hey, nice site! i have a 2.8 mpfi and want to rip it apart, was guna go small block but everyone does that, i like the look of edelbrocks intake then going the carb route with big cam, roller 1.7-1 rockers............ should be fun, what do yual think ?? any coments or power guess's??? with headers.
cheers keep up the good work Ant

 

I think you should keep searching...

Really, you probably should search about the 3.4 swap. Even for a carb engine, you ought to start out with as much displacement as possible.

 

yeah i know but ive riped and changed and swapped engines round before, in the end im keen to keep nos matching and replace block when it needs not just for sake, im sure i could blow it up soon anyhows - allways trying ;-)

 

Changing to carb from F/I will take some parts to get it to work. You need to change the distributor to mechanical/vacuume advance since the computer won't get a throtle position sensor signal anymore. Also the transmission (if automatic) will no longer know when to 'lock up' the tourque converter. This could be fixed with a lock-up kit.The F/I fuel system will need to be changed to support the Carb. You have an in-tank fuel pump that gives about 35psi. Way too much for a carb. You could run a fuel pressure regulator but that will not make the pump happy and it will fail. You should really change the fuel tank to a non-F/I tank if a standard pick-up & sender dosen't work in the F/I tank. (I don't think it will)

Why give up on Fuel injection? its much better than a carb for a street driven car anyways. There are hop-up parts for the F/I 2.8 because thats the engine that came in the Fiero and used for kit cars. fierostore.com
I'd say do the usual as with any fuel injected car;
Throtle body, headers, cam, injectors, heads....
You might be able to get close to 200-H/P in a hopped-up 2.8
I think the stock F/I 2.8 made about 140-H/P

Its always cheaper to do a car swap, than an engine swap. If you want a V8, go find a V8 car

 

i understand that FI is good for all round drivability but i prefer working on carbs its easyer to make the engine do what you like, also i reakon you can get more power from a good carb motor than a good EFI unit, the intakes on these are really bad so its easyer to slap on the nice edelbrock units to free it all up than tune the efi............. does anyone else make intakes for these engines????? what about bigger valve heads????????
thanks for the discussion guys

 

what year is your car? I think around 86 they went to bigger valves. If you have those and you want to put on a carb, those are the biggest you can get........without going and making a custom manifold. You can always do a P&P and get a little more out of the heads though.

 

hey, thanks for the info on heads, i have an 88 so that sounds good.

 

the stock 2.8 in the f-body was more like 120... the 3.1 in 92 was 140, and the 3.4 was 170 I think.

 

GM numbers say 2.8 = 135hp 3.1 = 140hp and 3.4 = 160hp.

Going to a carb setup isn't worth the effort. The stock mpfi intake manifold isn't the best design out there, but switching to the edelbrock manifold still won't help the stock heads which are the real restriction. You already have the best iron head casings available, which isn't saying much. The most you can hope for with the iron heads without proffesional porting is 200hp. You should focus on torque, the stock intake is designed like the TPI setup to boost low end power. A well tuned fuel injection system can beat a carb setup hands down, and still get better mileage. Fuel injection isn't that hard to understand, all it takes is a little experience.

 

i understand FI, dosnt mean i like it!!
as a rule of thum ive allways believed that an engine is as good as its cc's
so 305/5litre = 500hp so 2.8 i reakon 280 hp

 

That rule is not true. The later 2.8s made 135, 3.1s made 140, and some of the 305 only made 180 in the base models. A 280 horse 2.8 is possible but it would require better heads and FI for sure.

 

That rule of yours is heavily dependent on the intake and heads. The 2.8/3.1 have terrible stock heads and a terrible intake. The fuel injection isn't so much an issue. EFI allows for efficiency of fuel usage: It's able to be timed perfectly and in the correct amount, without needing to retune it during the spring tune-up.

 

An engine is capable of making whatever power level it's built to produce. Why else would we have 8,000hp hemi dragsters? I wasn't trying to call you out or anything, I just think fuel injection is a simpler way to tune. Hook up a laptop, log some driving and make some changes.

 

ref; EFI allows for efficiency of fuel usage: It's able to be timed perfectly and in the correct amount, without needing to retune it during the spring tune-up.

efi on these cars is very basic. unless an efi can use each injector individually then its not much cop in the tunning stakes, our efis work on a bank a time which is too basic and old, im up for new EFI's but you have to remember that these were the first systems out and not developed enough. carbs have been round for god knows how long and we already know everything about them and how to get the best from them............

 

OK I get it,
You want everyone to agree that a carbed 2.8 would be cool and make big horsepower...

Fine! Go for it.

You asked for opinions, you got opinions. You are going to do what
you want on the F/I issue. I think we all get that.

