DIY_EFI Digest Tuesday, 23 February 1999 Volume 04 : Number 127 In this issue: Re: Diacom RE: ECM wiring harness help Plasma Jet Ignition Connector Re: Connector Re: Delco 808 ecu info needed Re: Connector Re: Connector Re: Plasma Jet Ignition Fw: Ford Connectors (EFI) EGR Correction Question Re: Plasma Jet Ignition RE: EGR Correction Question Re: Plasma Jet Ignition Re: ECM wiring harness help Re: Plasma Jet Ignition Re: Plasma Jet Ignition Re: Plasma Jet Ignition Re: Plasma Jet Ignition Engine Control Question Re: ECM wiring harness help See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Roger Heflin Date: Mon, 22 Feb 1999 07:05:41 -0600 (CST) Subject: Re: Diacom On Mon, 22 Feb 1999, Scott Feaver wrote: > Anyone know how many frames per second in Diacom? I have some log files > that I want to put a time to.. Thanks. > > It depends on the car. Mine does just over 7 frames per second (93 LT1). How fast it goes depends on how many parameters are in the standard data stream for that vehicle, and from what I gather can and does vary. The best way I found is to time things, the other method is that if you have the raw ALDL data stream definition for your vehicle, diacom seems to put the entire data stream in the file even if it does not decode everything, and the part that has engine rumming time in minutes is actually encoded in seconds in the raw data file, so this would give you what was needed to determine exactly the number of frames. Roger ------------------------------ From: "Guenther,Max" Date: Mon, 22 Feb 1999 08:04:24 -0500 Subject: RE: ECM wiring harness help Somebody a while ago had mentioned that the plugs on the 727 where fairly vehicle specific. I got a set of 4 plugs from a v-6 something and I attatched it to a vette 727. Most of the pins that were not where they were supposed to be had a little rubber plug inserted. Also the connectors came out easily. But the B plug was molded differently and there is no way to hook up the vats(the car I got my harness from didnt have VATS). Its doable I guess if you get rid of the VATS in the memcal. Max > ------------------------------ From: bob@xxx.com (Robert Harris) Date: Mon, 22 Feb 1999 14:49:25 GMT Subject: Plasma Jet Ignition Reference: Internal Combustion Engine Fundamentals John B. Heywood ISBN 0-07-028637-x McGraw-Hill Professor of Mechanical Engineering, Director Sloan Automotive Laboratory, Massachusetts Institute of Technology 9.5.3 Alternative Ignition Approaches. Page 446 heading Plasma Jet Ignition Later details prechamber flame jets such as the torch cell ( more better name for anti-fouler ) and pre-chamber stratified charge - with fuel and with auxiliary valve ( like Honda Civic). Just enough details on how it works to tempt and not quite enough to design or fangle. All of these are distinguished between the true Texaco?MANN Stratified Charge Engines where direct mechanical injection of the fuel is timed to co-incide with the spark fired and are best described as spark assisted diesel engines. 