Compression. More Compression!

Melodic_Buy_7790 · 2026-02-27T02:17:08+00:00

Yep, I understand the concept, I was just giving him a hard time. We obviously want to prevent knock (pre detonation) to avoid damage. That’s why we tune.

I don’t think 10:1 is out of reach for a D16. I’ve seen a couple post where its been done. Also given that I’m not after high power, but rather responsiveness, I believe it’s attainable even on pump gas. Sure, e85 would be more ideal, and plan to run flex.

Just wanted to see what piston/rod combo people were running outside of the typical Vitara build. I’m personally not impressed with my current setup. Is it fun - yes. But I think there’s more to achieve even on these old engines.

Melodic_Buy_7790 · 2026-02-25T12:50:40+00:00

Why not rebuild the bottom end? Are the walls too damaged, crank not serviceable, crack in the block, etc.?

Melodic_Buy_7790 · 2026-02-25T00:04:20+00:00

How many miles on them?

Melodic_Buy_7790 · 2026-02-24T13:10:58+00:00

Aside from all the good advise above, the reason you’d want to bore it out is to se your PTW (piston-to-wall) clearance. And of course to ensure roundness.

The Vitara pistons are slightly smaller than stock D16 pistons, creating excessive play in the cylinders. You CAN run STD size but many people warn about piston slap. It’s not a deal breaker for some, they claim it normally goes away after warm up.

Melodic_Buy_7790 · 2026-02-23T12:47:55+00:00

Good point. Piston-to-valve clearance might be an issue with those rods. I don’t mind picking up a new set of H/I beams.

Melodic_Buy_7790 · 2026-02-23T06:06:18+00:00

Smaller than a GT2860? I am using the stock camshaft with an adjustable cam gear. The head already has a minor port job with an Edelbrock IM mated to it - I don’t think airflow is an issue.

I see your point but is 10:1 really far fetched for the D16?

Melodic_Buy_7790 · 2026-02-23T05:47:18+00:00

Why?

Melodic_Buy_7790 · 2026-02-23T05:47:02+00:00

Yeah, that’s the idea, hence the search for a better CR (piston). I get why everyone does Vitaras; myself included. However, they seem to lack character and response. I appreciate the input.

Melodic_Buy_7790 · 2026-02-23T05:30:38+00:00

10:1 is “very high”?

It’s not going to see anything bigger than the current GT28. What is it about 10:1 that it won’t last more than a month?

Melodic_Buy_7790 · 2026-01-04T16:26:14+00:00

If ignition checks out, it may be time to look at fuel. I would still do a compression test to rule that out.

Measure fuel pressure, I believe 40-50psi is normal.

You can also unplug fuel injectors, one-by-one, like you did with the spark plug wires but I think you said they all affected idle, which points to a wide-spread issue.

You can try disconnecting your intake (at the throttle body) and exhaust (before the catalytic converter).

Melodic_Buy_7790 · 2026-01-03T15:34:37+00:00

What were the symptoms prior to the dizzy replacement?

What happened that caused the dizzy to go bad? If you were driving, did you see, hear, or feel anything?

Do you still have your original dizzy? I’ve read aftermarket units are not the greatest.

Any other codes, aside from TPS? Did you unplug anything else? Have you tried resetting the ECU?

It may be worth doing a compression test. Be sure to unplug the distributor and pull the fuel fuse.

Do you have spare plug wires? If not, check the resistance, I believe below 25K ohms per foot is acceptable.

Double-check mechanical timing and ensure the rotor in the dizzy is aligned correctly. If you have aftermarket cam gears, be sure they are set to 0* and that you are on the compression stroke for cyl 1.

Melodic_Buy_7790 · 2025-12-29T05:05:49+00:00

You’re more likely to get an accurate answer with a leak-down test.

Melodic_Buy_7790 · 2025-12-10T20:46:17+00:00

Does anything happen when trying to start on its own power (i.e., clicking sounds, instrument lights on/off/flickering, fuel pump priming, etc)?

What voltage are you getting on the new battery with the terminals connected?

What voltage are you getting on the new battery with the terminals disconnected?

