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What compression ratio should I aim for?

This thread is getting bumped so I'll give an update. The head is back on, just needs the manifolds and cooling stuff which I will finish tomorrow.

That being said, this is the worst way to end a thread on compression ratio. I dropped the head off with the machine shop, and I told him just to take .035" off, and to reinstall the valves, that's it. When he called the next day to say it was done, I made sure to check that he removed .035" off, and he said he did. I picked it up that evening, and he said he took .035" off. He also painted the head silver, which I did not want. Well at least there's no overspray on the inside of the head right? lol nope. Last Saturday morning I got ready to slap the head on and I cc'd the chambers so I'd have a final number, and it was 52cc, a long ways from the 49cc I was shooting for. I had measured the height before hand, so I measured it again, to find that only .015" had been removed. I had no option to just put it together. I'm not happy about it. Final cr is 9.5:1, the head is painted silver, and the machining was far from a consistent cut. I hope it holds. I could rant forever about this, but I've had tire shops here in NYC just ugga dugga on my Virgos and bend the locating pins because the pockets didn't line up and the wheel was crooked and not seated on the hub. (I know the right thing is to run just bolts but the pins fit on mine). There is no competent skilled labor here.

DET17 said:
Going standard HG or MLS? As stated, lots of thickness options with MLS (assuming still available, I've got one or two left). If you go that route, spray a light coat of HYLOMAR on both sides.... and I do mean "light". So you believe you can run 87 petrol with a 9.9 dynamic ratio?
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I am running a stock Elring gasket because my block is not straight enough for me to be comfortable with a .036" MLS gasket.
 
ryanfay said:
That sucks. I’m sorry the guy screwed up the head and for that price.
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I'm not 100% sure where the failure is, no milkshake, no overheating, it's just pressurizing the cooling system. At first only after long highway trips, but now its happening at idle and in city traffic. If I can without a shadow of a doubt place the failure on the head surface, then I'll go back to the shop and ask for my money back. The head surface felt more like a freshly done flywheel than other heads I've had done, if that makes sense. It was flat but not smooth and I had the suspicion it was not right before I put it together.

Thankfully my car is still drivable, I'll just baby it and keep a close eye on things.
 
Ugh. I tried to give a machine shop that's close to my house a couple of tries, just because it's far easier to get to them. Had them skim my 531 head. I told them it needed to be smoother than normal because I was going to use an MLS gasket. It came back looking like they used 80 grit on it. Or maybe slid it around on the sidewalk. WTF??? They claimed the aluminum was 'soft' and had probably been overheated.

I took it to the good shop that's a little bit of a drive and it came back (several weeks later, they're busy, go figure) and it was nice and shiny.

When you pull the head off hopefully the gasket will show where the leaking was happening.
 
OVERDRIVE said:
I'm not 100% sure where the failure is, no milkshake, no overheating, it's just pressurizing the cooling system. At first only after long highway trips, but now its happening at idle and in city traffic. If I can without a shadow of a doubt place the failure on the head surface, then I'll go back to the shop and ask for my money back. The head surface felt more like a freshly done flywheel than other heads I've had done, if that makes sense. It was flat but not smooth and I had the suspicion it was not right before I put it together.

Thankfully my car is still drivable, I'll just baby it and keep a close eye on things.
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Sounds like a shitty finish.
 
Time for an update. If you don't feel like going through and reading, I was looking for advise on how to do the head on a V cam NA motor. I ported a 530, took it to a machine shop. Machine shop only took .015" off, not .035", and the head immediately started slowly pressurizing the cooling system, now we're here.

I put 3k miles on it like that while I ported another head. This one turned out better, I had learned a lot while doing the first head. The casting ridges in the bowl got knocked down, and the whole port on the intake and exhaust got a better "blend" than factory. The cylinder side of the intake and exhaust ports got a little biasing, mainly just before the bowl. The floor of the intake port got widened, the roof of the exhaust port got flattened since the bowl is basically a square and then bends into the runner, now it's a bit straighter and doesn't have the choke point where exhaust is slowest in the port (I assume this, but I've seen all of these changes I made brought up by other head builders so this isn't anything new) culberro also backcut the stock valves. I tried to not increase port volume, I just aimed to help get the mixture and exhaust around the valve and around the corner in the port. The chambers got an equal amount of deshrouding for the intake and exhaust. Ports are hard to take photos of, here's the chamber.
20240603_165010-min.jpg

I took the head to a performance engine shop that had great reviews and paid for it. $300 to get the head decked .050" and have the valves put back in. I told the machinist that I wanted a smoother finish than what they'd usually do for a composite gasket. I wrote this down on the paper. Well just like the other head, I didn't like the finish. I told the machinist this and he said he runs MLS gaskets with that finish. It was his word against mine, there wasn't anything I could do. This time I did measure that the correct amount was taken off before driving away.

I pulled the old head and as I suspected, combustion was getting passed the fire ring and into the coolant passages on all 4 cylinders, clearly from the surface finish as I had the suspicion about.
OVERDRIVE said:
the machining was far from a consistent cut.
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20240612_090015-min.jpg

The best part is, the new head had a worse finish than the old one, shown from the overhang which doesn't get compressed.
20240612_090742.jpg

Smorgesborg was building a similar compression V cam motor at the same time and basically bullied me into ordering a Cometic and Hylomar a couple weeks before I pulled the old head. I wasn't planning on using the MLS because of the surface and I knew my block was not a spring chicken. Knowing that I was going to have to correct the finish put me in the position to prep it for a .036" MLS gasket. After a couple of hours of sanding the head on a large granite slab with 220 grit glued to it, I was able to get the, what were essentially gouges, out of the finish. I measured the block, which was .0025" low in the center lengthwise, and .0035" low in the center when measured diagonally. A few places say that .001" per cylinder is acceptable for an MLS so I was in the clear. I sprayed the gasket with Hylomar on both sides, and torqued it down with used bolts and per Thomas Fritz's recommendation of going multiple passes at each stage so that each bolt it at the same tension before going to the next step.

