finding true top dead center


IHC in the early to mid-fifties.

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Golden Jubilee
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Post Wed Mar 14, 2018 6:08 am

Re: finding true top dead center

I agree that confirming TDC is important. I just installed a different flywheel on my BG265 was 8* out. I had the head off of my engine so I used a dial indicator to measure TDC and then I marked a new timing scale on the flywheel. When I measured the damaged SD240 that came out of my truck the rivet was at 2* BTDC using the same dial indicator and degree wheel method. Your method with the stopper is good for engines that are still assembled.

My interpretation of the manual was that the base timing was to be set using the flywheel mark and the scale at the distributor was to give you a frame of reference to adjust for “knocking” with different qualities of fuel. Perhaps I’ve got it all wrong.

It would be interesting to see where the rivet lands if you set your dist adv scale to 0* while your pointer is lined up to the TDC mark you made on your flywheel and then advanced the dist. per the dist scale and measure the ball w an adjustable timing light.
'55 IH R-122- BG265 w/TBI fuel injection
'64 Porsche 356 C
'68 and '73 BMW 2002s
‘14 VW Passat SE TSI
3 Vintage Sears garden tractors ('66-'74)
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Post Wed Mar 14, 2018 9:03 am

Re: finding true top dead center

I imagine your right in your interpretation of the manual. the page I got from kevin makes more sense than what I have. I only had my truck a short time before taking it apart to redo and it ran fine when I got it, it was just very tired. sometimes repair manuals elude me. some are written by a complete knucklehead that knows nothing about mechanics and where I think I should look for the info, its somewhere else. the cts11 manual I got online from the hansens and I can't seem to find the timing section in it. I relied on this forum for that.

I have talked to kevin about my "pinging" issues now that the turbo is on the bd240 that replaced my sd220 and I have a better understanding of what to do, I just need the time to do it. I will try your method to figure out where my rivet is and report back. we are camping with our vintage trailer group this weekend, so it will be after that.

here is the page I meant to post and if someone know where in this manual it tells you how to time the motor, I'd appreciate knowing.

thanks
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Post Thu Mar 22, 2018 1:57 pm

Re: finding true top dead center

VWJake wrote:It would be interesting to see where the rivet lands if you set your dist adv scale to 0* while your pointer is lined up to the TDC mark you made on your flywheel and then advanced the dist. per the dist scale and measure the ball w an adjustable timing light.



so I finally got around to installing my new Daytona carb, pertronix and turbo blanket. while setting the timing (with my new adj timing light), decided to do what jake asked, and sure enough, just like the page from kevin, the rivet is at 6 degrees. live and learn. now if only I can remember next time I have to set timing.... hahaha
1936 C1 Project
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Golden Jubilee
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Post Fri Mar 23, 2018 4:07 am

Re: finding true top dead center

unclejtl wrote:
VWJake wrote:It would be interesting to see where the rivet lands if you set your dist adv scale to 0* while your pointer is lined up to the TDC mark you made on your flywheel and then advanced the dist. per the dist scale and measure the ball w an adjustable timing light.



so I finally got around to installing my new Daytona carb, pertronix and turbo blanket. while setting the timing (with my new adj timing light), decided to do what jake asked, and sure enough, just like the page from kevin, the rivet is at 6 degrees. live and learn. now if only I can remember next time I have to set timing.... hahaha



Happy to hear you’re making progress. Let us know how it runs when you get it sorted.
'55 IH R-122- BG265 w/TBI fuel injection
'64 Porsche 356 C
'68 and '73 BMW 2002s
‘14 VW Passat SE TSI
3 Vintage Sears garden tractors ('66-'74)
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Post Sat Mar 31, 2018 12:10 pm

