D100 400 tuck motor build
06-29-2009, 09:15 PM
#1
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D100 400 tuck motor build
So i just picked up a 73 D100 with a 400 and have already ordered a Performer intake and a Holley street avenger 670cfm carb. The engine runs strong with no smoking or signs of any problems.
I'm already thinking about my next upgrade (my GF is pitching in for my B-day, so why not....) Both my exhaust manifolds leak and need new gaskets so I'm naturally thinking about headers and new exhaust. I'm having a hard time locating parts but today I found a full exhaust from summit that uses Dynomax headers and mufflers with 2 1/4" exhaust tubing for about $360, they said it will fit my 73. The headers are 1 3/4" with 3" collectors but I'm thinking 2 1/4" maybe too small, I was already planning on running 2 1/2" since I don't plan on any other upgrades besides an eventual cam.
On the other hand I think a cam would give me a better bang for my buck and on top of that I'm wondering if a 670 is too big with just an intake and full exhaust. I'm looking at Comp's 220/234 .477/.488 from 440Source
Keeping in mind I want a solid reliable hard working truck and not some street machine to haul ***** in, I'm I headed in hte right direction going Exhaust first? I do wanna get on it a little bit...
670cfm fine with just an intak/exhaust combo?
That Summit kit garbage? 2 1/4" too small?
Sorry for the long post.
TIA
I'm already thinking about my next upgrade (my GF is pitching in for my B-day, so why not....) Both my exhaust manifolds leak and need new gaskets so I'm naturally thinking about headers and new exhaust. I'm having a hard time locating parts but today I found a full exhaust from summit that uses Dynomax headers and mufflers with 2 1/4" exhaust tubing for about $360, they said it will fit my 73. The headers are 1 3/4" with 3" collectors but I'm thinking 2 1/4" maybe too small, I was already planning on running 2 1/2" since I don't plan on any other upgrades besides an eventual cam.
On the other hand I think a cam would give me a better bang for my buck and on top of that I'm wondering if a 670 is too big with just an intake and full exhaust. I'm looking at Comp's 220/234 .477/.488 from 440Source
Keeping in mind I want a solid reliable hard working truck and not some street machine to haul ***** in, I'm I headed in hte right direction going Exhaust first? I do wanna get on it a little bit...
670cfm fine with just an intak/exhaust combo?
That Summit kit garbage? 2 1/4" too small?
Sorry for the long post.
TIA
06-29-2009, 09:37 PM
#2
Admin
I installed, well more like tried to install, a summit racing exhaust on my 78 D200. Never again. I would rather have installed the headers and have a professional exhaust shop do the rest.
Since your manifolds are leaking, I'd do the exhaust first. You have a good running motor, the 1 3/4" tubes will be good for it, and 2 1/2" pipes will be great for low to mid power which will match up with the Performer intake nicely. The 670 is just fine for that 400 also.
Since your manifolds are leaking, I'd do the exhaust first. You have a good running motor, the 1 3/4" tubes will be good for it, and 2 1/2" pipes will be great for low to mid power which will match up with the Performer intake nicely. The 670 is just fine for that 400 also.
06-29-2009, 09:39 PM
#3
Admin
I'd hold off on the cam for the time being. At least til you are ready to pull the motor and freshen it up. At that time, I'd look for a good tow/RV cam for it since you will be using it as a truck.
06-29-2009, 10:18 PM
#5
Admin
The kit was a PITA to install, some of the pipes did not fit right, but the quality was great. With how many kits there are out there and the price of having an exhaust shop do it, I wish I spent the extra $200 on having a local exhaust shop do the work for me. It would have saved me a lot of time and headaches.
2 1/4" pipes are good for small block motors that have little to no upgrades. Big block motors shouldn't run on anything less that 2 1/2" pipes in my opinion (minus from the factory). A lot of people install performance carbs, intakes, and air filters because they are easy to do in the driveway. With a good amount of air going in, you'll want it to have enough room to be able to be pushed out, otherwise, what's the point of the upgrade. I'd get the headers and then take the truck to an exhaust shop and have them make up/install a kit for you. They will make sure that everything is supported and fitting just right.
