goinbroke2
Well-known member
77 Maveric with 250 six, carter carb.
Anybody know the CFM of this carb??
Thanks
Anybody know the CFM of this carb??
Thanks
Carb CFM question...
- Thread starter goinbroke2
- Start date
goinbroke2
Well-known member
FINALLY found it....it's a carter YF and it's 193 cfm.
goinbroke2
Well-known member
Well since I'm at it, I did a search and the best I could come up with is 155cfm for an intake port.(same engine)
Any others want to pipe up? Just curious I'm doing a comparison for racing, I realise the smaller 200 with the same head would out rev and probably out hp the 250, but I have a reason to build a 250 over a 200.
So,
1) what does a 250 (1977) intake port flow;
2) What other issues do 250's have for performance work? (weak rods/spun bearing/etc)
3) HP potential? (230hp possible with unported head)?
Thanks
Any others want to pipe up? Just curious I'm doing a comparison for racing, I realise the smaller 200 with the same head would out rev and probably out hp the 250, but I have a reason to build a 250 over a 200.
So,
1) what does a 250 (1977) intake port flow;
2) What other issues do 250's have for performance work? (weak rods/spun bearing/etc)
3) HP potential? (230hp possible with unported head)?
Thanks
230HP ??? With a stock head and a stock 1bbl carb?
I think you are going to come up short ,.....way short.
A good running carbed 300 with a much better head makes around 130-135
with the carb being one of worst limiting factors.
Of course the 300 1bbl intake isn't much better than the 1 bbl carb.
You might get 150 if you optimize everything else.
My HP figures I was using were net ratings.
I think you are going to come up short ,.....way short.
A good running carbed 300 with a much better head makes around 130-135
with the carb being one of worst limiting factors.
Of course the 300 1bbl intake isn't much better than the 1 bbl carb.
You might get 150 if you optimize everything else.
My HP figures I was using were net ratings.
goinbroke2
Well-known member
I'm allowed undercut stems, back cut the intakes, stock lift (.370) and any duration. No porting, stock chamber/intake/carb. Headers are allowed as are electric waterpump drive. Basically, just the alternator on the front and the tranny on the back.
(IHRA Stock Eliminator)
Right now it's rated at .48hp per cube (extremely low) and I've seen ford and chevy sixes go .8-.95 per cube
Thinking this could be a sleeper for V/SA...
(IHRA Stock Eliminator)
Right now it's rated at .48hp per cube (extremely low) and I've seen ford and chevy sixes go .8-.95 per cube
Thinking this could be a sleeper for V/SA...
That is not what I was thinking at all. When I think "unported head"
I think stock valves, stock cam, stock ... everything.
230 I think could be done with the right machining(quench,0 deck,... and othe reqired items like a cheater cam .
Sounds like fun.
I think stock valves, stock cam, stock ... everything.
230 I think could be done with the right machining(quench,0 deck,... and othe reqired items like a cheater cam .
Sounds like fun.
goinbroke2
Well-known member
Alright, where is Cometguy??? C'mon, I need a fellow Canadians input here! (especially if he's gonna run in the 14's) (current record is 15.27)
A problem with 200hp, let alone 230, because of the cam and carb restraints. 
I know that the venturi area to cubic inch ratio has to be 100 cubic inches per 1 sq in of venturi area to get 1.1875 hp per cubic inch where the cam is free for lift and duration. Doing a regression, a 230 hp engine needs more 125 cubes per sq in of venturi to work, needing a free cam lift and duration. Hence, I'd say 200 hp is it with the best lift compliant cam with about 275 degrees duration at lash
In Aussie, stock 9 port Holden I6's have 202 cubes. They find it hard to do 165 hp net with just a 260 degree cam and about 448 lift, headers and flat-top pistons. That's a 10:1 compression engine with over size 1.625/1.5" valves and electronic ignition. Carb is a very small Bendix Stromberg 1-bbl, like the old 50's Mopar sixes ran. Exhast is 2.25" collector tubeing headers into a big 2.5" pipe. Cube to ventuir sq in ratio is about 125.