Re: finding true top dead center

so, spent 4hrs on the dyno last night and still have things to figure out. got a good mixture at idle and 2200rpm (55mph with my gearing/tires), problem is, stomping on it at 2000rpm and bringing boost up, at about 2600-2700rpm, it leans out dramatically. I think the carb may be too small. now, if I just drive normal, and keep out of the boost, I can cruze at 3000rpm no problem. I think the turbo sucks the carb dry. I looked, and the airtex mechanical pump (it's new) on the motor puts out 20gph at 1800. should be enough? it runs and drives great, I just have to stay off the boost after 2500rpm till I figure it out. I brought down the boost from 10 to 5 for now. seemed to help a little.
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Post Sat Mar 31, 2018 12:47 pm

Re: finding true top dead center

Power enrichment is controlled by manifold (turbo inlet in this case) vacuum. Sounds to me at higher RPM the inlet vacuum is high enough to back out of power enrichment. I'd be looking at main jetting 1st, as this is what determines mixture until the power enrichment cuts in, sound too lean.
Remember "too small a carb" is the same thing as a partially closed throttle as far as the engine is concerned, so if you are too lean, then it is not the carb size but the jet size or float level that is the problem.
My guess from this end of the keyboard is: at lower rpm, when you open the throttle, the vacuum drops enough to go to power enrichment, but at higher speed it doesn't. If you are looking for max power that the engine can produce, then yes, the carb is the restricting factor, but if you go large on the carb, mid and low end will suffer.
a fuel pressure reading under load will show if the fuel pump or lines are restricting flow to the carb.
IIRC you are useing the Daytona 1BBL (Holley clone)?
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Post Sat Mar 31, 2018 1:13 pm

Re: finding true top dead center

yes, this the Daytona with the adjustable main jet. according to the dyno air fuel ratio was all good till that one point. guess I don't understand it good enough. I have a vacuum/boost gauge so I don't know what the vacuum is under the carb when the turbo is spun up cause it's showing boost. it comes on boost great, but after a few seconds (time it takes to get from 2000rpm to 2600rpm) it leans out really bad. the number changes quick, like turning on a light switch.
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Golden Jubilee
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Post Sat Mar 31, 2018 1:22 pm

Re: finding true top dead center

Your vacuum boost gauge is connected after the turbo correct? it would help to have a vacuum gauge between the carb and turbo for working on this problem.
I am assuming this is a draw thru system and not a blow thru. Turbo between carb and intake not before carb?

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Post Sat Mar 31, 2018 1:53 pm

Re: finding true top dead center

My experience is with Holley's but I think they are the same.
The "power valve" is mounted on the top of the main body and is held down with 3 screws. It is spring loaded down, which pushes on a lever that opens one or two check balls that add another passage for fuel to flow around the main metering jet. at lower throttle settings vacuum over comes the spring and pulls the "foot" of the valve away from the lever and springs behind the check balls seat the balls. When vacuum drops, the springs and opens the check balls. Early Holley's had one passage (all or nothing) later had two, one opening before the other for a "2 stage" valve.
If you take the valve off you can measure the fuel level in the float bowl. I have done this with the engine idling, but not sure I would try it under load on the dyno, I was never blessed with dyno time!
If the fuel level is dropping at speed, it has the same effect as a leaner jet.
The main metering system the main jet has less of an effect at the low end of the main metering band and more effect as it approaches the point where the power enrichment valve comes into play.
1st thing would be to check the float level.
I would try setting the main jet richer, and if too rich at the lower end, try leaning out the idle system.
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Post Sat Mar 31, 2018 6:54 pm

Re: finding true top dead center

cornbinder89 wrote:Your vacuum boost gauge is connected after the turbo correct? it would help to have a vacuum gauge between the carb and turbo for working on this problem.
I am assuming this is a draw thru system and not a blow thru. Turbo between carb and intake not before carb?



yes, draw thru system. this is the system Kevin has, its from keystone.

I will check the float level and look into the power valve. maybe it can be modified.

our problem last night was that I could adj the main to basicly all open (whatever size jet tat would be) and not see the lean drop, but then cruzing at 2200rpm it was way to rich. then I set it for cruzing, to lean under boost. thoughts have been popping in my head all day while doing yard work... maybe the power valve needs modified. I have some reading to do.

thanks for all the input!
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