1963 Ford C-600 Prison Bus Conversion "Home" 1971 Lincoln Continental 460 "Christine" 1972 "Whale" Mustang awaiting transplant 1978 Dodge Long Bed Peeek Up "Bundymobile" Habaneros - not just for breakfast anymore ------------------------------ From: "Guenther,Max" Date: Mon, 22 Feb 1999 12:58:13 -0500 Subject: Connector Does anybody know where to get the 66 pin connector on the 727 ECM for the memcal? I'm not real good at soldering and dont want to try taking it out. I'd like to make a little rig to reprogram the rom chip with out removing it from the memcal unit. Thanks, >Max ------------------------------ From: "Bruce Plecan" Date: Mon, 22 Feb 1999 13:51:15 -0500 Subject: Re: Connector - -----Original Message----- From: Guenther,Max To: 'diy_efi@xxx.edu> Date: Monday, February 22, 1999 1:37 PM Subject: Connector >From Digikey (800) 344-4539, get a AHW60G-ND Cut in two, and trim as nesecary for the memcal to fit it, and insert that into the burners ZIF. Bruce > > >Does anybody know where to get the 66 pin connector on the 727 ECM for >the memcal? I'm not real good at soldering and dont want to try taking >it out. I'd like to make a little rig to reprogram the rom chip with >out removing it from the memcal unit. >Thanks, >>Max > ------------------------------ From: Ludis Langens Date: Mon, 22 Feb 1999 09:00:03 -0800 Subject: Re: Delco 808 ecu info needed Wayne Macdonald wrote: > You say that this is a standard NatSemi part ?, Do you have the NatSemi part number ?. > > >O2 sensor amplifier. This is a standard NatSemi part. > > U5 44188 ???? The O2 amp is GM part number 34987. The NatSemi part number is LM1964 (old) or LM9044 (new). I don't know what the 44188 chip does. - -- Ludis Langens ludis (at) cruzers (dot) com Mac, Fiero, & engine controller goodies: http://www.cruzers.com/~ludis/ ------------------------------ From: Roger Heflin Date: Mon, 22 Feb 1999 13:16:57 -0600 (CST) Subject: Re: Connector On Mon, 22 Feb 1999, Guenther,Max wrote: > > > Does anybody know where to get the 66 pin connector on the 727 ECM for > the memcal? I'm not real good at soldering and dont want to try taking > it out. I'd like to make a little rig to reprogram the rom chip with > out removing it from the memcal unit. > Thanks, > >Max > Buy a smaller connector (say 50 pin) and modify it to fit the half of the chip you need. You will need to cut the end off of it and add some notches in it to match the memcal. You probably want to get a wire wrap socket as it has long legs and with a bit of bending can be plugged into a programmer without many problems. I have been using this sort of setup for a while. I searched for a 66 pin and did not have any luck finding one. Roger ------------------------------ From: "Peter Fenske" Date: Mon, 22 Feb 1999 12:08:46 -0800 Subject: Re: Connector Hi Max Go to rad shack and get some prototype solder board with some test pins.. solder two rows of pins in 0.100" apart and two rows further out 0.600" apart. Remember to cut the traces in the center.. This will adapt the calpak to the req eprom programmer Email me and I might be able to send you a pic :peter Does anybody know where to get the 66 pin connector on the 727 ECM for the memcal? I'm not real good at soldering and dont want to try taking it out. I'd like to make a little rig to reprogram the rom chip with out removing it from the memcal unit. Thanks, >M ------------------------------ From: "Gary Derian" Date: Mon, 22 Feb 1999 15:28:27 -0500 Subject: Re: Plasma Jet Ignition I do remember that article. I believe it was Hot Rod. The engine was a nail head Buick. The anti-foulers like things were welded in to provide cooling water around them. All the sparkplugs were connected together in a single circuit with a capacitor at each one. There was some kind of spark generator to create a high frequency spark. The inventor had all sorts of claims for better performance and economy. I have never heard of such