Northstar Mods, Improvements Y versus 9

[fleetwood_limited]

Hello, I have a number of questions, that I would like some input on, while I am rebiulding my 1999 Fleetwood Limited (12" stretch Deville).

1. I have a "Y" code, 275 horsepower. If I "need" new head(s) can the "9" code, 300 horse heads be bolted on my "y" code block? will it fit, will spark timing still work, what are the differences between these motors?

2. My deville "needs" premium gas because it is 10.3 to 1 compression. The 2000 and up devilles are 10.0 to one compression, and therefore only need regular fuel.(as far as I know) Does any body know how they lowered the compression, is it a different head, or different piston, or shorter connecting rods???

I would like to lower my compression, so I only need regular gas, any Ideas???

I am figuring they changed the "flat top" piston slightly to lower compression???

3. I am going to use the felpro gasket kits available, (conversion, for the block) cs261502 $118. Head set with head gaskets, no bolts hs26150pt1 $179. Head bolts es72186 $26 per head = $52. Or camshaft cover set vs50524r $46, plus exhaust manifold gaskets, and Use the factory headgasket and bolts at $200. I am unsure whether it is worthwhile using the "GM" headgaskets. I have read that the best gaskets are made of "graphite", but I have been unsuccessful in finding out what the "GM" or "felpro" are made of. Any info or experiences would be helpfull.

4. I have found on the internet "domesticperformance.com" list a performance chip for Northstar at $370. Has anybody heard of, or used this chip?

5.I have also found Pistons available for this northstar manufactured by "Enginetech", sold here in Canada, by C&C (519-364-6051) for less than $200 (US) per set of 8.

They also have rings at less than $90(US) a set, anybody used these? THANKS!!!

[JasonA]

1) Yes, VIN 9 heads will bolt right on, but you don't want to do that. All VIN 9 engines also had a 3.71 final drive gear to help compensate for the lower torque of that engine. The VIN Y engine has a 3.11 final drive. If you put VIN 9 heads on (or even swapped an entire VIN 9 engine) into your car and kept the current transmission, your performance would worsen, not improve. Especially with such a heavy car (limo), stick with the improved torque of the VIN Y engine.

2) The compression ratio was lowered, and a completely different combustion chamber design was used. Try 89 octane gas in your '99. Many people here even run 87 octane with no problems. Listen for spark knock. If you have any, you'll have to run premium.

3) A factory engineer who posts here recommends to use the GM head gaskets. Who knows what Fel-Pro makes their head gaskets out of.

4) The chips are normally for 93-95 cars, which are OBD-I. 1996 and newer are OBD-II computer systems, and nothing is available (that we know of) in terms of easy computer upgrades for the OBD-II machines.

5) I haven't used those pistons before. Why are you replacing pistons? Was one damaged, or did the block need to be honed? Typically, even during a rebuild, the original pistons are retained.

Good luck with your rebuild. Stick around for a while!

[fleetwood_limited]

Thanks for you're informative reply. I didn't know the "9" engines had less torque..

Could I bolt on a pair of 2000 and up heads with the new combustion chamber to lower my compression?

I was thinking of changing pistons, to lower compression ratio, I figured they where more of "dish" than a "flattop".

[TDK]

fleetwood_limited,

Maybe I missed it, but why are you rebuilding your 1999 Limo?

Is there a mechanical problem or do you want to improve performance?

If the engine needs work, (for example, because of a head gasket failure), then the bottom end (piston, crank, etc) should not need to be touched. From what this site has for posts; piston damage is relatively rare - but usually involves a new block as well.

If you want to improve performance, then it is important to determine what are area of performance you are targeting. With a Limo, your practical options are a bit limited (compared to an STS for example, where handling might be an area to invest some funds).

These relatively small engines (at only 287 ci or so) are already, "tricked out" considering they make either 275 or 300 hp, rather quickly, across a wide band.

