: thinking about getting mods on 4.5

04-20-11, 06:04 PM
Hi, I have 89 Deville with 4.5 L engine.
It has about 90,000 miles and I am trying to add few performance mods.
I know that there is virtually no performance parts available for 4.5 engine (I see more for 4.9) but I am going to still try to add few mods on my deville.

Why not go for deville with 4.9 engine and add performance mods? or change engine from 4.5 to 4.9?

I just really love this 89 Deville I have, and I have put in lot of time and money on it to make it reliable and runs strong. My main goal is NOT to race every car I see but rather just to have little more horsepower and torque on it. Do you guys know anyone with 4.5 (non Allante) with performance mods?

anyways I am thinking about putting
- exhaust system
-custom cold air intake
-fastchip (Ed from fastchip told me that they should have chip for 4.5 Deville but I have not given him the 4 letter caliberation id code yet.)

is there any other performance mods I can do other than these 3?
I am also considering Throttle Body Spacer because unlike 4.9, this 4.5 engine I have got is throttle body injection. Do you guys know if TB spacer would give me some performance gain?

and I am running K&N filter in my Deville, Is it wourth it (performance wise) to try to make custom cold air intake system when I am already running K&N filter? I have also heard stock air intake is more than enough to cover it as well.)


the recluse
04-20-11, 06:39 PM
Good luck with the cold air intake, not much room to work with.

I find it very hard to believe that the 2" hole behind the headlight can flow enough air to feed this engine. The Allente intake is good for a few ponies.

That said, I'm looking into making a set of headers for this engine. I think it'll be one of the best improvements on the overall performance.

When I took out my 4.9, I ported and polished the heads, did some intake and TB mods and put in some 19lb injectors. The bigger injectors would kill your engine, so I don't think that would be feasible in your case. All in all I noticed a stark difference in how the engine performed afterward.

They do make a cam for the 4.9, I don't know if they make one for the 4.5.

Good luck and happy wrenching...

04-20-11, 07:04 PM
The 2" circle is more than enough. Wanna test? Take the car down the street a few times at WOT. Pull over, remove the airbox cover and run a few more WOT's with the throttlebody wide open. Feel a difference?

If you are going to make your own air intake, at least make sure it remains a cold air intake like the factory already setup for you. Nothing annoys me more than people clamping on a cone filter inside the engine bay that's sitting inches away from the 200 degree engine, behind the 200 degree radiator, calling it a "cold air intake", getting high off the placebo from the increased intake noise.

04-20-11, 09:32 PM
The most effective thing you can do for more power is to advance the ignition timing 2 to 4 degrees. It costs nothing, but you MUST run premium (93) all the time. There's nothing else to do that will be more noticeable than that.

These are low-revving AND small displacement engines and as a result,they dont flow very much so there is little(if nothing) to gain from intake and exhaust mods. In other words, the capacity of the stock exhaust and especially the intake is already above what the engine itself can flow.

04-22-11, 01:19 AM
thanks for the replies!

hmm it sounds like that stock intake and exhaust are more than enough thus making performance intake (CAI or short ram), and exhaust system NOT as efficient (not too much performance gain) huh?

I might just get fastchip from ed, and maybe think about doing ignition timing

would TB spacer be waste of money on tbi engine????

04-22-11, 05:11 PM
Well I think a TB spacer on a TBI engine would have more merit than on a PFI engine but I still doubt that it would be enough to notice. Its an easy job though and you can get them used on ebay for cheap. Look under chevy 4.3L. Early 90's I think....

I dont think the cost of a chip is worth it. The most noticeable thing that a chip does is tweak the timing and you can do that for free! A couple other things it may do is lower the 'fan-on' temp and remove or raise the top speed limit (governor) which is already around 117 stock. I dont know about you but I wouldnt feel comfortable going 120+ in a 22 year old car!

04-22-11, 11:32 PM
ya I figured tb spacer would be more appropriate than 4.9 engine.
I am planning to try it within a month.
so do you think this one would work out okay?
'Swirl Torque' Throttle Body spacer from transdept performance
86-91 4.3 tbi part # 2533?
(they wouldn't let me post link because I don't have enough post or something)

and about the chip, and ignition timing,
I agree with you. I am not really trying to go more than 110 mph in 89 deville!!
I wanted it for better timing. So from what I understand It seems like I can run 91 on fastchip, but I don't know if I want to commit for 93 for changing ignition timing. (correct me if im wrong about 91 and fastchip)
However can you still tell me how to do it????????


04-23-11, 01:25 AM
Well put it this way... The engine requires 91 stock so any tweaks to the timing will require higher octane to run safely. If you do the math, you are looking at like 3 bucks extra per tank. Big whoop.

The swirl feature on a TB spacer is marketing nonsense. The air rushes right past those swirls like they arent even there so dont pay extra for a part that has them!

Do some googling on adjusting ignition timing if you've never done it before. Look for vids on youtube. Its hard to explain it in text from hundreds of miles away.

You will need a timing light and a 15mm distributor wrench. --Still cheaper than a fastchip!