a system since. Gary Derian >Barry Tisdale wrote: > >> Anybody remember an *old* spark ignition system that used conventional spark plugs & an anti-fouler extension w/ a *small* hole into the combustion chamber? The spark fired constantly, on compression, air/fuel would be squeezed up the tube, enter a small chamber around the spark plug, ignite & then shoot back into the combustion chamber. Apparently self-timing, self load compensating, etc. >> >> Wonder what ever happened to that - read about it in an old mag, '60s or so.. ------------------------------ From: "Bruce Plecan" Date: Mon, 22 Feb 1999 17:57:12 -0500 Subject: Fw: Ford Connectors (EFI) Just in case anyone needs em. Bruce >> Anyone know a source for Ford EFI connectors. other than from >> existing harnesses?. >Interactive Systems and Technologies, Canton GA >800-820-1082 ------------------------------ From: "Bruce Plecan" Date: Mon, 22 Feb 1999 18:02:52 -0500 Subject: EGR Correction Question Does anyone know of a GM calibration that takes timing out, or reduces the amount of fuel during EGR apply. As it apprears to me it's always, add timing, and add fuel. Please no quessing...... Thanks Bruce ------------------------------ From: Raymond C Drouillard Date: Sun, 21 Feb 1999 13:33:36 -0500 Subject: Re: Plasma Jet Ignition It'll go away when the capaciter discharges - the same as a xenon flash tube. Ray On Sun, 21 Feb 1999 22:12:29 -0700 Marc Piccioni writes: >Just a quick question, if you get the high current flowing how are you >planning on terminating it? > >---------- >From: Chris Conlon[SMTP:synchris@xxx.net] >Sent: February 21, 1999 1:00 PM >To: diy_efi@xxx.edu >Subject: Re: Plasma Jet Ignition > >At 06:50 PM 2/21/99 GMT, Robert Harris wrote: > >>Re-reading my Heywood and have become re-in-love with the concept of >plasma >>jet ignition. Essentially, a normal CD ignition fires the plug in a >cavity >>connected to the main chamber by an orifice. Once the arc is >established, a >>second low voltage high current capacitive discharge is routed into >the >arc. > >Hmm. Electrically, this is exactly the kind of ignition I'm trying to >build. Or rather, trying to get a buddy of mine who's already doing a >DIY coil-per-plug system, to try and build for me. My plate's too damn >full already. I figured, why should you have to choose between a >short, >hot spark and a longer, less hot one? But I have not read the book you >mention, guess I'd better try and get a copy. > >It's a lot like building a power supply for a flash lamp, which detail >it took me embarassingly long to realize. > >Do you have info or speculations on the benefits of just the >electrical >aspect of this idea, vs. just the mechanical aspects. (the cavity and >orifice) In other words, does either part of the system get you any >gain over a normal setup? I'm just wondering about the mechanisms >involved. > > Chris C. > > > >begin 600 WINMAIL.DAT >M>)\^(CD%`0:0" `$```````!``$``0>0!@`(````Y 0```````#H``$-@ 0` >M`@````(``@`!!) &`& !```!````# ````,``# #````"P`/#@`````"`?\/ >M`0```&$`````````@2L?I+ZC$!F=;@#=`0]4`@````!D:7E?969I0&5F:3,S >M,BYE;FM;VAI;RUS=&%T92YE9'4`````'@`", $````%````4TU44 `````>``,P`0`` >M`"(```!D:7E?969I0&5F:3,S,BYE;FM`0````,`_@\&````'@`!, $````D````)V1I>5]E9FE 969I,S,R+F5N9RYO >M:&EO+7-T871E+F5D=2<``@$+, $````G````4TU44#I$25E?149)0$5&23,S >M,BY%3DM``0````````#GD@!"( '`!@```!)4$TN36ECM" $$@xxx.```` >MSP<"`!4`%@`,`!T````L`0$@@ ,`#@```,\'`@`5`!8`"P`9````)P$!"8 ! >M`"$````S131$,C!