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Build Thread - B GT Miata Swap

Moss Motors
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ValveCoverGasket Avatar
Portland, OR, USA   USA
so as not to bury the lead: it starts/runs/drives!








we initially fought some issues with the crank wheel sensor position and second guessing our ability to count trigger wheel teeth eye rolling smiley
then it was onto clearing up the firing order - wasted spark, COP, with four individual drivers, MS3 doing the math for which coils to fire based on firing order rather than cylinder position. i had initially wired cyl 1-4 in sequence. easy enough to repin the spark driver output connector.
then we chased around a lazy rising edge trigger issue, luckily i brought an oscope around...
and finally we figured out that using alpha-n on the 1.3 code doesnt play well with realtime baro correction when running a single MAP sensor... i need to do more bench testing and see if thats an issue in the later code versions as that should be an easy check to make.
its kind of an oddball settings combo, but the failure we were seeing is that it essentially locks the calculated load and wont allow you to move through the vertical axis of the table. that issue probably took the longest to sort out. turning off realtime baro correction cleared it up, but i do want that working before it hits the road.

once that was all sorted we spent a bit more time finding the crank fueling sweet spot to get it to fire and idle.
after a few heat cycles id felt like i accomplished what i set out for the weekend - hearing it run (its pretty loud!) and burping the coolant.
i think i also need to pull off the overflow tank and give it a really thorough cleaning.
it seems to be making the coolant coming up through the burping funnel look like coffee, and i can feel a sort of silty layer on the inside of it. it was a new unit from moss, but who knows...

after dinner we had the thought - why not head back to the shop and tune it well enough for some short laps of the parking lot.


that worked out pretty well, and it even managed a couple burnouts smiling bouncing smiley


unfortunately... cue the ominous music... sad smiley

after all the vibrating and jerking from starting attempts, and finally reving it when we got to driving it around, it seems the line on the mechanical oil pressure gauge backed out (it did have that little washer in it!) and let loose about 3 quarts of oil down the drivers side of the trans tunnel. i probably didnt have the fitting quite tight enough, or maybe the washer compressed from sitting and it needed another go. confused smiley
it missed most of the larger carpet pieces but got some of the under carpet insulation and the forward part of the drivers side trans tunnel carpet.
theres luckily some holes in the floor and tunnel that it poured through so it didnt actually collect much in the floor pan - luckily - as that would have made a much bigger mess! luckily it was clean oil so it really didnt stink up the interior.

i need to get it back to andy's shop for round 2 of the carpet now, but i suppose it could have been a lot worse! the red carpet at least should be quicker to arrive than the red seat covers and door panels.
while its there id like to sort out the front end ride height, finish up the chassis electrical stuff, and fix some other minor things i noticed while we were running it.



all in all really close to roadworthy, but some (in the grand scheme of things, minor) setbacks.



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ValveCoverGasket Avatar
Portland, OR, USA   USA
cant believe how long its been since the last update, but i guess that happens living a state away confused smiley

had a chance to get at the car for a weekend... finally...

got all my chassis wiring weirdness sorted -
horn works now
blinkers and indicators work!
exterior lighting is bright





and the oil gauge that set us so far back last time works now, with a tight fitting and fresh leather washer tongue sticking out smiley


i was also able to verify the base timing with this custom trigger wheel, using my extremely janky COP extension (you dont wanna know whats under that electrical tape haha) but it worked!



still a couple more things to sort, but all relatively minor -
timing belt seems to be riding a bit too far forward on the pullies, need to release tension and recenter it. i think its rubbing a little on one of the plastic covers midway up the motor.
one wire alternator is drawing down the battery, maybe a bad diode. ive got that off being tested, worse case ill add an exciter wire, as it can be wired for either.
and finally im still getting some dirt in the cooling system, probably from it sitting at the junkyard, or maybe one of the new items in the system wasnt cleaned well after being built (heatercore, radiator, etc). either way, needs some more flushing




while it was off at andy's restoration shop he did the front springs, and im really excited with how the ride height came out. a proper picture outside now that its all level and whatnot... i know the wheels arent traditional, or everyones style, but it came out exactly as id envisioned, couldnt be happier. cant wait to drive it and give it a detailing and proper photoshoot once its tuned!



andy also built a really slick skid plate/engine mount brace, which i didnt get any pictures of since we didnt get it on the lift while i was at the car, but ill snap some pictures of that next time. that came out awesome as well.


anyway, to be continued, hopefully sooner than 6 months from now smiling smiley



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Edited 1 time(s). Last edit at 2017-10-02 07:41 PM by ValveCoverGasket.

