4 . 9 Questions

[AntiCooter]

I've got one of the even lower powered TBI 4.5 Caddy motors in my Fiero. It was cheap, I am cheap and I only have around $1500 tied up in the car. It was CHEAP! With that being said, I had no intentions of building a fire breathing monster out of this car. I wanted something quicker than the old, tired 2.8 and not have my retirement invested in it. I guess it turned out okay- I get 22 MPG in town, 30+ on the highway and it runs 14.9~15.1 second quarter miles on the G-tech. Do I think it is the best thing since sliced bread? NO- It is a good, dependable daily driver with enough power to piss off the punk kid in the stock Civic with a farting muffler.
I am saving the 3800 S/C that is in the back of the barn for when the "right" car comes along. Then, we will build something to have a little fun with. Until then, get out the turd polish

[scrabblegod]

The 4.9 is good for what it was designed for. Lots of low end tq and thats about it.


Scrabblegod on here if I remmeber right has ported heads, intakes and a cam. Maybe even a stall converter but he is using an auto tranny. I believe his best time is a 13.9? Maybe he will chime in on that.

For a while there was a lot of controversy around the 4.9 builds. Some swappers wanted to tout it as the swap of swaps. Like all of them, there are pluses and minuses.

They are an easy swap and inexpensive. They do not add much weight over stock.
They are fun to drive around town and short spirited runs, but leave some to be desired on 1/4 mile and top end runs. It is great in my autocrosser.

They suffer from a TOTAL lack of aftermarket bolt ons. Any search for performance increases will require grassroots hotrodding. If you can not do it yourself, better to find another engine if you want more performance.

I last got a 13.89 1/4 out of mine shifting at 5900rpm before I spun a bearing on the last run shifting at 6300rpm. This was with a 70,000 mile engine. It has a .502 lift cam, 10.0-1 compression ratio, home ported intake/exhaust manifolds, home ported heads, 2600 rpm stall converter and street tires. I am sure slicks would lower the times some, as launching at anything over ~1800rpm spins the tires so I can not load it up on the converter. Even so, I get mid 1.80s 60' times.
Two days before I broke it, it blew a tube out of the oil cooler and lost all the oil on the way to work. I am not sure if this may have caused some damage that led to the spun bearing, or if the rpm was just to much.

I am now working on a new engine and will be doing some tinkering.
I am going to destroke a 4.9 and work on getting the CR down around 7.8-1. I will then be adding increasing amounts of boost until either I am happy, or it breaks again. I want to find the limits.

I am not stuck on this motor. I also have an 87SE 3.4DOHC, have all the parts to assemble my 3800SC and sometime in 2006, I will be building a 412ci Pontiac powered street/drag car.

Research the swaps and evaluate what you want out of the swap, then go out and have some fun with whatever you build.

Gene

[Gooch]

Hey Gene

I actually met you at Ed's this year. Something had happened to your 4.9 on the way down to Ed's. There was 3 younger guys (22-23) that were staying at the same hotel as you. We were the ones that noticed a certain 3800 sc GTP with an SE nose.

No lie, I saw Gene's wife's GTP put down like 400+ ft lbs of torque. Totally stock! :afrocool:

HE HE HE! I bet he remembers that

[scrabblegod]

Hey Gene

I actually met you at Ed's this year. Something had happened to your 4.9 on the way down to Ed's. There was 3 younger guys (22-23) that were staying at the same hotel as you. We were the ones that noticed a certain 3800 sc GTP with an SE nose.

No lie, I saw Gene's wife's GTP put down like 400+ ft lbs of torque. Totally stock! :afrocool:

HE HE HE! I bet he remembers that

Yea., the starter (4 days old) on the 4.9 died 60 miles from home.
Called work and told them to go to the house and grab the GTP and bring it to me and drag the 4.9 home.

You will be happy to know the GTP now has the correct nose again. It will be leaving us soon, as I just bought my wife an 04 GTO.
It was rear ended and the guy got his attorney involved and forced the insurance company to total it.
I gave 7500.00 for it with 7,000 miles and still drivable. I have to sell her GTP to buy and install the rear clip. She will be stuck driving the stock 86GT for a month or so while I fix the GTO.