$040V0SE$,C$Q0D4Y0S0T-#4U,S4T,# P, `*!P$#D 8` >M\ 8``!(````+`",```````,`)@xxx.0! >M0KKQ(5Z^`1X`< `!````& ```%)%.B!0;&%S;6$@2F5T($EG;FET:6]N``(! >M<0`!````%@````&^7B'QLMH@33_)UA'2OIQ$15-4`````!X`'@P!````!0`` >M`%--5% `````'@`?# $````8````;7!I8V-I;VYI0&%T=&-A;F%D82YN970` >M`P`&$$PTXA@#``<0? 0``!X`"! !````90```$I54U1!455)0TM154535$E/ >M3BQ)1EE/54=%5%1(14A)1TA#55)214Y41DQ/5TE.1TA/5T%215E/55!,04Y. >M24Y'3TY415)-24Y!5$E.1TE4/RTM+2TM+2TM+2U&4D]-.D-(4DD``````@$) >M$ $```!S!0``;P4``, (``!,6D9UG9,,N?\`"@$/`A4"J 7K`H,`4 +R"0(` >M8V@*P'-E=#(W!@`&PP*#,@/%`@!P)S=&5M`H,SMP+D!Q,"@S02S!3% >M?0J BPC/"=D[%Y\R-34"@ <*@0VQ"V!N9S$P,R\44 L*%%$+\F,`0"!*`G43 >MP"!A('%U:4QC:QSA!Y!T:0(@+)(@!I @>0A@(&<1P `@=&AE(&AI9[AH(&,( >M@`C @&G#^;P/P&J >T!_0', 7H!X3?0M1;@,`( $"(!Z0!)!MC0N 81V0 >M( %I=#\*A4$*BVQI,3@P`M%I\"TQ-#0-\ S0)(,+65PQ-@J@`V 3T&,%0"U? >M)J<*AR5;## F)D8#83K')ZXF)@R"($-H!1 $( 4(4&X7,&Y;4TU48% ZM$7 K@4!/!1 %H!%P$< N;A' 73\G3RA=!F ","F/*IM&90ABM'= Q.3+@,L Z)" @S%!-+>\H751O,"\JFY!D:7E?#M;Q[@xxx.?+OYU8FHF836_*IO44F4\$% +8',`P!QP>1YQ >M26<#`!V2(J\CLS,N-B4G&]4F)D$%0# VK#HU,U(R@"\RD"\R\6Y'+$ =T @` >M8@20!4!(JPK *X)W)C(Z/VP^/?!:+1>@83>0( %M,G!(L&5Y=V\$MO1& =A[ 1! %H > (!>@^BT+@"T7,$?A`_ >H!Z3ZP6@+*!E!3%O'@`+43YA >MGT6F.] %0![P/P0N($P@xxx.;@6P`, #($-$2XM%Z $(!ZB"U!U(E$#H.T46F2<$MH/M!M $D$@`,G #D06P!I =$+LY4$P@3TGA'I,*P&,=X*\$(!UQ`: CX',>L&1- >M`9]%IA&P2<%'8!_!('8&\-\!D!Y@'MQ/L JP8S\11^&_-Y $\!&!5M$KD0-@ >M=5#R/PN 430*A50!3!$_;$AM\FU,$$5L)F$M$4S$'J!K*Y%40G@`T'1,X!Z3 >M:X\+@$=@2D%-YTDG;1Z0+S)@'_)1, J%8AT`;&2U3!!/!L')=`<]? >MQAY3'-!@L&1D,G!*0?M< 209?!/(BR $\+_70%103)A1X)@LQ^@!;$'@/U,$$TR< M1$]!CX5$P44#F >M9%(0/U9F=4S09 9,$/I)3F%G"'!5`F.P,G!4X/\(8&?Q'B)'PU$Q$7!'0!&P >M>4@!='<)X1S!;!$`("SW"H4@, 5 M9?@_($)9<&L11\--0 5 ]T92'I,&X&\=,!XA"H4'@/],D1VR:V!PLE]P9Z$1 >MP"&Q-VM,G"_:"(M/E `D!J@xxx.5 _;/Y$44!LAPN `A!2P6]1!9#_:E B$0(@ >M!" A@G+2"? WT;9T@=$>`&HM!X 1<0,`7+&$M7V&(2A)@T_#1W(*A5+5*3U,($E2L6%R1, %L&1S]QW09) ' >MD65)05)!"K&%%;\>P&:4'E,>(@!P4 9G4;+_2/%Z0DU%$;%YP'%@7W*#(_]' >M,$>0!G%DP@;@<9&&J3Y@^G-\!FY6@4?@8/ _;$PAWRME=KT_WR4G%6(R$K F >M)@L*A1;!`)CP``,`$! ``````P`1$ $```! ``O@% ``@P@(/( >;RR%>O@xxx.$Q >` >end > > ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866] ------------------------------ From: "Ward Spoonemore" Date: Mon, 22 Feb 1999 16:16:22 -0800 Subject: RE: EGR Correction Question This is a multi-part message in MIME format. - ------=_NextPart_000_0006_01BE5E7E.B0294EE0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Virtually all GM calibration's have both fuel and spark tables for EGR, the answer is YES. remember you are applying inert gas during EGR so the effective cyl vol is reduced, This is a source of better fuel mileage during part throttle op's. Ward > -----Original Message----- > From: owner-diy_efi@xxx.edu > [mailto:owner-diy_efi@xxx.edu]On Behalf Of Bruce > Plecan > Sent: Monday, February 22, 1999 3:03 PM > To: DIY_EFI > Subject: EGR Correction Question > > > Does anyone know of a GM calibration that takes timing out, or reduces > the amount of fuel during EGR apply. > > As it apprears to me it's always, add timing, and add fuel. > > Please no quessing...... > Thanks > Bruce > - ------=_NextPart_000_0006_01BE5E7E.B0294EE0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Virtually all GM calibration's have both fuel and = spark tables=20 for EGR, the answer is YES.

remember you are applying inert gas = during=20 EGR so the effective cyl vol is reduced, This is a source of better fuel = mileage=20 during part throttle op's.
