madmikeismad
So mad
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Will, your head is still stock right? Just valve train and gasket match?
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Sent from my DROID RAZR using Tapatalk 2
95' Junker Drag Truck
- Thread starter Big Blue24
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Big Blue24
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Also,
Since my pistons are out and easy to work on, I decided to open up the bowls a little to accept a little more timing before spraying completely out of the bowl.
Stock Piston Before:
Stock 52mm bowl
Side by side after cutting to a 55mm bowl:
Piston lightened up 7 grams from cutting
These were cut on a small hobby-sized 7x10 mini lathe with a 5" 4-jaw chuck, they need to be independent 4 jaw so the piston can be centered based on the offset bowl.
By calculation, I added 1.922 cc's of volume to the bowl for calculated compression drop of 0.54 which drops the factory 17.5:1 down to 16.96:1.
I also plan to run a .010" thicker gasket to give the o-rings a little more firering depth to bite into. This will drop the compression 0.668 assuming 4.16" gasket firering diameter multiplied by .010".
Therefore, the final compression ratio of this motor will be down to 16.29:1, so we'll call it 16.3:1. Should be high enough to start fine and that extra combustion space might add power, it's hard to say at this point and difficult to test since I plan to port and polish the motor along with the minor cam degreeing change when the crank gear is corrected and put back in-time.
Since my pistons are out and easy to work on, I decided to open up the bowls a little to accept a little more timing before spraying completely out of the bowl.
Stock Piston Before:
Stock 52mm bowl
Side by side after cutting to a 55mm bowl:
Piston lightened up 7 grams from cutting
These were cut on a small hobby-sized 7x10 mini lathe with a 5" 4-jaw chuck, they need to be independent 4 jaw so the piston can be centered based on the offset bowl.
By calculation, I added 1.922 cc's of volume to the bowl for calculated compression drop of 0.54 which drops the factory 17.5:1 down to 16.96:1.
I also plan to run a .010" thicker gasket to give the o-rings a little more firering depth to bite into. This will drop the compression 0.668 assuming 4.16" gasket firering diameter multiplied by .010".
Therefore, the final compression ratio of this motor will be down to 16.29:1, so we'll call it 16.3:1. Should be high enough to start fine and that extra combustion space might add power, it's hard to say at this point and difficult to test since I plan to port and polish the motor along with the minor cam degreeing change when the crank gear is corrected and put back in-time.
Big Blue24
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Just 60# springs, no gasket matching or any other upgrades to the head in the past.
straight 6 roar
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How come you didn't open up the bowls more?
Also do you mind taking pictures of the porting process? Or some measurements of the port before and after so I can get a feel of how far to go without hitting coolant...
Also do you mind taking pictures of the porting process? Or some measurements of the port before and after so I can get a feel of how far to go without hitting coolant...
madmikeismad
So mad
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I wish I would have thought to do that before I sealed my motor up a couple days ago. I guess I'll do it next time I have it apart. Save me from getting new pistons too.
I'm also curious why you didn't open them up more? And port measurements would be pretty cool.
Big Blue24
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I'm afraid the drop in compression will hurt performance more than the gains I'd receive with an even wider bowl. If I had planned to run a stock thickness gasket, I probably would have opened them up to 58mm which would have left me at close to 16.3:1 compression ratio.
jimbo486
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Awesome runner and build so far, Blue!! Lots of good info coming out of this thread, too! The Isky groove cutting tool is a great idea and perfect for a budget build. I'll definitely refer back to this thread when the time comes for my motor.
YOUNG GUNS15
Im AWESOME!!!!
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Ha that's sweet! Get that sucker thrown together! Clock is ticking!
97rada
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how far would you go?
Big Blue24
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I've been advised that 16-15.5:1 is the lowest I should go on compression for a drag motor. After seeing how little I can cut with the oversized gasket, I may need to pony up and buy a standard thickness gasket so I can cut more of the bowls and get closer to 100% delipped at just over 61mm diameter.
BlackSkyRacing
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Unless they are donated I think a good old set of 286110s would benefit him just as much without having to do some whacky work on the injectors... Maybe he should find an old non intercooled engine to rob the pistons out of, gotta be something dirt cheap out there, could resell the rest of the engine to recoupe the cost. At least with those he'd have the 14mm TRL and a bigger (62mm IIRC) bowl without the goofy lip
oke:
dvst8r
Unobtainium
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Unless they are donated I think a good old set of 286110s would benefit him just as much without having to do some whacky work on the injectors... Maybe he should find an old non intercooled engine to rob the pistons out of, gotta be something dirt cheap out there, could resell the rest of the engine to recoupe the cost. At least with those he'd have the 14mm TRL and a bigger (62mm IIRC) bowl without the goofy lip
I'm not convinced you would have to do any injector work to make them work. I'm sure he could find a donated set of used CR pistons, outside of the shipping from Canada would kill it, I think I have 5 good ones around.
Yeah 286110's would be a good proven option.
cumminsrulez
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Also,
Since my pistons are out and easy to work on, I decided to open up the bowls a little to accept a little more timing before spraying completely out of the bowl.
Stock Piston Before:
Stock 52mm bowl
QUOTE]
what was causing the injectors to spray outside the bowl?? timing? what was your timing at. just curious
Chrisd91
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Also,
Since my pistons are out and easy to work on, I decided to open up the bowls a little to accept a little more timing before spraying completely out of the bowl.
Stock Piston Before:
Stock 52mm bowl
QUOTE]
what was causing the injectors to spray outside the bowl?? timing? what was your timing at. just curious
Good to see you on CompD, Cody :thumbsup:
Big Blue24
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Timing was hovering in the 25.5-26* range. I think it's time to step up to the 28-30* range this year to see if the slow injection rate 160 pump likes more timing.
If you look at a dirty piston, it doesn't look like the spray pattern is too far out of the bowl, more/less hitting on the lip of the bowl. It wasn't until the pistons were mildly cleaned up that the weaker carbon deposits near the spray pattern came off and made it look like fuel is way out of the bowl.
Piston #6 for example:
If you look at a dirty piston, it doesn't look like the spray pattern is too far out of the bowl, more/less hitting on the lip of the bowl. It wasn't until the pistons were mildly cleaned up that the weaker carbon deposits near the spray pattern came off and made it look like fuel is way out of the bowl.
Piston #6 for example:
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