Timing for my 87 Vette
Thread Starter
5th Gear
Joined: Aug 2025
Posts: 5
Likes: 1
Timing for my 87 Vette
I have question. ....I installed new rings, rod bearings, timing set and 1.6 roller rockers
Which valve is supposed to be opening on #1 when the engine is being started?
To clarify, when #1 cylinder is at TDC with the timing marks lined up per the Corvette manual, which valve is ready to open, the intake or exhaust?
.
Which valve is supposed to be opening on #1 when the engine is being started?
To clarify, when #1 cylinder is at TDC with the timing marks lined up per the Corvette manual, which valve is ready to open, the intake or exhaust?
.
Last edited by 09Grandcaravan; Oct 21, 2025 at 05:53 PM. Reason: Clarify the post
Drifting
Joined: Jul 2022
Posts: 1,805
Likes: 365
From: Central Florida
Your going to have to re-word your question as I can't get a picture of what your asking. When the engine is being started all the valves are opening and closing. At top dead center (combustion stroke) on #1 everything should be closed / up. There is some small overlap I think on the exhaust stroke on L98.
If Your asking about which are which you can use the "W" of your exhaust manifold and see it is E II EE II E . But I am pretty sure your not asking that.
If Your asking about which are which you can use the "W" of your exhaust manifold and see it is E II EE II E . But I am pretty sure your not asking that.
Last edited by Vets-Vet; Oct 21, 2025 at 08:33 AM.
Drifting
Joined: Jul 2022
Posts: 1,805
Likes: 365
From: Central Florida
Think this through and make sure everyone is on the same page. I am not a professional mechanic so terminology is important here. AS FAR AS I KNOW, IN MY OPINION,
Top Dead Center is anytime the piston is at the top. This occurs twice per combustion cycle, compression stroke and exhaust stroke. On the Compression stroke (#1 cylinder), which is where we time our L98 engines, NO VALVE IS OPENING. Why would you open a valve just as combustion is occuring ??????
On the exhaust stroke TDC, the exhaust valve is just closing and the intake valve is just opening.
Also, the timing marks line up on both #1 cylinder compression and exhaust TDC's.
When we talk timing, we are talking about TDC on the compression stroke.
.
.
Top Dead Center is anytime the piston is at the top. This occurs twice per combustion cycle, compression stroke and exhaust stroke. On the Compression stroke (#1 cylinder), which is where we time our L98 engines, NO VALVE IS OPENING. Why would you open a valve just as combustion is occuring ??????
On the exhaust stroke TDC, the exhaust valve is just closing and the intake valve is just opening.
Also, the timing marks line up on both #1 cylinder compression and exhaust TDC's.
When we talk timing, we are talking about TDC on the compression stroke.
.
.
Last edited by Vets-Vet; Oct 22, 2025 at 07:56 AM.
Melting Slicks
Joined: Feb 2003
Posts: 2,677
Likes: 812
From: Saskatoon Sask.
I have question. ....I installed new rings, rod bearings, timing set and 1.6 roller rockers
Which valve is supposed to be opening on #1 when the engine is being started?
To clarify, when #1 cylinder is at TDC with the timing marks lined up per the Corvette manual, which valve is ready to open, the intake or exhaust?
.
Which valve is supposed to be opening on #1 when the engine is being started?
To clarify, when #1 cylinder is at TDC with the timing marks lined up per the Corvette manual, which valve is ready to open, the intake or exhaust?
.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
When the engine is at TDC on cylinder #1 both valves are closed (The engine is on the start of the power stroke). As the engine starts to rotate the exhaust valve will start to open by BDC.
If you have valves open at TDC you have the engine you are 1 turn off on your firing sequence, rotate the engine 1 full revolution and now both valves should be closed, and you can set your timing.
If you have valves open at TDC you have the engine you are 1 turn off on your firing sequence, rotate the engine 1 full revolution and now both valves should be closed, and you can set your timing.
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Drifting
Joined: Jul 2022
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From: Central Florida