4.1 intake on a 3.8 engine swap. is it REALLY worth the time and effort?

[MY85pontiac]

i have a 4.1 and a 3.8 and i am seriously contemplating putting the 4.1 4 bbl intake on the 3.8 but is it REALLY worth it? the difference between the two engines is only 15 HP. to some of you thats no big deal but to a 110 HP 3.8 thats quite a jump, but, they have different bores so im wondering how the bore comes into play here. does the bigger bore on the 4.1 lend a hand in the difference in HP? the 4.1 really does seem to have more power than the 3.8. some people have said this swap adds more than just 15 HP, some suggesting upwards of 35 HP. i strongly doubt that because there has never been any dyno tests before and after the swap to back up such a claim. maybe the 3.8's slightly smaller bore makes the difference? i dont know, i'm pretty confused about the whole matter and i'm only considering this swap just for the secondaries anyway but a jump in power would be nice as well.

also, its been suggested that the exhaust be more free flowing than stock for this swap because the 4.1 intake and carb REALLY likes to breath and a free flowing exhaust would make a difference. i happened to notice this difference with just a muffler swap and the 2 bbl still on the engine. so does anyone think i could gain MORE than the 15 difference with this swap? i'm figuring the cost of getting the intake gasket and everything else i need plus new sending units for a gauge cluster i picked to be right around 80-90 bucks. is it worth the money and time to do this? i also have found that the vacuum lines are routed differently, probably because of the previous owner of the 4.1 putting in a rebuilt 4.1 and apparently getting REALLY confused about where stuff went. anyone know where i can find a vacuum diagram for an 82 4.1 engine?

i also want to smooth out the primary side of the intake. the transition isnt exactly smooth. has anyone does some smooth/porting/polishing of a stock intake? think i'd be wasting my time? the primaries are HUGE then bottle neck. to me that would choke the engine and performance. from what i understand the 4 bbls like to run rich so wouldnt doing a little work on the intake help offset that and help the engine breath easier? i dont want to hog it out, just smooth it out here and there so it breaths better.

the car has to be smog legal so this is my only option other than waiting till its old enough for antique tags. i cant wait that long.

 

[Freddie's Buick]

Dude,

The 4.1 intake and Q-jet swap to a 3.8 is the cheapest and wisest upgrade one can do on these engines.

A better then stock cam added to this upgrade and you'll notice a dramatic improvement.

The Q-jet intake does'nt need anything. Port matching the intake to the heads all depends if the head's ports are smaller then the intake's ports. Bore, secoundaries all play into the plus in HP. It does'nt really matter were the gain is coming from. Bottomline is that it's a proven upgrade as is and you will notice it. I did! (Yep...my Regal only had 110 ponies. But she sure quickend up after I did the swap. Now god only knew what HP it stood on).

Also, a machinist told me the same thing about the exhaust ports on the heads....but I totally disagree! Although dated, the overwhelming sources of information I've read give the exhaust ports a thumbs up! It's the intakes that need help. And this is primarily for the '79-81 3.8 heads. Later heads get better.

The vaccum lines are almost the same for both 4.1 and 3.8 engines. But Pontiacs, Buicks and Chevy 3.8's tend to vary and change from year to year. You just gotta know how the basic set up is and take it from there.

If you're worried about smog then don't mess with the ECM system or the carb. Limit the carb upgrades according to the suggestions on Doug Roe's book 'Rochester Carburetors'. And only do them if you have the skill and knowledge to modify the Electronic Q-jet.

If you get this far get a fuel mixture gauge that attaches to the oxygen sensor. This lets you know if you have good burn since the engine/transmission is completely computer controlled and you're concerned with emissions.

Also, get an oil pressure gauge and a water temp gauge. These are must-haves on these engines. Have fun! These are great engines to play with....

 

[MY85pontiac]

i cant do a cam (NOONE makes a smog legal cam). i know a cam would go a long way for this engine though.


basically this is just going to be a bolt on and go deal. so i wont be messing with the carb at all (its been rebuilt with low miles on it since the rebuild and it works very well as is) and i know it passes the sniffer.

i already have gauges for the car i just need the sending units for them.

i guess i should pay close attention to the port sizes on the intake side and match em. i really want to smooth out the primaries on the intake for sure. the inside is dirty anyway and i doubt doing any work like smoothing would effect my emissions. it might increase the speed of the incoming air and make it more responsive and atomize the air fuel mixture better.


once i get this swap done i'll be testing it BEFORE taking my chances with the VET facility, i never take chances with those people.


i guess there arent any dyno tests on this swap. thats too bad, it would only make these engines seem more fun to play with. not all power comes from V8's and these engines can prove it.

 

[b4black]

I saw an episode of Horsepower TV where they were modify a Honda Civic. They added a "Air Inatke System" (relocated filter that required cutting the grille out of the fascia), a header, cat and exhaust (complete wiht fart can). The grand total (parts only) was $1000. Dyno before- 87 HP. Dyno after- 97 HP. That's 100/HP.