About the only performance bolt-ons (that actually make more horsepower than hype) are a freer-flowing exhaust (which will be louder, one has to question that choice in a Limo), and a higher stall-speed torque converter (for off-the-line higher rpm/etc for drags) which most would consider another odd choice in a limo).

If you get the impression that I might be discouraging pouring time and money in a 199 Limo's engine etc for more performance - you are right. There are better platforms for performance, but none better for well-engineered luxury. Now if you are asking about how to stout up the electrical for an "all out" audio, video, etc - the Limo is a great base - IMHO!

But its your ride, so do what makes you happy.

Please post a pic of your project!

PS In deference to some other recent posts, please don't paint it a front-to-back faded, metallic green and install too many antennas, wings etc LOL

[Bob D]

2. My deville "needs" premium gas because it is 10.3 to 1 compression. The 2000 and up devilles are 10.0 to one compression, and therefore only need regular fuel.(as far as I know)

It doesn't "need" premium, it's only 'recommended'.. Lots of pre 2000 drivers that have participated in this forum for some years now (including myself) have tried and in some cases continued to run 89 or even 87 with no ill effects. The computer will simply make the necessary adjustments to avoid damage. On a hot day going up hill with everything on, you might notice a little difference, but that's about it. The most you are going to notice is little WOT hp, and possibly a little mpg..

BTW...why are you rebuilding it? Is it broke? If so, how? I'm just curiuos, I know a guy that works for GM, and has seen fleet N* taxis and limos go 300.000 miles, when cared for properly. If you do ahve a problem ,and the heads need to come off don't forget the magic word "Timserts". Is an imperative that this be part of your 'overhaul'. Lots of info in the archives on thos subject.

[Ranger]

Don't mess with the compression. As mentioned you can use 87 and the spark knock detector will retard timing as required. I run 87 all the time with no ill effect, performance or milage wise.

[Matt]

Hi Bob, I would love to see a picture of your car from the side, if it's not to much trouble. Thanks. Matt

[Bob D]

Hi Bob, I would love to see a picture of your car from the side, if it's not to much trouble. Thanks. Matt

Hey Matt, try this: http://caddyinfo.onedgesolutions.com/cars/bobd.htm

Nothing has changed except the front bumper guards,(they are now white too).

[Matt]

Now That's What I'm Talking About.. Right On!! That is beautyfull, I love STS. Thaks for the link Bob, I saved the pics in my Caddy folder.

[95SLS]

LOL good 'ol Bobynski! LOL and Bob D! I wanna catch ya running that 87 with my 95, a tank of 96 and a great set of wheels! LOL "Y" engine baby look out!

Mike C

[95SLS]

B Here it is!

[fleetwood_limited]

fleetwood_limited,

Maybe I missed it, but why are you rebuilding your 1999 Limo?

Is there a mechanical problem or do you want to improve performance?

If the engine needs work, (for example, because of a head gasket failure), then the bottom end (piston, crank, etc) should not need to be touched. From what this site has for posts; piston damage is relatively rare - but usually involves a new block as well.

If you want to improve performance, then it is important to determine what are area of performance you are targeting. With a Limo, your practical options are a bit limited (compared to an STS for example, where handling might be an area to invest some funds).

These relatively small engines (at only 287 ci or so) are already, "tricked out" considering they make either 275 or 300 hp, rather quickly, across a wide band.

About the only performance bolt-ons (that actually make more horsepower than hype) are a freer-flowing exhaust (which will be louder, one has to question that choice in a Limo), and a higher stall-speed torque converter (for off-the-line higher rpm/etc for drags) which most would consider another odd choice in a limo).

If you get the impression that I might be discouraging pouring time and money in a 199 Limo's engine etc for more performance - you are right. There are better platforms for performance, but none better for well-engineered luxury. Now if you are asking about how to stout up the electrical for an "all out" audio, video, etc - the Limo is a great base - IMHO!

But its your ride, so do what makes you happy.

Please post a pic of your project!

