We are currently running on the new domain and server: www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Search found 85 matches

by LoganD
Mon Sep 16, 2019 10:39 am
Forum: Engine Tech
Topic: What happen
Replies: 27
Views: 2160

Re: What happen

Was this turbocharged or boosted in some way? From a purely visual standpoint it looks like the piston got too hot and the aluminum annealed, ruining the forging. As some have said, that scuffing looks absurd, but more importantly it's got surface pitting as if the surface hardness was very low. Som...
by LoganD
Mon Sep 16, 2019 10:12 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

So does anyone have a recipe how to cost effectively modify an oversized, small cam, early 1990’s dump port into a more modern tumble port? Or is that “go straight to the foundry with passing go” sort of proposition? This is going to be completely counter-intuitive for you, but the answer is to low...
by LoganD
Mon Sep 16, 2019 9:40 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

So does anyone have a recipe how to cost effectively modify an oversized, small cam, early 1990’s dump port into a more modern tumble port? Or is that “go straight to the foundry with passing go” sort of proposition? This is going to be completely counter-intuitive for you, but the answer is to low...
by LoganD
Sun Sep 15, 2019 10:06 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

Ok, so if the problem is low speed preignition, I can see how more tumble is better. If the problem is spark knock, then more tumble is not necessarily always better. If so, for downsized passenger car engines, or engines running very high octane fuel, more tumble the better. For a "tuner engine" r...
by LoganD
Sun Sep 15, 2019 9:08 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

"Why is it beneficial to transfer heat from the cylinder walls, piston, and combustion chamber roof into the charge on a pump gas, knock limited engine? This is not a rhetorical question." Hot spots act like a spark plug. Controlling hot spots is more important than an increase in pre-combustion ai...
by LoganD
Fri Sep 13, 2019 8:58 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

Modern turbocharged engines run a huge amount of tumble. Not only does this help with mixture uniformity, it actively cools edges in the cylinder and prevents hot spots. It's like....having a fan on the inside of the cylinder before combustion starts. This is true even for port injected engines, pr...
by LoganD
Thu Sep 12, 2019 12:30 pm
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

A lot of this is why I think performance on the 4 valve conversion heads suffer, just lack of knowledge of how these heads work. Would love to see someone rip off a modern Sport bike head (like a Ducati twin, with a 4.5” bore) and apply it to a pushrod V8 shortblock. Obviously it would cost a fortu...
by LoganD
Wed Sep 11, 2019 10:36 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

A lot of this is why I think performance on the 4 valve conversion heads suffer, just lack of knowledge of how these heads work. Would love to see someone rip off a modern Sport bike head (like a Ducati twin, with a 4.5” bore) and apply it to a pushrod V8 shortblock. Obviously it would cost a fortu...
by LoganD
Wed Sep 11, 2019 10:25 am
Forum: Engine Tech
Topic: Torque To Yield
Replies: 30
Views: 1017

Re: Torque To Yield

Yes, just use the old TTY bolts for clearance checking, then use the new TTY bolts for final assembly.
by LoganD
Wed Sep 11, 2019 9:20 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

Modern turbocharged engines run a huge amount of tumble. Not only does this help with mixture uniformity, it actively cools edges in the cylinder and prevents hot spots. It's like....having a fan on the inside of the cylinder before combustion starts. This is true even for port injected engines, pro...
by LoganD
Tue Sep 10, 2019 10:10 am
Forum: Engine Tech
Topic: Theory of 4 valve poly quad cylinder heads.
Replies: 98
Views: 3515

Re: Theory of 4 valve poly quad cylinder heads.

You don't want swirl in a gasoline spark ignition engine. If you're seeing combustion efficiency improvements with the introduction of swirl then the system simply didn't have enough charge motion to begin with. Tumble is what you want in a gasoline SI engine. High swirl rates produce fuel/air separ...
by LoganD
Tue Sep 10, 2019 9:46 am
Forum: Engine Tech
Topic: Low speed (1500-1800 RPM) driveability issue
Replies: 120
Views: 4110

Re: Low speed (1500-1800 RPM) driveability issue

I've seen carb intakes, both dual plane and single plane, with such bad distribution that one cylinder will be 16:1 and another will be 11:1. I'd weld bungs in each header tube and move the wideband around, you can use the jetting to help mitigate it but you'll never get it great. Get rid of the 4-h...
by LoganD
Tue Sep 03, 2019 10:37 am
Forum: Engine Tech
Topic: Big power N/A LS engine discussion
Replies: 33
Views: 1555

Re: Big power N/A LS engine discussion

Why would you waste your time checking valve lash and replacing valve springs when you can just put a turbo on a 5.3 and make 800 hp reliably? Turbos and EFI have killed the naturally aspirated engine if you want to go really fast. This sort of thinking really pisses me off, twin turbo this, blower...
by LoganD
Thu Aug 29, 2019 1:23 pm
Forum: Engine Tech
Topic: Big power N/A LS engine discussion
Replies: 33
Views: 1555

Re: Big power N/A LS engine discussion

They exist. Just most guys go turbo cuz its so cheap and works to well Stock ls3 heads and intake will make 600-650 hp na on the right motor, by 6000 rpm. Throw a good intake on it and cam to match, 700+ easily done Ls7 stuff has made 600-700 at the tire in vettes na with hyd roller cams At the 400...
by LoganD
Thu Aug 29, 2019 11:58 am
Forum: Engine Tech
Topic: Big power N/A LS engine discussion
Replies: 33
Views: 1555

Re: Big power N/A LS engine discussion

Why would you waste your time checking valve lash and replacing valve springs when you can just put a turbo on a 5.3 and make 800 hp reliably? Turbos and EFI have killed the naturally aspirated engine if you want to go really fast.