Converting that to 250 Ford logic. The stock 370 thou lift cam needs way more than 256 degrees at lash to run more than 205 hp, the power of a scaled up 202 with an extra 48 cubes. The carb will have to be 300 I6 spec, or a larger casting. Your gonna need some smart moves.
Good news is that even though the log is a dog in flow terms compared to a 2V or ME/SP or FSPP head, the D7 head is not likely to be the galling point for power. Around that year, Ford did a lot of work on the old monoblock casting, and it will take a lot of bad work for it not to flow well.
The cam is the issue, and your going to have to use some logic, and make a cheater cam for it.
I'd check with APT, and knock up some details to David Vizard, play the goiung rate, and have a custom cam made. That boy has been doing restricted class engines in SCCA and Mini X and other classes for decades, and even thougn he used to be a limey, he's as Yank as they come when straight line power is at stake.
I know that the venturi area to cubic inch ratio has to be 100 cubic inches per 1 sq in of venturi area to get 1.1875 hp per cubic inch where the cam is free for lift and duration. Doing a regression, a 230 hp engine needs more 125 cubes per sq in of venturi to work, needing a free cam lift and duration. Hence, I'd say 200 hp is it with the best lift compliant cam with about 275 degrees duration at lash
In Aussie, stock 9 port Holden I6's have 202 cubes. They find it hard to do 165 hp net with just a 260 degree cam and about 448 lift, headers and flat-top pistons. That's a 10:1 compression engine with over size 1.625/1.5" valves and electronic ignition. Carb is a very small Bendix Stromberg 1-bbl, like the old 50's Mopar sixes ran. Exhast is 2.25" collector tubeing headers into a big 2.5" pipe. Cube to ventuir sq in ratio is about 125.
Converting that to 250 Ford logic. The stock 370 thou lift cam needs way more than 256 degrees at lash to run more than 205 hp, the power of a scaled up 202 with an extra 48 cubes. The carb will have to be 300 I6 spec, or a larger casting. Your gonna need some smart moves.
Good news is that even though the log is a dog in flow terms compared to a 2V or ME/SP or FSPP head, the D7 head is not likely to be the galling point for power. Around that year, Ford did a lot of work on the old monoblock casting, and it will take a lot of bad work for it not to flow well.
The cam is the issue, and your going to have to use some logic, and make a cheater cam for it.
I'd check with APT, and knock up some details to David Vizard, play the goiung rate, and have a custom cam made. That boy has been doing restricted class engines in SCCA and Mini X and other classes for decades, and even thougn he used to be a limey, he's as Yank as they come when straight line power is at stake.
goinbroke2
Well-known member
Now that's what I was looking for...thanks!
I must run the stock lift but can have any duration/overlap/centreline etc.
(I would get Bullet cams, they are the experts when it comes to stocker ford cams)
I agree on the carb/headflow issue, I think it's too small.
Actually I think it's a pig nobody is racing because of the same reason nobody races a 351W. The stock heads on a 302 are too small, so add more cubes and the potential rpm and hp go down. At some point of diminishing returns you find out the increased torque from the cubes is offset by the lack of rpm.
Everybody (relatively) runs the 200 and say it's top end is limited as far as airflow, so yeah the 250 might really be hurting.
I just can't help myself...looking through the guide for a "sleeper" and where most engines are rated around .6-.65 hp per cube starting out, this thing is only .48. That's why I keep thinking there must be SOMETHING I can do with that!!
Any more thoughts....I already checked piston speed with the long stroke..AAHH, another problem...
I must run the stock lift but can have any duration/overlap/centreline etc.
(I would get Bullet cams, they are the experts when it comes to stocker ford cams)
I agree on the carb/headflow issue, I think it's too small.
Actually I think it's a pig nobody is racing because of the same reason nobody races a 351W. The stock heads on a 302 are too small, so add more cubes and the potential rpm and hp go down. At some point of diminishing returns you find out the increased torque from the cubes is offset by the lack of rpm.
Everybody (relatively) runs the 200 and say it's top end is limited as far as airflow, so yeah the 250 might really be hurting.
