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By mark9088 - 5 Years Ago
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getting close to the initial start on my supercharged, purpose built Y. any recommendations as to timing, jetting, cold lash allow for aluminum heads, cold belt tension, break-in valve spring pressure would be appreciated.
650 holley, modified mummert heads, purpose ground cam, 299 ci. girdle, steel crank, filled block...
my first supercharged build.
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By Ted - 5 Years Ago
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The lash with aluminum heads will increase 0.005”-0.006” from cold to hot. With this in mind, you can set the initial lash around 0.015”-0.016” for the cold start.
I prefer to start the engines up with at least 20° - 25° BTDC initial timing. This insures a good clean start and eliminates the back fires that occur when trying to start the engine at TDC to 6° BTDC. The 650 Holley will ultimately be too small for a boosted application but for start-up purposes, use the stock jetting.
I’ve seen and heard too many instances where the camshafts were broken in with reduced pressure valve springs and then failed after putting the correct springs back in place. I start all my engines with the correct pressure springs and if the camshaft and related parts are all good, then there are no problems. If the camshaft and/or lifters have an issue, then the weaker valve springs are only delaying the inevitable. Part of the key here is to insure the engine starts up immediately and the RPMs brought up to 2000+ right away to insure a proper burnishing of the cam lobes and lifters.
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By Rono - 5 Years Ago
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Mark;
In addition to what Ted has said, there are a lot of other details you should look into; Is the Holley carb you have a double pumper set up for blow through operation? Have you boost referenced the power valve? Are ll vacuum ports plugged? What kind of distributor are you planning on running? Are you using a boost control box to retard the spark at higher boost? What is the pulley ratio you are using? For initial start up it may be helpful to run a 10% underdrive. What type of fuel pump are you running..mechanical or electric? If mechanical make sure it has a high flow. Are you using a 3/8" fuel line or 5/16"? 3/8" would be better. Also, the higher compression aluminum heads could be a problem with pump gas. You may want to test run the engine with 110 octane race gas. These are just a few of the things I can think of right now.
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By mark9088 - 5 Years Ago
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THANK YOU GUYS FOR YOUR INPUT! Since I currently have the blower on a stock engine in a vehicle now, I plan on starting and breaking-in this hot engine on my run stand with just a carb and stock lo-lift rockers. After a lengthy run-in and re-torque, etc. I will install the blower and hi lift rockers and run it again before taking to dyno shop. I do have a boost referenced carb to switch to after run-in. I am running a dura-spark converted distributor curved for blower use. Any other needed gadgets will be added as needed. My shop is currently closed due to -25* ambient temps.
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By RB - 5 Years Ago
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Dean Can't wait to see that on the track. Are you in at Glory Days? You need to hang with our Y block shootout group now.. You will be one of the big dogs with a blown Y block.. Are you going to dyno at R&R performance?
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By mark9088 - 5 Years Ago
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RB,
thanks for the invite. I just got the approval email from Byron for the glory days race for my 56.
I broke it there last year and it hasn't run since. Probably good that it's a long ways off. lol
I think I will use G&S Dyno in Shafer MN for he Y-block. He is closer and I hate driving in the cities...
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By Rono - 5 Years Ago
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Will you be using an engine dyno or a chassis dyno?
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By mark9088 - 5 Years Ago
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Rono,
I plan on using an engine dyno after breaking in cam on my run-in stand. Plan on trying several different carbs and drive pulley sizes on dyno. Thanks for your interest.
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By RB - 5 Years Ago
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Dean is that a 471 or 671?
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By RB - 5 Years Ago
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OOOPS I guess I should read the post title
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By Dave C - 5 Years Ago
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Why are you not using the dyno to break in the engine? The dyno can load and unload the engine to perform break in. Or at least my buddies superflow dyno has a program to do that.
Dave
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By mark9088 - 5 Years Ago
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Dave,
running the engine on a stand allows time to address any unforeseen issues (leaks, etc) on my time. Running through several heat cycles before hand allows me to change from break-in valve springs and rockers to the performance parts and re-torque heads on my time. Also get in the ballpark on jetting/timing on an all new build that I am not sure what to expect. Preliminaries will be done. Rings will get broke in on the dyno. Dyno time isn't cheap.
Thank for your interest,
Dean
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By MoonShadow - 5 Years Ago
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When Ted was running my 4-71 motor on the dyno he said it really picked up horse power with one of those 1000 something CFM Holley's. Was a bit surprised. My engine was built to be streetable so its really not built for maximum power.
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By mark9088 - 5 Years Ago
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Moon shadow,
Ted had mentioned to me that I would need a bigger carb. I have a boost referenced 780 cfm carb I will try after break-in. I am negotiating with a friend on his 1050 cfm 3 barrel.
How many cubic inch and boost is your 4-71 motor, if I may ask.
Thanks for your interest,
Dean
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By Rono - 5 Years Ago
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Dean;
I broke in my 331 cu. in. blown motor with a 650 Holley double pumper but it was clearly too small of a carb. This was with my VS-57 set-up which I'm no longer using. Next test with the 471 blower will be with a 750 double pumper set up for blow through with no choke horn
Rono
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By MoonShadow - 5 Years Ago
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Ted finally set mine up with a 650 double pumper. For the street I would be concerned about the bigger carbs. On my drive home from Clevland last year I actually averaged just under 18mpg in the Vicky. I was amazed, of course the AOD overdrive and 3:80 gear helps. My engine is 325 cubes. I'm under driving the supercharger so about 6lbs of boost is all. Runs perfectly on pump gas too.
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By mark9088 - 5 Years Ago
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UPDATE ON Y PROJECT
Health and family issues have slowed progress, I have broken in the cam with the low lift stock rocker and weaken springs. then installed the high lift arm and brought the springs up to tension (shims), ran the engine with carb and stock intake through 3=4 more heat cycles, now have blower on and running, was trying a little higher rpm today and the water pump pulley broke at about 3k rpm. got to fix it before april 8, my dyno appointment is then at R&R performance in spring lake park MN  lake park MN
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By RB - 5 Years Ago
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Dean looking forward to a report on your day at R&R.. Hope the Y gave that dyno a good workout..
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By mark9088 - 5 Years Ago
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dyno results:
299 cubic inch
503 hp @ 6100 rpm
450 ft/lbs @ 5000 rpm
10.5 boost  
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By MoonShadow - 5 Years Ago
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Very nice numbers. What is the pulley ratio and how much boost are you getting?
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By RB - 5 Years Ago
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NICE! That mid-range torque should get your 56 down the track very swiftly.
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By mark9088 - 5 Years Ago
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Moon Shadow,
running 37/34 tooth combination (1/2 " pitch) to overdrive the blower, achieved 10.5 # at 6100 rpm. had topped out boost @ 8.9 # with 750 carb, boost (and power) jumped when 950 carb was installed. Blower is old school rebuilt for street use with no modern teflon coated internals. Power was still climbing @ 6100 but so was my blood pressure, stopped after reaching 500 hp target. thanks for your interest ! Dean
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By mark9088 - 5 Years Ago
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RB,
Thanks for the interest, hope to see you at a few events this year! Dean
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