Has anyone went from a sbc to a bbc and slowed down? I have!

Old 06-20-2008, 08:47 AM
  #11  
hammertime
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how did the converter swap turn out ?
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Old 06-20-2008, 09:06 AM
  #12  
Tod74
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Default Re: bbc

Originally Posted by topcat572
The 4.86 to me is a bit much. With a 4.00 stroke and that gear Your starting line ratio is killing You. .
Please explain? I have seen the SLR charts before but do not understand why a 4.86 is too much for 1/8 mile.. as long as it doesn't spin and the motor is still in it's powerband at the end of the run....I run a 5.14 gear with a 4.25 inch crank...but it is a heavy car. around 3100 lbs. 60 fts low 1.30's

The converter advice I agree with ...just trying to understand how a higher gear would pick up his short times if traction isn't a problem
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Old 06-20-2008, 02:04 PM
  #13  
I972Nova
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Sorry guys, It still ran the same.

I went from [email protected] to 5.923 all weekend at Pacemakers. I runner upped on Sunday (took 7 rounds and only paid $200r/u 800 win), but it makes me feel silly to have a bbc dragster that runs 5.90's

I think the compression is lower than I thought...

I have world merlin 320 runner heads with 119 cc chambers and a trw pistons with a .580 dome. The pistons had to have .090 cut off for piston to valve clearance with the big 2.300 valves.

I really just dont understand it, my $2000 flat top 406 with a flat tappet cam is faster than this 468 with pop up pistons and a .722 roller...

Wow, I guess I must need a new shortblock?

I had the timing at 36 degrees then bumped it up to 42 and it popped, is 36 a good place to start.
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Old 06-20-2008, 02:58 PM
  #14  
topcat572
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Tod, to answer the best I can. The SLR chart is an old ATI chart for figuring startling line ratios. It takes Your rear end gear(4.86) and multiplies it by 1st gear in tranny(1.80)? and gives You a SLR of 8.75. An ideal SLR for a 4.00" stroke in a 2000 lb. car is 9.00. You are close, I corrected ,my self above after doing the math. Any way, if Your number is too high, it hits the tires too hard, If its too low You are not hitting the tires hard enough. A lot of hook problems were starting to develope when all these Low tranny gear ratios were coming out and people were just killing the tires. My dragster with the 4.500 stroke and same weight, I am way under with my 1.80 x 3.89 rears, when I get the 4.30s in there, Ill be just about right. My ideal SLR is 8.00, due to the increased stroke. :wink:
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Old 06-20-2008, 03:25 PM
  #15  
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When You bumped to 42, could it have leaned it out? If You are running a crank trigger, did You rephase the rotor? : This is the 2 things I would look for if it was mine, not saying they right. ops:
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Old 06-20-2008, 03:31 PM
  #16  
I972Nova
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its a regular MSD 85551 distributor, The plugs were pretty good in color. I put the timing back and it doesnt pop now.
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Old 06-22-2008, 05:21 PM
  #17  
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figured out why it was so slow at Super Chevy... I ran 9.23 then 9.29 then 9.41... Now I have 4 pounds of oil pressure...

I would say it was built tight and spun a bearing. I havent pulled it apart yet. 19 passes on it and its junk, oh well there is always next year.
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Old 06-23-2008, 12:07 PM
  #18  
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Well I pulled the pan off and ALL 5 main bearings are destroyed, 2 are through the copper. The crankshaft is a total loss.




22 passes on these bearings!!!

I would say this is a good reason why the 468 was slower than the 406...
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Old 06-23-2008, 01:56 PM
  #19  
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:shock: WOW I wouldnt go with that engine builder again! Have you contacted him yet about it?
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Old 06-23-2008, 02:06 PM
  #20  
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If he said he would fix it free, I still wouldnt want it... I am going to bite the bullet and go to the best guy around here, when i get enough money. It took me 8 months to finance this one.
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