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PostPosted: Mon Dec 26, 2022 3:50 pm 
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Car Model: 69 cuda hardtop
hello everyone, while i ve read and reread tons of posts here, i am new and this is my first post. i m trying to find a good baseline start on my timing and timing curve as my 69 cuda sits on stands. i built the engine over 15 yrs ago, lost the build sheet and what i d done to it and am now LEARNING how important proper timing is so as to NOT destroy a perfectly good engine.
i m including the current data i have gathered and hope someone out there has a similar build and successfully dialed it in for the best results. time is of the essence for me at this point(health) so perfect isn t necessary, just a mechanically sound and safe running car is what i need, i can fine tune it for more power later.
my car is a 69cuda h/t. 225 w/904, 7 1/4 rear with 2.76 and 26" tires. what i recall  of the original build is, and if I m remembering right( I ve had her since 92’): --the engine has 10.5 to 1 stock size arias pistons, the block and head were milled to bring it to that static CR.  --the cam is a MP 268-108 .460 lift with a 52 overlap. Lash on IN @16 and ex @ 20. Recommended c/l @ 104. I had originally adv or ret the cambut had tons of issues with idle and eventually found a lot of black carbon in the intake runners of the offy manifold and so I put the 0 degree camshaft offset in and the cam should now be as though I used the timing marks on the chain set. --the head is a 75 or newer (no drool tubes), stock size valves with the backs cut and a mild cleaning up in the bowls and port matched to the offy. --my biggest concern and the reason I m reaching out is I m hitting 215 psi in the chamber and really don t know how much or when(rpm) this will contribute to knock and ping, my ears aren t what they used to be.
--holley 390 w/58 prim and 61 sec plate. 6.5pv, #28 squirter and an orange pump cam and It s on top of a 1’ phen spacer.
--lash set hot @ 13 In and 19 Ex
--the exhaust is a MP 6 into 1 header
--spark plug is a bocsh hr9bp, however I am installing a ur5 which is 1 colder
--standard electr distrib connected to a msd 6a box. I recently bought and installed the 4secflat plate(original is a 13r)), set it at 16 deg. to allow for 12 to 15 deg of initial timing and a total of 28 to 32 total mech adv. (distrib weights 1889264) I installed one new medium rate spring and left one original that was close but a little less in tension and also it is a bit longer. The vac can is an 8.5 and set to start at 9” and fully adv by 15” (approx.).

i ve done an initial base line no load test to find out when timing starts for both the mech adv with and without the vac can and starting with an initial adv of 14 deg btdc.
all timing checked with a dial timing
--mech adv w/o vac starts with 16 deg @ 1300 rpm with 33 deg showing and all in by 2500.

--mech adv with van can readings taken and starting 10" of port vac is 30 deg @ 1900 rpm(28 deg w/ vac disconnected) and fully in @ 16" port vac is 53 deg @ 2500 rpm(33 deg w/vac disconnected).
Note: just measured slots on 4flat plate and according to an article in MPconnect( ADD 14-HORSEPOWER TO YOUR SLANT 6) the 16 deg slot reacts more like the 18 deg should according to the articles measured and machine tested. the 14 slot measures more to what the 16 should have so i will be installing it on the 14 tomorrow( this cleared up a few questions i had while testing)

when comparing these numbers to ALL the articles HERE and there about all the various builds this timing curve seems to come in way to early. having just looked at emsvitil May 2005 fully documented experiment which shows mech adv starting in at 2k and all by 3500 seems to be a smarter curve for my build IMH and uneducated opinion. in another article i read they used the vac adv can to dial in their cruise timing, this also seems like a good way to go for me as well. these are my just my thoughts in regards to my engine.
i did try one test with initial timing to try and get some pinging to give me some reference as to the sound of it. because of the installed position of my distrib (please don t ask why b/c even i don t know the answer) i have about 7 deg btdc at its furtherest CW postion. by using the vac can to be fully in it allowed me to go as high as 29 deg btdc w/ rpm at 1450; i heard no knocking, but as i stated, my hearing isn t the best. moving on
the carb was adjusted to numerous articles i d read where i concluded running a bit on the richer side would help as far as detonation and can be dialed in at a later time by installing an A/F in the exhaust (again, time is a factor for me right now 3 wks left)
In the past i have run the this engine oh so many years ago (about 15) and did put about 1k miles and got good mpg(22 fwy) and didn t notice knocking or pinging at fwy speeds of 70 mph @ about 2700 rpm (this will be my normal driving habit in the future). if your wondering why i ve come to you for help it because of this: i had a ford bronco with a 400 i built in it. i got horrible gas mileage and had this constant sound that sounded like marbles in a blender. in trying to identify the problem i pulled and replaced the tranny and transfer case and it was still there. one day i started heading out and the engine blew. upon disassembly i found every single piston skirt cracked and ONLY THEN did the light bulb go on as to what the sound was. i m afraid of the responses i ll get from admitting this, but it IS the reason i am coming to you now for help, so please be merciful.
the art. and info from so many including emsvitial, aggress ted, /6dan, and others are very helpful, however i just read one from D idiot about a 10.3 CR built which continued to another build which had 11.4 CR and some timing info which allows him to run the street that makes me believe he may have the info(i m not saying he s the only one) i need for a basic start for timing on my build; however i ve lost it in my searches.

