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

I went from a 500 Horse SBC to a 700 Horse BBC and slowed from 5.8's to 5.9's.

I am wondering what experiences anyone has had with this, I think the converter is my problem. It was built for my 535 Horse 406. It stalled 5400 behind it. Now it stalls 6200 behind my 468.

I thought it would work, now I am thinking it is way too loose!...

Any thoughts or advice would be greatly appreciated...

My 468 is a 12:1 motor with a .722 Roller and World Merlin III 320cc heads that have 2.300 and 1.880 valves. It has a 1050 Dominator with 38 degrees of timing.

My car is about 1950 pounds with the bbc and me in it... It has 4.86 gears (set up for 1/8 Mile) It only sixty footed 1.30 with the BBC and it had a 1.23 with the 406.

Thanks,
Josh

The torque your making now with the big block will make that converter stall much higher and seem alot loosier than behind your smallblock, or you might have just broke something in it.
I'd pull the trans pan and look for metal which would be a good indication that something let go in the converter.
I would have a new one built especially for that motor rather then trying to tweak your old one.
Also dont forget to figure in the weight difference between your sbc and the bbc which effects things like weight transfer, center of gravity etc. Maybe a chassis adjustment is all that's needed?

JMO
Goodluck, Charles

I have a 477 in a 1950# dragster and it runs 5.30's in the 1/8th. I'd say converter should fix it. I have it for sale in the classifieds if you know anyone interested.

Steve

Re: Has anyone went from a sbc to a bbc and slowed down? I h
 

Sure... Easy advice.

1. Call your current converter manufacturer, tell them your new combo, give them the serial from your current converter, and ask them if they can adjust it.

2. If they can't adjust it, post said SBC combination on RJ and put the converter for sale. Then get a new converter from your favorite converter manufacturer.

A converter is a hydraulic coupling that is made specifically for a given combination. Change the combination and the fluid coupling no longer responds as intended.

converter. and onebadgmc said it so well 8)

bbc
 

The 4.86 to me is a bit much. With a 4.00 stroke and that gear Your starting line ratio is killing You. For 1/8 mile with Your weight I think 4.30s would be the most I would put. Ran a 468 in a 2150 lb. roadster with 4.11 and ran a lot better than that, and this was a 1/4 mile car. I also had a 5800 converter, You may not be that far off. Good luck.

Re: Has anyone went from a sbc to a bbc and slowed down? I h
 

Converter needs to be adjusted 5800 stall max, you need some help getting going with a 468, 6200 stall would be good for 540+ ci in a dragster. What did launch and shift at ? Your compression is hurting your HP #'s I'd bet its in the mid 600HP range not 700 also after seeing the #'s. A converter makes and breaks what a car runs for sure. 60ft is slow you need to get up and going. A little help it should be easily faster then the 406.

I only shift at 6600 and was leaving on the converter at 6200.

Thank you all for your advice, I have a friend who has a group 1 TCI converter we are going to try in it, it stalled right at 5000 behind his 468 and I think with shifting at 6600 that should be a good start.

I can live with around 650 or so. Thats not bad for a poor ol truck driver ...lol...

I pulled the pan and everything looks great in there, A new filter and fluid never hurts though.

It is a hard tail car so no rear suspension to play around with, The car works great as far as planting the tires and going it just feels like my motorhome taking off after the initial hit.

The 4.86 gears were on the winter change list, but with the Aerospace rearend I have to buy the hi dollar gearset, so they got put on the back burner. If it would be consistent and run in the 5.40 - 5.50 range I would be very happy with that.

It hits great then gets lazy, I had 1.135 in my delay box and had a .006 first round. I was thinking converter myself so thank you all for confirming it... I am going to a 3 day race at Dragway42 with the TCI converter and i will let y'all know how it does up there...

Thank you ALL again,
Josh

Leave off a chip not the converter the motor doesnt have (i'll say) enough "ass" to get it going leaving on the converter. I think you can make the 486 gear work, see it done all the time around here. Launch it at 4400 shift it at 6600. I hope the converter stalls atleast 5500 with your motor.

BBC
 

Just found my SLR chart, You good on that, My bad. :oops:

how did the converter swap turn out ?

Re: bbc
 

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

Sorry guys, It still ran the same.

I went from 5.895@117 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.

SLR
 

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:

pop
 

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. :oops:

its a regular MSD 85551 distributor, The plugs were pretty good in color. I put the timing back and it doesnt pop now.

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.

Well I pulled the pan off and ALL 5 main bearings are destroyed, 2 are through the copper. The crankshaft is a total loss.

http://img210.imageshack.us/img210/2616/058ml0.jpg
http://img210.imageshack.us/img210/2650/060yo4.jpg

22 passes on these bearings!!!

I would say this is a good reason why the 468 was slower than the 406...

:shock: WOW I wouldnt go with that engine builder again! Have you contacted him yet about it?

