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Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.
I’ve been having a hard time believing my exhaust p2v clearance and am more and more suspcious I bent a valve putting in the check springs and it’s not seating all the way diminishing the travel for clearance checking.
Leakdown tested again this time with the headers off.
cyl #1 (the one with the checksprings on) leaks 20% today. I can neither hear nor feel any air coming out the exhaust pipe which is large and far away. However with the headers off I can certainly feel a slight breeze coming out the port. I put some cling wrap over the port to see how much it would inflate and it inflates quickly and bulges out far.
All the other cylinders also have some small amount leak to the exhaust port too but the most (gross leakdown) is like 8% some are close to 3%. Even on the 3% you can still feel a the coldness of the air leaking past the port with the header odd and your finger in the port. It’s less of a breeze though. Coverng even the 3% port with cling wrap it also inflates the cling wrap however more slowly and less of a bulge.
Thinking back on last year when I knew nothing of this stuff and I just had a machine shop rebuild the motor they said the valves were fine and no valve job was needed. I acquired this motor with 200k miles on it... knowing what I know now I probably should have insisted on a valve job anyway.
So after another long description of where I’m at here’s my question: After a valve job and new valves should the port seal perfectly / 0% leak through the valve? I realize probably no leakdown test is 0%. In a perfect brand new engine that has already had the rings worn in when that leaks a few % is only leaking past the rings? And lastly say some valves have a lot of miles on them, for example 200k miles. Realistically by that point is it typical for them to have a slight leak to them or should they actually still have a near perfect seal as long as the valve is not bent?
A full set of valves and valve job may be in order here. I’m about to take the head off for final confirmation but wanted to see the answer this post and reflect on this past week first haha.
It should be very close, if not a 100% seal then too close to measure with what you have.
With that apparent mileage on the head, I would have expected the guides to have needed replacement, but if it was very well maintained and/or had had recent work on it it may have been acceptable for a commuting vehicle. My runaround/shopping basket recently had the head off, for a weeping core plug, at around 110k miles, and it was still in very good condition. I checked the guides which were showing negligible wear, and the valve seat sealing with solvent in the ports which showed no leakage - not unexpected as the seats showed no evident wear. I didn't even have to clean of any valve or head deposits as there was only a very light film of carbon on it - not unlike the semi-transparent carbon film buildup on an old lantern's glass.
However, your engine isn't a commuter and seems to have a lot of miles on it. Fresh guides, valves if required, and the prerequisite careful (3 angle?) recutting of the seats and re-facing (2/3 angle?) of the valves would have been part of the build process, as would a light skim to clean up the head gasket surface. If money's a little tight, and the guides are good and no valve shows signs of contact, you may be able to use some grinding paste to improve the seal, but that's more a band-aid than cure.
While it should be unlikely that the leakage you have is due to a bent valve, it is possible - but something else may be causing it. Is there any chance you mixed up the valves - the valve and seat do wear microscopically, even with modern materials, over that mileage and if they don't quite match...
Breaking news! Valves not bent but seats leak. Also now confident my clearance measurements were correct. Attached is pic of water dripping out of the valves when I filled the ports with water. It’s a slow drip, takes 15 minutes to form each droplet before it drips but as I understand it now it should not be doing that. I think it should evaporate at a faster rate than it leaks through no?
Should have had that machine shop last year when they did the rebuild do the valves too even though they had blessed them as just fine. Didn’t know much about this stuff at the time, still don’t but learning. The machine shop did service mill the head at that time just to clean it up. That appears to still be good based on my precision straight edge.
The white specs in the photos on the head are just bits of paper towel from wiping it off.
As I said, the head may have been done before you bought the engine, so it could be in excellent condition. One drop in 15 minutes is a very low leakage rate - I'd probably give them a light grind with some FINE paste, to see what affect that has, if the valve guide clearances are in good condition - but the best thing would be to accept the cost and have a competent head specialist rebuild the heads, so you KNOW they're good - depending on the casting, you may even have them lightly re-worked/ported.
However, I don't know exactly what your head is like, so in the end it'll be up to you and, maybe, your machine shop. On that, there are many 'shops that do excellent 'jobber' work for normal use engines, but a 'performance' head takes a little more care - and will cost accordingly.
Oh, there is a heavy deposit build-up on the head - if this was all cleaned up when it was checked, what sort of mileage has it done?
Yep so my plan is come Monday to shop a valve and port job at some performance places. Portflow is not far from here so will call them, and I got a bid from a local Honda shop already. If you or anybody have any other shops they reccommend that are in the Souther California area let me know.
I acquired the engine Nov 2019 with 200k+ miles. It came on a crate in pieces with all the nuts and bolts just sitting in a big bucket full of oil all mixed up. I spent a while sorting through all that and figuring out and collecting all the missing bits and pieces which once I had gathered I had the engine rebuilt at a local jobber type machine shop. The valves had those deposits when I got it and the machine shop said they cleaned them as well as they could and that they would run fine like that, which it did.
Had it tuned by someone else and it dynoed at 173whp which was a good result I thought with stock beting 140 and the cams are light.
I’ve gotten a bit deeper into this hobby since then and hopefully a little more knowledgable and agree the valve situation is a bit out of place with the rest of the motor.
Attached are a photo of the car and engine. I’ve had this car for 25 years and it sat rotting on a friend’s driveway with no cover for 4 of those years while I lived in Insonesia. Suffice to say the car looked every bit of 25 years old when I started the restoration project. I did all the work myself except for the machine shop that did the original rebuild and Synchrotech did my transmission (they are incredible). Had never removed or put in a motor before this.