The end result is just a kiss over 10.1:1 compression, .033" piston to head clearance, and a V cam straight up. ~.062" or so is in between the stock belt and a pinto belt. Currently I have a pinto belt with a maxed out tensioner. It works but it's not the best option in my opinion fyi this .055-.068" off the deck and head gasket thickness range should be avoided.

I've ran this setup for a couple months now and I was super impressed at how much the tight squish helped with power. It had so much grunt off the line even compared to the previous setup when the cam was advanced and I was running more timing. It made great power but I started to suspect that the V was not actually the fit for me and this car, which is an automatic and spends a lot of time idling or cruising on the highway. I swapped in a T cam, knowing very well how much it would shoot the DCR up even higher, and I gotta say, ported head and a T is under rated. 0-60 is just as fast as before, if not faster, and I don't believe I'm encountering any knock with 87 even in the heat with the AC on.
 
That’s great to hear that it’s all working out!

The computers are probably pulling timing to keep it from pinging too much.

If you do a tank of premium and notice a big change, you’ll know that’s the case.
 
culberro said:
That’s great to hear that it’s all working out!

The computers are probably pulling timing to keep it from pinging too much.

If you do a tank of premium and notice a big change, you’ll know that’s the case.
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Yep, I'll check with a tank of premium. I don't "feel" it pull timing but that might not mean anything. I was going to shim the T to around .012" to help keep the DCR down but I was missing some of the shims I needed so it only got .015". Retarding the cam a few degrees will also drop the DCR so I have some stuff to play with. I'm basically just trying to find out the best combo, but I'm liking it how it is right now. Stock injectors were just cleaned and flow tested, so I shouldn't have a lean cylinder.
 
OVERDRIVE said:
Yep, I'll check with a tank of premium. I don't "feel" it pull timing but that might not mean anything. I was going to shim the T to around .012" to help keep the DCR down but I was missing some of the shims I needed so it only got .015". Retarding the cam a few degrees will also drop the DCR so I have some stuff to play with. I'm basically just trying to find out the best combo, but I'm liking it how it is right now. Stock injectors were just cleaned and flow tested, so I shouldn't have a lean cylinder.
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You should be fine. Volvo cams have a lot of duration from the factory (for a variety of reasons), so they end up having relatively low DCR. That's why upping the compression on these motors helps so much!
 
culberro said:
I found that 10-10.5:1 is really the limit with 87 before timing starts getting pulled with LH2.4. If you run premium at that point there’s a slightly noticeable improvement in performance.
That was with a B cam and vx3 and m47 cars.

If you do some chamber work you can probably raise the CR a bit higher. In stock form they leave a lot to be desired. Marking the dish diameter on the head will show you where the squish band is. Everything else overhanging that is just limiting combustion efficiency and making it more knock sensitive.
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Jesus, I need to get it together and send you a head to build for my B23 engine before you die or wise up that doing machine work for us is a waste of time.
 
Good old Thomas Fritz, aka StealthFTI, may he rest in peace.

We exchanged a lot of emails about 12 years ago..... I pasted all his thoughts into a single Word doc. He was quite a guy!

OP, I also used the Hylomar (lightly sprayed both sides) and the tight squish MLS, along with Stealth's bolt torquing method. Let us know if the 10:1 SCR engine runs with 87 octane.... that would be a huge victory for these old tractor engines if it works reliably and maximizes NA power.
 
DET17 said:
Let us know if the 10:1 SCR engine runs with 87 octane.... that would be a huge victory for these old tractor engines if it works reliably and maximizes NA power.
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It works on a V and 87, that's not a crazy dcr and has been documented. I'm out of town and haven't gotten a good feel for the T at 10.1:1. Stealthfti documented a flat top B23 with a B21FT scp 398, tight squish, T cam, and K-jet. Allegedly it was 10.9:1 but needed tuning to make it run right. The T on 87 does match the V's 0-60 with a sluggish automatic, which would point towards it performing well, but it's not idling as well as a lower comp B230FT. I think the really high cranking pressure is making the engine "wiggle", and that could be exaggerated with reduced timing from knock detection. A smaller chamber created by the tighter piston to head clearance seems to like less timing anyway.
 
OVERDRIVE said:
...... and that could be exaggerated with reduced timing from knock detection. A smaller chamber created by the tighter piston to head clearance seems to like less timing anyway.
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Don't know your wagon details. Stock NA LH2.4? Letting BOSCH self tune the new setup, or are custom chips / custom ECU in the mix?

Lean mixture, more advance.... rich WOT mixture, less advance. Did you change the shape of your chambers? If you are still LH, one can hope it could tune within range of existing tables for fuel & spark. Apologies, not much coffee yet this morn and I'm casually following this thread ;-)
 
DET17 said:
Don't know your wagon details. Stock NA LH2.4? Letting BOSCH self tune the new setup, or are custom chips / custom ECU in the mix?

Lean mixture, more advance.... rich WOT mixture, less advance. Did you change the shape of your chambers? If you are still LH, one can hope it could tune within range of existing tables for fuel & spark. Apologies, not much coffee yet this morn and I'm casually following this thread ;-)
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its not like you can add a ton of power to NA redblock with the headwork done. Can LH compensate for +20% hp?
 
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