I just can't help myself...looking through the guide for a "sleeper" and where most engines are rated around .6-.65 hp per cube starting out, this thing is only .48. That's why I keep thinking there must be SOMETHING I can do with that!!
Any more thoughts....I already checked piston speed with the long stroke..AAHH, another problem...
can you run 2V 
if not it might be possible i have a 250 here in aus and it has the feel of around 110rwkw or about 150rwhp so 200hp but i dont know what port work has been done and the cam is massive (it starting pulling at 4000rpm and trys to break the taco to self imposed rev limit of 6000)
personaly id see if you could sneek a 240bb six in.
or build a torque monster from the 250 get some aussie 200 rods (6.27in) and pistons bump the comp to 11.0:1 (100 octane will run it with out detation)
sand blast the intake and exhaust as much as possible with a superheavyduty blaster.
then the biggest spacer plate allowed under the carby with a ram air horn on top of the carby.
use a square profile cam (very hard on cams and lifters) but it will throw the lifter off the camincreasing valve lift also run the heavyest fly wheel you can find then bolt the converter on.
and run in the lightest car your allowed with the lightest driveline.
you whouldent have the end of the 1/4 speed the others have but you could be very qick to half track.
also some cheating may be in order as well cut the log off your head then off anther say 1/4in lower sand blast the inside out for hours then have weld back and blasted again an old speedway trick out in aus looked standerd and being a log nobody really checked but made one hell of a difference.
drift
if not it might be possible i have a 250 here in aus and it has the feel of around 110rwkw or about 150rwhp so 200hp but i dont know what port work has been done and the cam is massive (it starting pulling at 4000rpm and trys to break the taco to self imposed rev limit of 6000)
personaly id see if you could sneek a 240bb six in.
or build a torque monster from the 250 get some aussie 200 rods (6.27in) and pistons bump the comp to 11.0:1 (100 octane will run it with out detation)
sand blast the intake and exhaust as much as possible with a superheavyduty blaster.
then the biggest spacer plate allowed under the carby with a ram air horn on top of the carby.
use a square profile cam (very hard on cams and lifters) but it will throw the lifter off the camincreasing valve lift also run the heavyest fly wheel you can find then bolt the converter on.
and run in the lightest car your allowed with the lightest driveline.
you whouldent have the end of the 1/4 speed the others have but you could be very qick to half track.
also some cheating may be in order as well cut the log off your head then off anther say 1/4in lower sand blast the inside out for hours then have weld back and blasted again an old speedway trick out in aus looked standerd and being a log nobody really checked but made one hell of a difference.
drift
goinbroke2
Well-known member
Xtasy,
1) you said "I know that the venturi area to cubic inch ratio has to be 100 cubic inches per 1 sq in of venturi area to get 1.1875 hp per cubic inch where the cam is free for lift and duration".
Where did you get that? Is that Vizards calculations?
2) You said "Doing a regression, a 230 hp engine needs more 125 cubes per sq in of venturi to work".
Wouldn't that be the other way? Since I'm not trying to get 1.1875per cube it would make sense to me that I would require LESS than 1 sq in of venturi. Like 80 cubes per 1 sq in only gives .95 hp per cube in.
Or how about this way, since I'm limited to 125 cubes per sq in of venturi I can't get 1.1875 hp per cube. I will only get .95 hp per cube.
250 x .95 = 237.5hp
Drift Cortina, "can you run 2V "?
No, I must use the carb that came with that engine for that year. (NHRA has a carb list as well as casting numbers for the head that is required etc).
"personaly id see if you could sneek a 240bb six in"
HAHAHA! No, they check eng spec's/part number/etc during tear down, and they would find that a problem!
"get some aussie 200 rods (6.27in) and pistons bump the comp to 11.0:1 (100 octane will run it with out detation)
They check rod length and pistons on approved list. Blueprint and you can bump the compression but it must only be to max factory spec's. (for example, your allowed .015 stroke so everybody strokes the motors .013 to be on safe side) And as far as octane, you must run approved fuel which IS checked along with weight every pass. (actually the octane is too high for most low HP engines and with the slow flame front actually kills a bit of power. More than one guy has complained to me their 8 to 1 compression car is quicker with street gas but of course won't pass tech.