I ve done my best to include the known info on my engine/car and what i m trying to accomplish for now. any and all suggestions will be greatly appreciated by any and all that have gone through the grueling and pain staking task of actually documenting their experiences and results while on their venture for the best running /6 possible. my intentions for the use of my cuda are to be running as a weekend driver for pleasure with the occasional itch to punch it down just for a thrill, but no drag racing of any sort as i don t want to unnecessarily replace the rear end at this time.

Thanks again Mike


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PostPosted: Mon Dec 26, 2022 8:05 pm 
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Good write up! Did you have EGR? I'd back some of that Vac Advance out if you don't.

I tend to build things a bit myself. 10 degrees max initial, max all in with mechanical 28-32 sounds good. Usually, there won't be enough cylinder fill to cause an issue when the vacuum pulls in. Your running a 390 Holley, so at higher RPM operation it's possible you'll see enough signal in a high speed cruise to pull that 52 degrees total. With that much compression, less advance might be the better solution. I take it your not trying to squeak the last drop of fuel out of it. Maybe back the vacuum can out. If you don't have EGR, then take the vacuum can out of the equation entirely. If your hitting detonation at WOT, then I'd be looking for hot spots. Once again, no more than 10 degrees initial. The combustion chambers aren't the fanciest, what being designed 50 or 60 years ago. Any sharp edges in the combustion chamber, or carbon build up may cause an issue. Your running a peanut, so no extended plugs. That can be an issue with Drool tubes running north of 10:1 compression. Don't run small electrode iridium or other. The small electrode can create a hot spot.

Retarding the cam will move your torque up the engine envelope. Since these things don't react well to high rpm, it's best to advance the 4 degrees, though normally built into aftermarket cams. Don't know anything specific about the cam your running. I ran one of Doug's RDP cams for a while, and was getting pressures in that range. It didn't breath at high rpm though. The 390 wasn't enough carb once I put enough cam in to play at the strip. 500 was plenty, 600 was slower.

My two cents... There are plenty of folks out there that know stuff...

CJ

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PostPosted: Mon Dec 26, 2022 8:26 pm 
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215 psi is a lot of cranking compression. But have you checked the cranking compression with a second gauge? You only have 10.5 to 1 compression and a fairly large cam that should be letting off some of the compression. For example, the slant in my 68 Barracuda has a calculated 10.5 compression and I have a smaller cam and the cranking compression is in the 190’s. I run a good grade of premium pump gas and have had no pinging.
Fortunately, the open disk combustion chamber on the slant is fairly robust against pre ignition. I also run an intake duct that brings in air to to intake that is from outside the engine compartment.
The second-generation Barracudas are somewhat light weight. But with 2.76 rear gears if the motor was going to get into pre ignition, I think it would be under load, accelerating up a hill from lower highway speeds, 50 to 55 mph where the rpm’s would be low to a higher rpm and speed.
So my recommendations are:
1) re check the cranking compression with a different gauge
2) run a good grade of premium gas
3) rig in an outside air supply to the air cleaner
4) check for pinging at highway-up hill conditions
And lastly
5) be conservative with the timing curve and vacuum advance till you know more about the engine. Watch the carb tune, don’t let the fuel get lean with the engine in a loaded condition.

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PostPosted: Tue Dec 27, 2022 6:07 am 
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I am assuming that you did already re-check the valve adjustments. 215# is a lot of compression. If it was mine and I was not going to be highway cruising all the time, I would ditch the 2.76 gears for a set of 3.23 or 3.55. It will make the car feel as though it has 50 more horsepower! :D

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PostPosted: Tue Dec 27, 2022 11:29 am 
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Yes, that is a LOT of cranking compression for pump premium gas. I have run that before, but it pingedon premium with any kind of advanced timing. I recommend starting with 26 deg timing at full mech advance and maybe walk up to 28 or 30, but no higher than that.

