z20s compression issues?

[YodaVsTheWorld]

Hey guys, I came up on a 81 510 goon a few weeks ago. I'm curious about a couple things and maybe you guys have a couple answers? There is a hole in the muffler, maybe an inch in diameter. Would that be enough to cause an issue in horsepower? I know back pressure in the exhaust is needed but I don't know exactly how much it would affect the engine's performance. I've also never dealt with a carb on an engine before. I thought at first I heard a tick in the engine but as I moved closer to listen I actually heard what I thought was a very short length whine coming from the air filter/carb area. Any insight into this engine would be greatly apreciated. I apologize if this has been asked/spoken of already. Let me know if you guys have anymore questions that might help answer this. Thanks guys.

[flatcat19]

Check your timing.

Move forward.

 

Welcome to Ratsun!

Now gets some pics of your Datto up!

[datzenmike]

Are you saying you bought this car or you're just wanting to assess it's running and might buy it?

 

Probably hard to hear anything with a hole in the muffler. Get a couple of large gear clamps and a piece of soup can and cover the hole. Now you can better diagnose any sounds the motor may be making. Holes in the exhaust make negligible changes to engine output. A car this old may have been ignored maintainance wise. Anything you do to it will probably improve running.

 

Good signs:

Still running and being driven daily. Way better that sitting for three years and things rusted and seized up, flat tires, missing parts, won't start because battery froze and split the sides. If driven it likely has brakes and anything wrong isn't likely serious enough to prevent being driven.

Starts easily every time, idles, rad is full of clear green coolant , oil clean and full, no vice grips holding the battery terminal on.

All lights and signals working.

All glass in good shape.

Interior and exterior in good shape, but not a deal breaker as it is over 30 years old and like a woman, performance and comefort are more important than looks.

 

 

Ticks are ok and likely a valve lash adjustment. Loud knocks that vary when you rev with the gas peddle..... walk away.

 

You mention compression issues in the title yet no question or description of any.

[YodaVsTheWorld]

I apologize for the title being confusing. I had driven my friends 80s bmw before and he had a compression issue. It just feels like that in this car when I drive it. That very well could just be me being unfamiliar with this car.

 

To answer your question, I own the car. It's a long story, but I inherited it from my girlfriend. It was actually her first car. It is completely stock from what I see.

 

Also, I will po. Ill post thatst pictures asap, probably tomorrow in the 510 car forums so I don't clutter up this thread/forum with general 510 intros.

 

Thanks for the quick replies though. I think I am going to speed up the timing a bit.

 

Is it normal for these cars to run a bit sluggish? It takes me a bit of time to get up and go and it doesn't seem to ever want to go above 3.5k rpm, it always shifts first.

It has the 3 speed auto trans on it and im humming at around 3k rpm going 60 on the freeway. Is that to be expected?

 

All those good signs are present that you posted datzenmike. Starts everytime, real quick actually. All lights work. Oil is clean and full, and radiator is good to go with the green. brakes are very responsive. nothing is zip tied, nor clamped on with vice grips. The heater core had to be disconnected due to coolant leaking inside of it and causing quite a foul fish smell. Good fun.

 

It really just doesn't like to push past 3.5k rpm at all. Is that normal?

[datzenmike]

Anything you do to it will probably improve running.

 

Unless you know when it was tuned up last it may need some adjustments. Valve lash is easy enough to do yourself if you have a few tools. If it starts and idles I would leave the carb alone for now. Timing can be set by ear. But maybe fix the muffler so you can hear the engine better. Unless you know when the air and gas filters were changed last.... change them .

 

I have an automatic L18 and it rocks. (not as much fun as my 5 speed L20B) It will scream through both gear changes and I have had it do just a hair under 90 MPH on the highway. It should be capable of higher than 3,500 in any gear.

[zed]

no vice grips holding the battery terminal on.

as it is over 30 years old and like a woman, performance and comefort are more important than looks.

 

 

:rofl: this is hilarious

[YodaVsTheWorld]

Not sure about the last tune up. I checked the air filter and it is clean as a whistle. I'm gonna change the oil this week for the hell of it and give her some clean oil and a new filter. Ill have to check the fuel filter. Is it on the frame rail like most fuel filters?

 

and this valve lash, How exactly would I go about adjusting it.

 

Also, the hole in the exhaust is very small, and its on the muffler so its rather far from the engine. When it is idling it doesn't make much more noise than I would expect from a muffler without a hole. Although, I'll see if I can get under there and tack weld on a patch for the time being until I can replace it. That won't be until this weekend however.