The first thing that came to my mind was how much of a bargin the 4.1 Carb/Intake swap is. Even if it cost $100 and only brought 10 HP, it would be a factor of 10 times better than HPTV's Civic.

I'll see what I can do about scanning a 4.1's vacuum diagram.

 

[Freddie's Buick]

Smoothening out the sharp inner edges of the primary and secoundary bores on the 4.1 intake is the only thing one can do to assist the fuel atomization transition.

But really.......this only comes into effect if one is traveling at a very high rate of speed. If you feel comfortable cleaning it up why not? I guess it would'nt hurt anyway....

Oh yeah.....I put a Kenne Bell cam on mine and I had no trouble passing inspection.

 

[MY85pontiac]

wow! guess this upgrade doesnt seem so foolish now!!! at least my car still wont sound like a wet fart in a plastic chair when i'm done like their car.

i guess whatever i gain for the amount of money and time put into it would be worth it. at least i dont have to remove a distributor like a chevy!!! that cuts down on reassembly time. also give me the chance to put in a new thermostat and coolant temp sending unit in the intake before i put it in. saving me some headaches later on.

i just hope i can get this slug of a car into the mid 11's in the 1/8th mile at the local track. mid 12's sucks. so i'm hoping this and a gear swap later on will do the trick. 19 seconds of 1/4 mile fury isnt exactly exciting me one damn bit. i actually had a honda beating me with 10.5 second times.

thanks in advance just for looking for a vacuum diagram.

 

[MY85pontiac]

hmmm a kenne bell cam? did you have to deal with the sniffer test? what were you're results?

i have a 50,000 volt super coil from accel and it burns very clean right now. i think replacing the valve springs might help also. the engine has over 130,000 miles on it and i'm thinking about replacing it anyway in the next year year or so so i'm kinda planning what i might do if i replace this engine with another 3.8.

 

[87regal]

I cant say for sure...but I sure am hoping a mild cam will pass emissions.

Im in CA so the emissions are pretty strict, I just ordered a 204/214 cam today, and its going in my new motor, if it passes great, if not, ......but I would think anything from stock up to maybe a 212/212 would pass CA emissions, I hope so at least, might even be able to pass with a 218/218 in other "not so strict on emissions" states.

 

[MY85pontiac]

i dont know, all the cams i've seen from comp, crower, crane, edelbrock, etc. all say for non computer controlled engines and not emissions legal. rather than take a chance on getting busted failing the sniffer and having to undo the work i've done (and probably getting fined for it in the process), i've decided to hold off on such work until i dont have to worry about it. seeing as how there are junkyards here that have 3.8's as far as the eye can see i'm not worried about finding a good core to build up a 3.8. people see those 2 barrels and automatically dismiss the engine without a second thought.

i'm kinda interested in seeing how a 3.8 would run with a mild cam and headers and none of the emissions/CCC crap on it. i'd like a 250 HP 3.8 for daily driving, they're good engines and unlike some people who get a g-body with the 3.8 i didnt look at it as a plague or something to get rid of for a SBC. i viewed it as a challenge to see what i can do with it while being smog legal. i'm just glad this swap is smog legal.

i truly believe you can make good power with these engines without having to add a turbo to them. nothing wrong with turbos but i'm tired of everyone telling me to put a turbo on it. its this stigma buick V6's are stuck with, its like if it doesnt have a turbo on it its just a boat anchor and i'm sure i'm not the only one who wants to prove people wrong on this misconception. these engines just arent being given a fair shake by the after market companies or car enthusiasts in general. it just sucks having one of these engines and having no smog legal parts to play with.


i'm glad i found this group, now i dont feel quite so down trodden about this engine. here i can actually read people giving me positive feedbacks about my engine. everywhere else i get nothing but insults and jokes.

 

[Freddie's Buick]

I don't know what the emissions test requirement are like in Kentucky. I know that they change fron state to state. In south Florida all they were looking for were N0X and CO2 levels on the sniff test.

Thank god that within the last year the people of state of Florida finally figured out that these stupid test serve no real pupose other than to line the private contractors pockets with our hard earned cash and voted it out!

The state was'nt interested in monitoring commercial vehicles and trucks. Just the passenger vehicle. So this noble idea did not improve upon the enviroment much in any way.

Dude, the swap is'nt gonna give you 11's on the 1/8 mile track that's for sure. But it's a good start. There is much more that one has to do to get her up to 250 HP. And it is possible. (That's my goal too)! I'm getting Dyno-2000. It's gives one a ballpark on horsepower right on ones PC.

Also, my cam is relatively mild......but much better than OEM. The more radical grinds I stay away from. They're geared more towards track speed and they're lobey. I like a smooth quiet drone sound at idle, but a growling beast when I floor it. Good headers and a Flowmaster muffler should yield this target for me.

I agree.....this engine is great and people are coming around to it.
The 3.8 and the 4.1's are certainly gonna be up there with the great muscle car engines someday. For now it's the turbo stigma that people are going to be fixated on. It's all good though....