PS In deference to some other recent posts, please don't paint it a front-to-back faded, metallic green and install too many antennas, wings etc LOL

I am rebuilding because exhaust gas (or straight combustion)is getting in the collant and causing it to overheat. I am the kind of guy that likes to do "the whole job" while the engine is out of the car, and using this forum has been a very informative process. I think after reding all these posts I will leave the bottom end alone, unless I see piston or cylinder wall damage when I take the heads off. I am not "wanting" to spend more money than necessary, but I want a reliable engine, when it goes back in. The factory compression is only at 10.6 to 1 and probably the rings leak a little more than when it left the factory, so you are right about it being Okay to use 87 or 89 octane, and not have to worry too much about detonation. I was talking about changing the pistons

A - if I need to, and,

B - to lower the compression ratio to use regular gas.

(which I guess really is'nt neccesarry. I was wanting to improve the performance because A- The engine was going to be out of the car, and,hey, if I can, why not.

B - If I NEED to rebuild the bottom end it why not get a few extra horses.

[fleetwood_limited]

Interesting that you are wanting to both improve performance and run regular fuel...two mutually exclusive things.

Stick with the engine package you have. Switching to the L37 cams would hurt your performance in that car due to the mass of the vehicle, the loss in torque with the L37 and the lack of the 3.71 final drive in the trans.

You can run lower octane fuels as is. If you read your owners manual it clearly states that premium is only recomended....not required. Try lower octane fuel and see. The engine will run fine and will automatically adjust the spark advance via the knock control system to account for the lower octane fuel. If the performance is fine for you then use the lower octane fuel.

The Northstar engine was sustantially redesigned for the 2000 model year. I would caution against trying to mix and match parts from a 2000 or later. The heads, valve train, intake manifold, water crossover, etc....were all different and not interchangable on a piece meal basis. And, you would gain little or nothing in the process.

The L37 and LD8 heads are the same for 1999, BTW. The only thing different about a 1999 275 and 300 HP engine were the exhaust cams. That is all.

Personally, if you want a little more low end punch for the limo I would mill the heads .5 mm while they are off and run premium fuel. The added compression ratio will help the low end a little and give the car slightly better performance.

What needs "rebuilding"..??? Typically the lower end of that engine is good for several hundred thousand miles and I have never seen the need to replace pistons. Look at the bores if it is apart. Likely there is absolutely no ridge at the top of the cylinder and the original honing marks are present from the factory. Leave it alone.

I would recommend the OEM head gaskets that come with the new head bolts. The OEM gaskets are the best quality parts available for that application, period.

I was inquireing about the L37 heads, in case mine are cracked, and it is not just a head gasket problem, I wanted to know if there were any advantages to the l-37, and apparently not without changing the final drive ratio, which I don't want to do, I like the "low revs" at high way speed. I will be usuing the "factory head gaskets, bolts, and (exhaust gaskets if required) and fel-pro for the rest of the gaskets and seals.

I just recieved the "northstar timesert kit". and will be giving to my mechanic for the job. From what I have gathered from this site, there seems to be a low percentage recurance of this head gasket problem once the time serts are installed.

[JasonA]

Once the Timeserts are installed, it's pretty much a 100% effective fix, if done right. Even from the factory, a very low number of these engines actually have head gasket problems. A recent poll here indicated that about 1 out of every 10 Northstar engines, whose owners participate on this board, have had problems. Just like your situation, I surmise that a fair number of those folks started participating here because of that problem, so I feel that 10% is higher than the actual number, because that only reflects folks on this board. Couple that with the relative age and mileage on most of these engines, and I'd say that's a good record. Again, most of us haven't had a single problem (yet).

I also like the 3.11 transaxle. I can drive almost 80 mph and still be below 2000 rpm. It just lopes along on the highway. This is such a great road car. Power everywhere is just effortless. And because of that 3.11 transaxle, it returns great mileage...usually between 27 and 31 mpg on the road.