If you want to decrease your compression, you can retard the cam 4 deg, and that should be fine (RPM range-wise) with that relatively small camshaft.

I had an engine with similar specs and cranking comp to this back in the early-mid 90s. I pulled the head, used TWO Felpro gaskets, sprayed copper permatex sealer between them, and put it back together. Head bolts torqued to minimum of 90 ft lbs. Ran it that way for a few years with no trouble. The cranking comp went down to about 180-190 and it was easier to tune and drive that way.

Lou

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PostPosted: Wed Dec 28, 2022 6:03 am 
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Joined: Sat Dec 03, 2022 8:03 am
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Car Model: 69 cuda hardtop
thanks for all the replies guys.

CJ, there is no egr and the exh is wrapped. i ll give your 10* a starting point and have read 28-32 is ideal but i m wondering at what rpm it should start to come in and then what rpm it should be at when it s all in. i m considering starting the mech adv at around 2k rpm and all in around 32-3300 as a starting point and using the adjustable vac can to have the adv at cruising speed set a few degrees before any knocking starts, that will be around 70 mph at 2700 rpm. i have 18 to 20 hg if i recall properly. during my testing i was at 22 hg w/o a load....... as far as resetting the cam i pulled the adv/ret of 2 or 4* offset and reinstalled the 0 because of the black soot i found in my intake runners and assumed that may be the cause. i just read last night in a M/T article,https://www.motortrend.com/how-to/0607phr-camshaft-basics/, on overlap that that very well could have been the issue. i ll find out after she runs a bit by sticking a bore scope down the runners. there has been an improvement in ideal since i set the cam back to zero though. however, i took readings before the 215# test and back then i was at 195 to 200; i didn t expect any change when i set the cam back to the original install marks.
D/T, that was my second gauge and it verified the first. i m running the highest i can at the station, 91, and added lucas octane booster. whether it actually boosts octane i don t know, but i DO know it keeps the carbs clean on the inside. i use it in my chopper and when i had a look in the carb it was shiny new looking. i will definitely keep my ears open on a load test up as you ve suggested and respond accordingly. i may in the future get some fresh air to the cleaner but for now it ll have to wait.
R/C, yes i did check the valves and currently they are at 13 IN and 19 exh. I ve been thinking though that maybe increasing the hot lash on the intake to the spec of 16 or maybe even open it up to 17/18 (less lift) and then decreasing the exh lash from 19 down to around 12 (more lift) that i may reduce the amount of intake and increase the amount of exh thereby reducing the chamber PSI some. i looked at other cam co. and found the Hughes cams run 04 on the In and 06 on the EX for hot lash settings. any thoughts and opinions on that idea are welcome from any and all. i would like change out the gears but that ll have to be a future project, also finding a 3.23 r/g for the 7 1/4 isn t easy. no plans to put an 8 3/4 in and i d consider a an 8 1/4 but i wanna keep the 14" on the car for now.
D270, thanks and i follow your 26 adv advice, sound like a good safety blanket. also if the future allows i ll do the 2fer on the head gaskets; i assume you are using the steel ones? if so what is there installed crush thickness, if you recall. at least when i do that i ll be able to verify the SCR.

thanks to all for your input, i ll keep more detailed notes and let ya know how it s going.


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PostPosted: Wed Dec 28, 2022 7:14 am 
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If you get to the point where you want a thicker head gasket and don't want to try putting two together, my son had some MLS head gaskets made up. I know they can be had in any thickness you want, but they are not cheap. I am not sure what thickness he may still have. But let me know if you get to that point and I can check.

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PostPosted: Wed Dec 28, 2022 4:07 pm 
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Today's aftermarket head gaskets are already double the thickness of the original shim steel ones. If that's not enough I'd look into an Aussie slant 6 head gasket, which is what I put in my most recent build, it's like 60 thou thick (3x steel shim head gasket thickness) and I measured 51 thou, torqued and compressed. I'd go this route before I stacked doubles. I don't know what was available "back then" and there's always a lot of "do what ya gotta do" in this line of work, though. I wouldn't go there just yet, I'd try to tune your combo as best as it can be, maybe experiment with some higher test fuel or even a can of "octane booster" before I tore it back apart.


