nineno
Newbie
Hello friends. I’m back after a prolonged hiatus due to some account trouble. (Shout-out to the admins that were able to explain what happened and fix the situation. Thanks, admins!)
A couple of months back I bit the bullet and purchased a set of Hooker cast iron manifolds with silver ceramic coating, part number 8527-1HRK. I bought the manifolds direct from Holley in late April when they were on sale for $308 (about $180 off MSRP) and only a few bucks more than the non-coated (raw cast iron) version.
Here's a fluff/marketing piece from Holley related to the SBC cast Hooker manifolds from when they were introduced a few years ago, if anyone wants to know more about them.
I’ll spare everyone the long story and just say that Holley had to ship me 3 sets of manifolds, over the course of 3 weeks, before they got me all or the right parts, undamaged.
I think the manifolds themselves look pretty good, installed.
Over the Independence Day weekend my good friend helped me install the powertrain (among several other projects that I'll detail in subsequent posts). The manifolds fit the truck chassis pretty well. If anyone else is considering using the Hooker cast iron manifolds, I believe the exhaust-side faces on the Gen 2 LT1 are about 1” narrower (overall width) than typical production small block heads, and the ports sit a bit higher (1/2”, perhaps) in the head as well. So, if you’re installing a more conventional small block in a GMT400 application, the Hooker manifolds might touch the passenger side rear upper control arm pivot. (See below.) There seems to be ample clearance everywhere else.
I will admit, the hardware, gaskets, and collector flanges provided with the manifolds leave a bit to be desired, but I’m happy enough with the manifolds to stick with them. And, while it was frustrating to have to return the first 2 sets to Holley, the customer service staff was helpful and polite.
The supplied bolts were run-of-the-mill grade 5 hex head bolts (visible in the first picture) and the points of the hex interfere with the casting at the trailing bolt location on both (left and right) center runner. This was all especially inexplicable because the manifold casting is clearly relieved most places for bolt head and socket clearance. I guess we'll have to assume that providing clearance at that location would have resulted in a bump inside the exhaust runner that was deemed unacceptable - or something like that.
My solution for the bolt fitment situation was to use studs that I had around from another project, and purchase some ARP compact-head 12-point nuts for all 12 exhaust fasteners. These just fit the manifolds at the trailing central runner location, and have ample clearance at the other 5 locations on both sides. (In the second picture you can see the middle 2 nuts/studs installed, temporarily.) Clearly, I could have just put compact-head fasteners at the two problematic locations, but vanity prevailed and I decided to match all the manifolds fasteners.
As for exhaust port alignment, I’ll ruin the surprise and say that the manifolds match the heads very, very well. When I was evaluating headers and manifolds, none of the options provided dimensional information, which seemed odd. When I bought the manifolds, all I could do was compare the product pictures to the ports on the heads. They looked pretty close, so I crossed my fingers and clicked "Buy."
Below is a bit more information about the exhaust ports, because I never really found a single-source for useful information elsewhere.
Holley offers two exhaust ports on the Hooker cast small block manifolds: typical square ports with rounded corners, and the manifold set that I bought which is described as having a "raised D-ports."
The Hooker cast manifold "raised D-Ports" (left) and Gen II LT1 exhaust ports (right) look like this:
Several Gen II owner/enthusiasts simply call these "D-ports," but they're often told that these are not true D-Ports, and that a true (Chevy) D-Ports are taller. However, most people can agree that the stock Gen II exhaust ports are not round, not square, and are shaped like a D laying on its flat side.
I did find one helpful article about various port shapes. The article suggests that "D-Shaped Port" is the proper (or, at least accepted) name for this exhaust port geometry, while "D-Port" is a specific geometry that is significantly taller than it is wide. (In addition to port shape, there is also the location of the bolt hole, relative to the height of the port, of course.)
There was conversation around D-Ports on a Pontiac GTO forum, as well. I believe this is because Pontiac blocks had heads that had symmetric (or "Siamese") D-shaped ports, where the flat sides faced each other. There is a picture of the Pontiac-specific D-Port in the forum. The same picture also shows something referred to as a "Round Port" that looks very similar to the OE Gen 2 exhaust ports. Dimensions aren't provided for either type of port, unfortunately.
