JCan

Im adjusting the distributor at 15deg btc without the vacuum advance connected. I suspect that the vacuum advance will advance it well beyond 22 deg... But I can check tomorrow.

Xnke. I'm not sure what my timing map is however I did have my distributor rebuilt by advanced distributors (17495 Marystown Road - Shakopee, MN 55379 (612)-804-5543). He not only completely rebult the distributor I gave him, but he retimed it AND checked the vacuum advance for me. Today Brian and I will try to get the car ready to drive for the first time in at liest 12 years (to the best of our knowledge). We have some work to do, but should have the car ready by 5pm today.

If I had time (or had thought of it earlier) I might have planned to purchase a wedge then wait the 3 days for it to come in the mail. However for those of us who need a wedge, the one I built took me 30 minutes to build using a chop saw and some old beach hardwood I had laying around. Tony, SRgunz et al. Once you order your wedge, it would be nice if you would measure it and post it here. Then when somebody is in a position I was in earlier, they can pull out their chop saw and make a wedge that actually holds the chain tensioner over my wedge design. (which has never failed me!) Thanks in advance!

Both you and my brother want me to remove the custom gasket I purchased (0.063 thickness) and install the stock gasket back in it's place (0.049), Brian and I have a lot of things to do on the car that are of higher importance at this time. Our plan is to complete the assembly of the car then, once the car is fully running and broken in, revisit: - Piston to head height (currently it is ~0.040, with a stock gasket it will be ~0.026 is my best guess given the accuracy of the measurements I made) - Cam choice. Current cam causes the engine to lope too much and the exhaust is loud. I expect we will visit this modification in the summertime this year. We are hoping to complete the drive train this weekend (actually test drive the car even though it does not have hood, hatch, windows, interior etc.) and complete the car in late March. Thanks for asking Jim

Xnke - I hadn't thought about the seat! Thanks for the heads up! I'll be sure to look at the valves more often to ensure they are gapped properlly.

we'll wait till the car is assembled before cutting springs. However this issue is kindof bugging me because I do not have a sure solution (which is why I am asking for advise). Your advise above is for me to remove the spring from the shock housing and check how much of the spring I can cut such that it fits without slop in the shock... right? Thanks Jim

yes they are! Now the car does not have an interior, glass, front bumper, and hood, but you can see that the ride height is a bit too high.

Hello I have a 240z with tokico illumina HP springs. This setup has variable rate front springs with single rate rear springs. I have read many threads which state I should purchase 280z single spring constant springs for the front suspension. What do we know: We know the front springs are progressive springs. This means that the top of the springs compress at a lesser constant than the bottom of the springs. The rear springs are linear. We also know that the front springs (9 turns) the first two turns touch under the weight of the stock 240z, and the remainder 7 turns have approximately 0.5" gap between the individual coils. The ride height of my car needs to be reduced by 1 inch (see pic) As I currently own these springs, I wanted to try to cut them to drop the ride height 1" and try them before we discard them and purchase 280z springs Since the rear springs are linear, I can easily determine how much to cut off to reduce the ride height another inch. My question. In order to reduce the height of the front of the car, Should I cut the top of the front spring or the bottom of the front spring? I will tell you why I ask. If I cut the bottom of the spring - plus... then the spring constant is linear at the bottom and it is easy to determine how much to cut off. - Minus... the non linear spring rate is maintained. If i cut the top of the spring - Plus... The spring rate becomes more constant (because I am cutting off the portion of the spring that has a lower spring constant - Minus... It seems to me that the uncompressed spring should be taller than the shock when the shock is completely decompressed. I could probably could cut off 2 turns on the top to achieve 1 inch reduced height, However I would have to reduce the travel of the shock because the spring uncompressed will probably be shorter than the shock uncompressed What do you think? Thanks Jim

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Xnke. Do you know what causes the valves to get tighter? Heat maybe? I am happy to say that the valves are finally behaving in my setup. they are much quieter than my fuel pump, unfortunately the car is a bit loud ( I went overboard with the cam ). regarding valve adjustment period, you are saying as they seat, they get quiet before they open up. When I was a kid, we adjusted the valves 3 times (cold, hot, then after the first 1-10 miles). Then we drove 100miles and varied the RPMs 0-5500, and adjusted the valves, then we drove the next 900 miles being sure we varied the RPM 0 to 7000 RPM being very careful not to stress the engine as we wanted the rings to seat at high RPM. we adjusted the valves, air fuel mixture, timing. At this time we considered the engine broken in. Keeping on topic, Valley head service (the folks that worked on my head) numbered and adjusted the thickness of each lash cap independently as they adjusted each rocker arm / cam geometry. I really like this technique and (in my opinion) applies to Ben'z problem.