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PostPosted: Fri Dec 30, 2022 3:37 am 
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No, I mean the standard FelPro composition gasket to double up. Those are around 0.034" compressed thickness (stock steel shim is about 0.020"). So, with 2 FelPros you will be at 0.068", which will give a significant drop in compression. I don't know if this will work for everyone or every set of engine parts, but it worked great for me and I raced the car, drove it cross-country (over mountains) with 1000+ loads - plenty of hard use.

What is your torque converter stall speed? I would not run anything less than 2500 RPM stall speed with that engine buildup, and I suggest a 2800-3000 RPM unit. See https://edgeracingconverters.com/ as they make about the best ones for our engines - Andre is very helpful. That will make your ign timing curve much easier to tune and the car will be much faster.

Lou

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PostPosted: Fri Dec 30, 2022 2:28 pm 
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Car Model: 69 cuda hardtop
thanks again for the responses.
changing out the gasket will happen only as a last result, although i don t remember what i have in there and would rather change it while in the d/w verses having it blow on the road. i would rather go with a thicker one piece steel than have two; it s just another seam to blow through imho.
D270, i m running a stock converter as of the moment. i really only have a basic understanding of converters. if im not mistaken though, a higher stall in front of a 2.76 ring gear would not be ideal, it d be slippage of the converter throughout my entire rpm range seeing i m only at 2700 rpm at a 70 mph cruise speed; or am i incorrect on this.

as of 2 days ago i ve tried some of the ideas shared here. i also changed of the distrib springs to change the mech curve and it was only by luck/chance that it ended up close to my intentions, even if my intentions are incorrect for my application.

previously i started with 15* int and the mech adv started coming in at about 1300 and was all in by 2500. i had one 4secflat med spring and one orig med spring although a bit weaker and the adv plate installed for 16* .
i changed out the orig spring with a 4sec heavy spring, left the 4sec med spring, had the plate at 16*(wanted to put it at 14* but forgot) and tested it. i was shooting for a 2k start and all in by about between 32-3400. luckily my mech adv starts coming in a 1800 and all in by 3200.
ceej- i did try starting at 10* int but she wanted nothing to do with it. h2o temps hit 200+ at idle (prev test was around 175) and wouldn t go down below 190 at higher rpms so i put her back to 15* and set idle to 970-990 and dialed in the highest man vac to 16" and the temp went back to 175* and idles smoother. I am reading 33 to 34* at 3200 however and will change the plate down to 14* slots if i hear some knocking at the higher rpm level. i noted earlier that the 4secflat plate slots are actually bigger than what they should be, giving it more adv than i was planning(18* instead of 16* as etched in the plate) on. this is according to the math numbers from other adv curve testers in other articles i ve read. i ll run some load tests first though before changing setting.
i m going to try and dial in the vac adv to start coming in right off in gear idle, which is 670 to 700 rpm. i plotted both manifold vac and ported vac while doing my mech adv curve test for every inch of vac created. i m trying to figure which will be best for increasing my adv. since the mech adv won t start until 1800 rpm. the new vac can was tested to prior to install and can be activated with as little as 3" hg to as high 15.5" hg with my mityvac and has 6"hg between from closed to fully open. in contemplating which, i have to consider that mani hg is at 16" in park but drops to 10-11"(it fluctuates) when put into gear. port vac at park idle (mani vac being 16"hg at 970 rpm) doesn t start until 1100 rpm w/ 1"hg and has to reach 1400 rpm before it can have an influence on the vac can if the V/C is set at 3"hg initial activation and fully adv by about 1700 rpm. (NOTE: vac can shows about 6"hg from closed to fully open for a total of 17* of adv from the V/C alone: the arm has 8.5 on it. also, if the adv is linear, then there should be an add' adv of 2.8* for ever inch of hg supplied ) if set as just stated that would/should mean that i d have 32* adv at this rpm, and at cruising speeds of 23-2700(60-70 mph) rpm, i d be between 37*-42* total adv, int+mech+vac. i think this would allow for a safe (lower) amount of adv to help avoid knocking for a start and be adjusted accordingly and really fine tuned at a later date.
D270- i ve read stall is about 1800 on a stock converter. since i have no intention of racing what are your thoughts on a 2200. it d be nice to smooth out the idle in gear and not having the converter react and such a low rpm.

once i get the V/C set and road tested i ll give a report. i plan on having a dig tach and vac lines to both mani and port vac to measure the results.

thanks again to all for your input


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