What will my 340 run? and what intake and carb?

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mshred

mshred

The Green Manalishi
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Hey guys,
my dad finally found the build sheet for his 340 (will be my motor)...It has been bored .30 over with forged sealed pro pistons, 10.5:1 compression ratio, crank journals turned down .20". The cam is a comp grind (very old part # CRS 280H-10) that specs out with a gross valve lift of .480 int/exh, with a duration at .06 tappet lift of 280 int/exh with lsa of 110 degrees (its a high energy model but not sure as to what type of cam). I planned on runing this motor with heddman 1-5/8 inch headers, into a 3 inch x pipe exhaust with either borla xr-1 or dynomax ultraflow mufflers dumped at the axle. The heads are stock x heads with aftermarket valvesprings added, and they are slightly home ported by my dad...with a thermoquad, and open 2.76 8-3/4, and 727 manual vb with stock converter my dad ran 14.2 with this motor in a 78 aspen... So i have a few questions if you guys dont mind helping me- im very interested to hear your opinions

first off, what intake manifold and carb do you guys recommend? I was thinking rpm performer air gap or an M1 single plane, but not sure about carb...i think 650 would be good (this car will be seeing the street 95% of the time), but was thinking of maybe using the Holley 3310 (750 VS carb) since it will be mainly a street car (my only concern is that my car is stick and may suffer from VS limitations when shifting gears??)

Second, what do you guys think the car will run in the 1/4? It is minitubbed, with a 28x12 inch street/strip tire, 3.91 suregrip rearend, t5 manual tranny with 3.35 first gear (giving me an overal first gear ratio of 13.1), pinion snubber, either SS springs or stiffened factory springs, slant six t bars, no ac...I figure the car will weigh in around 3300-3500 hundred pounds...Will have the above mentioned motor, with some combination of intake and carb as well (decided by your help)...any projected outputs for it? I think it should run around a 13.2...does that sound optimistic? pessimistic? interested to hear what you guys have to say


this car will be my daily driver (I know she's gonna be a pig on gas) with track outings only a couple of times a year- however, performance on the street is very important for me, dont ask why:lol:...any recommendations you guys have or any info that im leaving out for you guys to help me let me know

thanks
Matthew:thumbup:
 
Well Matthew, I'd say your being realistic on the 1/4 mile times that you would like to achieve. Id say that there is nothing wrong with the intake and carb. that is presently on the motor. Is it just a stock cast iron and thermo quad?? I'm not really experienced with the 340's. I've never owned one. But with what the motor has in it I'd say that the 13's should be realistic. Another, Matthew
 
A 1971 factory 340 ran 13.91; factory tires, etc, 3.91 posi, no headers; auto, everything factory. I saw it. Ran it 4 times.
 
Hey man I have a 340 in my duster. I like an eldebrock super victor intake and a good 750 carb be it holley or whatever you like I run a proform. I think that your gear choice is great for street and strip but if you are going to run strip more than street i would run a 456 or 488. When I got my car it had the same headers you are planing on running they are ok, kind of a wire burner and makes changing plugs a pain. I moved up to the 1 7/8 but they rap the frame (disadvantages to both). I think that you are close to right on what you are thinking it will run in the quarter. The one thing that I would tell you to do different than I did is to save for the good parts and not subsitute with something that won't get you what you want if performance is what you are after.
 
forgot to mention that the motor used to be shifted at just a little over 6k...i was planning on shifting it at around say 6200 rpm...the block is a 69 block with forged crank as well...there is no carb for it right now, but the stock iron intake is still intact...I have to get a carb (the tq is in peices all over the place) so if i do get a carb its going to have to fit the intake, which means new intake...will also be running a 2 step on the motor as well, but not sure what rpm i should leave at...clutch setup will be something from ram or mcleod with a billet steel flywheel...going by the mopar chassis manual i estimate about 13.2, but im curious to hear what you guys have to say
 