"biggest spacer plate allowed under the carby with a ram air horn on top of the carby"
....just a minute, I'll post the rules instead of going on and on.
1) you said "I know that the venturi area to cubic inch ratio has to be 100 cubic inches per 1 sq in of venturi area to get 1.1875 hp per cubic inch where the cam is free for lift and duration".
Where did you get that? Is that Vizards calculations?
2) You said "Doing a regression, a 230 hp engine needs more 125 cubes per sq in of venturi to work".
Wouldn't that be the other way? Since I'm not trying to get 1.1875per cube it would make sense to me that I would require LESS than 1 sq in of venturi. Like 80 cubes per 1 sq in only gives .95 hp per cube in.
Or how about this way, since I'm limited to 125 cubes per sq in of venturi I can't get 1.1875 hp per cube. I will only get .95 hp per cube.
250 x .95 = 237.5hp
Drift Cortina, "can you run 2V "?
No, I must use the carb that came with that engine for that year. (NHRA has a carb list as well as casting numbers for the head that is required etc).
"personaly id see if you could sneek a 240bb six in"
HAHAHA! No, they check eng spec's/part number/etc during tear down, and they would find that a problem!
"get some aussie 200 rods (6.27in) and pistons bump the comp to 11.0:1 (100 octane will run it with out detation)
They check rod length and pistons on approved list. Blueprint and you can bump the compression but it must only be to max factory spec's. (for example, your allowed .015 stroke so everybody strokes the motors .013 to be on safe side) And as far as octane, you must run approved fuel which IS checked along with weight every pass. (actually the octane is too high for most low HP engines and with the slow flame front actually kills a bit of power. More than one guy has complained to me their 8 to 1 compression car is quicker with street gas but of course won't pass tech.
"biggest spacer plate allowed under the carby with a ram air horn on top of the carby"
....just a minute, I'll post the rules instead of going on and on.
goinbroke2
Well-known member
ok I'm a dummy......I scanned the stupid page but I can't attach it here.... 
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goinbroke2":1hp8bhqn said:
Yep, your right. Less than 125 cubic inches per sq in of venturi can give up to 1.1875 hp per cube. So maybee there is a hope to get 230 hp.
Blue print rules are what they are. Smartest cheater is the cam and the carb size. Wahts the biggest carb venturi you can run?
goinbroke2
Well-known member
Whatever it came with. I'm not familiar with venturi sizes on the 6, perhaps someone else could wade in with an answer. (I'm guessing throttle plate is 1 1/2" and venturi is probably 1" or so)
damn they make it harder but not impossible.
are you allowed to balance the engine?
if so your crank is way out of balance and will look like a 2yr old has attacked it with drill should be able to drop at least 5pound out with out reducing the size of the crank.
leave the main journels the same size stroke it out and reduce the big end size then blue print the rods for same weight (of corse as light as possible)
are pistons open?
how often do they tear an engine down and how do they measure comp?
send rules to my email ill have a look over them
drift
are you allowed to balance the engine?
if so your crank is way out of balance and will look like a 2yr old has attacked it with drill should be able to drop at least 5pound out with out reducing the size of the crank.
leave the main journels the same size stroke it out and reduce the big end size then blue print the rods for same weight (of corse as light as possible)
are pistons open?
how often do they tear an engine down and how do they measure comp?
send rules to my email ill have a look over them
drift
goinbroke2
Well-known member
Wow, time is flying by!! sorry for not responding quicker, the temp has been quite cold and I'm a heavy diesel mech...I'll leave it at that!
Yes I can balance the bottom end and aftermarket rods are now allowed(same centre to centre length). Approved pistons only (there are none for the 250 yet)
Teardowns are not too often, but if you set a record or win class you'll be "goin to the barn". They can check something as simple as intake or carb #'s or cam lift or they can make you pull a piston and weigh it. They might CC your head, check your wheelbase is not more than 2" out.
Car weight,fuel sample,secure ballast, a million things.
3 angle valve job allowed with the seat being 45*, no grinding or polishing anywhere. (Change plugs and valve depth to modify chamber CC after milling "close".
