive tape. Always fold the tape so - the edge can cut thru the tape and give you a nasty gash in your finger...
IMG_5294.JPG (89.54 KiB) Viewed 3791 times
IMG_5295.JPG
17. micro-honing with Flexhone and engine oil. The bore dimension will not change at all but this hone will remove folds and tears and create the perfect bedding-in texture that cast-iron needs. 240 grade silicone carbide is used - ideal for CP race rings. I always protect the block deck (face) because the hone will score it badly and potentially create tiny leakage paths that could cause the gasket fire-ring to leak. The hone does a great job of finishing-off the chamfer at the top of the bores. After honing (and the instructions on the hone packet could not be simpler) I wipe the bore with paper cloth soaked in detergent and hot water before washing in Jizer. Not essential (I've only just started doing it that way FWIW) but oil just contaminates the parts washers.
IMG_5295.JPG (141.32 KiB) Viewed 3791 times
IMG_5298.JPG
18. washing in Jizer and much use of brushes all over...
IMG_5298.JPG (166.11 KiB) Viewed 3791 times
IMG_5299.JPG
19. 'stoning' working surfaces with a fine carburundun stone. Front, rear, sump region, bearing journal housings...
IMG_5299.JPG (131.06 KiB) Viewed 3791 times
IMG_5300.JPG
20. to clean the threads for the head bolts I use an old M10 x 1.25 tap and reversing drill. Yes doing it by hand is safer - so I do this very carefully. To date I have never messed up on this op...
IMG_5300.JPG (144.46 KiB) Viewed 3791 times
IMG_5302.JPG
21. block after being subjected to 1/2hr in the hot-wash at 60 deg C with the fairly aggressive Guyson 'Formula' cleaning and corrosion inhibiting additive. Once cool, the block will get final pre-paint cleaning with brake cleaner and airline, inside and out and the bores wiped over and over with clean white paper and ATF until there is no trace of grey on the paper at all. The cross-hatch induced by the Flexhone is clearly visible here. It has had 20 sec at 30 deg with final 10 sec at 45 deg.
IMG_5302.JPG (140.85 KiB) Viewed 3791 times

tmvolumex
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by tmvolumex » Fri May 25, 2012 3:17 am

Guy,
Great pics and text.
Very nice!
Now I see what that VX head I bought from you went through.
Tom
GC_31

Urbancamo
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Urbancamo » Fri May 25, 2012 9:54 am

Guy

Your meticulousness always amazes me! Thanks for sharing this kind of information, it's very satisfying to read & learn.

This really shows how much there is things to do when building a proper engine.
GC_25

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Fri Jun 01, 2012 9:51 am

moving along..

GC
Attachments
IMG_5303.JPG
1. dressing the bore for the new front oil gallery plug. You have to test the fit, you can tap it lightly with a hammer but it must go in easily.
IMG_5303.JPG (109.46 KiB) Viewed 3791 times
IMG_5304.JPG
2. new OE plug offered up...
IMG_5304.JPG (123.9 KiB) Viewed 3791 times
IMG_5305.JPG
3. Light smear of Loctite hydraulic sealant in the bore and the plug is lightly tapped in and then 'peened' in the middle to spread and lock it.
IMG_5305.JPG (136.25 KiB) Viewed 3791 times
IMG_5306.JPG
4. coolant core plug bores have been dressed very lightly with 120 grade tape and then smeared with this silicone product which in my long exp is one of the best around. Core plugs are bashed into place using an OE tool and a hammer. I do that because Natasha always hits her fingers.
IMG_5306.JPG (119.88 KiB) Viewed 3791 times
IMG_5309.JPG
5. the block painted. The wrong color because I forgot. It is going to be repainted black today.
IMG_5309.JPG (119.48 KiB) Viewed 3791 times
IMG_5321.JPG
6. gauging the bores to ensure the fit of pistons to bores is right
IMG_5321.JPG (109.04 KiB) Viewed 3791 times
IMG_5322.JPG
7. picking up the deck height so I can order the pistons. This dimension controls the compression height.
IMG_5322.JPG (132.17 KiB) Viewed 3791 times
IMG_5307.JPG
8. crank and flywheel after balancing. FW is steel item with integral ring gear
IMG_5307.JPG (102.66 KiB) Viewed 3791 times

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Fri Jun 01, 2012 1:43 pm

contd...