Heim said:
Hey man I have a 340 in my duster. I like an eldebrock super victor intake and a good 750 carb be it holley or whatever you like I run a proform. I think that your gear choice is great for street and strip but if you are going to run strip more than street i would run a 456 or 488. When I got my car it had the same headers you are planing on running they are ok, kind of a wire burner and makes changing plugs a pain. I moved up to the 1 7/8 but they rap the frame (disadvantages to both). I think that you are close to right on what you are thinking it will run in the quarter. The one thing that I would tell you to do different than I did is to save for the good parts and not subsitute with something that won't get you what you want if performance is what you are after.
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vacuum or mechanical secondaries? I want to move up to a 4.56 gear, but i just got a set of mint 3.91's for dirt cheap so i kinda feel dumb not using them...like i said, this trannies first gear is a 3.35 as opposed to a 2.65 first in a mopar 4 speed, so im thinking i have enough gear for now...the beauty of this setup is that i dont really have to touch the motor for now since its already been mildly reworked...just bolt on an intake and carb, tweak the suspension a little and go! whats your duster run?
 
As it will be driven a lot on the street on Ontario weather I'd get an RPM performer intake and a 650dp Speed Demon carb with electric choke.
They will work great on your combo.
 
I run a vaccum secondary but it is really what your more comfortable with I have ran both and didn't see much of a difference.
 
I think it depends on your shifting and how well the T5 (World Class?)trans holds up. You should be making enough to break it if the car hooks. I would stay away from the single plane intakes. I like that cam choice. Yes, it's old, but the series worked very well. So I'd go RPM or Air Gap, I prefer vacuum sec carbs to double pumpers for street cars. Tuned properly, there are no issues running a stick. I think you have the oppoertunity to run faster than 13.20s, but it will depend on the tuning, suspension, and shifting.
 
Thanks for the info moper...i know the t5 is notorious for breaking, but its also notorious for luckily holding up...I dont have a slipper clutch in mind, but im hoping that tire spin will help the tranny live a little. The air gap intake was my first choice for an intake...what carb do you recommend? and what size? vacuum secondaries does seem to make more sense for a street car, but what would you recommend for a dp as well? Good to know that the cam im running fares well by an experienced mopar guy, so i guess im good there...didnt plan on changing it anyways since it seems like just enough cam for me right now...with the suspension setup i plan to run (ss springs and snubber), nailing down my shifting, and some good tuning, whats an optimistic number that you could see being possible?
 
How much tire slip do you think you will have with a 12" wide drag radial?

You are going to grenade your transmission.

BTW My 340, 4 speed runs 13.2 @ 105mph through manifolds turning old skinny Bias Ply E70-14 Tires.

13.2 should be realistic without some of the mods in your build.
 
no drag radials, bias plies...also, with my overall first gear ratio there is quite a possbility for it in my opinion...your so sure that im going to grenade the tranny, but neither you or i know what will happen for real, so for now we'll see what happens- there are just as many guys flying with bone stock t5's into the low 11's as there are guys breaking them, so its all luck of the draw...hoping that im on the lucky side...thats why im also going with a clutch that will slip a little more to help out there as well...I too think that if i can nail the shifts i can run faster than 13.2, but curious as to anyone elses speculation for an e/t...what do you mean when you say realistic without some of my mods?
 
Well, this is what I would do following your guide line of 95% street.

IF your going to use the T-Q, put it on top of a Weiand Action Plus intake. It's designed for the T-Q's secondaries huge size.

IF your going with a new carb, a squarebore, a RPM intake would be my choice. Ethier cabr size will work well. I'd just would get a double pumper. Because it is a manual tranny.
My personal choice would be a 650 cfm.

When you get to the track, try shifting at different RPM's and see what your times are. Pay attention to your 60 ft. times and every thing else on the slip. With the cam you have now, I don't see much of a reason to shift above 6,000 rpm's.
 
With a stick car, I'd get a double pumper. A 650 should be just about perfect. Quickfuel makes a good carb for a good price.

