valves sealing ?
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Joined: Nov 2003
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From: Norn Iron
valves sealing ? This query relates to a strange boost drop I seen on an engine I threw together to race recently.
It was a forged 346, WCCH Edelbrock heads, 1.7 YT's, 224/230 on 115 0.581/0.588 cam
All of these same parts had been used on my 382, for some 10k, but I recently had to switch back to an old 346 setup, albeit using the same bolt on gooodies ( with supercharger )
But the boost kept dropping for some reason. I tested pipework, and fixed a couple of small leaks.
then....
I am in the middle of removing the engine, and did another test.
I removed the rockers, and did a pressure test on the intake.
As expected, leaks....first of which are the rocker bolt holes lol.
Next up, TB flange has some very slight leaks, intake at circa 6psi. The TPS is also letting a bit of air out ( Accufab/Ford 85mm TB ), well a lot really.
But....more worrying, is some of the intake valves seem to be making a very poor seal. Ive removed 6 plugs ( not cyl 6 and 8, too awkward with headers on ) and pretty much all the intake valves are letting air past. With the front cylinders 1 and 2 letting quite a bit past.
Not really sure how this would affect performance ??
I havent done a compression test.
Now I only checked the intake. But why would the intake valves be leaking so much when tested from the intake side ? It will be a day or 2 before I have the engine stripped.
The engine ran fine, apart from once I hit circa 6300rpm, the engine got horrible, and boost dropped a bit.
It was a forged 346, WCCH Edelbrock heads, 1.7 YT's, 224/230 on 115 0.581/0.588 cam
All of these same parts had been used on my 382, for some 10k, but I recently had to switch back to an old 346 setup, albeit using the same bolt on gooodies ( with supercharger )
But the boost kept dropping for some reason. I tested pipework, and fixed a couple of small leaks.
then....
I am in the middle of removing the engine, and did another test.
I removed the rockers, and did a pressure test on the intake.
As expected, leaks....first of which are the rocker bolt holes lol.
Next up, TB flange has some very slight leaks, intake at circa 6psi. The TPS is also letting a bit of air out ( Accufab/Ford 85mm TB ), well a lot really.
But....more worrying, is some of the intake valves seem to be making a very poor seal. Ive removed 6 plugs ( not cyl 6 and 8, too awkward with headers on ) and pretty much all the intake valves are letting air past. With the front cylinders 1 and 2 letting quite a bit past.
Not really sure how this would affect performance ??
I havent done a compression test.
Now I only checked the intake. But why would the intake valves be leaking so much when tested from the intake side ? It will be a day or 2 before I have the engine stripped.
The engine ran fine, apart from once I hit circa 6300rpm, the engine got horrible, and boost dropped a bit.