Xtasy asked whats the biggest carb venturi I can run...the stock 193cfm carb. I can modify air bleeds/drill a hole in the throttle plate for idle quality/change needle and seat sizes/change jets. And blueprint the carb to the best spec's. That's it, any funny stuff and it WILL be picked up by tech.
Just wondering if anybody on here has run a performance N/A 250? And if so, what did it run like? Was it a pig that wouldn't go past 4500 no matter what you threw at it or was it reasonable to extract power from.
Yes I can balance the bottom end and aftermarket rods are now allowed(same centre to centre length). Approved pistons only (there are none for the 250 yet)
Teardowns are not too often, but if you set a record or win class you'll be "goin to the barn". They can check something as simple as intake or carb #'s or cam lift or they can make you pull a piston and weigh it. They might CC your head, check your wheelbase is not more than 2" out.
Car weight,fuel sample,secure ballast, a million things.
3 angle valve job allowed with the seat being 45*, no grinding or polishing anywhere. (Change plugs and valve depth to modify chamber CC after milling "close".
Xtasy asked whats the biggest carb venturi I can run...the stock 193cfm carb. I can modify air bleeds/drill a hole in the throttle plate for idle quality/change needle and seat sizes/change jets. And blueprint the carb to the best spec's. That's it, any funny stuff and it WILL be picked up by tech.
Just wondering if anybody on here has run a performance N/A 250? And if so, what did it run like? Was it a pig that wouldn't go past 4500 no matter what you threw at it or was it reasonable to extract power from.
basically, your....
The regs are too restrictive in this case, unless you cheat. And cheating will get you barnhoused.
The real issue is the 103 thou piston short-fall stock. It'd be hard to improve on that unless you'd loose 100 thou by milling the block (not a good idea, the deck is easiliy fractured and the bolts and water galleries have a thin 250 thou deck), the 255 pistons (80 thou taller) are not legal, and neither are the 6.06" or 6" HSC rods. You could resize the rods 60 thou and get any non approved piston because of the lack of definition on pistons.
Reiterating the cam choice is the key. Carb is quite okay. The maximum power is about 205 hp, if the cfm at .370 thou lift can be 175 cfm at 25" Hg. You could get close to that if you select castings and flow bench them.
The regs are too restrictive in this case, unless you cheat. And cheating will get you barnhoused.
The real issue is the 103 thou piston short-fall stock. It'd be hard to improve on that unless you'd loose 100 thou by milling the block (not a good idea, the deck is easiliy fractured and the bolts and water galleries have a thin 250 thou deck), the 255 pistons (80 thou taller) are not legal, and neither are the 6.06" or 6" HSC rods. You could resize the rods 60 thou and get any non approved piston because of the lack of definition on pistons.
Reiterating the cam choice is the key. Carb is quite okay. The maximum power is about 205 hp, if the cfm at .370 thou lift can be 175 cfm at 25" Hg. You could get close to that if you select castings and flow bench them.
goinbroke2
Well-known member
That's funny...but disappointing
I talked to some who run the 200 and say it's the only way to go.
Damn!
I was looking for an untried combo that could be a sleeper, one I know for sure is the 82 mustang with the 302 2bbl. It's rated at 170hp like all other 302 2bbl of '70's vintage, but has better cam/heads/carb/intake/etc. Problem is, I wanted to run a six.
And I don't like following in others footsteps, so I'd rather not do a 200. I looked at the guide for the 144-170 but they are rated around 75-85hp and have four mains etc.
Well, thanks for all the help.
Gotta keep looking......
I talked to some who run the 200 and say it's the only way to go.
Damn!
I was looking for an untried combo that could be a sleeper, one I know for sure is the 82 mustang with the 302 2bbl. It's rated at 170hp like all other 302 2bbl of '70's vintage, but has better cam/heads/carb/intake/etc. Problem is, I wanted to run a six.
And I don't like following in others footsteps, so I'd rather not do a 200. I looked at the guide for the 144-170 but they are rated around 75-85hp and have four mains etc.
Well, thanks for all the help.
Gotta keep looking......