Clutch has everything to do with a) hook and b) transmission life expectancy.
I would research this very carefully. A hard hitting clutch is going to suck to drive on the street, shock the tires too hard, and dramatically shorten your transmission's life. Mcleod makes some really excellent single disk diaphragm clutches (for Mustangs anyway).

I don't think low 13s is overly optimistic. It sounds like you're going to have the horsepower to run mid 12s, if you get the chassis squared away.

Steve
 
LXguy said:
With a stick car, I'd get a double pumper. A 650 should be just about perfect. Quickfuel makes a good carb for a good price.

Clutch has everything to do with a) hook and b) transmission life expectancy.
I would research this very carefully. A hard hitting clutch is going to suck to drive on the street, shock the tires too hard, and dramatically shorten your transmission's life. Mcleod makes some really excellent single disk diaphragm clutches (for Mustangs anyway).

I don't think low 13s is overly optimistic. It sounds like you're going to have the horsepower to run mid 12s, if you get the chassis squared away.

Steve
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your a 5.0 guy right? do you think the t5 is going to hold up behind this setup?
 
I'd go with a 750vs for your setup myself. Or a 670 Street Avenger VS.

As far as it holding up.. your car is heavier than the Fox body... closer to the Camaro... And those tires are not going to turn once...lol. So be careful on the leaves. That 340 at 3500rpm will be able to make the torque to break it should you not break the driveshaft and the tires hook. They will last forever when driven smartly. They will explode when really thrashed. The world class is a little better. I'm not sure why, but I think the published load limit on it is like 400 pound feet or something. The Fox Mustangs only made about 250 stock. I had a friend who raced a roots blown 302 for two years. He broke 4 world class ones leaving at 3500 and making 500 or so feet of torque. The car when working would run low 11s. Dont plan to drop the clutch at 4K, don't power shift it, just learn to use the clutch and shift smoothly. Also, you may find starting out in 2nd and running out 4th to be a good thing. You lose time every time you shift, and 1st gear will be gone before the car moves 60'.
 
mshred said:
your a 5.0 guy right? do you think the t5 is going to hold up behind this setup?
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Depends I guess. Like I said, the clutch makes a huge difference. I'd really eyeball that. I don't know what kind of clutch gets used in these 5 speed swaps. If you can use a Mustang clutch I know exactly what you need. Additionally, there are a lot of year to year differences in T-5s. The 80s models are horribly fragile. I think a lot of the bad rap these trannies get is based on the crappy early models.

Most often, in any year, its 3rd gear that has the issues.

Get a good shifter. Back in the day anyways, lots of guys were bending and breaking shift forks from over-shifting. Of course the early shift forks were cast instead of bronze.

You also want a good synthetic fluid that has lots of anti-clash additives. Something like Red Line MTL or Royal Purple Synchromax would be my recommendation.

It seems to me like these things last a lot longer when they're power-shifted than when they're speed or granny shifted. But, you've got to have the clutch set up right, or you'll destroy it fast.

You'll also give up miles of ET from starting in 2nd. The torque multiplication from the low first gear is worth a ton. Hell, the 3.35 first is worth ET over the 2.92. First gear is also the strongest gear in the transmisson. Unless you've got a gigantic cog in that car or are shifting below 5500 RPM, you'll go past the 60' before the first to second shift.

Most of the street/strip Fox cars weigh around 3100-3200 pounds. I can't believe a Scamp is going to weigh more than that, especially with a T-5. My Dart sure doesn't.

A buddy of mine has a Fairmont wagon (5.0 Mustang in granny clothes). He runs a stock T-5 with a built 302 with nitrous. He runs 7.20s in the 1/8th, and gets a lot of passes out of a transmission.

To be honest, its always a crapshoot, unless you've got one of the new G-force or Astro built T-5s, but with a good model to start with and some care, you can get a lot of use out of one of them.

Steve
 
LXguy said:
Depends I guess. Like I said, the clutch makes a huge difference. I'd really eyeball that. I don't know what kind of clutch gets used in these 5 speed swaps. If you can use a Mustang clutch I know exactly what you need. Additionally, there are a lot of year to year differences in T-5s. The 80s models are horribly fragile. I think a lot of the bad rap these trannies get is based on the crappy early models.