While this should not be used for any crucial performance or fitment decisions, here is a basic drawing showing the approximate dimensions of the Gen 2 LT1 exhaust ports (which matches the ports on the Hooker 'raised D-Port' exhaust manifolds). The minor (lower) radius corners are approximately 1/4" and the major (upper) radius corners are approximately 0.66" by my measurements.
I'll wrap this up, but since it was mentioned in the prior post, I should certainly acknowledge the issue of engine performance.
So, I have knowingly made a choice that does not maximize the performance of my 1995 LT1. This may be an unforgivable sin for many folks, and I can accept that, too.
However, the Hooker cast manifolds have significantly larger runners than the OE 1994-1996 F-body manifolds, and are roughly equivalent to the center-dump 1994-1996 Corvette manifolds. Sure, the Hooker manifold runner-lengths are not tuned; they're just designed to come together at the chosen collector point. But the Hooker collector outlet is designed to fit 2.5" exhaust pipe (3/8" larger than the F-Body manifolds and equivalent to the Vette configurations). Maybe I'm leaving some horsepower on the table, but if maximum power were crucial, I never would have started with a bone-stock 29 year old engine. The Hooker manifolds fit the engine and chassis nicely, the exhaust leaks that can plague headers shouldn't be an issue, and it should be relatively straight forward to plumb the rest of the exhaust system. So the trade-offs I made were acceptable - at least to me.
I'm also struck by the reality that my 2019 model year daily driver sedan is much faster, better handling, better stopping, and more comfortable than this (currently) 35 year old truck will ever be. With that said, a 300hp (+/-) Gen 2 LT1 makes about 3x the power of the V6 the truck was built with and 2x the power of 1989 5.7L/350 V8. All-in-all, the truck will still be pretty well motivated.
I hope there is some useful (or at least entertaining) information in here for someone.
In my next post or two I'll give an update on the engine/trans install, and swapping out the rear axle that took place over the Independence Day weekend.
A couple of months back I bit the bullet and purchased a set of Hooker cast iron manifolds with silver ceramic coating, part number 8527-1HRK. I bought the manifolds direct from Holley in late April when they were on sale for $308 (about $180 off MSRP) and only a few bucks more than the non-coated (raw cast iron) version.
Here's a fluff/marketing piece from Holley related to the SBC cast Hooker manifolds from when they were introduced a few years ago, if anyone wants to know more about them.
I’ll spare everyone the long story and just say that Holley had to ship me 3 sets of manifolds, over the course of 3 weeks, before they got me all or the right parts, undamaged.
I think the manifolds themselves look pretty good, installed.
You must be registered for see images attach
Over the Independence Day weekend my good friend helped me install the powertrain (among several other projects that I'll detail in subsequent posts). The manifolds fit the truck chassis pretty well. If anyone else is considering using the Hooker cast iron manifolds, I believe the exhaust-side faces on the Gen 2 LT1 are about 1” narrower (overall width) than typical production small block heads, and the ports sit a bit higher (1/2”, perhaps) in the head as well. So, if you’re installing a more conventional small block in a GMT400 application, the Hooker manifolds might touch the passenger side rear upper control arm pivot. (See below.) There seems to be ample clearance everywhere else.
You must be registered for see images attach
I will admit, the hardware, gaskets, and collector flanges provided with the manifolds leave a bit to be desired, but I’m happy enough with the manifolds to stick with them. And, while it was frustrating to have to return the first 2 sets to Holley, the customer service staff was helpful and polite.
The supplied bolts were run-of-the-mill grade 5 hex head bolts (visible in the first picture) and the points of the hex interfere with the casting at the trailing bolt location on both (left and right) center runner. This was all especially inexplicable because the manifold casting is clearly relieved most places for bolt head and socket clearance. I guess we'll have to assume that providing clearance at that location would have resulted in a bump inside the exhaust runner that was deemed unacceptable - or something like that.
