I already got a recurve kit for my HEI, and have read through here a bit. I also looked at the www.buickthunder.com link posted in this thread. In that thread, it stated that on the HEI, the center plate limits the mechanical advance like the brass bushing on the points distributor. It stated, one of the best combos for most GM cars was 375 center plate, and 41 weights. On my recurve kit, there were a couple of center plates to choose from. A small one, and a large one. Which one would be best for recurving?
The larger center plate probably limits weight travel. That restricts the amount of mechanical advance. That would be my choice.
Thank you! I will make sure to install the larger plate once I get the running. Hopefully that where get me the desired mechanical advance. :TU:
When you say center plate, you are talking about a wider one? This is the part labeled 235 in the pic I attached? If so, a wider plate makes sense to me. It would restrict the weights from going out all the way like you said Larry.
Mike has an HEI, not a points type distributor. It is much easier to replace the center piece on an HEI, and the weight kits typically come with them.
This morning I timed my 350 to about 8 degrees initial, and a bit under 30 all in. It had been around 2 degrees initial. It seems to work great, but now it is very hard to crank. I have the ignition cut off switch trick, so this is not a big deal, but it doesn't seem right. It is 10:1 compression, GM HEI, with a Tilton starter, so I would think it should crank easier. Anyone else have this problem?
Something is wrong. There should be no hard cranking when hot with only 8* initial timing. Are you using good 2 gauge battery cables? Are the connections at the battery and starter clean and tight? What distributor are you using?
The dist is a stock GM HEI (1975 I think), with lighter springs to get all the timing in before 2500. The cables are good, but the positive lead is very long since the battery is in the trunk. I believe they are 2 gauge. I can hear the pre-ignition while the starter is cranking, whereas with 2 degrees initial the cranking was very smooth. I recall back in the 80s my brother broke the nose off a couple of starters for a similar problem with this same car and engine. He ended up putting in the ignition bypass switch for cranking, and he never broke another starter. One interesting thing though. The timing marks are on a bolt on piece, not part of the timing cover (picture attached). The cover was changed before I inherited the car, and the marks do appear to be in the correct location. The car doesn't ping under acceleration, so I am at a loss as to the cranking issue.
GM HEI's typically have a lot of mechanical advance. I know lots of guys love them because they are cheap and parts are readily available, but it would be my last choice to use one. You say that you moved the initial timing from 2* to 8* with 30* total. That says to me that you have 22* of mechanical advance, unusual for a GM HEI, but it also means that at 2* of initial timing, total timing would have been 24*, and the engine should be down on power like that. One of the BIGGEST mistakes made is underestimating when all the mechanical advance is in. I think you probably have a lot more than 22* in that distributor, and if it seems to run with good power, that means there is more advance in the distributor. That's why I like the Crane springs that come with their adjustable vacuum advance. The yellow ones get the advance in by 2000 RPM in most cases. If you set your total advance with them, you can be fairly certain it is all in. Not sure why your battery is in the trunk, but that longer run of cable probably has something to do with the hard cranking.
I like the MSD distributors. They have a fully adjustable mechanical advance. Unfortunately, they don't make one for the 350 except the pro billet one, and that one has no vacuum advance. You also need to use it with a box. http://www.msdignition.com/Products..._Buick_V8_215-350_Pro_Billet_Distributor.aspx Their ready to run line can be used stand alone or with a box, but they only make it for the 455, http://www.msdignition.com/Products..._400-430-455_V8_Ready_to_Run_Distributor.aspx The only difference would be the gear. I often wonder why MSD didn't just offer the above distributor with a 350 gear. The next best thing would be a Mallory unit. http://www.taperformance.com/proddetail.asp?prod=TA_MAL4764301 Or, you could send an old points distributor to Dave Ray. http://www.davessmallbodyheis.com/
Only problem with that is that you don't get to pick a distributor with the amount of mechanical advance you want. You get what you get. I prefer a distributor with 20* or so of mechanical advance. The ability to adjust the mechanical advance is even better which is why I like the MSD distributors.
About restricting the pull pin travel to .086" for 8*, or .104" for 10* vacuum advance. Is it the same distance on all distributors, for example my MSD 8552 ready-to-run distributor? I guess it should be since the vacuum advance canister should be universal, but just want to be sure before I do something bad. I will make own limiter or test the MSD advance kits 84281, but not sure if it fits - mailed the MSD support. Thanks
Some have shown their vacuum limiting solutions and this is mine based on MSD 8552 R-T-R distributor and 99601 Crane vacuum canister, square shaped weld nut. (Havent tested it yet since Im still working on the engine.)
