building a 3.0L plus...

[280zgod]

Ok guys, I have a 75 280z with FI and my engine is dying so over Christmas break i'm going to rebuild or have a shop rebuild my engine and head along with doing some mods to the head. This is my plan (tell me if you think its a good one): Bore out the block to 3.0L put in the flattop ka24 pistons, completely redo my N42 head, port and polish it, and install a stage 3 cam in it whose specs are lift .460/.460 and duration 270/280. heh i like high end power. also im looking to take my friends differential out of his automatic Z because the gears are supposedly longer then my own and i like long gears so ill be switching to his 3.36 differential from my 3.54 differential. Correct me if im wrong on the 3.0L stuff i thought it was ka24 flattops but now im not sure thats right. Oh well you get the jist of it so tell me what you think. Thanks! Oh yeah any other recommendations you all have on a good setup would be much appreciated i.e. shorter gears, different size tires, lsd, etc. Thanks again.

[texasz]

Here's a site that may help you with your piston question: http://www.geocities.com/inlinestroker/

[Phred]

Reconsider the large overbore on a 75' block. The bores will not be stable, and I have seen a few blocks with core shift, that became unusable after a .120 bore job. If you really can't control yourself, and you must bore, get an F-54 casting, and a diesel crank. Then at least it should hold together. Also keep in mind, the longer the stroke, the more torque you get, so high revs are not as important to make HP. Thats the neat thing about stroker/big bore motors, they make great HP without the high revs.

Phred

[280zgod]

thanks for the input:

Phred- yes i actually have an f54 block but its missing bearings and bearing caps but i think the n42 caps would work and the bearings as well i hope or i can go get an f54 for 50 bucks at the picknpull, but anyway yeah i know the diesel crank would give me more power but i dont have enough money to get a diesel crank and have all that engine work done cuz from what ive heard thats pretty expensive and just boring out a block without putting in the crank still gives some power but its alot cheaper especially in my case where i need a rebuild badly and have a somewhat tight budget, but thank you for the input... i had considered it but not possible at the moment...but would the setup im suggesting work good? in my car i am going to do mostly freeway driving and drag on the weekends at the local track so would my setup work good for that in your opinion? thanks again for the input

texasz- thanks ill check the site out and see cuz im really interested in boring my engine out for a lil extra power since i need a rebuild cuz my engine aint gonna last much longer thanks alot.

yeah by the way my compression is 80/120/120/120/120/100 so thats what condition my engine is in right now

also just wondering if having short gears like 4.11 in the differential actually makes your car run a faster quarter mile cuz i mean i have long gear and my car does the quarter in 3 gears and my friend who im possibly getting the longer gears from can do it in 2 gears which is ridiculous and im thinking all that shifting would slow down your time so just curious as to the science or math of it thanks again bye bye

[280zgod]

i could wait a lil longer and get the stroker and do that if everyone thinks it would be a better idea then a high end power l28...well which would be better in the long run and for my purpose as stated in the reply to phred thanks.

[panchovisa]

I'd seriously reconsider drag racing with a 3.36 rear end, unless you use 10" rims off a Mini (have to consider the final drive ratio).

[texasz]

yeah by the way my compression is 80/120/120/120/120/100 so thats what condition my engine is in right now

Got that beat, my compression is 120/120/120/40/120/120 and she will still lay rubber to the road from a dead stop (when she's warm, when she's cold she runs awful). Amazing little cars!

[Gav240z]

If you can't afford to do the bottom end properly focus on the top end for now. Since your compression is stuffed I'd say it's the rings for sure but you never know could be a bent valve or something.

That's what I'm doing anyway.

I have an ok running motor in my Z at the moment but I know it's getting tired.

I'm building up a P90 F54 combo, Port work, Cam, Flat tops, diesel crank and overbore. Doing piece by piece as i can afford it on the side and the benefit is I still have a running car.

Do it once and do it properly i think. I'm still thinking if I should rebuild the gbox and carbs while it's out. Then I'll have all new running gear except for the diff in my Z. It would be a huge difference that's for sure.

Remember all this extra power your gonna need a better clutch see how that budget blows out of proportion?

BTW diff ratios make a big difference.

[kmack]

thanks for the input:

just boring out a block without putting in the crank still gives some power but its alot cheaper especially in my case where i need a rebuild badly and have a somewhat tight budget

also just wondering if having short gears like 4.11 in the differential actually makes your car run a faster quarter mile cuz i mean i have long gear and my car does the quarter in 3 gears

If you want the power of a stroker motor, but you say you don't have the funds to do it right, why even start it? You've already got the FI and associated electrics, go back to the pick-n-pull, find a Turbo motor, rebuild it and transplant it in the car. You'll get the same increase in HP, but for a total under what the stroker would run (even with the limited mods you're talking about). Pick-n-Pull here in San Antonio wants $250 for a turbo motor (when they have them). Figure at least another $500-1000 (if you have to replace the turbo) to rebuild, although you could do it for less. And you'd still be less than boring and stroking your current motor.

A 3.0L (done right) can run upwards of $3500+. You done a turbo swap and get close to 300hp with only mild mods. I'd go the turbo route unless you have your heart set on a NA stroker motor. But I'd only go the 3.0L route if you can do it right. The first time.

[280zgod]

well texas that was my compression about 6 month ago haha but with how i drive (frequently at 7k) i dont doubt its lower now. but yeah shes still pretty quick. these things have a knack for running strong on 5-6 cylinders. my friend with an auto is running on 5 cylinders right now and that thing still hauls on the high end not so much before 40 tho but anyway cool stuff.

Gav, kmack- so for now you think it would be best to do the head work and just get new rings for the pistons until i can afford to do the stroker all at once? if thats the case i guess that would be cheaper right now and more helpful in the long run cuz i have a month time limit for the rebuild til college starts up again and at the moment this is my only running car (mostly cuz im too lazy to fix my 720 cuz i dont know jack $H!T about carbs). anywho so it looks like ill do that for now rebuild the head do those lil mods to it and leave it a 2.8L for a while. Thanks guys youve helped alot. Any other suggestions about gearing or anything i might want to consider?

[kmack]

we Any other suggestions about gearing or anything i might want to consider?

If you still plan to run the car on the strip, DO NOT get the lower ratio diffy. Your off-the-line acceleration will suffer greatly.

Low ratio gearing is great for low rpm/high speed driving and good gas mileage, such as freeway driving. But it will take you longer to get to those higher speeds.

High ration gearing puts the power down quickly, but top end speed suffers. I have a 3.54 rear end in my 240 w/ a '73 4-speed. I run about 3800 rpm at 70 mph. If I put a 3.34 in, my rpms would be lower at the same speed of 70 mph. But my accelration from a standing stop would suffer greatly. I'm actually on the hunt for a 3.90 rear end right now.

[texasz]

I'm actually on the hunt for a 3.90 rear end right now.

We should talk next Saturday at the Z show.