I have the 400+ torque run sheet here somewhere. Everyone knows dynos don't lie

Gene

[Gooch]

I think I hate you.

J/K working in that yard gets you ALL the deals.

I need a OBD1 Northstar. You want to help a brother out?

[The Dark Side of Will]

I last got a 13.89 1/4 out of mine shifting at 5900rpm before I spun a bearing on the last run shifting at 6300rpm. This was with a 70,000 mile engine. It has a .502 lift cam, 10.0-1 compression ratio, home ported intake/exhaust manifolds, home ported heads, 2600 rpm stall converter and street tires. I am sure slicks would lower the times some, as launching at anything over ~1800rpm spins the tires so I can not load it up on the converter. Even so, I get mid 1.80s 60' times.
Two days before I broke it, it blew a tube out of the oil cooler and lost all the oil on the way to work. I am not sure if this may have caused some damage that led to the spun bearing, or if the rpm was just to much.

I am now working on a new engine and will be doing some tinkering.
I am going to destroke a 4.9 and work on getting the CR down around 7.8-1. I will then be adding increasing amounts of boost until either I am happy, or it breaks again. I want to find the limits.

I'd like to know more about your build. I've been thinking about messing with a '90 4.5 (best rod/stroke ratio of the engine family.

[scrabblegod]

I'd like to know more about your build. I've been thinking about messing with a '90 4.5 (best rod/stroke ratio of the engine family.

I also like the bore/stroke ratio of the 4.5.
The problem for me lies in getting the compression ratio down alot (7.8-8.0).
I am looking at using the 4.9 block (stronger than 4.5 and better oiling).
I am going to use the 4.5 crank (3.30 stroke vs the 4.9s 3.62) with the 4.9 rods (5.70" vs the 4.5s 5.903").
This will give me the same bore/stroke as the 4.5 but drop the piston assembly .30 down the bore and should give a CR of 7.9-1 with the current heads I have.

This also gives a 10% slower piston speed and a better rod angle with less side loading on the pistonwalls/liners (a plus with the removable liners wanting to move under great loads).
I will also benefit from the lighter crank (smaller counter weights). I will get both the cranks weighed in the next couple weeks as we are buying a house Jan 1 and the premove/move will take up hobby time.
Modeling say this should decrease internal frictional losses by 12% and increase the mechanical effiency 2.5%.
It also decreases the intake air requirement 10% which is the same as increasing the flow of the heads 10%
It increases the IMEP 9%.
All these figures are at 6000rpm.


Any thoughts are appreciated,
Gene

[Shaun41178(2)]

hte pistons will be .30 further down or .030? .3 is a hell of a lot man.

[The Dark Side of Will]

I'd like to know more about your build. I've been thinking about messing with a '90 4.5 (best rod/stroke ratio of the engine family.

I also like the bore/stroke ratio of the 4.5.
The problem for me lies in getting the compression ratio down alot (7.8-8.0).
I am looking at using the 4.9 block (stronger than 4.5 and better oiling).
I am going to use the 4.5 crank (3.30 stroke vs the 4.9s 3.62) with the 4.9 rods (5.70" vs the 4.5s 5.903").
This will give me the same bore/stroke as the 4.5 but drop the piston assembly .30 down the bore and should give a CR of 7.9-1 with the current heads I have.

This also gives a 10% slower piston speed and a better rod angle with less side loading on the pistonwalls/liners (a plus with the removable liners wanting to move under great loads).
I will also benefit from the lighter crank (smaller counter weights). I will get both the cranks weighed in the next couple weeks as we are buying a house Jan 1 and the premove/move will take up hobby time.
Modeling say this should decrease internal frictional losses by 12% and increase the mechanical effiency 2.5%.
It also decreases the intake air requirement 10% which is the same as increasing the flow of the heads 10%
It increases the IMEP 9%.
All these figures are at 6000rpm.


