Good point, but I'm tired of having to stay late at work to fix it so I'm going to go ahead and replace the dizzy and inspect the harness along with the plug wire repairs/rerouting that I had planned just to eliminate most of the probable causes. I am also going to double check the pins at the pcm connectors for proper pin tension and repair as needed.
Based on my experience using the L31 camshaft / TBI distributor combination, I install a new Melonizied distributor gear.
http://paceperformance.com/i-6251232...rnal-coil.html
It's my understanding the steel used in the L31 camshaft will destroythe cast iron TBI distributor gear.
Maybe, just maybe the TBI cast iron distributor gear and L31 steel camshaft are the source of the knocks?
dave w
Last edited by dave w; 06-26-2012 at 07:46 PM.
Simple answer would be I replaced the dizzy gear during the engine swap as the old one was shot and made sure to verify that it was a melonized gear. But FWIW, by TBI distributor I am assuming that you are probably referring to an L03 or L05 C/K truck engine distributor as those were the most widely used TBI engines. However, the L03 and L05 truck only applications were the only SBC engines that did not receive the roller cam upgrade in 1987. All other gen 1 SBC engines from 87 up were equipped with roller cams and used the same distributor regardless of induction type including the car versions of the L03 and L05. Just an FYI, LT engines are considered gen 2 and L30/L31 applications were considered gen 1+. While 86 and prior SBC engines using flat tappet cams and perimeter bolt valve covers are considered gen 0 with the exception of the 86 corvette L98 which used both benter bolt heads and a roller cam. I am stepping out on a ledge here and assuming that the distributors installed in the roller cam engines used a melonized gear as they did have a relatively acceptable service life. Nowadays, these 20+ year old high mileage distributor gears do require replacement due to wear and sometimes wear enough to actually lose contact with the cam and thus not rotate. But it is my understanding that a cast iron distributor gear won't last maybe 20K miles or so when mated to a billet steel roller cam. Nowadays most OE style replacement small cap EST HEI distributors have been consolidated to a single part number and are equipped with a melonized gear and I am under the impression that a flat tappet cam is compatible with a melonized gear. And even cheap replacement gears for roller cam applications are in fact melonized. But, that's way more info than needed.
Now, I don't mean to come across as argumentative I just have thought the issues through over and over again. Gotta go for now, need some sleep bad,
Phil
Cool, your using a melonized distributor gear. Didn't know until I asked.
dave w
Yeah and from what he said I need to change my distributor! 140K flat tappet TBI truck motor. Maybe using synthetic with zinc and phosphorous all these years has paid off besides the lifters?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I hope you didnt think I was being a smartass dave because I wasn't. I respect and appreciate all of you veteran gearheads posting ideas and suggestions in this thread. I was just sharing some info in case you didn't already know.
Mark, in my experience the C/K L05 had almost no issues with the lustered even at mileages past 200k. They did, however, frequently require replacement of the distributor gear at higher mileages. If you haven't had the distributor out in some time I would check the gear. In many cases even severely worn gears may not exhibit any noticeable driveability concerns. This was the case with the dizzy in the old 305 that came out of my car and I do realize that I am jumping back and forth between roller cam and flat tappet engines, but the issue was fairly consistent across the board with the small cap distributors of the era. Back to my car, I had pulled the distributor last year for reasons I can't remember and noticed a severely worn gear but didn't replace it because I was unsure of my plans at that point. I did have one ready come time for the engine swap. By then you could probably have shaved with the teeth they were so thin, yet thre were no driveability issues at all. It did probably affect performance, but on a 200k+ mile engine it would hard to tell. And regarding zinc and synthetic oil, I am a firm believer in both. The assembly lube that GM used called engine oil supplement or EOS for short is loaded with zinc and one of the uses listed on the label for years was as an additive to engine oil, but it was removed from the label after a link between zinc and catalytic converter damage was made somehow. Well gotta go,
Phil
We're good. Didn't think that you were being a smartass at all. The discussion of using a melonized distributor gear is "valueable information" to this thread.Originally Posted by pmkls1
I'll also add, the "off-shore ~ $$ Cheap" aftermarket TBI distributors (1987 ~ 1995) use an 11mm shaft. The link I posted for the GM melonized gear will not fit an 11mm shaft!
dave w
I read on TGO that this pcm does a knock test on startup and knock counts are normal (only at startup). I get a bunch of bogus knock counts when I crank mine too, but it has never posed a problem for performance. I get no knock counts after startup and no KR.
