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Search found 488 matches

by GRTfast
Thu Oct 22, 2020 2:42 pm
Forum: Engine Tech
Topic: Ignition advance at cruise rpm?
Replies: 44
Views: 1785

Re: Ignition advance at cruise rpm?

Lots of variables to consider, but probably in the neighborhood of 10-15 degrees more than the mechanical is providing at that RPM. If you are all in at 35 degrees at 2500, then you could prolly be at 50 degrees or so when cruising
by GRTfast
Sat Oct 17, 2020 7:49 pm
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

Great question! Poorly atomized fuel and bad wet flow characteristics have a big impact. But last time I tried to stick my head in the combustion chamber which the engine running ended poorly, so I have to imagine what is going on based off of experience (of my own as well as others). Testing timin...
by GRTfast
Thu Oct 15, 2020 2:25 pm
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

GTR, What intake, carb & spacer are you using? How does it run now compared to when you posted a year or so ago that it was surging at cruise before the new cam? RPM air gap QFT 1050 1 inch 4 hole phenolic spacer Runs best it ever has. Bucking/surging all but eliminated. Very happy with it. The eng...
by GRTfast
Thu Oct 15, 2020 6:50 am
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

What is your altitude? The higher, the more timing is needed. Is your WOT-AFR maybe a little lean? Dont go leaner than 12.5. Could also contribute to timing hunger of the engine... What pump gas exactly? 93? Burns slower so more timing can be necessary. remember: measured from the perfect amount of...
by GRTfast
Thu Oct 15, 2020 6:50 am
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

GTR, What intake, carb & spacer are you using? How does it run now compared to when you posted a year or so ago that it was surging at cruise before the new cam? RPM air gap QFT 1050 1 inch 4 hole phenolic spacer Runs best it ever has. Bucking/surging all but eliminated. Very happy with it. The eng...
by GRTfast
Wed Oct 14, 2020 9:27 pm
Forum: Engine Tech
Topic: power valve circuit myths
Replies: 39
Views: 2352

Re: power valve circuit myths

If the power valve opens at 8.5 and he's idling at 6, the valve will sit there open but not flowing until there's enough depression to draw from the boosters, correct? Yeah I think this is true. I had my main jets fall out once and the car ran fine until the main circuit was activated. AFRs were de...
by GRTfast
Wed Oct 14, 2020 9:05 pm
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

Circlotron wrote: Wed Oct 14, 2020 7:40 pm Unusually small plug gap?
It’s 0.035, plugs are bkr5e
by GRTfast
Wed Oct 14, 2020 7:13 pm
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

Performance engines are spoiled brats. When you give them what you want they are pains in the neck. Give them what THEY want and they are great ( just like my kid). Compression, cam event timing, chamber shape, spark plugs used, measured squish, fuel and afr, intake design and many other variables ...
by GRTfast
Wed Oct 14, 2020 7:07 pm
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Re: Ignition timing questions

The strange thing (to me) is that the optimal timing curve seems fairly advanced compared to almost all the recommendations I see for timing... ...All the recommendations I see out there for an engine like mine are in the range of 14-18 initial, 34-38 all in. If I use those settings the engine feel...
by GRTfast
Wed Oct 14, 2020 10:24 am
Forum: Engine Tech
Topic: Ignition timing questions
Replies: 22
Views: 1123

Ignition timing questions

Just throwing out some thoughts/questions for discussion. I have a 9.5:1 big block chevy, aluminum heads. It has a Jones HR cam, 110 separation, .600 lift, 240-ish duration at 0.050 makes about 160 psi cranking pressure. The engine runs magnificently, pulling hard from down low to well north of 6000...
by GRTfast
Wed Sep 02, 2020 1:55 pm
Forum: Show & Tell
Topic: Show us your Race Car(s)
Replies: 122
Views: 72248

Re: Show us your Race Car(s)

prairiehotrodder wrote: Wed Sep 02, 2020 10:33 am IMG_20200815_141310 (1).jpg
Love the color. Very clean.
by GRTfast
Thu Aug 27, 2020 3:30 pm
Forum: Show & Tell
Topic: A little outside the norm for this forum (racing karts)
Replies: 3
Views: 414

Re: A little outside the norm for this forum (racing karts)

I'd like to share something that just happened over the last few days. Way back in the early 90's when I was a teenager, we started racing dirt track karts. There was an unlimited class and my dad ended up building 6-7 500cc two stroke powered dirt karts, of which one was mine. We raced as a points ...
by GRTfast
Thu Aug 13, 2020 11:51 am
Forum: Engine Tech
Topic: preventing fuel from boiling in the carb
Replies: 22
Views: 694

Re: preventing fuel from boiling in the carb

Are you using a mechanical fuel pump? If so, these pump insulators have shown to be effective. www.summitracing.com/parts/ctr-85-000 https://www.summitracing.com/parts/ctr-85-010 I use this mechanical pump insulator, I have a restricted return line after the fuel log. Also, a 1 inch phenolic spacer...
by GRTfast
Thu Aug 13, 2020 7:00 am
Forum: Engine Tech
Topic: preventing fuel from boiling in the carb
Replies: 22
Views: 694

Re: preventing fuel from boiling in the carb

Guys, When running a carb I've seen numerous issues with the carb getting heat soaked after shutting the car down for a short time and then restarting. Not sure what happens, but I assume that the lead free fuel starts to boil in the carb due to it getting heat soaked and the vapours ending up in t...
by GRTfast
Tue Aug 11, 2020 2:17 pm
Forum: Offtopic Forum
Topic: All time favorite song.
Replies: 35
Views: 2482

Re: All time favorite song.

Super hard question, I will answer with a twist: Favorite Classic Rock Song: https://www.youtube.com/watch?v=-sUXMzkh-jI Favorite soul: https://www.youtube.com/watch?v=ho7796-au8U Favorite Hip Hop: https://www.youtube.com/watch?v=wai13EbZCCM&list=OLAK5uy_l1ZbIBceHVeub4bT3edWQ4ccSoa1-voZc Favorite Pu...