 

[b4black]

Originally posted by MY85pontiac
seeing as how there are junkyards here that have 3.8's as far as the eye can see i'm not worried about finding a good core to build up a 3.8. people see those 2 barrels and automatically dismiss the engine without a second thought.

Instead of finding a good 3.8 to build up, why not do a 4.1? I doubt the extra displacement can have any great effect on the emissions concentrations.

 

[MY85pontiac]

the kentucky legislature has passed a bill and has been signed into law getting rid of the emissions testing in my county as well as a couple of other counties that have emissions testing. the testing is SUPPOSE to end november 2003 when the contract runs out. however because of this issue and that issue (mostly people who MIGHT fail BEFORE the contract is over and have to go to court, blah blah blah) the facilities might not shut down until 90 days AFTER november 2003. that would put it into february 2004. i have to reregister every march and knowing my luck 'ill have to get this car tested in 2004 too. IF my county fails to meet air quality standards (its never had a problem meeting them before) then they will probably go to a testing schedule of every two years and cars younger than so many years is exempt from testing. however the fee will DOUBLE in price. like these people dont get enough of our money already. what they have been looking for is hydrocarbons and carbon monoxide. the standard for hydrocarbons in PPM (parts per million) is 220 both idle and loaded readings. in 2000 my car did 33 at idle and 32 in the loaded reading. the standard for carbon monoxide is 1.20%, both loaded and at idle, my cars readings were .00 at idle and .02 loaded. i dont have the 2001 results because they're in the car still (state law says it has to be in the car for any cop to see if they request it). but they are almost the same readings. i havent tested yet this year. i will soon and i expect to pass.



as for building a 4.1.....i havent seen too many pistons available for 4.1's (all cast, none forged). not only that there are more 3.8's to be had around here. why not go for whats more readily available? there jsut seems to be more parts for the 3.8, if they had forged pistons available for the 4.1 i'd use the 4.1 i have now, its a good motor. the PAW catalog looks like a good source for buick V6 parts but they lack forged pistions for 4.1's they have cast and forged piston kits for 3.8 though. i'd like forged so i could run nitrous on it.


other than the bore being different what other differences are there in the 3.8 and the 4.1?? internally i mean. i heard its not the same block. is that true?

 

[b4black]

Originally posted by MY85pontiac

thanks in advance just for looking for a vacuum diagram.

Sorry, but I can't find one. I'll keep looking though. They don't print them in the service manual.

 

[MY85pontiac]

so i noticed! i have a helms manual for my 85 and it doesnt have any there, but tons of wiring diagrams though! lol

helms DOES make a vacuum diagram manual. someone had one for sale but i couldnt get it at the time. maybe i oughta check out acdelco.com, they sell helms manuals there, just not sure about this particular manual though. they also have owners manuals and body manuals! i was kinda surprised by that.


on a lighter note i went to the track last night. i did OK. i can tell the carb and gear are slowing me down and screwing up. i gotta get this 4.1 intake swap done soon. this carb is driving me insane!!!


thanks for the help!!!

 

[Ttype83]

OK you went to the track.....lets see the slip
Don't worry about the E.T. time, only a couple here has good times or times at all. It will give you a good bench mark for upgrades. Keep a log of your times and what mods were done that way you can see the improvements.
Jim

 

[MY85pontiac]

ok last year i went to the track once and ran 5 times.

the average ET was 12.5 with a 54-55 speed and a 3.0 60 foot with a fluke 2.9.

this year with taller tires (1/2" taller) new muffler and a shift kit i did a 13 (the average) with a trap speed of almost 57 MPH.

so my MPH went up but my ET and 60 went down. its the tires.
my carb was bogging on me (i KNEW i should have changed the accelerator pump! and i even have one!) so my reaction times prettymuch suck and were varied because the guy running the tree was rushing all of us for some odd reason so iw asnt able to stage the same way twice. mostly it was shallow staging but my best r/t for the night was a .026.

this is my second trip to the track and actually running the car. i have been keeping track of my mods (although really there isnt much yet). the two i REALLY need to do are the 4.1 intake swap and a rear gear swap. i have 2.41 gears and they hate the pre 81 th-350 i have in the car. they dont get long so i have a 3.42 and posi carrier swap planned later this year. i figure these two mods will go a long way in improving performance and should give me the best bang for my buck. it should at least get me under the 3 second mark for the 60 foot. a 2.5 would be nice!

 

[1badTTA]

OK, this is the thread I have been waiting for. I am interested in doing the 4.1 intake and carb swap also, but also doing different heads since I have '78 heads which REALLY SUCK. I'm thinking that 4.1 heads would be the best to look for, just what years? Also, if there are any other heads I should keep my eye out for, what are they?

Thanks for any help.

 

[b4black]

4.1 and 3.8's use the SAME head. Anything from '79 and on is good. Casting '8445 is considered the best and was use from '83 on, but it is only SLIGHTLY different than the 79/82 heads.

Whatever engine you take the 4.1 intake/carb from would be the engine to get the heads from. 4.1's where available from 1980 thru '84.

Find a complete running 4.1, and you'll have a back up shortblock, so you can not worry about breaking the 3.8.