Any thoughts are appreciated,
Gene

As Shaun said, dropping the pistons 0.300 is a LOT. I haven't looked at 4.x chambers.... is there much quench volume?
Personally I would be very wary of just dumping quench characteristics like that, especially on a forced induction engine.

I wasn't terribly interested in the bore/stroke ratio, although I do like short stroke engines. I was looking more at the '90 4.5 for its rod/stroke ratio. The PFI 4.5 uses the same piston compression height as the 4p9, unlike the earlier TBI 4.5's that had more compression height. Thus the PFI 4.5 has the longest rods and largest rod/stroke ratio of the engine family. This translates to several benefits, among them greater detonation resistance, greater mechanical efficiency and lower bore loading due to smaller rod angle, etc.

I believe Bud Adelman, the proprietor of http://www.gr8grip.com/ has or can get oversized sleeves for the 4.x engines.

[scrabblegod]

hte pistons will be .30 further down or .030? .3 is a hell of a lot man.

It is .30
It works out to 33cc additional compression area at piston top center.

The only other option I know of is custom pistons to get the CR down.
This will be used with my current heads and gives me a calculated cr of 7.9-1.

I am a little concerned about quench area. Unfortunately, I am not an engineer so I am not sure of the ramifications of doing this. That is why I have asked for opinions.
I am also going to spend some time chatting with some of the people I know on some turbo sites from my Turbo Coupe (2.3 4 cyl, 24lbs boost, radiator sized Saab double stacked intercooler) days.

Gene

[Shaun41178(2)]

I think .3 less is going to make the compression much much less then 8:1.

The fiero has HO pistons. The fiero pistons sit .020 higher in the boreover the standard LO pistons, and this alone bumps compression from 8.5:1 to 8.9:1. So half a point with only .020 increase. Mulitply the drop that you consider by 15 and thats .30 See where I am going with this? Your compression would be like 5:1(not doing the math)

Good luck getting anything to combust.

Get custom pistons. Spend the money and do it right.

[Aaron]

Get custom pistons. Spend the money and do it right.

I couldn't agree more.

If you are spending this much time and research to get the bore/stroke ratio right, your intentions are obviously for higher power applications. And you already said you plan to boost it to hell. Why not just start off right, build it up, then figure out where the limitations are?

If you are blowing a motor with just 10:1 compression and a big cam, imagine it with 8:1 and 20psi of boost. It'll be gone in no time. That shouldn't be your objective. And havn't you already figured out that the weak point is the bearings?

[p8ntman442]

And havn't you already figured out that the weak point is the bearings?

Havent you figured out your weak point is your mouth?

:tool:

[The Dark Side of Will]

I am going to use the 4.5 crank (3.30 stroke vs the 4.9s 3.62) with the 4.9 rods (5.70" vs the 4.5s 5.903").
This will give me the same bore/stroke as the 4.5 but drop the piston assembly .30 down the bore...

Oh yeah... surprised I mised this the first time. You're missing a /2. Should be 0.157 lower. It still scares me a bit. Even with extremely low compression, you'll be limited by the factor pistons. What rings will you be using? Bore size?

[rockcrawl]

I believe Bud Adelman, the proprietor of http://www.gr8grip.com/ has or can get oversized sleeves for the 4.x engines.

Bud can bore your stock liners. He did a set for a guy I sold some Northstar pistons to (1mm over). I made a fixture to lathe bore them and it seems to do a pretty good job, but I never had the balls to do a set for an engine that was actually going to be assembled. I just finished boring my snowmobile engine with great results, so my confidence is up a little.

[scrabblegod]

Oh yeah... surprised I mised this the first time. You're missing a /2. Should be 0.157 lower. It still scares me a bit. Even with extremely low compression, you'll be limited by the factor pistons. What rings will you be using? Bore size?

You know, that is why is is good to put ideas out there. I should have majored instead of minored in math. I do not know how I missed that /2.

Now I will have to do some new calculations both with stock heads and my modified set to get new CR figures.

I have not ruled out another set of pistons and I am currently looking for something in an off the shelf performance piston that will fit.

Gene