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tdwpgtp Peter M
North Royalton, OH, USA   USA
This build makes me feel sick every time I see you post. All that I can think about each time is how I will never have the time or skills necessary to do something like this. There isn't much I'd change with this car, and I can only dream of having something like it.

Keep up the work, even though it makes me sad! smiling bouncing smiley

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ValveCoverGasket Avatar
Portland, OR, USA   USA
really appreciate the kind words!
this thing has been such an incredible team effort though that i cant claim credit the talent and hard work thats gone into it so far! needless to say ive learned so much about LBCs along the way also



on my timing belt note from earlier, i did some more digging on the miata boards and i think my complaint may just be the nature of this belt:
will probably just give it one more tension and cover interference check rotating by hand and let it be

In reply to a post by 949racing

Gates Racing Timing Belt
90-05 Miata MX5 1.6 1.8 - Familia 323 Protege with B6 1.6 or BP 1.8 engine

Reinforced, high temp

300% stronger than standard replacement belt. Up to 3x the heat resistance of OEM belt.

Recommended for
- competition
- sustained RPM above 7500rpm

Optional pulley kit includes new idler pulley, tensioner pulley, tension springs

Note: This belt squeaks loudly on startup and when cold. Not a good idea for a daily driver if noise bothers you.

i wouldnt describe it as a squeak, but more a hum. you can really only hear it when youre a foot away from the timing cover.
some guys on miata.net reporting that it whirs a bit for the first couple hundred miles, but no squeaking, which seems to match my experience - so far.



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ValveCoverGasket Avatar
Portland, OR, USA   USA
couple of followups from my last issues list -

alternator will need an Ign+ exciter wire after all.
currently jumpered - as delivered from summit - for an always hot setup that assume you're running a battery cutoff. so i'll run a short wire over there. but happy to have confirmation that nothing is actually wrong with it.

also on the timing belt, after talking it over with some miata guys i may just run only the lower portion of the cover section (with the timing mark) and leave the top two sections off. its also likely the belt will get a bit more quiet with use but the noise is normal



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ValveCoverGasket Avatar
Portland, OR, USA   USA
de-gunking the cooling system was a success! after lots, and lots, and lots, of water.
i guesstimated a bit under 50 gallons based on the number of times i emptied my drain pan and the number of system warmups and flushes...


i set out with a little DIY flush kit - that i think will come in handy for boat and other car work.



first i took out the thermostat, then stuck the hose end on the waterpump inlet, and another turn down on the radiator outlet, i flushed for a while with warm water, then switched sides.



then with the thermostat still out, i did a fill with water and zerex cleaner.. let it warm up with a few heat cycles and dumping out that hot mixture a couple times and refilling (that lower radiator hose screw clamp got a workout!)
it finally started to come out fairly clean.
the zerex was probably grabbing other stuff beyond the brown gunk, so i did this a couple extra times.



then once that drained clean - that took probably 5 cycles - i reassembled the thermostat, filled with zerex asian blue coolant and bled it. then flushed again, and refilled and bled.
ill probably do one more round of this next time as well, now that it will have sat for a while with coolant in it, just to be safe.



it was really satisfying to see the nastiness finally start to go away! and finally start to make some real progress haha


im pretty happy with the warm idle now after all these warm up cycles... next time out will be tuning focused (after that last coolant drain and fill)
cant wait to get it out on the street for some pulls!



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Edited 1 time(s). Last edit at 2018-01-30 11:23 AM by ValveCoverGasket.

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ValveCoverGasket Avatar
Portland, OR, USA   USA
and a short engine running clip...





