Thread: 2/4bbl/blown slantsix

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i have a .080 over 225 slant six with 4-71 blower ,5494 carter fuel pump,and 2/650 double pump carbs with 25degs timing. the problem is the car 60fts well at 1.57et and 1/8 mile at 7.55et but in third gear full throtle the car dies but as you lift the car starts to pull again. if any one can help please reply.

Monitor fuel pressure at the carb bowl entry for minimum 5 1/2 lbs.

Sounds cool! Gotta picture?

everytime i ever run my blower motor lean it either blew a head gasket or burnt a hole in a piston, wouldnt be doing that to often.

thanks for the response,do you think the fuel pump at 72bls/hr is enough flow to keep 2/4bbl feed? i have been told it might be over carbed, she is leaning out because plugs show signs of damage but over jeting or reduced to doesnt help.i have pitcures post at http://community.webshots.com/user/terrylittlejohn. do a webshots shearch for slant/4-71/blower.i dont know how to post pitcures at this site.

sorry this is pitcure of 4-53 blower i ran last year with no trouble dont know how to change it but you can see them at webshots.[IMG]community.webshots.com/myphotos?action=showphoto&albumID=441136909&photoID=4808894335&security=vjnrsh[/IMG]

" i have been told it might be over carbed"

Ya Think?????

Here's the formula from BDS for cfm...
The size of carb(s) or CFM required for a given application can be calculated by the following formula A: {(CID x RPM) ÷ 3456} x {Boost ÷ 14.7) + 1} = CFM required. The amount of CFM required will determine carburetor size and quantity. If you try to use a carb with less CFM than required, performance and economy may be greatly reduced.

Giving you the benefit of a doubt, let's say that you spin this motor to 6,500 and are puttin' 10 lbs. of boost into it.

Your motor is 235 cid, times 6500 divided by 3456 times 10 divided by 14.7 plus 1 = 742 cfm

Originally posted by techinspector1
" i have been told it might be over carbed"

Ya Think?????

Here's the formula from BDS for cfm...
The size of carb(s) or CFM required for a given application can be calculated by the following formula A: {(CID x RPM) ÷ 3456} x {Boost ÷ 14.7) + 1} = CFM required. The amount of CFM required will determine carburetor size and quantity. If you try to use a carb with less CFM than required, performance and economy may be greatly reduced.

Giving you the benefit of a doubt, let's say that you spin this motor to 6,500 and are puttin' 10 lbs. of boost into it.

Your motor is 235 cid, times 6500 divided by 3456 times 10 divided by 14.7 plus 1 = 742 cfm

and that would be the reason you're not blowing head gaskets,

thanks for the formula it is nice to know were i should be with cfms. i have changed to 600vac after going throught the engine i have to replace a burnt ex vavle and head gasket hope it all works out.

i would look at the fuel psi when it leaves the line .do you know what the psi is at??it will take more fuel psi than what you have if it leaves hard the fuel will not want to go up the fuel line this works the pump harder

as far as fuel pressure i have 6bls at idle, maybe i need two 72bls pumps or one holley 140bls pump what do you think?

also the 60ft are better at 1.57ets with this blower compared to the smaller 4-53 blower.

you can try one more pump to match the one you have. 6 psi is ok with the afbs. but you need to know how much you have when you leave the line. and run a fuel line back to the tank so you will have a return line is the best way to go and is easy on the pump that way you will not dead head the pumps . on the line size i wound run the two pumps in one line the pumps AN 8 to a Y block and to an 10 then AN to the carbs AN 6 or AN8 then run the return AN 8 to the tank and you need a sump in the fuel tank try to keep the pumps at the lowest point and on the the carbs run the off road seats in the carbs : whacked:

"but you need to know how much you have when you leave the line."

That's what I was thinkin'. Not only that, you need to know the pressure at the carb through the entire run, cause from what you're sayin', it sounds like the motor is layin' down at about 3/4 track.

yes that is the way i would decribe it, as this is the first time i have tried 2/carbs and a blower with this slantsix combo.