SN95 New 5.0 Car Build Bogs At Hit Of Throttle

Daddys girls GT's · Sep 13, 2015

Guys I need some help! Just finished a 306 build with big heads, equal length headers, single plane intake, .554 cam and a Holley 750 ultra street carb. Runs great after 2500rpm but bogs at the hit. Bogs with a 1700rpm power brake and a 2300rpm trans brake launch. I adjusted carb and timing several times with no real change. The plugs look perfect also. You guys rock so I know somebody has an answer!
Sam

mikestang63 · Sep 13, 2015

too much cam , carb, and a single plan intake . What is your coverter stall? Your stall needs to be probably 2800-3000 with those mids.

TOOLOW91 · Sep 13, 2015

This is like playing sharades . I'd give the full cam specs head specs . Rear gear . What TRANS etc to give the guys a better idea to help .

Sent from my iPhone using my fingers while my auto correct makes me seem illiterate

TOOLOW91 · Sep 13, 2015

And in this case what size tire .

Sent from my iPhone using my fingers while my auto correct makes me seem illiterate

Boosted92LX · Sep 13, 2015

A 750 is too much carb for a 306. Period. End of story. There are calculators online to determine how many cfm you need based on c.i.d and max rpms you are going to turn, but anybody that's ever run a carb on a 302/306 on the street will tell you that the calculator is not needed. Buy a good vac secondary 600 and be done. Oh, and I'm with Mike. Unless you are spraying that thing at the track, ditch the single plane and get a good dual plane like a rpm air gap. That little motor needs all the torque it can get.

jrichker · Sep 14, 2015

Take the air cleaner off, start the engine, let it idle. Be aware that if it backfires with your face over the carb, you may get burnt.

Stick your head to where you can see the accelerator pump squirt when you quickly press the throttle. Watch to see if the accelerator pump squirts when you begin to goose the engine. You may find that you need to play with the accelerator pump settings so that it starts to squirt when you first hit the throttle.

Daddys girls GT's · Sep 14, 2015

mikestang63 said:
too much cam , carb, and a single plan intake . What is your coverter stall? Your stall needs to be probably 2800-3000 with those mids.

Looking for a 3800 stall this Winter since I have the trans brake. I just don't understand the bog. 11:1 compression and all the right parts I thought. Thanks for your reply, I appreciate any input.
Sam

a91what · Sep 14, 2015

Is this car full race? If you plan to put it on the street 3800 is way too much converter, it will be obnoxious.

My (smallish) cam says no less than 2500 stall converter, get a 2800-3200 stall. If it is just for racing you can give it more converter.

A single plane intake will make poo torque below 2500 rpm. They are for high rpm engines. We use one on our 327 stroker with an 1100 dominator carb BUT we spin it well past 7500rpm and add lots of nitrous..... and occasionally blow it up.

Boosted92LX · Sep 14, 2015

jrichker said:
Take the air cleaner off, start the engine, let it idle. Be aware that if it backfires with your face over the carb, you may get burnt.

Stick your head to where you can see the accelerator pump squirt when you quickly press the throttle. Watch to see if the accelerator pump squirts when you begin to goose the engine. You may find that you need to play with the accelerator pump settings so that it starts to squirt when you first hit the throttle.

I've found that to fix an off idle bog you do follow this advice.. ^^

If your squirters aren't coming in when you crack the throttle, advance the accel pump cam to bring it in sooner. However...my guess (from past experience) is that big honkin 750 that is set up for an engine big enough to handle it.. is over fueling the poo out of your engine.

Have a look at this. Skip down to where it says "what size holley?" I'm not pulling it out of my butt.

Holley Carburetor Basics - Mustang Monthly Magazine

@Daddys girls GT's

Daddys girls GT's · Sep 15, 2015

Thanks for all the opinions guys! I noticed today that my fuel bowls are NOT halfway full even at an idle. I am going to try and correct that first. The car screams above 2500 and pulls well over 6K. Engine builder that did the heads and the cam grinder both agreed that 750 was the right choice for my needs. This is my 20 yr old daughters car that she has raced since 14. She said make it faster and barely streetable is fine. We all spray but wasn't going to hookup until she was used to new motor but will be spraying up to 150 or 200 eventually. Thanks for all the help, you guys rock! Look up my little team at mtndragracing.com sometime.
Sam

hoopty5.0 · Sep 16, 2015

I just checked out the web page, pretty cool to see young folks involved in racing and doing it the right way. Keep us posted!

