I have a 1994 F150, with a 5.8. I also own another 351w which sitting in my garage. The question I propose is: is it possible to Stoke the 351 to 393 and still make it live with the computer. If so, what kind of computer changes are necessary, and what kind of cam will work. The engine is non-roller, and my truck is NOT mass airflow equipped. I obviously intend on keeping it EFI'd, so what changes would be in order there.

I thank you in advance for answering this question, as it has bothering me for some time.

 

If they make a mass airflow kit for your truck, you would probably have to buy it. The original efi works off engine speed and manifold vacuum. It "assumes" how much air is flowing in the engine and how much fuel is needed since the factory programmed the computer for that engine combination. Any variation from the factory set-up, and the computer will not know about it, unless it can measure actual air flow with a mass air meter.

 

you can avoid mass air and have a custom chip made. im making over 400 rwhp without mass air and just a chip and a tuning session. however if this 393 has any kind of good cam and breathing heads then a fuel system upgrade will be in order. the stock fuel system will not support that kind of air movement. trust me i know from experience. (see sig) im stretching the stock fuel system way past its limits.

 

LIGHTNING2FAST what is the level 10 mean in your sig? Are you runnin a 10 sec 1/4?

 

level 10 is a company who deals with tranny parts.

 

>I have a 1994 F150, with a 5.8. I also own another 351w
>which sitting in my garage. The question I propose is: is
>it possible to Stoke the 351 to 393 and still make it live
>with the computer. If so, what kind of computer changes are
>necessary, and what kind of cam will work. The engine is
>non-roller, and my truck is NOT mass airflow equipped. I
>obviously intend on keeping it EFI'd, so what changes would
>be in order there.
>
>I thank you in advance for answering this question, as it
>has bothering me for some time.

i believe you can do what Lightning has done or you can by a mass-air conversion kit from motorsport. you can also rape a 5.0 mustang for parts. it makes a difference what tranny you have believe it or not. it depends on wether your tranny is computer or vacuum controlled. my 1988 c-6 is vacuum controlled so it is more difficult to find conversion kits. the computer controlled transmissions need the correct harness to comunicate with the puter or you can get error codes etc. For me i need parts from a mustang with a standard transmission even though i have a c-6 auto. that's cause the puter won't be comunicating with the tranny in a 5-speed just like it wouldn't on a vacuum controlled auto. either way (kit or mustang) i believe you will have to play with injecter firing orders. cost wise it may be similar to do what lightning did through a chip and fuel system upgrades as it may be for a $600 US mass-air conversion kit. i can't say which is the better way to go though. come to think of it though you will probably still want a chip for your stroker even after you convert to mass-air - so it might be more expensive. maybe Lightening can give us an idea of costs to do it his way?

 

level 10 is a trany company dealing in h/p trans parts. im running one of their shift kits. my truck so far has run a best of 12.2 @106 in the 1/4 mi. it will go 11's next time i visit the track. and it is a full weight of 4600lbs. now yes you will have to go the chip route even with a mass air conversion. that is to get the most of your new setup. the best route is to upgrade the injectors and have the truck dynotuned via a chip. itll cost about 600$ but youll have a much better tune than if you just slapped a mass air setup on there. i never plan on going mass air. its not needed. a good tuner will get the truck to run correctly on speed density. and believe it or not most of my lightning buddys are switching back to speed density because of the severe tuning problems with the mass air system. and theyre making more power from the swap.

 

>level 10 is a trany company dealing in h/p trans parts. im
>running one of their shift kits. my truck so far has run a
>best of 12.2 @106 in the 1/4 mi. it will go 11's next time
>i visit the track. and it is a full weight of 4600lbs. now
>yes you will have to go the chip route even with a mass air
>conversion. that is to get the most of your new setup. the
>best route is to upgrade the injectors and have the truck
>dynotuned via a chip. itll cost about 600$ but youll have a
>much better tune than if you just slapped a mass air setup
>on there. i never plan on going mass air. its not needed.
>a good tuner will get the truck to run correctly on speed
>density. and believe it or not most of my lightning buddys
>are switching back to speed density because of the severe
>tuning problems with the mass air system. and theyre making
>more power from the swap.

just what i wanted to hear Lightning! so let me get this straight- if i build up a 393 stroker on a speed density system with cam, heads, crank, headers etc. i can stay with the speed-density? and what EXACTLY do i need? new injectors, high pressure fuel pump, and a chip? anything else? and what you are saying is "dynotuned via a chip" what does that entail exactly? sounds like i need a computer programmer geek at the dyno place! please elaborate a little - this mass-air cost is what is holding me back cause it will cost $1000 Canadian just for the kit. the whole motor will only cost me $4000.Thanks for the advice

 

well you need to get a chip and bring the truck to a dyno tuner who can tune it for hp and smooth any driveability problems you may have. you will need a good fuel pump and bigger injectors. hopefully the stock lines will feed the combo you choose. and you can have a custom cam made that will not aggrivate the speed density and it will still make stout power. cam motion is a good cam place to call. terry has ground many s/d truck cams that will work for you. an off the shelf cam may not work too well and the driveability problems will be harder for the tuner to eliminate.

 

just so that i am clear. you get a chip burned for your custom motor first? then get it tuned all together on the dyno? so i just tell the chip guys that i have such and such cam, heads etc. and they will burn a chip with that in mind? am i getting what you mean now? sorry, i am a little thick!

 

yep you can tell the tuner what your combo is and theyll ballpark it. then tune it in person. or if you swap the engine and cam in and it is driveable then you can go to the tuner and he'll supply you with a chip and tune just the same. it really doesnt matter but id get the chip first. thats what i did. then i went to get it tuned and gained 60hp and 60ft/lbs from the tuning session. not bad

 

Great. Just when I'm getting a really good grasp of how these EFI systems work, YOU have to show up! I've already swapped my '87 F-150 5.0 to mass air and I'm getting ready to pull it back off because I'm selling the truck. (Pretty sure nobody will give me any more for it cuz of that!) I had intended to use it on the EFI 5.8 I'm trying to stuff in my '51. Everybody always preaches that you can't tinker with your cam or heads without mass air. So I guess my question is this: Mass air supposedly gets you better idle quality and adaptabilty to changes in volumetric efficiency. What is the benefit of going to such great lengths to retain your speed density system? Is there something I'm missing? I'd love to have a good reason to sell the mass air kit and stick to what I've got. Also, what was the pricetag on the custom chip and tuning session? Thanks in advance!

 

well tha mass air kits for me are over 1000$ forget that. you can have cams etc custom meade to keep the s/d happy so whay spend all the money? and mass air isnt easy to tune either. it has its limits. the chip was 250$ the tuner wanted 150$ for his time and the dyno runs were like 40 per pull. i got carried away and made 8 pulls, lol. i already had the chip so the whole session cost me under 500$. i gained alot of power and he fixed a driveablilty problem i had. ive preached alot about the topic of mass air on the 87-96 truck forums. if you search it youll find me.

 

thanks lightning. i'll check into all that. but first....i'll have to get rid of that "chuck engine" light and code 31 which has me stumped. i'll take it to my mechanic buddy. he's got one of those million dollar snap-on diagnostic machines. maybe he can figure out the code and give some speed-density advice as well. thanks again.
i'll keep ya posted!

 

code 31 is for the evp. egr valve position sensor. im 99% sure that the evp is bad. its the little white plastic sensor on top of the egr valve. ive seen enough of them at the dealer to be confident enough thats what it is. id go ahead and replace it. its not too expensive. just replace it and disconnect the battery for a few minutes.