That's what Ztherapy prescribes also. I have not yet added oil to the carbs. I also believe SUs are sensitive to vacuum and because the vacuum is is not constant, (due to the cam) I believe it makes idling more difficult. I guess If I add oil it will help. I have an email to Steve to ask him what oil weight he suggests I use. I just purchased a timing light. This weekend, Brian and I will: - time the engine (easy) - install the two oxygen sensors in the 2 pipe of the headers and adjust air fuel mixture (I hope it works, we have narrow band sensors and a multi meter and oscillioscope. Thanks for the advice.! Jim

Grrr. Were using su carbs. I think I might be able to idle at 900 rpm. But it will take all the finesse I can muster. Exhaust is loud. Thinking about adding glass-packs in addition to the dynomax turbo muffler ( the most quiet muffler they sell )

Pete - I had valley head service do the lash cap side of the rockers and did not touch the rocker to cam interface (it looked pretty good). They did spend a lot of time with the valves and cam geometry. The guys didn't think that the rockers needed any work and that is why they didn't touch them. In general they are pretty competent guys! At least that is my illusion... lets not burst my bubble now! Grin....

I'll bite. '73 240z goal was to make the car look as close to stock as possible, however we could not resist making some changes ('77-L28 block, '83-P90 head, '70-SU carbs, '83 Distributor/electronic ignition)

I just spend 3 weeks with my head trying to determine why I could not (set the lash?) adjust the gap between the cam and the rocker arm. It is my humble opinion you should NOT grind a substantial amount of material off your rocker arm. I had mine re-shaped (which probably removed 0.001 or less of material.) I like the idea of using a cam tower shim, however once you do this, you are going to have to check how the cam rubs against the rocker arm to ensure your geometry is correct. (it is easy, get a sharpie and blacken the rocker arm and check the wear after one revolution) In general, when you change a cam one has to review the cam/valve geometry to ensure it is correct. A shop adjusts this by changing the thickness of the lash caps. The lash caps on my car vary approximately 5mils (from ~0.150 thick to ~0.160 thick). As an alternative to the above, You could chose to grind down your lash pad 0.010 which would give you a max gap of 0.017 and allow you to achieve a 0.008-0.010 gap. Please note that if your lash pads are stock they are probably ~0.120" If you do this, I suggest you do have the rocker arm resurfaced so that they can mate properly. Jim

PMC raceengines (pete?) You were right! You know, prior to grinding my rocker arms I could not adjust the cam/rocker gap properly... Now that the rocker only touches the lash pad/valve interface in one spot, it is so easy to adjust the gap.! This engine is a monster! I think I may have gone a little bit too far with the cam I chose (280 degree duration) with SU carbs. Idle at 700 rpm seems difficult to achieve and the exhaust is a bit loud... No matter, the car is running and I am very happy! Thanks again for your help! Jim

Good news! Car is working!!! little to no head noise! Alright, what caused the issue. Rocker arm to cam gap was not correct. Why? Remember the lash pad marks? one on each side of the lash pad with nothing touching the center of the pad. What would happen if the planes defined by the cam lobe/rocker arm was not parallel with the lash pad/rocker arm plane? If the rocker arm was soft, it would cause the rocker arm to twist until the two planes are parallel? I believe this was my problem. Once I had the portion of the rocker arm that touches the lash pad ground down do that it touches the lash pad on one spot and in the center of the lash pad, I could accurately adjust the valves. (note: during adjustment prior, the rocker arms seemed to rock, now they are steady) I re-assembled the head, and was careful to gap the exhaust/intake at 0.010"/0.008" respectively. Started the car, and warmed up the engine (the engine was a bit quieter, however it was still loud). once the fan kicked on, I turned off the engine and re-gapped the valves. Started the engine and WOW it is running quietly now! YEA! Thanks very much for everyone who took the time to help me on this thread.!!! Jim

I think there are two sounds. One is the valve trane ( I will gap it hot this time) the second is a violent tapping which seems to come from the back side of the valve cover. When I lifted the valve cover while engine was running the noise did not change. This time during assembly I'll pay very close attention to rocker arms and will check gap as a function of angle.

