Printable View
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. :HMMM:
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
and that would be the reason you're not blowing head gaskets,Quote:
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
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:whacked:
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.
pay attention to what tech. is trying to tell you . your fuel pressure is ok at the start of the run but 3/4 in the pressure is not holding up .
i did not mean to sound like i was not listening,i am just trying to give you all the info that i have learned this race season and try to cover all the possible bases so next season i mite be closer to the right tune up for this combo,thanks
i said this??????????????????:HMMM:
denny i think its more like head gasket not plural:LOL:Quote:
Originally posted by lt1s10
and that would be the reason you're not blowing head gaskets,
Quote:
Originally posted by gassersrule_196
denny i think its more like head gasket not plural:LOL:
i meant head "gaskets" gassersrule_196, i understood that he had done this more than one time, and if he had went threw the 1/8 of the mile with no fuel prussure, he would have blown a gasket everytime. two or more "runs" = two or more head "gaskets". :whacked: how did denny get into this? :HMMM::LOL: i believe you've been sniffing to much racing fuel. :LOL:
terrylittlejohn, i ran blowers a lot of years and had about every problem you can think of, but one thing i just thought about and was one of the hardest things to find is i had a float in a 750 holley that would sink under load and do the same thing yours is doing. everybody told me there was no way a 471 blower would sink a float, so i didnt do anything about it untill there was nothing else to do. at the time they had a blower none sinkable float. that fixed mine. you're not playing out of fuel you are flooding it, and as soon as you let up the purssure in the carb. decrease and the float will come back up. if you have cork floats you need to change them anyway.
thanks for that tip, but i only have brass or plasitic floats, can you explain what a cork float is?
it looks like black styrofoam and you can scratch it with your finger. then you have a harder plasitic and the brass, im not sure what i had or what i ended up with, but the brass ones would be the best ones i would think. go over to blower serv. and see what they have. they was the ones that told me i didnt need new floats and 2 mos. later 6 or 7 trips to the drag strip and falling on my face i bought them anyway and fixed the car. i wouldnt run nothing but the brass. ill check on it to ,if i find out anything ill let you know.Quote:
Originally posted by terrylittlejohn
thanks for that tip, but i only have brass or plasitic floots, can you explain what a cork floot is?
thanks i need a little help, thats what my summer was like,either jetting through the roof or taking all the timing out and seeing the same results, hopfully some of these ideas will cover my problem.
you are lucky, i started off lean and have 25 head gaskets and 6 or 7 sets of pistons to show for it. that how i know you ant running lean.Quote:
Originally posted by terrylittlejohn
thanks i need a little help, thats what my summer was like,either jetting through the roof or taking all the timing out and seeing the same results, hopfully some of these ideas will cover my problem.
you said you loss a head gasket and all the ex valves if you are not lean then what are you? and i have afbs edelbrocks and have been lean but did not hurt any thing i have not see the floats sink from a blower?? how dose this happen?? but from to much fuel psi and have done it with holleys and afbs - edelbrocks:whacked:
boy is it that dam hard to put a fuel psi gauge on this ??to find out what you have for psi ?? do what you want . i think you should start here and a fuel pump that is rated at 72 feeding two carbs and four float bowls. this is not going to cut it .and you may not have it running lean but when you get the bog out and get it to run a full pass it will run out of fuel .:whacked:
if you think i can help you terrylittlejohn, you can pm me. pat seem to have all the answers though. pat just because you never sank a float dont mean it cant be done. if you dont know what make them sink im not gonna tell you. ive had a lot of them sink on reg. motors, so i know they will sink on a blower motor. :HMMM:
yes ,at the first few times at the track when the car did not feel right, witch was usually high gear full throtle, i would lift and when i checked the plugs you could see porislen and electrode damage.after jetting up till you could breath in the car with no change and still finding plug damage i tried timing, after reducing it to 15deg total, witch was 2deg retarded at idle,i still had the same outcome.so the last run i had on the last weekend,i threw all causion to the wind and stayed in it, when i shut the car off it would not restart.after i got home and pulled the engine i found the head gasket burnt between1&2,5&6 and #5ex burnt also 3 of the piston had cracks in the skirts.all i can say in first & second the car never felt or perform better, so whether i am over carbed, under fuel pump or pressered i will have to see after i put all these great suggestion to work,so keep them coming, thanks
you should have added all that the first time terrylittlejohn thats a dead give away its lean. i didnt get the blown head gaskets out of the first post. falling on its face and blowing up is a lot dif. from falling on its face and not blowing up. :HMMM:
sorry about that but i was just trying to understand what was happening and some of the causes or problem that i might have created trying to make this combo work. as for the engine damage ,i did not dissasemble the engine till after i asked for imput from this site,hope i can be fogiven.thanks
no problem im good at not reading all of the post. :CRY:Quote:
Originally posted by terrylittlejohn
sorry about that but i was just trying to understand what was happening and some of the causes or problem that i might have created trying to make this combo work. as for the engine damage ,i did not dissasemble the engine till after i asked for imput from this site,hope i can be fogiven.thanks
hey s10 get off may back i did not say i have all the answers but i know when some thing is running ouy of fuel
The cut was from the float remark, you good as told me I was lying, just because you haven't seen a float sink under load just tells me how much auto.repair work you've done. when q-jets first came out it was a major problem. I know when a motor is playing out of fuel also, and if you say a blower motor can play out of fuel at wot and not do no damage then you have never played out of fuel on a blown motor. I said I didn't see the head gasket post. when the whole story came out what i said was true.
who s is taking about Q jets ??? we are taking about afb s and edlbrock s and they do not have foam floats they are brass and i have tune many blown car s and did not need more than the set of pistons that came in it .if you want to try running 400 + hp with no fuel with a blower go for it ?and q jets have one float that why .i do not give a give a dam what you think you are way off on this and i was rigth
i did have a lean problem with my chevy but fixed it before i burned the engine down check the ex temp and i do know something it is 548 big block with 10 je pistons in it and 10 boost and beat the shi$ out of it for the last 5 years and run it to 7000 rpm what do i know i guess not much according to you but i do not give a dam . come by some time and i will show you some 50 chevy tail lites :LOL:
i believe he said he was running 2/650 double pump carbs i assume he meant holleys. they can have either floats. if he has the Nitrophyl Floats they will get heavy with fuel and sink under load. i was using q jet as a example because that had a lot of trouble with the Nitrophyl Floats. :HMMM:
yes they did and have put some in. and so did the two barrels have fixed brass floats solder them when i was a younger and tested them in a glass of water and used a pencil and some thing to hold them down this was over 25 years a go. have you work on cars longer ?maybe but i work on Q jets that look like they sat on the bottom of the ocean when i work it the boat yard and had to scrap the in side to clean them out and got them to work very good i did not think i need to give may past on what i work on ?that dose not have much to do with this thred:HMMM:
i was working in a ford dealership in 1960, you do the math. **)
i dont see nothing