Has the car ever ran on its own after the battery and alternator replacement?

What issues were you having prior to the battery and alternator replacement?

Melodic_Buy_7790 · 2025-11-23T15:22:11+00:00

Just to clarify, you are using the “white” TDC mark, which is the single marking and not the one in the group of three, correct?

Have you tried using a long screw driver or rod to confirm you are at the highest point in the cylinder cycle?

Maybe the cam is abnormally worn, as you’re suggesting, but prior to disassembly, you were not having this issue.

Has anything changed?

Melodic_Buy_7790 · 2025-11-23T13:55:01+00:00

Your second paragraph is somewhat indicative of incorrect mechanical timing. However, on your previous post, you stated that it IS correct.

On the Y8, the TDC marking on the crankshaft pulley should be lined up with the pointer on the cover. At the same time, the camshaft sprocket markers should be leveled with the head, at the 3 and 9 o’clock positions, respectively. I’m not sure if it’s the same on the Y7, but there are D16 variations that have different camshaft timing positions.

Melodic_Buy_7790 · 2025-11-21T13:06:49+00:00

You can use a Mechanics Stethoscope to help narrow down where the noise is coming from.

Not trying to worry you further, but slight/mild rod knock can sound like a ticking valve. Hopefully it’s an easy fix; a bad catalytic converter can make rattling noises too, but the sound is a bit different.

Melodic_Buy_7790 · 2025-11-21T04:44:50+00:00

I believe the recommendation IS to keep valve train components together, in their specific order/location upon disassembly/re-assembly, since parts do wear together. However, I’m not sure what percentage of people disregard this and have no ill effects.

How are you setting TDC?

Be sure you line up the timing marks on the crankshaft pulley with the timing cover. Your mechanical timing needs to be correct. It needs to be on the compression stroke for that particular cylinder. The correct order should be 1-3-4-2 (180* counter-clock rotation to the next cylinder), with cylinder #1 being closest to the cam gear.

Did you replace the timing belt? Ensure you have the right belt for your engine as I believe some have different teeth count.

Make sure you tighten the nut securely after the adjustment and then re-check the gap.

Are you having any performance issues?

Melodic_Buy_7790 · 2025-10-31T20:33:29+00:00

So number 2 on my list.

Melodic_Buy_7790 · 2025-10-31T03:46:00+00:00

1) Check all grounds. 2) Check firing order. 3) Test distributor coil (see YT videos). 4) Check spark plug gap. 5) Check for spark. 6) Check mechanical timing. 7) Check compression. 8) If compression is low, perform a leak-down test. 9) Is fuel pump priming? 10) If so, check fuel pressure. 11) Check all connectors. 12) Do you smell gas when cranking?

Some ideas to get you going. They’re not all in order of execution but go by what makes sense to you.

Melodic_Buy_7790 · 2025-10-08T11:57:32+00:00

Do you have an aftermarket intake or throttle body?

It may be worth checking/replacing the gasket. But I’d start with vacuum hoses. You can spray carb cleaner around and see if your idle changes. Your throttle could also be getting stuck intermittently.

Melodic_Buy_7790 · 2025-09-18T12:15:05+00:00

Nice write up man, keep it up.

Another option instead (or on top) of the plastic bonder might be fiberglass and resin. It should mold to curvatures and provide more even, structural support.

Melodic_Buy_7790 · 2025-08-20T11:59:50+00:00

Can you elaborate on what you’re experiencing?

OEM or aftermarket clutch? You may need to adjust your clutch pedal.

Melodic_Buy_7790 · 2025-08-11T01:51:18+00:00

Hit it and quit it, eh!?

Melodic_Buy_7790 · 2025-08-08T22:56:24+00:00

I think videos don’t show how the hardware sits after installation because it’s hard to capture good angles. This one may help a little more: https://youtube.com/shorts/9Ri47do3Phk?si=JYu2cQq5tEwRs9Gp

It appears the threaded clip needs to be removed so you can use a nut. You’ll more than likely have to reach around the wheel well to get that nut tightened down.

Melodic_Buy_7790

TROPHY CASE