2 1/4" pipes are good for small block motors that have little to no upgrades. Big block motors shouldn't run on anything less that 2 1/2" pipes in my opinion (minus from the factory). A lot of people install performance carbs, intakes, and air filters because they are easy to do in the driveway. With a good amount of air going in, you'll want it to have enough room to be able to be pushed out, otherwise, what's the point of the upgrade. I'd get the headers and then take the truck to an exhaust shop and have them make up/install a kit for you. They will make sure that everything is supported and fitting just right.
06-29-2009, 11:30 PM
#7
Admin
If you can find a kit that is 2 1/2" or even 3" I'd go with that. I had issues with the kit that I had going up and over the rear axle and turning out all at the same time. Maybe it was just me though.
06-30-2009, 12:47 PM
#10
Admin
With just a full exhaust kit? Towing will be a little easier as the motor is allowed to breathe better. You should feel a little something but nothing major. Once you add on the intake, carb and a good air intake, you should nothing better throttle response, more power throughout the RPM range, maybe less gas mileage but nothing bad. the positives definitely outweights the negatives.
07-02-2009, 10:12 AM
#11
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That sounds like what I was expecting. Not to call anyone out but just saying I have my doubts but when I talked to a vendor they were telling me I would see about 40-60 with just the intake and 390-420 with intake/exhuast/mild cam.
Anyway, I checked the compression across the cylindrs the other day and came back with 95-120, that's more of a spread then I was hoping for. I'll see how the engine performs after some time, if it's suspect I'll do a leak down test on it. I did have 2 plugs that were pretty folwed with oil (both were 120) after pulling the intake and valley pan it looks like oil was getting in from under the pan and fowling them up. I'll have the new gaskets in and everything bolted up later today.
Can I get the title of this thread changed to "D100 400 tuck motor build"?
Thanks.
Anyway, I checked the compression across the cylindrs the other day and came back with 95-120, that's more of a spread then I was hoping for. I'll see how the engine performs after some time, if it's suspect I'll do a leak down test on it. I did have 2 plugs that were pretty folwed with oil (both were 120) after pulling the intake and valley pan it looks like oil was getting in from under the pan and fowling them up. I'll have the new gaskets in and everything bolted up later today.
Can I get the title of this thread changed to "D100 400 tuck motor build"?
Thanks.
07-02-2009, 11:53 AM
#13
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LOL, yeah. I'm sure I sounded like I didn't know about motors but iwas just trying to figure out where the weak link is in the 400 truck motor since it's a new motor to me. The intake does seem pretty restrictive and after some reading I don't feel the 346 heads are too bad compared to all the other stock heads.
I just hope the new gaskets stop the fowling up and there is no other probs. I feel real good about it though, like I said earlier the motor is real strong and there is no smoking, besides those 2 plugs the rest looked good.
Thanks for the title change.
I just hope the new gaskets stop the fowling up and there is no other probs. I feel real good about it though, like I said earlier the motor is real strong and there is no smoking, besides those 2 plugs the rest looked good.
Thanks for the title change.
07-05-2009, 01:11 PM
#14
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I installed the intake and carb along with new a filter, pump, and plugs. It idles great but I have some tuning issues to sort out. If I rev it hard sometimes it will back fire when in park. The real problem is under load, it backfires a ton.
So far I've made sure there are no leaks and I've checked the float level. I'm going to check the accelerator pump isn't coming on too soon next. My other thought is that 670 maybe too big for the 400, it should be drivable even it was, but I'll still look at that as a cause. I'll go over the timing again but I didn't even touch it during the install. After that I'm not too sure since it should be pretty good out of the box. I'll just have to keep looking for some cause.
I don't think there is any mechanical issues with the motor since and didn't backfire like this before. I did stumble and pop once in a while ith the old worn out carb but it was drivable. Now it barley gets around the block.
So far I've made sure there are no leaks and I've checked the float level. I'm going to check the accelerator pump isn't coming on too soon next. My other thought is that 670 maybe too big for the 400, it should be drivable even it was, but I'll still look at that as a cause. I'll go over the timing again but I didn't even touch it during the install. After that I'm not too sure since it should be pretty good out of the box. I'll just have to keep looking for some cause.
I don't think there is any mechanical issues with the motor since and didn't backfire like this before. I did stumble and pop once in a while ith the old worn out carb but it was drivable. Now it barley gets around the block.