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Diurno Avatar
Diurno Carlos S
Lowestoft, Suffolk, UK   GBR
Hey Vedran,

Great progress as always. We are almost up to your stage, although we have already been driving the car for coming up to 6 months, it is going to be taken off the road for a couple of weeks to have some work done on the head and possibly also going down the ITB route or maybe turbo?? Still undecided.

Anyhow, quick question, what crankshaft pulley did you use as I recall yours was a single slot of groves pulley rather than the OEM dual? Been thinking about just getting the OEM machined to remove the extra set of groves but would be interested in seeing what you used instead.

Keep up the excellent work!

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ValveCoverGasket Avatar
Portland, OR, USA   USA
hey, thanks!

factory equipped these bp4w motors had a serpentine belt, i have a buddy (same guy who built the header) whos really into miatas and i rummaged through some of his parts bins and found a mix and match set of v-belt pullies from his stash... but i did end up having to have the crank pulley machined so it only has the single groove in order to save space and not have to shift the steering rack even further up.
there may be pictures in the thread earlier during the engine build, but anyway it was a fairly simple thing for the machinist who did the head work to take care of



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Hemidavey Avatar
Hemidavey Dave Rudziensky
Grosse Isle, MI, USA   USA
I trimmed off the outer serpentine pulley with a sawzall to remove the bulk and cleaned it up on the lathe. Whole job took about 1.5 hours.

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Deluxe Kjetil A
Haugesund, Rogaland, Norway   NOR
This build is so, so good. I remember messaging with you a few years ago about the swap. Nothing has come of it for me so far, but I've stopped buying B-series engine parts and I'm still really keen to do it. I'm just worried that my insufficient skills will make it a moneypit that I eventually have to sell as an unfinished project.

I am also a little worried about losing the noise of the car, as that's one half of the fun for me at this point (all looks and noise, no speed nor comfort). But I watched your video on repeat about 10x and that idle sounds really purposeful. I would love to see some more videos of it driving.

Yours looks stunning as well with the wheels and the exterior/interior colour combo.

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ValveCoverGasket Avatar
Portland, OR, USA   USA
appreciate the kind words

for the noise, i think its still there. its a similar sized and designed engine... but with a lot more power spinning smiley sticking its tongue out

this is the miata build i copied, and hes got a lot of videos with better quality sound than my in-the-shop-cell-phone video



i think it still sounds pretty nice and you can tell its a warmed over 4 cylinder still



also this:

In reply to # 3685109 by Deluxe I would love to see some more videos of it driving.

will happen once i get back up there to finally road tune it now that its sorted. hoping next month, but either way itll happen before early spring



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Edited 1 time(s). Last edit at 2018-02-27 06:32 PM by ValveCoverGasket.

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ValveCoverGasket Avatar
Portland, OR, USA   USA
well ive had some good distractions the last few months, and some not so good ones, but had a few hours between some family stuff to get the car out over the last sunny weekend.

took some time to wipe the dust and grime off it as well, which has me rather excited to actually detail it at some point.

but so far the tune is driveable at lower speeds, but still needs some cleanup at higher loads and higher speeds.
idle is solid once warm, but ive got it on my list to dial in the idle valve to help a bit with cold starts.

next up is an alignment before i put any more serious miles on it, could hear the tires fighting with the windows down hah


couple of shots, and proof that it did make it out of the shop spinning smiley sticking its tongue out






inching along...



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Bealey Avatar
Bealey Silver Member Joe & Barb Hahn
East Wenatchee, WA, USA   USA
1971 MG MGB "Bealey"
1974 MG MGB GT
Great looking ride, makes me want to start working on our GT project again! smiling smiley
e

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bills Avatar
bills Bill Spohn
W. Vancouver, , BC, Canada   CAN
It's funny, but I recall the days when I suggested this swap and the opinions varied between 'it won't' fit' and 'why waste time on a garbage 4 cylinder swap'.

That died down after Frontline did it and did it well, if rather expensively. Nice to see someone just plunging ahead, making progress. Looking good.



Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (350 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

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