Most often, in any year, its 3rd gear that has the issues.

Get a good shifter. Back in the day anyways, lots of guys were bending and breaking shift forks from over-shifting. Of course the early shift forks were cast instead of bronze.

You also want a good synthetic fluid that has lots of anti-clash additives. Something like Red Line MTL or Royal Purple Synchromax would be my recommendation.

It seems to me like these things last a lot longer when they're power-shifted than when they're speed or granny shifted. But, you've got to have the clutch set up right, or you'll destroy it fast.

You'll also give up miles of ET from starting in 2nd. The torque multiplication from the low first gear is worth a ton. Hell, the 3.35 first is worth ET over the 2.92. First gear is also the strongest gear in the transmisson. Unless you've got a gigantic cog in that car or are shifting below 5500 RPM, you'll go past the 60' before the first to second shift.

Most of the street/strip Fox cars weigh around 3100-3200 pounds. I can't believe a Scamp is going to weigh more than that, especially with a T-5. My Dart sure doesn't.

A buddy of mine has a Fairmont wagon (5.0 Mustang in granny clothes). He runs a stock T-5 with a built 302 with nitrous. He runs 7.20s in the 1/8th, and gets a lot of passes out of a transmission.

To be honest, its always a crapshoot, unless you've got one of the new G-force or Astro built T-5s, but with a good model to start with and some care, you can get a lot of use out of one of them.

Steve
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Hey steve,

i really really appreciate your insight here...As far as clutch goes, its going to be a mopar pressure plate with the 10.5" 10 spline ford clutch disk..What is the clutch that you recommend? i dont really want to go dual friction since they are expensive, plus i think the holding power might kill the tranny a little quicker..i was looking into either a ram or mcleod unit...My t5 came out of a 90 mustang, which had the 300lb/ft rating (highest besides z spec i think)...I hear some guys say they are rated more, but im not sure...I was definatly going to invest in a good shifter with adjustable stops...whats the difference of speed shifting and granny shifting from powershifting? i hear powershifting is the worst thing you can do for a t5- your probably the second guy who told me its okay lol...I really do like the fact of the 3.35 first gear, and yes i wouldnt start in 2nd, dont care how good for the tranny it is...I mean you hear of a lot of guys running them no problem, and then alot running them and always breaking...what worries me is the size tire im going to have (28x12) and the power and weight of my car...I thought a stock fox body is around 2800? my scamp will be atleast 3300 with me in it, as i havent removed anything from it to lighten it (ive actually added with the stereo system and such)...have you had any luck with g-force or astro t5 stuff before?
 
mshred said:
Hey steve,

i really really appreciate your insight here...As far as clutch goes, its going to be a mopar pressure plate with the 10.5" 10 spline ford clutch disk..
What is the clutch that you recommend?
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Well, these guys do a Mcleod "custom" pressure plate and clutch disk for Mustangs that is simply awesome. They do sell the disk separate.

www.promotionpowertrain.com

Basically you want the "stage 1" Mcleod disk that goes with their red pressure plate (in a Mustang). Sadly I'm no help on the Mopar pressure plate. Maybe ask them what series the Mcleod pressure plate they use is, and get the Mopar version. That would be my best guess. The kit they sell for the Mustangs is awesome. Lower than stock pedal effort, and it held a 550 rwhp supercharged 5.0 for two years of constant passes. Replaced the disk and its still in there. Spec also makes good clutches, but historically I found them to be harder hitting than this Mcleod deal. Its been years though, and I've heard Spec has changed.

mshred said:
whats the difference of speed shifting and granny shifting from powershifting? i hear powershifting is the worst thing you can do for a t5- your probably the second guy who told me its okay lol...
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Power shifting is where you don't lift your foot off the gas when you shift. You DO use the clutch (if you don't, you'll really tear stuff up). It takes practice, but doing it right is worth about .2 in the quarter. It also helps keep the car from unloading the tires between 1st and second. Again, this works in a cable clutch mustang. You'd probably have to have a Z-bar setup dialed to make it work well.

