Stroker.. Or ???

[peng155]

Hi Everyone...

I've been trying to figure out what to do with the current motor in my Z.. I currently have the original stock motor, hooked up to a newer 5sp connected to the original stock differential..

The choices that I've narrowed my list down to are...

A) Rebuild the stock 2.4L motor..

Swap in a lightly messaged 2.8L motor..

C) Build a 3.1 Stroker..

The car is my Summer week-end driver... No auto-crossing, or track racing.. Just a summer night, week-end cruiser.. I'm looking for some more pep, torque and power..

I kinda ruled out the 2.4 rebuild..Since I'm going on the bigger is better adage.. That leaves me with either a 2.8L swap, or the 3.1 build.. I'd like to stay with the SU carb setup for no other reason other than simplicity sake...

For those of you who have done either the 2.8 swap, or 3.1 build could you please post your comments about your experience with your setup.. Pros, Cons... what would you change, would you do it again, or go a different route.. and even if you haven't or are currently doing engine work let me know what you think...

Thanks for your comments.....

[CoastGuardZ]

Phil-

Sounds like you and I are/were in the same boat. I have a L28 in my garage that I have been contemplating using for a swap and just keeping the numbers matching L24 around as a "just in case I decide to go back stock." A few years ago I thought I wanted a 3.1 and decided to start gathering parts... the block was as far as I got... but then for simplicity's sake I decided to go for a mild 2.8 build - I'd like about 225-250hp. I too am interested in hearing other people experiences vice just their opinions. We've got a lot of experienced peopled here at the site so I'm interested to see where this goes. Also, similar questions have popped up here before, so some creative searching might net you some previous answers from members that haven't been heard from in a while.

BTW- looks like your VIN is missing a digit.

~Nate

[Arne]

My series I already has an L28 in it ('83 F54/P79 with SUs), and while it's not totally happy right now (bad oil rings) it does pull well and feels torquey (as long as I keep fresh plugs in it). I don't see much downside to having a mild 2.8. I've heard that the SUs might be a touch small for a real hot 2.8, but that's no problem for me at this time.

Interestingly though, I'm looking at probably going back the opposite direction as you. My car's original engine is who-knows-where, gone before I bought the car. But I do have a spare L24 ('72 w/E88 head), and I think I will probably rebuild it instead of the L28. No real reason, other than the fact that it is already out of the car and handy, and for the way I plan to drive the car I really won't need the extra 15-20 HP that the L28 will give over a similar L24.

Plus, it will be a bit different in this world where many 240Z's have L28s and five speeds to have one with an L24 and Type A four speed, even if neither the engine or transmission are original.

[peng155]

Hey Nate....

Thanks for the heads up on the VIN... You were right I was missing a digit... Must have been my wishful thinking :cheeky:

My thinking exactly on the stock motor

I have done a bit of searching on both the 2.8, and 3.1 motor.... But most of what I found was how-to's.. After doing some more reading I know the stroker will run me about 3-5k for a correctly built motor...

I figure I might be able to do the 2.8L motor for about 2.5-3.5k... Something I should also point out I'll need to farm most if not all of the work out since I've never built a motor before.. With summer coming up, and Spring around the corner.. I'm getting real excited to hit the hotrod/car shows

-Phil

[Arne]

I figure I might be able to do the 2.8L motor for about 2.5-3.5k... Something I should also point out I'll need to farm most if not all of the work out since I've never built a motor before.. With summer coming up, and Spring around the corner.. I'm getting real excited to hit the hotrod/car shows

I'm figuring around $1500 in parts so far, for a mostly stock 2.4. Add a couple-three hundred for machine work, and I expect mine to cast me $1800 or so, doing the actual assembly work myself.