I thought Id add my experience for discussion by the more knowledgeable members and maybe help someone in the future. Some history. The car is a 65 with what appears to be a 73 model 350/2bbl. I got the car last fall and initial timing was set to 0*. I thought I had it set correctly and bumped it to about 8*. Car felt better but was pinging some. I installed a set of aftermarket gauges so I could at least monitor the vitals. Noticed it overheating slightly. Recently found the trans cooler was leaking trans fluid into the coolant. I installed a cooler 180* stat and verified water pump was in good order. Better but still overheating some. Today. I went back and re-read everything. I do not have a dial back light, just a standard one. I carefully measured 1.75 clockwise and marked the balancer. Im by myself so I couldnt see what rpm it stopped moving at but once it did, I moved the distributor and set it at 30* total with vac disconnected. I rechecked initial and its at 12*. I drove the car quite a bit today and got on it a little more than usual. I also filled up the tank with 90 octane pure gas. One of the benefits of having so much boat traffic by the house going towards the lake is that they stock it for boats. I checked vacuum while I was at it and its fairly steady at 17. It moves maybe between 16 and 17 but no more. I noticed that I had no vacuum at all to my distributor vacuum advance coming from the carb so I swapped to manifold vacuum. That certainly got the vacuum advance working. Drove the car quite a bit today to run errands before work and the difference is huge, the car really likes it. Overheating issue seems to be much improved. Car never got over 190* and when running it a bit harder than normal or idling in traffic it would creep up a bit but once moving normal it would drop down again. I heard just a little pinging, ever so slightly a couple of times when I romped on it. Most of the time I heard nothing. Points gap is a hair under .020. Of note: I read some bad reviews on the FRAM oil filters. I took this one off and replaced it with a Purolator and my oil pressure seems to have come up. I had another thread about oil pressure and Ill cross post this info but at hot idle, after driving or at a stoplight I am now seeing 12-15psi. Previously it was well in the single digits. Sorry for the wall of text, just trying to be thorough. Thoughts?
Have you changed the weight springs? Most stock springs don't allow full mechanical advance until upwards of 4000 RPM. When you set the total advance, you must be absolutely sure that all the mechanical advance is in. If it isn't, then you may think you are setting the total advance, but the timing may still advance beyond that. Setting your total advance is much easier with very light springs. Once the total is set, you can put the stock springs back in and be confident that you have accurately set your total advance. The lightest springs are great for adjusting the total, but they are frequently not good for everyday driving as they can alter the timing when going from Park to Drive. You can also swap in different springs to bring the total in earlier than stock (2500-3000 RPM), but when you do that, you usually have to limit the vacuum advance degrees so that the engine doesn't ping when going from light load cruising to high load acceleration. It is best to leave the vacuum advance disconnected and plugged, and work with total advance (initial + mechanical). Set the total advance and make some full throttle runs from low and higher speeds. Listen for ping. Once you have that nailed down, then connect the vacuum advance and check for part throttle ping. Adjust accordingly.
How much total timing is too much, even without ping? The reason I ask is Im getting 45 total with no ping. Can even go higher with no ping and Im concerned it is too much. Heres where im at.. 68 points dist. Dwell @30 18# on the vacuum gauge. Mr gasket bronze bushing and lighter springs 11* initial w/o vac adv. Vac adv limited to 10* Mech advance starts about 1100rpm and all in @ 2800 Total is 45* Seems higher than what I've read should be ran. But I get zero ping. the car idles and runs great right there. If i try to back the timing off it stumbles and loses vacuum. If I advance it past 14* it will have a definite miss at idle and part throttle but will still not ping. Why is that? Should I be ok with the 45* total or is that still too much even if I dont hear any ping? This is without vac adv hooked up (wich ads another 10) The motor is the original 68 350. But has bigger valves, springs, and a crower Level3 sitting 4* advanced. And stall. Larry you were in my cam swap thread a few months ago so you may remember. Should I still try to limit the pin slot in the distributor to get closer to 36 or so? or is the 45 + vacuum adv safe?
What you have wrote says there is 34* in the distributor even with the bronze bushing installed? You aren't including the vacuum advance in the 45* are you? It should be pinging. 30-34* is what most all iron engines want at full throttle. If you had the car on a track or chassis dyno, you would see a drop off in trap speed or rear wheel HP. The stock distributor for a 68 350 is 1111330. It is supposed to have 26-30* in the distributor. A bushing should bring that down.