Speed shifting is about what you'd expect. Letting off the gas and shitfting as fast as you can. Granny shifting is the slowest possible, most careful way to do it.

mshred said:
what worries me is the size tire im going to have (28x12) and the power and weight of my car...I thought a stock fox body is around 2800? my scamp will be atleast 3300 with me in it, as i havent removed anything from it to lighten it (ive actually added with the stereo system and such)...have you had any luck with g-force or astro t5 stuff before?
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That is a LOT of tire. Your probably at as much risk from bogging the car as anything else.

I've built a bunch of Mustangs and I can assure you (other than maybe a no option Fairmont post car) NO fox chassis comes close to weighing that little stock. A Fox GT in stock form typically goes 3400+, and the LX notchback is 100 to 150 pounds lighter. You don't get them down to 2800 pounds without some serious efforts (light racing wheels, tube front suspension, aluminum heads, race seats, pull the AC, power steering, aluminum heads, driveshaft, gut the sound deadening, etc).

Weight does play a role, but it's not like your car is super duper heavy by comparison.

As for luck with the G-force stuff, in a word, YES. Those transmissions are awesome. The 3.35 gear first was crap (they don't offer it anymore) , but the 2.92 had no issues. I have several friends running them on my recommendation. An 11.70 car with 200 passes (over 3 years) and no trans work needed, the previously mentioned supercharged car, etc. these are fuly synchronized street transmissions.

I used to run a heads-up race car in NMRA Pure Street. 2003 I went through 3 TKOs. 2004 I ran the G-force T-5 all year. Had to raise the launch RPM from 400 RPM because of the first gear issue, but other than that no troubles at all. This was a very high RPM car at 3200 pound race weight (shift point at 8000 very often). T-5 Also shifted a helluva lot better than the TKO. Quit racing the circuit the next year, but the trans continued to soldier on for another couple of years in limited use before I sold it.

These days they are about $2200 (synchro) from vendors like Pro Motion.

Steve
 
The World Class IIRC was after '88, so you've got the better one. I've never heard slower shifting hurts a T5. But I'm not into Fords...lol.
 
I'm not a transmission CSI guy, but my theory is that the herky-jerky loading and unloading is what gets them, whereas with proper power shifting the trans is pretty much loaded all the time.
 
LXguy said:
Well, these guys do a Mcleod "custom" pressure plate and clutch disk for Mustangs that is simply awesome. They do sell the disk separate.

www.promotionpowertrain.com

Basically you want the "stage 1" Mcleod disk that goes with their red pressure plate (in a Mustang). Sadly I'm no help on the Mopar pressure plate. Maybe ask them what series the Mcleod pressure plate they use is, and get the Mopar version. That would be my best guess. The kit they sell for the Mustangs is awesome. Lower than stock pedal effort, and it held a 550 rwhp supercharged 5.0 for two years of constant passes. Replaced the disk and its still in there. Spec also makes good clutches, but historically I found them to be harder hitting than this Mcleod deal. Its been years though, and I've heard Spec has changed.



Power shifting is where you don't lift your foot off the gas when you shift. You DO use the clutch (if you don't, you'll really tear stuff up). It takes practice, but doing it right is worth about .2 in the quarter. It also helps keep the car from unloading the tires between 1st and second. Again, this works in a cable clutch mustang. You'd probably have to have a Z-bar setup dialed to make it work well.

Speed shifting is about what you'd expect. Letting off the gas and shitfting as fast as you can. Granny shifting is the slowest possible, most careful way to do it.



That is a LOT of tire. Your probably at as much risk from bogging the car as anything else.

I've built a bunch of Mustangs and I can assure you (other than maybe a no option Fairmont post car) NO fox chassis comes close to weighing that little stock. A Fox GT in stock form typically goes 3400+, and the LX notchback is 100 to 150 pounds lighter. You don't get them down to 2800 pounds without some serious efforts (light racing wheels, tube front suspension, aluminum heads, race seats, pull the AC, power steering, aluminum heads, driveshaft, gut the sound deadening, etc).