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.

find a cheap gm crank it'll work great, I had 22 passes or should I say 22 passes 200ft last year losing a motor early sucks !! Good Luck finding parts

Yep, that'll slow it down allright. It's a wonder it cranked when it was hot. I've got a Crower 4 inch stroke crank in the classifieds if you're interested.

Steve

i have a gm steel crank that is turned .030/.030 fresh. if you want it come and get it. if you need rods i also have a set of gm dimples.as long as it never spun any bearings you'r alright.

thats the wierd thing is the rod bearings look great. just the mains are thrashed. The bearings didnt spin, the lowers are just destroyed, the uppers dont look anywhere near as bad, but they are into the copper.

This might be the dumb question of the day, but Does the crank need to be balanced to the rods and pistons? I already have external balance flywheel and good external balance balancer...

Performance, where are you located at? Are you saying I can have the crank, or how much do want for it?

Thank You.

Yeah I couldnt understand why this thing was 185 when i got back from a run and hard to cool down, I have never had a bb before so I thought that was normal.

Josh even with a ext balanced flywheel/balancer it still needs balanced. Not a stupid question I didnt have a clue untill last year either.

Josh,
I wish you luck in getting back to the track soon. Although I do not know you, you seem to be one helluva nice guy! I hate this for you.

Man hate to hear about your big block.That sux!!!Hope you get her fixed up cheap...and right :D

I think it needs to be balanced. I wouldn't put one together without it. It sounds like they didn't clearance the main bearings. It should be put together and plasti guaged first for the clearance. The rods could be ok and the mains too tight.


Steve

josh are the main cap discolored badly? one or just some, think i would have block align-bored or honed, or checked at any rate, good luck man.

Definately needs to have been balanced. All GM's with external balancing have to be balanced when adding after market rods and pistons. The factory rods and pistons will alway be a different weight than after market products.
After market rods are usually matches sets within a couple grams and so are after market pistons. These two added together plus rings and bearings add up to the swing/bob weight that the crank needs to be balanced too, along with the flywheel and balancer. What you have is a classic case of crank harmonics/distoration which beat the mains out. Clearance could have been a little tight on the mains, but non the less it would have still beat the mains out if the crank was not balanced for the proper bob/swing weight. The stock units was meant to run max 4500rpm and factory balanced to run that. but the minute you start running 6500/7000 rpm you are in deep DOO DOO.
As mentioned before, you will have to check the alienment on the blk. now because it may be distorted, i'm a little surprised you didn't spin the bearings with that much heat involved.
I know it's a hard and expensive learned lesson, it's something the person who assembled the engine should have warned you about. I personally would have not assembled the engine for no price for a customer without having it balanced.
But atleast when you're able to get her up and running again you'll have a better engine and a faster one.

Zip.

I was asking about balance for future reference... I am going to have the setup rebalanced with a new crank... I was hoping to make it through the year with this one and keep it for a spare, but what are you going to do??

I bought this as a shortblock and had it freshened up with a turned crank and new bearings, It was already balanced.

Thanks for the kind words guys, I am hoping to get to the track again here sooner rather than later...

Sorry my bad :oops: , i misread the post, thinking that it hadn't been balanced as an assembly before. Good luck on the new assembly.

Zip.

dragster josh. i live in orrville, oh. just 6 miles east of wooster,oh.. if you make the trip the crank is you'rs.. i run a hiperformance engine machine shop and don't have time travel. yes it's FREE FREE. thanks and good luck on next build... looks to me that you had either to close clearances, and or possibly oil pump failure. b/b need extra clearance AND A GOOD PUMP. doing a new 511 b/b for a customer that got 4 passes on his 468 that was built down south.

AWESOME Thank you!!! do you do balancing there? If so how much? I could bring you my rods and pistons so they would all be matched up..

Thank You,
Josh

TWO THUMBS UP FOR performanceengin

Great guy !!! I am sure he really appreciates it.

josh. you bring rods, pistons, rings, balancer, lower timing gear, flexplate ,also 2 rod bearings and i'll do the high speed nascar balance down to 1 gram or less for $150.00. this is what i offer as a racer dicount. be glad to help in any way. i know what you'r going through. i have many customers learning the same way you did. give me a call 8-5 weekdays (330)683-7223

I cannot thank you enough!!! I was thinking my racing season was done. With 2 kids, a house and 1 income its hard to afford to go racing let alone rebuild the motor at mid season!!!

I will pickup the bearings at Jegs tomorrow and call you to set everything up...

THANK YOU VERY VERY MUCH!

Josh

josh. if you go for bearings try to get the king race bearing in .030x. the x is for extra clearance. if not king get federal mogal.. DON'T get clevites, i've had probs with them. any questions call me at 330-682-7223 days .

Performance Sorry I have been out of town on work... I 100% want the crank and will have you balance it, but it could be a week or 2 before I can get up there...

Also, someone I talked to said I should have the block line bored since all the mains were junk. Do you know where I could get that done and a ball park of price?

Thanks again,
Josh