Lazeum - I am using the same lash pads. Xnke - I believe the ticking noise is at the valve speed. If it continues, I plan to determine which valve it is by cutting the top off the valve cover. More to come! Jim

Update! I took the rocker arms to the head builder and showed him the tappet wear and the matching rocker arm wear. He was of the opinion that this was not the problem but did grind the rocker arms so that they would naturally touch the center of the lash pad instead of the edges as shown above. (picture of modified rocker arm, orig rocker arm, and lash pads -attached). We're pealing the onion here... First steps, reinstall cam lash pads and rocker arms. Blue (sharpie marker on the pad where the rocker arm comes in contact with the cam) rocker arms and check each rocker arm / cam surface to ensure the arm is properly mating to the cam. While I am doing this be sure to check the rocker arm is pushing the valve in the proper place. Next, with the engine cold, gap both intake and exhaust valves at 0.008" Next, start the engine, let it warm up, turn it off and regap intake and exhaust valves at 0.008 intake and 0.010 exhaust Start engine and see if it is quieter. If I still have a problem, I have located an old valve cover and I am going to cut the top off, mount it to the head and run the engine to see if I can tell which valve is making the tapping noise. Next steps if the noise persists, is to swap my beautifully rebuilt P90 head with squish to a N42 head ... sigh... Jim

Heroez - Just build the one I provided dimensions for above. It is simple and works great. Just wedge it in with your fingers. I have used the above wedge 4 times. Jim

Leon. You must race cars often you seem to know a lot about Zs in particular and cars in general. (When I was a kid my brother and I terrorized LA and that is where I learned what I know.) Getting back to your comment, once I fix the head problem I am having (taking way too long) we'll concentrate on reducing noise (I have a loud fuel pump and exhaust is a bit louder then I like) then start on suspension. We are planning three passes. First we'll modify ride height by cutting springs. the car is about an inch too high now, have tokiko illumina variable rate springs on front, it'll be tricky as the rate is not linear and we will have to trial and error the cuts. Once the car ride height is ok, then we'll work on suspension. First my son will take it to his HS shop and measure camber, caster and toe, he'll fix toe on front, and using a tension and compression kit in the front be able to adjust caster (I think). This might be the time to check the torque of the suspension as you have suggested. The car should be drivable then (no interior, windows, door latches, hood, hatch etc). I'll look at the printout and see what needs to be done additional. I fully suspect we'lll have to add offset bushings in the rear to fix camber, possibly we can stretch the rack if required. Then we'll install what we can at home and take the car to a real suspension shop and have it professionally aligned. Lastly, I want to understand what the car does when it is under load. I heard of a neat idea of affixing a camera under the suspension and adding a straight edge and monitoring what the suspension does as a function of speed. WE can record these settings and compress the springs and re-align the car so that it handles optimally at speed... Sounds like a fun summer task doesnt it? Either way, thanks for your inputs. Jim

Seems like the rocker arms are only touching the lash pads at the sides... right?

Update. I reduced the valve gap to 0.006/0.008" intake/Exhaust. and restarted the engine with no change. Next, I removed the cam followers and lash pads. I noticed the lash pads I removed completely flat on the bottom (as opposed to the stock lash pads which have rather long walls and seem to cuddle the valve. I also noted the lash pads (top side) did not have the groove on either side and the cam follower wore two small lines on either side of the middle of the lash pad. The lash pads measured 0.155" thick. see pictures: Left pictures are the stock lash pads right pictures are the isky lash pads that were installed on my head.

yes. I did a compression test. 230PSI on #6, to 190 PSI on #1. I believe the difference was caused by the motor being on a slant and had more oil on #6. Youtube link is Thanks Jim