Decided against 347......

5.02GO · Sep 21, 2005

Titles says all...

Was going to purchase a 347 this winter. Have done alot of research and posted several threads. I knew i was going to have to upgrade to 42lb injectors. I almost got a set a few days ago. I decided to do a search an found out that you have to get that tweecer thing or that PMS deal. :damnit:

I am just not into dealing with the computer like that. Dont know what to set parameters at and all that. Dont understand the whole "tuning" thing.

SO, i am now considering a 306. Will i be just wasting money? Should i just get another 302?

I just dont know what to do. Any suggestions?

Oh, i am not into drag racing anymore. Just want a good street motor. Similar to what i have now, only BETTER.

I will be basically running my same setup that i have now. Mods are at the bottom. 5-6 psi on the novi.

Rick 91GT · Sep 21, 2005

You do not NEED a tuner, although it helps ANY COMBO make the power it is capable of.

Your wasting money buying a 306, if you have to buy internals go with a stroker it is free HP. With boost I would build a 331.....IMO

Just a builders opinion....

Should make over 425RWHP with a 331 and your above combo with 8psi. Plenty of power to break a stock block

Daggar · Sep 21, 2005

If you plan to run forced induction, you're going to need a tune regardless of what displacement you choose.

5.02GO · Sep 21, 2005

Rick 91GT said:
You do not NEED a tuner, although it helps ANY COMBO make the power it is capable of.

Your wasting money buying a 306, if you have to buy internals go with a stroker it is free HP. With boost I would build a 331.....IMO

Just a builders opinion....

Should make over 425RWHP with a 331 and your above combo with 8psi. Plenty of power to break a stock block

Well, i dont have a problem with a 331. Just figured extra power for same price, 347.

From what i've read, i need that tweecer or pms. I have read that people are unable to get their motor started and that they cant get it to go beyond 2000 with 42lb injectors.

I just thought you needed a calibrated mass air and the injectors.

Rick 91GT · Sep 21, 2005

I build them all the time, not everyone has a tuner... I recommend them to get the most of of the combo but they will run fine on the stock EEC.

For a boosted combo I'd go 331....

5.02GO · Sep 21, 2005

Rick 91GT said:
I build them all the time, not everyone has a tuner... I recommend them to get the most of of the combo but they will run fine on the stock EEC.

For a boosted combo I'd go 331....

Well sir, i surely hope your right. After i did a search about the 42's, i was like "now what am i gonna do"

So, shouldnt have any idle problems or extreme rich problems? I think someone even wrote that the "pulse width" or something was just too much with 42's.

Yeah, i have read some of your replies. I have read that you recommend 331 for boost applications.

Why? Is there any paticular reason? Just curious. I am still trying to learn these strokers. I might add that you are highly recommended for building strokers.

Thanks for the help..

5spd GT · Sep 21, 2005

Your going to get (N/A) rich problems with 42lbers...but with boost anyway you will want a dyno tune or something similar.

Daggar · Sep 21, 2005

5.02GO said:
Well sir, i surely hope your right. After i did a search about the 42's, i was like "now what am i gonna do"

So, shouldnt have any idle problems or extreme rich problems? I think someone even wrote that the "pulse width" or something was just too much with 42's.

Yeah, i have read some of your replies. I have read that you recommend 331 for boost applications.

Why? Is there any paticular reason? Just curious. I am still trying to learn these strokers. I might add that you are highly recommended for building strokers.

Thanks for the help..

Something that you may be overlooking in this scenario is that with a N/A 347, you're likely not going to need injectors as large as 42s. I'd bet a dollar that you can do just about everything that N/A stroker can do with 30s.

5.02GO · Sep 21, 2005

Daggar said:
Something that you may be overlooking in this scenario is that with a N/A 347, you're likely not going to need injectors as large as 42s. I'd bet a dollar that you can do just about everything that N/A stroker can do with 30s.

347 with 5-6psi and use 30's? I definetly dont want to use an FMU. I think they are junk.

Here is the deal with a "tune". I dont know of where i can get a tune where i live. I dont know enough about it to actually use a pms or tweecer. However, guess no one does until they try.

What about using lower fuel pressure to use with 42's?

Thanks again.

Grn92LX · Sep 21, 2005

Daggar said:
Something that you may be overlooking in this scenario is that with a N/A 347, you're likely not going to need injectors as large as 42s. I'd bet a dollar that you can do just about everything that N/A stroker can do with 30s.

Last time I checked my PMS at appx 5,000 rpm I was @ 70% duty cycle. I have not looked at 6,500pm what it is, but I bet its near the safe limit of the injector which is appx 80% from what I have read. I will have to get the girl to look at the duty cycle next time I have the car out. I don't like going fast and not looking at the road. This is at stock fuel pressure though, i'm sure if I raised it, i'd lower the duty cycle a tad.

I'd be looking at a 42lb if I had more head, cam and I was spinning higher.

By the way Rick, I gotta get this f'n thing to the track!

Daggar · Sep 21, 2005

5.02GO said:
347 with 5-6psi and use 30's? I definetly dont want to use an FMU. I think they are junk.

Here is the deal with a "tune". I dont know of where i can get a tune where i live. I dont know enough about it to actually use a pms or tweecer. However, guess no one does until they try.

What about using lower fuel pressure to use with 42's?

Thanks again.

Sorry, I skimmed through the other posts and didn't see reference to your intention to use forced induction. I don't blame your not wanting to use an FMU.

Edit: As far as your not being able to tune it well... With the PMS and a wideband, I don't think that you'd have much difficulty figuring it out.