[beandip]

Phil, Just recently I installed a '82ZX NA engine in my '73 . I found the engine and paid $500. for it complete with all manifolds even a alternater. I did pull the pan to check the lower end and all was real clean as I had expected , being the oil when I checked it was rather clean. I just cleaned it up, painted it and I did replace the rear main seal since it was right there. The difference from the L-24 is dramatic. I am running my old SUs , in fact today because the weather was good and the location was right I kicked her up to 90 mph and she pulled hard and was still pulling when I shut her down. I don't know if you were into the hot rod era , but I was . We used to bore and stroke the engines back in the day to increase the performance . It was not that easy then . By going with a ZX engine, you have a bored and stroked L-24 and the difference is amazing. I have only put 1800 miles on the car since I have her back on the road and am still playing with the performance end . I would certainly recommend the later engine that was built for our unleaded fuel and is the latest evolution for this fine engine. My 2 ¢ Gary

[zguitar71]

I have a 2.8 with an e-31 head and a mild cam with SU's. It is certainly a fast car, rev happy and fun to drive. The extra tourque from the 2.8 is nice in a 2300 lbs car. If you can go to a 3.1 I say do it. I like the 2.8 but there is no replcement for displacement though. But the 2.8 is the cheaper way to go and you can still make a fast car with it. Try to go with flat top pistons for the higher comp ratio, you'll get better power throught the rev range and you could use a hotter cam too.

[jackboxxx]

Hi Everyone...

I've been trying to figure out what to do with the current motor in my Z.. I currently have the original stock motor, hooked up to a newer 5sp connected to the original stock differential..

The choices that I've narrowed my list down to are...

A) Rebuild the stock 2.4L motor..

Swap in a lightly messaged 2.8L motor..

C) Build a 3.1 Stroker..

The car is my Summer week-end driver... No auto-crossing, or track racing.. Just a summer night, week-end cruiser.. I'm looking for some more pep, torque and power..

I kinda ruled out the 2.4 rebuild..Since I'm going on the bigger is better adage.. That leaves me with either a 2.8L swap, or the 3.1 build.. I'd like to stay with the SU carb setup for no other reason other than simplicity sake...

For those of you who have done either the 2.8 swap, or 3.1 build could you please post your comments about your experience with your setup.. Pros, Cons... what would you change, would you do it again, or go a different route.. and even if you haven't or are currently doing engine work let me know what you think...

Thanks for your comments.....

Hey Phil,

Last time around I went for the 2.8 swap deal, and upgraded it a bit to run about 15 sec in the 1/4, and was very happy, buuutttt....

this time around I went 3.1L, and damm...there is no comparision between the 2, the 3.1 just plain hauls arse! it pulls so hard all the way to 6500+rpm, and seems like it would prefer to be roadracing all day long...

I can explain the difference like this, in my 2.8 car I felt like I was

able to be competitive with most of the small sports cars out there,

but in the 3.1 car, it truly feels like i have no competition with other cars

in my class..( 2-3000lb 3 litre 6 cyl, (non turbo,supercharged, or nitrus'ed) sport coupes) not to mention the big arse grin I get on my face whenever

I jump on the gas pedal a bit.

[jmortensen]

The advantage that a 3.1L has over a 2.8L is simple... 10%.

If the two are built to the same specs, you do the same port work, same induction, all that, you'll see a 10% gain. So the question is how much is that extra say 25 or 30 whp on a pretty aggressively built barely streetable engine worth? If your answer is $2500 or $3000, then the stroker is for you. $100/hp is a little steep for me.

Above and beyond the displacement the stroker has no advantages compared to the 2.8L, and has some disadvantages in rod/stroke ratio. Potential redline is NOT really compromised, as Dan Baldwin has shown in some previous threads. Piston speed goes up something like 50 fps between the 2.8 and the 3.1 at 7000 rpm, but the r/s ratio should mean that the 3.1 would be more detonation prone than the 2.8. Quantitatively how much of a difference does that make, I really don't know. Might be the difference between 93 and 94 octane, couldn't really say, but it is a disadvantage.

[peng155]

Hi Everyone....

Thanks for the comments so far....

Arne.. nice website on documenting what your doing to your car... I wish I has as much dedication to do something like that... heck I've been trying to dust off the digital cameral and take some pics of my car, and get them posted up on the board since I got the body, and paint work done... and it's been done since last summer... ANd I'll be visiting your site alot to snag any tips on what your doing to your car for mine :nervous:

Gary... your comments are the type of input I was hoping for.. Like I said I was hoping to stay with the SU setup raher than have to figure out how to get the F.I. wired in correctly, and working...