Weight does play a role, but it's not like your car is super duper heavy by comparison.

As for luck with the G-force stuff, in a word, YES. Those transmissions are awesome. The 3.35 gear first was crap (they don't offer it anymore) , but the 2.92 had no issues. I have several friends running them on my recommendation. An 11.70 car with 200 passes (over 3 years) and no trans work needed, the previously mentioned supercharged car, etc. these are fuly synchronized street transmissions.

I used to run a heads-up race car in NMRA Pure Street. 2003 I went through 3 TKOs. 2004 I ran the G-force T-5 all year. Had to raise the launch RPM from 400 RPM because of the first gear issue, but other than that no troubles at all. This was a very high RPM car at 3200 pound race weight (shift point at 8000 very often). T-5 Also shifted a helluva lot better than the TKO. Quit racing the circuit the next year, but the trans continued to soldier on for another couple of years in limited use before I sold it.

These days they are about $2200 (synchro) from vendors like Pro Motion.

Steve
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Hey Steve,

i will definatly look into going with the Mcleod clutch. There back under old management now too, which means better tech help and prices. What you are saying about powershifting makes sense since regular shifting is an on/off shock on the tranny, its just kinda funny since everyone says dont powershift a t5...i want to be able to powershift it without being scared of breaking since powershifting is funner and faster:toothy10: When you talk about tire size and bogging the car, what exactly do you mean by that? ive heard about bogging down before, but not sure what that is...does it mean i have to leave at a higher rpm? what rpms does your buddy with the fairmont leave at, and what does it turn in the 1/4? or is only an 1/8th mile car? I figure my car is around 3400 pounds, and if stock 5.0 weighs that much and the t5 can handle that plus upgrades, then i guess i should be okay...thanks for the info on the g-force stuff, i hear alot of mixed opinions on it (as with anything else)...I really appreciate your help and input- i hear alot of guys telling me i will be fine, but every once in a while the bad stuff i hear really worries me and makes me wonder if the whole t5 thing was a good idea...
 
mshred said:
Hey Steve,

i will definatly look into going with the Mcleod clutch. There back under old management now too, which means better tech help and prices. What you are saying about powershifting makes sense since regular shifting is an on/off shock on the tranny, its just kinda funny since everyone says dont powershift a t5...i want to be able to powershift it without being scared of breaking since powershifting is funner and faster:toothy10: When you talk about tire size and bogging the car, what exactly do you mean by that? ive heard about bogging down before, but not sure what that is...does it mean i have to leave at a higher rpm? what rpms does your buddy with the fairmont leave at, and what does it turn in the 1/4? or is only an 1/8th mile car? I figure my car is around 3400 pounds, and if stock 5.0 weighs that much and the t5 can handle that plus upgrades, then i guess i should be okay...thanks for the info on the g-force stuff, i hear alot of mixed opinions on it (as with anything else)...I really appreciate your help and input- i hear alot of guys telling me i will be fine, but every once in a while the bad stuff i hear really worries me and makes me wonder if the whole t5 thing was a good idea...
Click to expand...

I think a lot of people think that powershifting means not using the clutch, and that WILL tear things up fast.

He drives the wagon 50 miles each way to the track. I don't think he's ever run it 1/4 mile, but he will be at Pinks All Out in Indy at the end of May. I guess we'll find out.

Good luck with it, just remember its not my fault if you're walking home! LOL!

Steve
 
well goodluck to him...now i appreciate your advice, but i wont hold you liable no worries lol...but in your honest opinion, you havent really said if you think she'll hold up...whats your opinion on that- coming from a mustang guy? you think it'll hold or it'll crap out...i know you cant be sure, just interested to hear what you think...thanks for the help so far, its been great info
 
Matthew,let me know when you get your car up and running?And your first trip to the track.It takes some experience,so don,t expect to much your first few attempts.Bring your toolbox cause you,ll want to be doing some adjustments!See ya at the track!
 
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