GC
Attachments
IMG_5441.JPG
1. applying Loctite 'Metalset' adhesive over the oil gallery plug. This is state-of-the-art stuff & very hard IF you mix it right @ 4:1 by volume. They never come out because the oil pressure just doesn't create enough force on such a tiny thing to do that but applying this adhesive will stop it from ever 'weeping' oil. This a 'technique' I copied from 'works' units.
IMG_5441.JPG (91.71 KiB) Viewed 3780 times
IMG_5451.JPG
2. threading out the aux driveshaft after cutting off the fuel pump lobe that can strike numbre 2 con rod on TC engines of stroke 79.2mm or longer (the 2 liter is 90mm).
IMG_5451.JPG (122.08 KiB) Viewed 3778 times
IMG_5452.JPG
3. After thorough cleaning and polishing of the journals the 1/8NPT plug is fitted with a bit of Loctite Hydraulic on the threads.
IMG_5452.JPG (104.48 KiB) Viewed 3778 times
IMG_5453.JPG
4. Actually painting it the requested color.
IMG_5453.JPG (158.19 KiB) Viewed 3778 times

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Fri Jun 15, 2012 9:38 am

mving along with the head prep for Guy Croft spec head....

the conversion to 43.5mm inlet valve with 36mm OE standard exhaust, plus porting and seat mods will give a head easily capable of 180bhp + and in this case with the IIID/IIIA combo on 44IDF likely be similar to Miroslaw's Polish Rally Gp4 replica in performance.

Guy Croft
Attachments
Fiat TC 43.5mm inlet valve seat insert.JPG
here is the design drawing used for the installation of the Trojan copper-alloy inlet seat inserts. Extra tip height is an advantage with competition cams (with smaller base circle than standard) and this is achieved by giving the region outboard of the new insert quite a wide 30 deg top cut. That is also good for lower lift flow if combined with the same angle grind on the non-firing side of the valves. If you radius the edges of that cut the benefit is lost completely.
Fiat TC 43.5mm inlet valve seat insert.JPG (108.83 KiB) Viewed 3616 times
IMG_2127.JPG
new seats installed. Ideally the machine used for this op - a Serdi - will generate all the right dimensions 1st time so little correction is needed.
IMG_2127.JPG (117.98 KiB) Viewed 3616 times
IMG_5581.JPG
seats after lapping and post-insert port correction with burrs and bands
IMG_5581.JPG (62.8 KiB) Viewed 3616 times
IMG_5577.JPG
the back-grind goes on after lapping, it is easier to perfect the contact face width in the head than do it the other way round. The lapped contact face on the valve should right out to valve OD. The back-grind is then imposed right up to the lapped region.
IMG_5577.JPG (87.95 KiB) Viewed 3616 times
IMG_5579.JPG
valve with back-grind (right) and without (left). These valves - in case I did not mention it earlier - have already been reground by me at 45 deg to widen the contact face region and reduce the had thickness.
IMG_5579.JPG (78.55 KiB) Viewed 3616 times
IMG_5629.JPG
finished seats and head refaced, all sharp edges thereafter remaining have been very lightly and carefully deburred with a small fine burr
IMG_5629.JPG (118.14 KiB) Viewed 3616 times
IMG_5630.JPG
view down inlet ports, tapering from 36mm dia at entry to 35mm at controlling section.
IMG_5630.JPG (97.12 KiB) Viewed 3616 times
IMG_5628.JPG
RTB - ready to build!
IMG_5628.JPG (120.19 KiB) Viewed 3616 times

Biancorally
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Biancorally » Sat Jun 16, 2012 9:26 pm

Hi Guy,

can you show us the hidden part of your work done during the installation of valve seat insert, with the Serdi? Thing that interests me enormously, never seen here before! Just a few picture, if possible, at opportunity.

Many thanks


Daniel
GC_17

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Thu Jul 12, 2012 3:42 pm

Whilst I did do that op for years and years using a milling machine it's done by one of our first tier suppliers. Don't have any photos but will try.

In the meantime GC.CP forged HC pistons are now here so on with the build..

GC
Attachments
IMG_5907.JPG
IMG_5907.JPG (115.49 KiB) Viewed 3253 times
Guy Croft, owner

Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Thu Jul 12, 2012 3:45 pm

Here is the piston design data. If everyone went to these lengths (which they do not) forged piston manufacturers' lives would be a lot simpler and far fewer inappropriate-ups would occur...