 

I did open up the datto on the highway this morning, it was actually purring down the highway at around 3.5k at 75mph. Even though when I left off the gas it sounds like a 2 stroke 125 dirt bike with a straight pipe on it. haha.

 

Still can't get it to pull passed 3.5k without shifting unless i manually shift it up through the gears.

 

And I'm pretty jealous of that 5 speed you're talking about datzenmike. I can only imagine have a 5 speed in my goon. That would be the bees knees.

[flatcat19]

And I'm pretty jealous of that 5 speed you're talking about datzenmike. I can only imagine have a 5 speed in my goon. That would be the bees knees.

 

Not a hard thing to do.

It's harder finding all the parts then to do the work.

[datzenmike]

I'll check the gear ratios when I get home tonight. I think the HL510 uses 3.545 or something worse to lower revs and improve economy. I think you have an H-165 axle so maybe you could find a 710 or 200sx axle and swap the rear gears. This will give you better acceleration and because it's revving higher in 4th it wil be making more power to push it faster. Right now you are geared too low and power limited.

[ggzilla]

There is a hole in the muffler, maybe an inch in diameter. Would that be enough to cause an issue in horsepower?

 

No, it will not cause an issue with horsepower whatsoever. On the other hand, if the muffler is plugged/partially plugged it will. Sometimes when they get rusty an internal section will break loose and cause a restriction.

[datzenmike]

 

 

Still can't get it to pull passed 3.5k without shifting unless i manually shift it up through the gears.

 

And I'm pretty jealous of that 5 speed you're talking about datzenmike. I can only imagine have a 5 speed in my goon. That would be the bees knees.

 

 

I'll check the gear ratios when I get home tonight. I think the HL510 uses 3.545 or something worse to lower revs and improve economy. I think you have an H-165 axle so maybe you could find a 710 or 200sx axle and swap the rear gears. This will give you better acceleration and because it's revving higher in 4th it will be making more power to push it faster. Right now you are geared too low and power limited.

 

Oh yeah it's way worse than I thought. The Z20 cars came with 3.364 rear axles. (un friggin believable) Yes they have H-165B rear ends so find a

 

710 standard tranny. They have 3.889 gears. Wagons had 3.70s.

S-10 1st gen 200sx '77-'79 standards were 3.889 and auto were 3.70

S-110 2nd gen 200sx '80-'81 standards and autos were both 3.70

[YodaVsTheWorld]

No, it will not cause an issue with horsepower whatsoever. On the other hand, if the muffler is plugged/partially plugged it will. Sometimes when they get rusty an internal section will break loose and cause a restriction.

 

Not real familiar with mufflers but I know there is a bit of surface rust in different places of the car so that very well could be an issue. Is there a certain sound to listen for/a way to check this without removing the muffler?

 

Oh yeah it's way worse than I thought. The Z20 cars came with 3.364 rear axles. (un friggin believable) Yes they have H-165B rear ends so find a

 

710 standard tranny. They have 3.889 gears. Wagons had 3.70s.

S-10 1st gen 200sx '77-'79 standards were 3.889 and auto were 3.70

S-110 2nd gen 200sx '80-'81 standards and autos were both 3.70

 

Do all the standard transmissions bolt up to the z20 engine? And if they do, would I have to replace the current driveshaft and differential or do those still fit with these standard transmissions? I know sometimes there are length or power distribution issues between different trans/diff/driveshafts in some cars.

 

I'm thinking a diff swap would be necessary too simply cause i'd go from a 3 speed auto to a 4 or 5 speed standard (not sure how many gears those three standard transmissions you listed have.)

[datzenmike]

The rear ends (3.889 and 3.70) will work with auto, 4 or 5 speeds. I'm saying the one you have now is very low 3.364. Moving up to a 3.70 or 3.889 will improve the performance way way more. A 4 or 5 speed will make it even more fun but a differential change only takes a morning to do with a 12mm and 14mm ratchet.

[YodaVsTheWorld]

The rear ends (3.889 and 3.70) will work with auto, 4 or 5 speeds. I'm saying the one you have now is very low 3.364. Moving up to a 3.70 or 3.889 will improve the performance way way more. A 4 or 5 speed will make it even more fun but a differential change only takes a morning to do with a 12mm and 14mm ratchet.

 

Rad. I'm on the hunt for one of those then. Thanks a million man.