87 4Runner, 15" spring lift, 3" body, chevy vortec 355, 5.29 gears, 38.5x15.5x15" Boggers, 280hr, 16168625 running $0D
93 S10, 36x12.5x15 TSL's, custom turbo headers, 266HR cam, p&p vortec heads, $0D Marine MPFI with 8psi boost.
05 Silverado, 2' lift, 4" exhaust, Bully Dog programmer,
Sorry it took me a couple days to reply, but I developed a nasty sinus infection that hit me pretty hard. Well, you just told me something about the cheap offshore distributors which I believe come from china and are knock-offs of the original part # units. The cheap aftermarket parts I was referring to would cardone and bwd, which are probably of significantly higher quality in comparison with the china made parts. I also had a momentary lapse in brain activity about part # consolidation. It is the complete distributors and NOT the gears that have been consolidated to a single part #. The gears listed on the autozone and advance differ by application but a complete distributor has one part # for all. You will also find the same to be true for some other aftermarket distributors marketed to fit "late model efi applications" such as in the performance parts sector. I know that jegs sells one under their brand that mentions nothing about camshafts until you read the instructions and then steel roller camshaft is mentioned. Otherwise, though, information is a little difficult to come by regarding what type of gear is on the distributor as many will just claim to fit 87-95 applications for cars and trucks. I cannot find it now, but I swear that I saw a note on the BWD gear for a roller cam application indicating that it was such during my search for some sort of evidence that the part I would be buying would be melonized. The info I found may have actually on a sheet included with the part. The important thing would be that the gear is "supposed" to be correct for the application.We're good. Didn't think that you were being a smartass at all. The discussion of using a melonized distributor gear is "valueable information" to this thread.
I'll also add, the "off-shore ~ $$ Cheap" aftermarket TBI distributors (1987 ~ 1995) use an 11mm shaft. The link I posted for the GM melonized gear will not fit an 11mm shaft!
dave w
As far as GM parts go this is what I do know. I know that the GM catalog has been updated many times and that most of the original part numbers have been superceeded, but the OE GM distributors must have all had the same diameter shafts as the parts catalog shows the same part #'s for the housings, shafts, and gears. The gear you listed p/n 19052845 is also listed in the catalog as the replacement p/n for all applications and is installed on the distributor p/n 1103952 that is sold both as a service replacement for the trucks and cars. It is also sold through the GM Performance parts catalog as a "late model efi distributor". That part number is a fairly old part number and is easy to tell because it is a 7 digit number. 7 digit part numbers are numbers that have been around for a long time and are technically an 8 digit number with the first digit being 0 that can be and normally is left off. Oddly enough, I recently had a conversation with one of the parts guys at work that was on this very topic. I have a lot of confidence in anything he says and trust him especially on vehicles of that era since he has sold chevolet parts longer than I have been alive. When it comes to parts from "the good ole days" he can still remember many of the commonly used parts and pull them right up in the computer without having to look them up. I asked him about a small cap distributor and he instinctively pulled up that number without hesitation. I asked if he had sold many of that number and he said that was the only distributor he knew of for 87-95 applications and had sold tons of them.
One last note that I will add is that in the GM performance parts catalog in the distributors and components section there are a couple notes stating that a melonized gear MUST be used be used on all crate engines or serious damage will occur. The odd thing about that statement is that many of their crate engines use flat tappet cams. Their standard big cap HEI that they sell out of the catalog for carbed applications also comes standard with a melonized gear. Anyhow, long story short, it would appear that a melonized gear is compatible with a standard flat tappet cam and that many of the trucks have had this distributor installed
How would you go about getting a new small cap EFI distributor? I tried GM Performance online and that part number and no go?
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
I'm not sure what site you went to, but you can get that distributor anywhere including jegs and summit or the local gm dealer. Just google 1103952 distributor and you'll get tons of results.
Must have sucked at search cause that worked good! Thanks!
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
No prob. And back to the topic of my ignition problems, I happened to stumble across another finding. As I was double checking the listings for distributors and gears this weekend I found an error in the catalog for my car. If you look up a distributor gear for an 89 firebird formula 5.0 "E" in the bwd catalog (which is the brand that advance auto parts carries) they list a gear for a standard flat tappet cam. I only realized that the part number was wrong after comparing a few vehicles. But, if you look up a gear for an 89 camaro 5.0 "E" the correct gear is listed. So, long story short, I am NOT running a melonized gear on my dizzy giving me yet another reason to buy a new dizzy. Since I do not know the cause of the erratic distributor reference signal and do know that the module and pickup are cheap aftermarket pieces and that the gear is incorrect I would want to replace all 3 components. And, the combined cost of those components from GM is nearly as much as a complete distributor. I don't have the $$$ for a new dizzy this week, but luckily the weather forecast looks like I'll be riding the bike a lot.
I did resolve the CCP issue and it is now functioning. I also have a timing curve that seems to work well overall. I haven't done much with the VE tables yet, but really don't plan on doing much more tuning until I get the ignition system straightened out.
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