You must be registered for see images attach
My solution for the bolt fitment situation was to use studs that I had around from another project, and purchase some ARP compact-head 12-point nuts for all 12 exhaust fasteners. These just fit the manifolds at the trailing central runner location, and have ample clearance at the other 5 locations on both sides. (In the second picture you can see the middle 2 nuts/studs installed, temporarily.) Clearly, I could have just put compact-head fasteners at the two problematic locations, but vanity prevailed and I decided to match all the manifolds fasteners.
As for exhaust port alignment, I’ll ruin the surprise and say that the manifolds match the heads very, very well. When I was evaluating headers and manifolds, none of the options provided dimensional information, which seemed odd. When I bought the manifolds, all I could do was compare the product pictures to the ports on the heads. They looked pretty close, so I crossed my fingers and clicked "Buy."
Below is a bit more information about the exhaust ports, because I never really found a single-source for useful information elsewhere.
Holley offers two exhaust ports on the Hooker cast small block manifolds: typical square ports with rounded corners, and the manifold set that I bought which is described as having a "raised D-ports."
The Hooker cast manifold "raised D-Ports" (left) and Gen II LT1 exhaust ports (right) look like this:
You must be registered for see images attach
Several Gen II owner/enthusiasts simply call these "D-ports," but they're often told that these are not true D-Ports, and that a true (Chevy) D-Ports are taller. However, most people can agree that the stock Gen II exhaust ports are not round, not square, and are shaped like a D laying on its flat side.
I did find one helpful article about various port shapes. The article suggests that "D-Shaped Port" is the proper (or, at least accepted) name for this exhaust port geometry, while "D-Port" is a specific geometry that is significantly taller than it is wide. (In addition to port shape, there is also the location of the bolt hole, relative to the height of the port, of course.)
There was conversation around D-Ports on a Pontiac GTO forum, as well. I believe this is because Pontiac blocks had heads that had symmetric (or "Siamese") D-shaped ports, where the flat sides faced each other. There is a picture of the Pontiac-specific D-Port in the forum. The same picture also shows something referred to as a "Round Port" that looks very similar to the OE Gen 2 exhaust ports. Dimensions aren't provided for either type of port, unfortunately.
While this should not be used for any crucial performance or fitment decisions, here is a basic drawing showing the approximate dimensions of the Gen 2 LT1 exhaust ports (which matches the ports on the Hooker 'raised D-Port' exhaust manifolds). The minor (lower) radius corners are approximately 1/4" and the major (upper) radius corners are approximately 0.66" by my measurements.
You must be registered for see images attach
I'll wrap this up, but since it was mentioned in the prior post, I should certainly acknowledge the issue of engine performance.
I completely agree that headers provide more performance potential than even good aftermarket exhaust logs.
So, I have knowingly made a choice that does not maximize the performance of my 1995 LT1. This may be an unforgivable sin for many folks, and I can accept that, too.
However, the Hooker cast manifolds have significantly larger runners than the OE 1994-1996 F-body manifolds, and are roughly equivalent to the center-dump 1994-1996 Corvette manifolds. Sure, the Hooker manifold runner-lengths are not tuned; they're just designed to come together at the chosen collector point. But the Hooker collector outlet is designed to fit 2.5" exhaust pipe (3/8" larger than the F-Body manifolds and equivalent to the Vette configurations). Maybe I'm leaving some horsepower on the table, but if maximum power were crucial, I never would have started with a bone-stock 29 year old engine. The Hooker manifolds fit the engine and chassis nicely, the exhaust leaks that can plague headers shouldn't be an issue, and it should be relatively straight forward to plumb the rest of the exhaust system. So the trade-offs I made were acceptable - at least to me.
I'm also struck by the reality that my 2019 model year daily driver sedan is much faster, better handling, better stopping, and more comfortable than this (currently) 35 year old truck will ever be. With that said, a 300hp (+/-) Gen 2 LT1 makes about 3x the power of the V6 the truck was built with and 2x the power of 1989 5.7L/350 V8. All-in-all, the truck will still be pretty well motivated.
I hope there is some useful (or at least entertaining) information in here for someone.
In my next post or two I'll give an update on the engine/trans install, and swapping out the rear axle that took place over the Independence Day weekend.