GC
Attachments
NIX piston data.GIF
NIX piston data.GIF (23.03 KiB) Viewed 3253 times
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Guy Croft
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Sun Jul 29, 2012 12:39 pm

Building up the head with GC 3D/3A combo and 3VSR springs, OE turbo stem seals and race spring bases.
Attachments
NIX_head build.JPG
bits and pieces cleaned and oil, counted (VERY) important to count out ALL parts before fitting. If you find one left over at the end or one short you will have to strip the whole thing and check it again. That applies especially to dressing the finished engine - you could drop a washer into the engine and not even notice...
NIX_head build.JPG (177.53 KiB) Viewed 3124 times
NIX_head build (1).JPG
valve contact faces and stems oiled and offer up, next op is fit the stem seals. They will stop the valves falling out when you pick the head up so for fit them all at once
NIX_head build (1).JPG (137.16 KiB) Viewed 3124 times
NIX_head build (3).JPG
springs fitted to bases and installed. The GC springs are way-soft, I use a motorcycle spring compressor which is half the size of a car one
NIX_head build (3).JPG (147.65 KiB) Viewed 3124 times
NIX_head build (4).JPG
checking there is a few thou clearance betw the top-hats on the inlet side and the collets. I have given the valve tips a light tap with a dead-blow mallet to settle them. If you don't check this (and I always send out a GC 'How To' data sheet with top hat shims) the things can bear on the collets during running and your valve clearances will be all over the place. I started with 2mm top hats but had to go down to 1mm with the 3D cam. I do record the tip heights but it's always a bit of a guess the first time. I wonder if some think I just bolt this stuff together in 1/2hr? No chance....!
NIX_head build (4).JPG (149 KiB) Viewed 3124 times
NIX_head build (5).JPG
bolting down the inlet cam with all new stainless capscrews and spring/flat washers. Naturally the threads in the head are in good condition and clean and the bolts have copper grease on the threads and oil on the underheads. The latter is important because stainless and zinc-plated gall badly if not oiled prior to tightening.
NIX_head build (5).JPG (148.95 KiB) Viewed 3124 times
NIX_head build (6).JPG
inlet torqued and here are the clearances ith 1mm top hats and (thin) 3.45 shims. Easy to finish this side which will get done next day after gasket settlement.
NIX_head build (6).JPG (141.41 KiB) Viewed 3124 times
Nix_cams fitted.JPG
Next day inlet bolts relaxed and retorqued,final shimmed and ex fitted and prelim shimmed. Cam timing now - by using protractor method you can set the cams up without having to worry about precise valve clearances.
Nix_cams fitted.JPG (144.84 KiB) Viewed 3124 times
Nix_in LATDC.JPG
here is the lift at TDC inlet with the 3D - you do get fractional differences from cam to cam but this is in line with previous ones I've recorded. The inlet clearance is 01.016" in this case. Note protractor held to pulley with Blu-Tack and rigid sharp pointer bolted to front of head - forget to tighten it up and you will get a heck of a shock when you take it off, because that will mean your settings (and records of FL and LATDC) are wrong and will have to be done again.
Nix_in LATDC.JPG (152.22 KiB) Viewed 3124 times
IMG_6048.JPG
cams scribed on rear journal with a similar line on the alloy housing. The cams are left at that posn when the head is bolted down. I will stress that during the shimming and timing ops you have to examine the valve to valve proximity or you will bend a valve in seconds and unless you check the head after completion of these ops with a vacuum leak-tester you will not find out till you start the engine.
IMG_6048.JPG (134.07 KiB) Viewed 3124 times
Guy Croft, owner

Piotrek125p
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Piotrek125p » Sun May 01, 2016 4:39 pm

GC, I don't want make a new thread so I decide to ask you here about one detail of this engine.

You done here a 43.5mm intake valve conversion, so why you decide to using a top hat shims ? I know that your valve-seat combo and stem heights are really detailed designed before you do this kind of op, are you took into account the change of the camshaft in the future ? It its a only reason for me why you decided to use a top hat shims if you can fit a valve seats with any height.

Why I asking about it now ? Because I will make a 43.5mm intake valve conversion in my II stage head and I want to make a valve seat with 30-45-70 degree only for your IIIA cam, I don't want in a future change this cam for any and I want to avoid using a top hat shims.
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Re: GC 2 LITER TC TWIN-CAM PREP FOR LADA

Post by Guy Croft » Sun May 01, 2016 6:37 pm

crikey, that post is TEN YEARS OLD!!

I had no idea the forum had been going so long.

As for top-hat shims it depends on the cams, finished valve seats and valves.

Grinding the seats to make the valves deeper is not always an acceptable solution - because I have to have a parallel lower throat region and 70 deg narrowing grind and if you grind the contact face too deep (eg 1 or 2mm deeper than standard to accommodate a small base circle like GC 3A or 3D/4A you will have no seat insert left at all.

Of course I can design new seat inserts that fit deeper than standard but I don't ever do that unless I need bigger diameter ones. And even then I avoid going too deep into the head, you have to be careful about the thickness of the casting..

And - very very important - the deeper the valve - the bigger the chamber, which is one very good reason why forged pistons should NEVER be ordered before the head prep is finished and the cc measured...

GC

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