Edelbrock looks like the only one making a manifold that takes a 4-barrel
They recomend a 390cfm Holley 4-bbl
They make a cam for it too or check out www.fierostore.com for more choices and hard parts like pistons, heads ETC...
Pacesetter and Edelbrock both make headers for it
The 2.8 was not a high reving engine so a good ballance / blueprint
will extend that range.
MSD makes ignitions that fit

Good luck and tell us how it turns out

 

hehe glad ive changed all your minds !! not ! ill shut up now ;-) ive also found westcoastfiero.com to have a good chunk of 'stuff'
its a shame edelbrock dont make smaller than 500cfm carb, i think 500cfm would be pushing it - the idle and low down power would be pants. im an edelbrock fan, i dont know a huge amount about holley's but as you say they do the 390, what are they like to work with ???? anyone else have any prefrences????

 

oh apart from efi that is

 

carbs are great but the carb manifold for the 2.8 is not that great. even with the work edelbrock put into it they aren't all that good. the reason is this... due to the narrow angle of the Vee there is no room to have any runner length so they don't produce the torque that a longer (read tuned length) intake would and torque is what brings in the bacon. if you look at the edelbrock intake

there is little room to build velocity so torque suffers. You might see 160hp with a 4 barrel headers and a cam...... might........

if you want power with ease of tuning try these guys http://mckinneyracingproducts.com/intake.htm

 

zs&tas- Our computers may be basic, but that doesn't make them inferior. Because of how extensively some (namely the '165 and '730) have been hacked into reprogramming or writing new programs for them however you can imagine is possible. There's nothing wrong with batch fire injection either, given the amount of time the intake valve is actually open making a complete injection in that time span isn't always realistic, and furthermore injecting onto a closed valve not only cools the valve but also enhances atomization by evaporating on the back of the hot valve. I actually believe batch fire is better for performance engines than sfi.

MPNolin- Our engines are actually capable of high rpm use, the limit is the stock valvetrain. With a better valvetrain continuous use @ 7k rpm is possible.

If you preffer to go carb do it, we're just trying to help you out by telling you that you'll probably loose low-end grunt. And mileage. It will make for a cool old-school looking engine, but why not go to a tbi setup? Looks like a carb setup with a little creative wiring and has all the benefits of fi.

 

Use a 3400 top end and and 6 webber carbs on top of the LIM. Now THAT would be cool. You would still need an ECM to control ignition (or an MSD Dis4 maybe)...

 

dude, that looks awesome and all, but how would you tune that thing?

 

hey firstfirebird, now thats what im talking about!!
86v6CP - i was a little concerned about the lack of runners.... and also did consider some sort of lower plenum to carb set up to get round it
the 3.4 bolts straight up then eh??????? what about different heads from the 3.1/3.4 engines do they have higher compression ratio's and do you think they could work nicely?????????
nb. thanks all the healthy chit chat guys

 

I'm using a 3.4 block and heads from a 3500-powered Malibu (3.5litre). It is going to have about 11.5 or 12:1 depending a few final details.

 

damn thats alot ! what fuel you guna run???? be hard to stop preignition ?? if you back the timing off then surley youl just lose ultimate power. let us know how it goes?

 

12.6:1 has been done on pump gas and a good tune. The aluminum heads allow more compression because of the rapid heat dissipation qualities of the metal. Iron heads don't like to see much more then 10:1 or so.

The timing really needs to be backed off anyways with aluminum heads.

 

That's cncguy's (over on 60degreev6.com) engine isn't it? He can whip up some neat stuff.

Just by swapping in the 3.4 block you get about 9.5/1 cr and boatloads more torque. Definately a good starting point.

 

ahh course i see, so back to head swap question, does anybody know the combustion chamber sizes on the 28/31/34 to see if i could gain any compression with an easy head swap?
3.5 mali block/heads the same also then?
its a well used and proven block, i guess i just wanna show some v8 guys what it can do, any body can just stick a small block in - ive done that b4 looking for that ultimate different kick **** build----- cncguy's manifold looks easy to do as its still running efi, theve just put 6 small throttlebodys on each intake......

 

ive thought as previously mentioned about the lack of runners on edelbrocks intake that taking something like this intake and re-machining to sit a carb on top therefore keeping all the runners, i could open all them up myself with a bit of dremelish work, could be interesting - do think edelbrock had height problems when designing for this motor??????? thats only reason i can see its not the normal design thed usually churn out........

 

I hope you grabbed the lower intake and heads to match because the runners won't match up to the stock 2.8 3.1 lower or heads.
the 2.8 and 3.1 are virtually the same engine with the 3.1 having a longer stroke. if you go with a series 2 60* (3100 3400) you are getting into a better airflow situation and will make more power. if you want to go with a carburetor on that upper intake you will need a hood scoop to clear it but it would be a unique setup.

 

The Gen2 was still called 2.8/3.1 (aluminum heads). The 3100, 3400 and 3500 are Gen3.

Please read:
http://en.wikipedia.org/wiki/GM_60-Degree_V6_engine

 

If you are going to try to put a carb on top of a gen 3 intake (need upper and lower intakes), the dizzy wont fit into the block. Back runner covers the dizzy hole, so you will need to swap to DIS and have a computer to run it.