Ward



> -----Original=20 Message-----
> From: = owner-diy_efi@xxx.edu
> [mailto:owner-diy_efi@xxx.edu]On = Behalf Of=20 Bruce
> Plecan
> Sent: Monday, February 22, 1999 3:03 = PM
> To:=20 DIY_EFI
> Subject: EGR Correction Question
>
>
> = Does=20 anyone know of a GM calibration that takes timing out, or = reduces
> the=20 amount of fuel during EGR apply.
>
> As it apprears to me = it's=20 always, add timing, and add fuel.
>
> Please no=20 quessing......
> Thanks
> Bruce
> =

- ------=_NextPart_000_0006_01BE5E7E.B0294EE0-- ------------------------------ From: Chris Conlon Date: Mon, 22 Feb 1999 20:36:55 -0500 Subject: Re: Plasma Jet Ignition At 01:33 PM 2/21/99 -0500, Raymond C Drouillard wrote: >On Sun, 21 Feb 1999 22:12:29 -0700 Marc Piccioni writes: >> >>Just a quick question, if you get the high current flowing how are you >>planning on terminating it? > >It'll go away when the capaciter discharges - the same as a xenon flash >tube. Ray is exactly right, of course. I did say it was like a flash lamp driver. ;) In this case though I'm looking at 2 possible ways to end the spark. First, I'm planning to use a relatively high frequency step-up transformer, and a relatively small capacitor. I can just turn off the drive circuit, and the spark will die out in short order. (Yes, this will put me in for a relatively inefficient circuit.) This will probably be all the control I need - I *want* the spark to last for 90-120 crank degrees, if possible! Second, an idea stolen right from flashlamp stuff, you can have an SCR or the like set up to "dump" the voltage when you want the spark to end. Camera flashlamps use this as a way to abort the flash at a desired instant and control exposure. This stuff is still a bit uncertain because I simply don't know how much voltage or current will be needed to sustain the spark after it's begun, and the circuitry gets a lot trickier if you're talking about 3000V vs. 300 or so. Chris C. ------------------------------ From: "Fran and Bud" Date: Mon, 22 Feb 1999 19:03:26 +0000 Subject: Re: ECM wiring harness help Peter,(0r DIY List) I have found a low mileage "98" 4.3 as a replacement for my "93" C1500 4.3.(160,000 mi.) I plan to use the "93" TBI as is on the "98" but was warned by Chev parts guy that subtle differences in engine years may cause problems. Does anyone know of any hidden Gotcha's??? Also does anyone know if there is anything that would interfere with using new "99" cylinder heads. It should be a couple of no-brainer's, but the factory has been known to slip in a sneaky thing or two. Bud - ---------- >From: "Peter Fenske" >To: diy_efi@xxx.edu >Subject: Re: ECM wiring harness help >Date: Mon, Feb 22, 1999, 6:22 AM > > > >Hi Bill > >I put a 97 4.3 vortech into a 91 S10 using a 730 ecm and J car harness >Use a map and you don't need the MAF.. Email me off list fer details > >:peter > > ------------------------------ From: "Bill the arcstarter" Date: Mon, 22 Feb 1999 19:27:23 PST Subject: Re: Plasma Jet Ignition bob@xxx.com (Robert Harris) wrote: >Re-reading my Heywood and have become re-in-love with the concept of >plasma jet ignition. Essentially, a normal CD ignition fires the >plug in a cavity connected to the main chamber by an orifice. Once >the arc is established, a second low voltage high current capacitive >discharge is routed into the arc. Hey - I like the sound of THAT. Did someone get this working? This reminds me of the arc stabilizers you find on TIG welders - a high frequencyt current starts the pilot plasma/arc which then allows the main welding current to flow on through... Keep me advised as to your success! :) - -Bill ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com ------------------------------ From: "Tony Bryant" Date: Tue, 23 Feb 1999 16:40:39 +1200 Subject: Re: Plasma Jet Ignition > bob@xxx.com (Robert Harris) wrote: > > >Re-reading my Heywood and have become re-in-love with the concept of > >plasma jet ignition. Essentially, a normal CD ignition fires the > >plug in a cavity connected to the main chamber by an orifice. Once > >the arc is established, a second low voltage high current capacitive > >discharge is routed into the arc. > > Hey - I like the sound of THAT. Did someone get this working? > > This reminds me of the arc stabilizers you find on TIG welders - a high > frequencyt current starts the pilot plasma/arc which then allows the > main welding current to flow on through... > I've also been toying with this idea for a while, but I can't see how you can connect a HV, LC and a LV, HC source