Was I around during the hot Rod Era... Kinda denpends on how far back your talking

3 of my high school class mates had 67, 68 Camaros, another had a 72 Cuda... For kicks on Friday, and Saturday nights during the summer we head to the local beach and have what we called race nights at Golden Gardens.. we didn't actually race per say... Most of the guy's, and gals would just park hang out, drink beer, and cruise up and down the parking lot... And actually I've been contemplating looking for a 65 Mustang Fastback to have some fun with...

Chris, and JackBoxxx... A 3.1 build is seriously on my mind from what I've read and understand done correctly a 3.1 motor sounds like a killer setup.. But I think jmortensen brings up some valid point on a 3.1 build...

Some of the things that I worry about on a 3.1 build is... what kind of mods will need to be done to the fuel system to feed the 3.1 ?? If I've read correctly I don't think the dual stock SU's will provide enough fuel.. hence the need for F.I., or a triple carb setup....

Will I have to worry about melt down if I can't get good enough quality fuel from the corner gas station?? I'll need to go back over the threads on a 3.1 build and see what the compression ratings were.. but I seemed to recall they were about 9.5:1 or so... use to have a turbo 320i, ran high compression, hi boast.... I fricked up on not running high enough quality gas in it, and blew the head gasket, and warped the head from detonation... Ended up being a real costly experience I don't really want to re-live

And than there is the question of will I always have to be fiddling around with it to get it to run correctly???

So keep those comments coming in... And thanks for the input so far...

-Phil

[zguitar71]

If you build a 3.1 and use the P90 head off the ZX Turbo (stay away from the P90A with hydro lifters) then the comp ratio would be around 9.5:1(mabey slightly less). I think they are the head to use for the stroker motor, they are said to flow better than the other heads out there because they are designed for a turbo. A set of bored SU's from Rebello should work for the stroker, stock ones probably would work too but the rpm would be limited due to the small size bore and only two of them. Tripple 45mm Webbers or 44mm Mikuni's carbs would be great though.

[jmortensen]

As zguitar says, keep the compression 10:1 or under and you should be able to run pump gas. The other thing that helps is a big cam. The more duration on the cam, the more compression you can run without detonation.

I built my last engine too hot for street gas. About 11:1 compression, and with my .490/280 cam I need about 95 octane to prevent detonation at 35 degrees advance. You'll find people who back off the timing to run high compression, again this is just my opinion, but I think that is a big waste. There is a lot of power in the timing, and I'd rather have 9.5:1 with the proper ignition advance than 11:1 with the timing cranked down. I could probably get a cam with a duration over 300 degrees and be marginally able to run pump gas without detonation and keep my advance, and I've considered doing that but I've got too many other things going on right now. I'd suggest a cam similar to mine if you're going to run compression in the 9's. If you go for more compression then get something bigger.

Back to your octane question. I get the 95 octane my engine needs 2 ways, one is to mix my own octane booster. There are threads here about it I think, but you can mix 5 galons of 91 octane up to 95 octane with a gallon of octane booster at a cost of about $10. So that is expensive. The other option I've used is AVgas, which is aviation fuel. It comes in 100 octane "low lead" which is illegal for street use, but when you cut it 50/50 with 91 octane you get 95.5 octane. Not very convenient, the AVgas is relatively expensive, and this is an option for me since I don't drive my Z on the street anymore.

As far as carbs go I estimate that swapping from SU's to Mikunis gained me ~40 hp. It was a huge difference. This was on a 2.8L also. I would consider running the bored SU's on a stroker for a street engine, or 44 Mikunis or 45 Webers. The bigger triples will be able to fully utilize the cam and give your car more top end at the expense of low and mid range power. I'd forget about stock SU's or 40 triple carbs. You could get the car running on the stock SU's then do something else down the line, but if you're building an engine to make lots of power the SU's are going to be a serious limitation IMO.