Ho- 302 that lacks power

[Rowdy Fitzgerald]

Hey guys I'm stumped. I'm in the tail end of my swap and im havin trouble. I have a 88 HO 5.0 that has procomp aluminum heads, a E303 cam, bored .030 over, weiand intake, shorty headers, holly 570cfm streetavenger carb oh and full roller with 1.60 rockers. I set the timing at 10 deg. I pulled the vac hose, plugged it then set the timing. It lacks power and has poor throttle response. Anybody have a clue what's wrong?

 

[lairdt]

Hey guys I'm stumped. I'm in the tail end of my swap and im havin trouble. I have a 88 HO 5.0 that has procomp aluminum heads, a E303 cam, bored .030 over, weiand intake, shorty headers, holly 570cfm streetavenger carb oh and full roller with 1.60 rockers. I set the timing at 10 deg. I pulled the vac hose, plugged it then set the timing. It lacks power and has poor throttle response. Anybody have a clue what's wrong?

I'd say that you need to tune your carb. Assuming the timing is at 10BTDC and everything else is good, then I'd say you probably need a different accel pump cam setting (assuming that circuit is adjusted correctly) to address the throttle response issue. It might be that your stock red/orange cam going from hole #1 to #2 would also make a noticeable difference or you might need to go to a green #2 and see if gets better. Assuming your idle is around 700-750rpm or so, this should tell you if you're going in the right direction if there's better power. There's more too it than this, but it's a quick change.

You need to address any timing issues before you can tune your carb. Don't know what timing curve you have setup, but after you get that figured out you can come back and tune your carb for power. With that cam I'd expect 10-12BTDC initial, with mechanical timing coming in around 1800 and all in about 3700 with 25 degrees as a start.

 

[Rowdy Fitzgerald]

I don't mean to sound dumb but what is red/orange, green cam? I don't know much about carbs. This is the first time I've messed with carbs.

 

[lairdt]

I don't mean to sound dumb but what is red/orange, green cam? I don't know much about carbs. This is the first time I've messed with carbs.

Ok, then you've *got* to get a Holley carb tuning manual or otherwise find someone that can tune your carb for you, and do some research on carbs either way so you know how to adjust/maintain it going forward.

On the backside of the throttle arm on the carb there is a small plastic cam that activates the accelerator pump arm. This circuit adds gas when you're starting to rev the engine, too little it will stumble when you try to rev (worse under load).

 

[kimcrwbr1]

Try setting your timing using total advance Find around 38 degrees and make a mark and set total advance at 2500 rpm. You may need to mess with the advance curve but ford V-8s run best at max advance possible at high speeds dont worry too much on base timing it will take care of itself. Especially with a built engine. Your goal is to sync advance with fuel delivery. try different springs in the dizzy is the vacuum advance adjustable and maybe jet the carb different unitl you find the sweet spot. Your at the point start writing down what you do so you have a referance. Get a vacuum guage to adjust the idle air for max lean vacuum pressure or you can also use a tach for highest lean rpm. GL The best way to adjust the timing is to advance it until the engine pings at WOT around 50 mph then slowly back off on the timing until it stops pinging and then check it with a timing light for future referance. Then adjust the idle air you must adjust the idle air every time you adjust the timing.

 

[kimcrwbr1]

Sorry I meant 32 DBTDC max advance.

 

[Rowdy Fitzgerald]

Ok Thanks guys I'll get the Manual and start reading. Then I'll start from there. I appreciate the input.

 

[kimcrwbr1]

Go to ponycarbs there is alot of good info on tuning the 302.

 

[kimcrwbr1]

http://mustangforums.com/forum/clas...353-holley-570-carb-tuning-getting-there.html Interesting thread on the 570 holly

 

[Rowdy Fitzgerald]

Ok so I rebuilt the carb yesterday. It has more power but still lacks power. I'm thinking it might be my trany. I'm gonna swap it back to a manual trany. But that's all gonna have to wait till May when I get back home.

 

[Jfive]

Maybe you need a stroker motor. You have 35s on a ranger. Not gonna act like a race car when its setup to mud bog. C6 trannys are super stong, but not good for high rpms. They have such heavy parts the rotating mass is not good in high rpm setups. A lower rpm stroker motor would definatly help turn big tires, and help the tranny survive as your power band will shift lower. 570 seams a bit small, but you might want to get a narrow band o2 to see what your A/F is will idle, cruise, and under load. Also have you checked for vacumn leaks. I have had issues with that before causeing timing to be too high to make it idle ect.

 

[Rowdy Fitzgerald]

Jfive- my axels are re-geared to 4.56's which with 35's calculates to about stock tire size. I'm going to swap out the c6 for a ZF5 so I can get away from the power sucking c6. As for the carb I am not sure what I'm gonna do. Might swap it out for EFI. Would cost the same as a new carb but I don't have a computer to read the O2 censor and I don't want to spend the $ for one that has the read out you mount in the cab. Had issues with vac leaks and I already fixed them. No more leaks as far as I can tell.

 

[baddad457]

Jfive- my axels are re-geared to 4.56's which with 35's calculates to about stock tire size. I'm going to swap out the c6 for a ZF5 so I can get away from the power sucking c6. As for the carb I am not sure what I'm gonna do. Might swap it out for EFI. Would cost the same as a new carb but I don't have a computer to read the O2 censor and I don't want to spend the $ for one that has the read out you mount in the cab. Had issues with vac leaks and I already fixed them. No more leaks as far as I can tell.

The ZF is gonna take as much effort to turn as the C6 does. The 570 is not too small. Bigger is not better when it comes to a carb. The 570 is perfectly sized. You may have cam timing issues, who installed the timing set ? And how did they set it up ? As for the ignition timing, if you're running it on ported vacuum, you do not need to plug the vacuum hose nor disconnect it to set the initial timing. When the carb is idling, there will be no vacuum signal to ported vacuum. And you don't need an O2 sensor to adjust the carb's mixture (if it's jetted out of the box, it should be dead on for a 302) Learn to read the spark plugs. Grayish plugs are lean, blackish are rich. You're looking for a plug that looks as close to what it looks like "out of the box"

 

[Rowdy Fitzgerald]

Baddad457- I'm not sure on the timing. My sister assembled the motor. She worked at a mustang shop but that's the next thing I'm gonna check. It's pretty much gutless. I'm out of town for a couple more weeks so I can't work on it. I prefer a manuals trans though. The c6 was easy to come by so that's what I used. I like the thought of havin OD too. You wouldn't happen to know what the compression should be would you?

 

[baddad457]

Baddad457- I'm not sure on the timing. My sister assembled the motor. She worked at a mustang shop but that's the next thing I'm gonna check. It's pretty much gutless. I'm out of town for a couple more weeks so I can't work on it. I prefer a manuals trans though. The c6 was easy to come by so that's what I used. I like the thought of havin OD too. You wouldn't happen to know what the compression should be would you?

No way to estimate the comp ratio with a 302 that's been rebuilt and has aftermaket heads. Only way to know for sure is to pull the heads (head) and see what pistons are in there, measure the deck clearance and the chamber volume.