together. The seemingly inevitble problem is the LVHC source must be low impedence, and therefore absorbs the HV in preference the spark gap? How are these TIG welders arranged? ------------------------------ From: "Clarence L.Snyder" Date: Mon, 22 Feb 1999 22:58:35 -0500 Subject: Re: Plasma Jet Ignition Tony Bryant wrote: > > > bob@xxx.com (Robert Harris) wrote: > > > > >Re-reading my Heywood and have become re-in-love with the concept of > > >plasma jet ignition. Essentially, a normal CD ignition fires the > > >plug in a cavity connected to the main chamber by an orifice. Once > > >the arc is established, a second low voltage high current capacitive > > >discharge is routed into the arc. > > > > Hey - I like the sound of THAT. Did someone get this working? > > > > This reminds me of the arc stabilizers you find on TIG welders - a high > > frequencyt current starts the pilot plasma/arc which then allows the > > main welding current to flow on through... > > > > I've also been toying with this idea for a while, but I can't see how > you can connect a HV, LC and a LV, HC source together. The > seemingly inevitble problem is the LVHC source must be low > impedence, and therefore absorbs the HV in preference the spark > gap? How are these TIG welders arranged? Something called a DIODE, I think. Actually on the TIGs it may be an SCR. ------------------------------ From: Jim Davies Date: Mon, 22 Feb 1999 20:47:32 -0800 (PST) Subject: Re: Plasma Jet Ignition On Mon, 22 Feb 1999, Gary Derian wrote: > I do remember that article. I believe it was Hot Rod. The engine was a > nail head Buick. I remember it too...funny how you can remember things like this but not the wifes birthday ;=> The anti-foulers like things were welded in to provide > cooling water around them. All the sparkplugs were connected together in a > single circuit with a capacitor at each one. There was some kind of spark > generator to create a high frequency spark. This thing was on the cover, the engine was in a rod. I remember the single, boxlike spark "unit" but not the caps at each plug. The inventor had all sorts of > claims for better performance and economy. I have never heard of such a > system since. > HotDog said it was wunnerful, so it probably didnt even work...but IIRC, the claim was that it was self timing, the plugs fired continuously and the restriction into the plug chamber delayed the admission of a burnable mixture into the proximity of the plug until the proper time. Thus, IIRC, a cap would be uneeded. ------------------------------ From: "Scott Feaver" Date: Mon, 22 Feb 1999 23:53:28 -0500 Subject: Engine Control Question I have been monitoring my engine with diacom and have found out a few things about it.. One of which leaves me wondering why... Here are the details 91 Sunbird 3.1L V6 Engine Automatic, 2.53 Axle When speeding up from a dead stop at WOT, the fuel injector pulse width is around 12.2ms. Once it goes above 3700 rpm or so, it starts to slowly decline until it hits 5200 (right before shifting). At 5200 rpm the pulse width is 9.8ms. Why would this be? Is this so the engine doesn't melt :), or for emissions reasons. If this stayed at 12.2ms right to the shiftpoint, would this generate more power? Also, this thing has the 730 ECM. How many frames per second on this baby? (I asked this before, but now know exactly what to specify :) Has anyone found out anything about the MEMCALs for this ECM? I have the eeprom loaded in if anyone wants to take a look.. Thanks, Scott ------------------------------ From: "Peter Fenske" Date: Mon, 22 Feb 1999 23:07:54 -0800 Subject: Re: ECM wiring harness help Hi Bud I am sure the manifold is different on the 99 to 93. Bolt angles different You should be able to visually confirm this. With the 97 just a matter of hooking up the 92 3.1 F body stuff and using a older ecm controlled dist. :peter I am not sure either if a 99 is different from the 97 either. Peter,(0r DIY List) I have found a low mileage "98" 4.3 as a replacement for my "93" C1500 4.3.(160,000 mi.) I plan to use the "93" TBI as is on the "98" but was warned by Chev parts guy that subtle differences in engine years may cause problems. Does anyone know of any hidden Gotcha's??? Also does anyone know if there is anything that would interfere with using new "99" cylinder heads. It should be a couple of no-brainer's, but the factory has been known to slip in a sneaky thing or two. Bud - - ------------------------------ End of DIY_EFI Digest V4 #127 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".