airbrush1

Figured out my smoking issue, I burned some exhaust valves!
Leakdown showed 2%, 42%, 45%, 3%... I can hear air coming out my exhaust.

Looks like I'll be pulling my head in the next week or so to check out what the damage looks like, I'll be sure to post pics.

Good news is I'm picking up 2 99-00 blocks and a 99-00 head this week also, so I'll have a spare head to send to the machine shop.

What sort of cost should I be looking at when I drop the head to the machine shop? As of now I'm thinking I'll just get the head "refreshed" with new valves and a valve job, and any ancillaries...

Also, since I'll now have 2 heads, would it be worthwhile to do an exintake swap while everything is apart?

In addition, do you think it would be worth the cost to have port work done, or oversized valves installed?

I'm sure I'll have more questions as i get farther into this. Hope to have the car back better than ever in less than 2 months. Be on the lookout for my for sale thread, as I'll have some parts to sell off to raise some fundage!

patsmx5

iTrader: (16)

Tell the shop the head is going on a turbo motor, and to cut the exhaust seats a little on the large side to help cool the exhaust valves. Will cost you a few HP, but it's a reliability thing. I'd say .080 on the exhaust seats. And IMO you don't need bigger valves in any way, form, or fashion. Exintake FTW. I got a spare exhaust cam I'm waiting to put in my 99, after I get rid of my damned ignition miss. (need two more Millenia COPS to fix it)

You had a pretty stout car before. I say do some DIY headwork while it's off.

y8s

iTrader: (8)

making mental notes here... do you run lean anywhere? what AFRs under boost and cruise?

I'd not be surprised if you had a quote from the shop for just the routine machine work pushing a grand. or at least that's what I'm scared to prep for for mine

airbrush1

To the best of my knowlede, the car doesn't run lean anywhere normally. I'll have to check with my tuner to see if he still has the AFR logs from the last tuning session.

I have 2 suspicions as to the cause of the valve issue

1. a couple weeks ago I did a highway pull with a 997 Carerra-s cabriolet, 60mph roll to about 110mph. Friends in the caravan behind us said they saw some smoke coming from my car, but couldn't tell at what point the car began to smoke. Incidentally my exhaust failed on the way home, a piece of 2.5" stainless just snapped in half. I drove around 60 miles with only a downpipe at about 80mph on the highway.

2. I'm running Rx7 460's I don't have a whole lot of headroom in them at my current power level. If I overboosted the car at all, that could be the problem; however, I run an EBC that logs peak boost, and I have NOT seen a reading over .9bar at all, even on that higway run (during which my peak boost was .85bar if I remember correctly) The car SHOULD be safe at this level, as I turned the boost back a bit from it's setting during my 292whp run on the dyno. ALso, the rx7 injectors are notorious for being leaky, and I haven't had them flow tested or cleaned. It's quite possible a couple of them did something stupid and the car suffered the consequences (the injectors are going out for a cleaning and flowtesting sometime in the next few weeks to figure out if they might be the culprit.

I'm hoping the head on the motor I'm picking up this week is still good, I'll have the machine shop check it out for me just in case. If it's in good working order, I'll prolly just do an exintake swapout, and a timing belt/water pump job one sunday.... I have beer and a grille if any locals want to have a cookout/install/tech day when I do this....as I haven't done it before and could uses some guidance!

KPLAFIN

iTrader: (1)

I'd be down for helping learn...Never done it before either.

oilstain

Yeah, let me know too. I'm always up for tearing into a car, even if it is just to learn summat. I've gotten deeper than cams into my integra before, so if you have a shop manual for the miata, I can try to help keep you from breaking ****.

I don't remember if you have a machine shop that you are happy with, but these guys in Essex (J & D Automotive Inc 126 Eastern Boulevard Essex, MD 21221 (410) 574-6714) quoted $45 to mill the head of my integra, which is a decent rate. They were able to give me a quote over the phone, so I'd call and ask them, even if you don't want to go with them.

Unless it manages to sell for a decent price, I'll yank the head again and have it milled this time and let you know how they did.

y8s

iTrader: (8)

don't put the new head on without getting larger injectors. I'm not sure you can run 292 rwhp on 460s without going lean (except that you did it). in theory, 550cc injectors can barely support 300 rwhp!

also if you run a wideband for closed loop, and it was after the open downpipe... that would affect AFR.

Incidentally, I have the graphs from earlier this year and your AFRs look OK. leanest run in boost was 12.26 at redline but it was also only 268 rwhp. I dont have the 292 run. (you ARE Ken, right?)

airbrush1

Y8's, That is the same boost level I have been running on the street, so I would imagine that unless something failed.... I shouldn't have had an issue. The 292whp tune was done at an earlier date.

I don't run my wideband, I simply have the stock primary O2 sensor in place.

y8s

iTrader: (8)

it could be any one of a lot of things. cold day dense air (and no headroom) or bad tank of gas or who knows what.

I'm mostly curious though since I dont run very rich in boost--similar to you (low 12s AFR) and pretty lean in cruise.

Faeflora

iTrader: (2)

I'd be glad to join in on your work day. Post how the headwork turns out. I am looking for a good machine shop in the area for my block...

Arkmage

iTrader: (3)

sounds like I'll be looking for a set of 550cc or larger injectors soon... that's going to make cold start even more of a *****.