Daddys girls GT's · Sep 16, 2015

Thanks man! I wanted to make sure my 3 kids stayed in racing when I'm gone so I'm building a network of support folks for them. Will let you know when I adjust the floats on Kaytlyns car. Thank again for you help.
Sam

FoxMustangLvr · Sep 16, 2015

Daddys girls GT's said:
Thanks for all the opinions guys! I noticed today that my fuel bowls are NOT halfway full even at an idle. I am going to try and correct that first. The car screams above 2500 and pulls well over 6K. Engine builder that did the heads and the cam grinder both agreed that 750 was the right choice for my needs. This is my 20 yr old daughters car that she has raced since 14. She said make it faster and barely streetable is fine. We all spray but wasn't going to hookup until she was used to new motor but will be spraying up to 150 or 200 eventually. Thanks for all the help, you guys rock! Look up my little team at mtndragracing.com sometime.
Sam

What gears are you running to help with that cam? I think you can make that big carb work you're just not getting enough fuel at the bump of the throttle and you may need to play with the converter and gearing as well to get a good launch. What do your plugs look like at idle?

Daddys girls GT's · Sep 16, 2015

Thanks for asking! I have 4:10's, locker rear end, full manual valve body with trans brake and B&M ratchet shifter. I plan to do a converter during the Winter but my problem is carb I feel. The plugs look great but that is with the carb leaned almost all the way out. I did notice yesterday that my bowls are NOT halfway full and need to adjust for that and retest. Not sure how I missed that earlier because I had a real time getting pressure down to 6/7 pound range. I actually had to use a 1/2" return line off the regulator back to the tank! Yes it is a killer fuel pump! Thanks for all the help and look my kids up on the website.
Sam

jrichker · Sep 16, 2015

The tag with your post says SN95. Is this a 94-95 Mustang? If not, what year?

If you are still using the EFI in tank pump, you are asking for trouble.

Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. If the add on pressure regulator fails, you will flood the engine with gas and wash all the oil off the cylinder walls. That will cost you big time $$$. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.

Daddys girls GT's · Sep 16, 2015

Oh no I built a pickup tube with a sock where the EFI pump used to be. I made the old return line into my new vent line and put a 1/2" return line from the regulator into the top of tank fitting that used to be the vent. I have everything correct but I just found out the bowls are very low rather than at the halfway mark so I may be running out of gas at the hit. Will work on that this weekend. Thanks for the advice!
Sam

SN95 New 5.0 Car Build Bogs At Hit Of Throttle

Daddys girls GT's

Member

mikestang63

TOOLOW91

If you're the village idiot what's that make me?

TOOLOW91

If you're the village idiot what's that make me?

Boosted92LX

It's only an inch or two. What's the big deal?

jrichker

StangNet's favorite TOOL

Daddys girls GT's

Member

a91what

SendMeUrDataLog

Boosted92LX

It's only an inch or two. What's the big deal?

Daddys girls GT's

Member

hoopty5.0

mechanicus terribilis

Daddys girls GT's

Member

FoxMustangLvr

I love my Pimp

Daddys girls GT's

Member

jrichker

StangNet's favorite TOOL

Daddys girls GT's

Member

Similar threads

SN95 New 5.0 Car Build Bogs At Hit Of Throttle

Member

If you're the village idiot what's that make me?

If you're the village idiot what's that make me?

It's only an inch or two. What's the big deal?

StangNet's favorite TOOL

Member

SendMeUrDataLog

It's only an inch or two. What's the big deal?

Member

mechanicus terribilis

Member

I love my Pimp

Member

StangNet's favorite TOOL

Member

Similar threads

Privacy & Transparency

Privacy & Transparency