Daggar · Sep 21, 2005

Grn92LX said:
Last time I checked my PMS at appx 5,000 rpm I was @ 70% duty cycle. I have not looked at 6,500pm what it is, but I bet its near the safe limit of the injector which is appx 80% from what I have read. I will have to get the girl to look at the duty cycle next time I have the car out. I don't like going fast and not looking at the road. This is at stock fuel pressure though, i'm sure if I raised it, i'd lower the duty cycle a tad.

I'd be looking at a 42lb if I had more head, cam and I was spinning higher.

By the way Rick, I gotta get this f'n thing to the track!

The other thing worth mentioning is that the 80% you mention is for steady state operation under power. It's a safe zone so that you have the other 20% for WOT bursts. In other words: If you're running WOT / balls to the wall an JUST reaching 80% duty cycle then you're GOLDEN! You've got all kinds of injector left.

Grn92LX · Sep 21, 2005

Andy I was under the impression that appx 80% duty cycle is the max you wanna see at WOT? I will have to see what duty cycle i'm at, at 6,500 rpm just for personal knowledge.

These 30's will do me fine, I can't afford head porting and all that other crap I'm trying to save for the future so I can be an old family man like you

kck6894 · Sep 21, 2005

I have never used a Tweecer but I have a PMS and they are very simple. You will get a start-up program when you buy it that will get you close enough to run and drive. After that you can fiddle with it till you have a little better understanding of how it works. If you have a wideband to go with it you shouldn't have any problems weather your computer literate or not.

Killer50stang · Sep 21, 2005

Rick 91GT said:
You do not NEED a tuner, although it helps ANY COMBO make the power it is capable of.

Your wasting money buying a 306, if you have to buy internals go with a stroker it is free HP. With boost I would build a 331.....IMO

Just a builders opinion....

Should make over 425RWHP with a 331 and your above combo with 8psi. Plenty of power to break a stock block

Rick,

Still interest in a 347 too, what can my combo make?

Daggar · Sep 21, 2005

Grn92LX said:
Andy I was under the impression that appx 80% duty cycle is the max you wanna see at WOT? I will have to see what duty cycle i'm at, at 6,500 rpm just for personal knowledge.

These 30's will do me fine, I can't afford head porting and all that other crap I'm trying to save for the future so I can be an old family man like you

I think that the 80% rule is mostly overgeneralized. There's actually a load scale that goes along with that 80%. Example: 80% injector duty cycle + 90% of engine load = safe injector zone. The idea though, is not to end up at the peak of your engine's ability to use that gas and run out of injector. So if you've still got 20% of your injector left and you've got the car wound up as tight as it will go then you're not going to run out of gas and lean out. As I'm sure you're already aware, at 80% duty cycle the injector is open 80% of the time and closed 20% of the time. No harm can be done tothe injector just by leaving it open longer. It's a good rule to follow so that you're don't find yourself in a position where 100% duty cycle won't give you enough fuel to keep your AFR where you put it.

TC93 · Sep 21, 2005

5.02GO said:
From what i've read, i need that tweecer or pms. I have read that people are unable to get their motor started and that they cant get it to go beyond 2000 with 42lb injectors.

I just thought you needed a calibrated mass air and the injectors.

I ran a blown 331 with no FMU, 42# injectors,with 10#'s of boost on a stock computer(A9P), to a best of 11.19. A chip or tuning probably would of helped, but didn't want to mess with anything at the time. I did have a ignition box and a boost timing retard box though. I ran 40#'s of fuel pressure and and took out about 1 to 1.5* of timing per pound of boost just to be safe. Just make sure you have decent fuel pump(s). I ran 255HP intank and T-rex inline.

A chip and dyno tune would of been nice bt I didn't want to spend $700+ at the time. The one problem I did have was a start up, the car would idle uo for a second or two when I 1st cranked it up.

mfewtrail · Sep 22, 2005

Grn92LX said:
Andy I was under the impression that appx 80% duty cycle is the max you wanna see at WOT? I will have to see what duty cycle i'm at, at 6,500 rpm just for personal knowledge.

These 30's will do me fine, I can't afford head porting and all that other crap I'm trying to save for the future so I can be an old family man like you

What kind of fuel pressure are you running with the 30# injectors in there? Just wondering.

Grn92LX · Sep 22, 2005

mfewtrail said:
What kind of fuel pressure are you running with the 30# injectors in there? Just wondering.

Stock fuel pressure, appx 39psi. All my fuel needs is done the right way, through a tuning device. I have a afm pms and a wideband

stangbear427 · Sep 22, 2005

5.02GO said:
Yeah, i have read some of your replies. I have read that you recommend 331 for boost applications.

Why? Is there any paticular reason? Just curious. I am still trying to learn these strokers. I might add that you are highly recommended for building strokers.

Excellent rod ratio. Also, a 331 adds some good cubic inches without the long stroke of the 347, so theoretically it should rev up quicker. With a centrifugal blower (like a Novi) boost is directly related to RPM's, so the faster you can rev up into your powerband the better. N/A I would go 347 for the extra kick, but with boost it won't be necessary, or necessarily beneficial. Your current heads and intake are also better sized for a 331 than a 347, although I'm sure they would perform admirably on either.

Grn92LX said:
Stock fuel pressure, appx 39psi. All my fuel needs is done the right way, through a tuning device. I have a afm pms and a wideband

Daggar said:
I don't blame your not wanting to use an FMU.

Edit: As far as your not being able to tune it well... With the PMS and a wideband, I don't think that you'd have much difficulty figuring it out.

:OT: sorry:
Am I to understand that a PMS will do the job of an FMU? (what's so bad about FMU's?) I have a complete Aeromotive fuel system from tank to rails waiting to go in, the only part I don't have is an FMU and this system is a huge overkill for my current combo so I thought I needed one. Before this engine blows and the big one goes in, I'll be adding an Anderson PMS and Eugo... any thoughts?

Decided against 347......

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