07-09-2009, 04:27 PM
#16
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I've messed around with the timing after taking a look at it where it was set. Somehow it was way advanced, around 25. I tried all the from 0-18ish and it gets better in the 5-8 range but it's still not great and will backfire at times. The manual syas to set it at 5. I pulled the cap and there is some surface rust on the reluctor tips but nothing major, I'll do more of an inspection once it cools a bit. Speaking of cooling, this engine gets real hot. I drained the raditor and refilled it but it's still real corrdied in there, I'm wondering if that's not contributing to the backfires.... it wouldn't be the cause either way.
07-09-2009, 05:35 PM
#18
Admin
It's been a while since of messed with the timing on a mopar motor, but I THINK you have to have the vacuum advance disconnected and plugged to adjust teh timeing properly. I could be wrong though. AMC motors are like that.
07-09-2009, 05:36 PM
#19
Mopar Lover
some things to ponder:
Is your vacuum advance working correctly? {the vacuum needs to go to the "ported" outlet on the carb.}If you have it connected to a full vacuum sorce, then yes it will have a ton of advance at idle and it will be hard to tune. The smog year dizzy's used a bunch of vacum advance {like 15-20 degrees}
I think you may have a hard time getting that original dizzy to work good with your combo. The smog motor years {400's} used a very slow advance to deal with the smog equip. Then there's the vacu. advance which added a ton of advance to cope with the egr system etc.
If you can find a decent dizzy from a 66-70 383. that would probably work better.
To see if your vacuum adv. is working, use a handheld vacuum pump and see if it holds vacuum or connect the dizzy's vac. line to a full vac. sorce and see if the timing moves while the engine is running [use a timing light.]
These are only my ideas without seeing the actual truck. Please disregard if they dont apply. .........ENJOY!!!........
Is your vacuum advance working correctly? {the vacuum needs to go to the "ported" outlet on the carb.}If you have it connected to a full vacuum sorce, then yes it will have a ton of advance at idle and it will be hard to tune. The smog year dizzy's used a bunch of vacum advance {like 15-20 degrees}
I think you may have a hard time getting that original dizzy to work good with your combo. The smog motor years {400's} used a very slow advance to deal with the smog equip. Then there's the vacu. advance which added a ton of advance to cope with the egr system etc.
If you can find a decent dizzy from a 66-70 383. that would probably work better.
To see if your vacuum adv. is working, use a handheld vacuum pump and see if it holds vacuum or connect the dizzy's vac. line to a full vac. sorce and see if the timing moves while the engine is running [use a timing light.]
These are only my ideas without seeing the actual truck. Please disregard if they dont apply. .........ENJOY!!!........
07-09-2009, 07:52 PM
#23
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Arghhh man I've never had such a hard time sorting this out before.
I've tried all kinds of variations with the timing and the vacum. I' noticed a bit of play on the shaft, noy side to side but with the plates, seemed normal though. I've also had a couple instances where the timing seemed to jump a couple degrees when I have the light on it. So something maybe loose??
When I get on it hard it does the best but will still pop sometimes.
Where else should I look? The jetting couldn't be causeing these problems, could it? I disconnected the choke just to make sure it wasn't still on.
I've tried all kinds of variations with the timing and the vacum. I' noticed a bit of play on the shaft, noy side to side but with the plates, seemed normal though. I've also had a couple instances where the timing seemed to jump a couple degrees when I have the light on it. So something maybe loose??
When I get on it hard it does the best but will still pop sometimes.
Where else should I look? The jetting couldn't be causeing these problems, could it? I disconnected the choke just to make sure it wasn't still on.
07-10-2009, 11:07 AM
#24
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*que Rocky music*
My truck is running.... like a champ!
I ended up picking up a new dizzy for $50 after realizing mine needed a rebuild (I'm pressed for time) so naturally I also grab a new cap and rotor. When I'm pulling the wires two of them break off in the cap and one was a little loose. After I swapped the wires over I realize that they were alll wrong! They were almost 180 out but even then it was all over the place. I couldn't believe it even ran after looking at it.
Goes to show you not to assume and always start from the begging so to speak. I know better too!
It does run awesome now!!
My truck is running.... like a champ!
I ended up picking up a new dizzy for $50 after realizing mine needed a rebuild (I'm pressed for time) so naturally I also grab a new cap and rotor. When I'm pulling the wires two of them break off in the cap and one was a little loose. After I swapped the wires over I realize that they were alll wrong! They were almost 180 out but even then it was all over the place. I couldn't believe it even ran after looking at it.
Goes to show you not to assume and always start from the begging so to speak. I know better too!
It does run awesome now!!
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