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1.75" Headers?

A

Aegis43

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Gilbert AZ
Looking for help from you experienced guys, as I have very, very little.

I have a 385" stroker sbc with AFR 195 heads in my Blazer. It's got a "medium" performance Lunati hydraulic roller (225/229 @ .050, .592/.592 and 112 LSA) which I know is wrong for this truck. It was originally in my 2nd gen Camaro, but I went to a big block. The 5.7 in my Blazer was tired, I had the engine from the Camaro in my garage, so it got swapped in. Currently I have mismatched 1.625" round tube headers and 2" exhaust, which I believe is significantly choking exhaust flow. As many would know, AFR 195 heads have square-ish exhaust ports which are larger than the primary tubes on my headers. Fortunately, the flanges on my Hedman's are thick and large enough that I don't have an exhaust leak.

My question is if any of you guys have 1.75" square port headers on your K5s? If so, what brand? Thank you in advance.
 
Are you certain about those valve lift numbers - .592 is awfully high for an old school SBC that’s in a “medium” category ?
 
tarussell said:
Are you certain about those valve lift numbers - .592 is awfully high for an old school SBC that’s in a “medium” category ?
Click to expand...
I was thinking that too.
In my head, I went, “Wow, this guy is going for it!” That’s got to be missing the top of those pistons by a kitty fur!
I had a cam that provided 0.500 lift, I was worried badly about it.
 
I would stay with the 1⅝ to help with the low-mid range torque.
 
@tarussell @BoondocK5

Remember, I built that engine for my '70 Camaro SS. After running it for a year I just had to put a big block in that car. Rather than the small block just collecting dust in my garage, I swapped it into the Blazer (original 5.7 tired). I know it's the wrong cam for a 4,600 lbs 4-wheel drive. What can I say? But those AFR heads want bigger headers, I'm sure of it.

As a "free" member I can't post a picture of the cam card :frown1:
 
Do you have any pictures of the mismatched header vs exhaust ports? Are they shorties or long tubes? What size is the collector?

The gains depend on your current header. If its a 1 5/8 long tube with a 3" collector, you may be just want to upgrade the exhaust. If its a shorty header with a 2.5" collector, then I would get new headers too.

If I put your engine in my app I come up with 1 3/4" primary tubes and 3" collectors as optimal for around a ~6K peak with your camshaft being 225@050.

What would your budget for headers be? You thinking mild steel painted or stainless or somewhere in between like ceramic coated steel?

I can see what's available.

Also, what is your trans, converter (if auto), and gearing/tire size?

Screenshot_20251003-174026.png
 
folkenheath said:
Do you have any pictures of the mismatched header vs exhaust ports? Are they shorties or long tubes? What size is the collector?

The gains depend on your current header. If its a 1 5/8 long tube with a 3" collector, you may be just want to upgrade the exhaust. If its a shorty header with a 2.5" collector, then I would get new headers too.

If I put your engine in my app I come up with 1 3/4" primary tubes and 3" collectors as optimal for around a ~6K peak with your camshaft being 225@050.

What would your budget for headers be? You thinking mild steel painted or stainless or somewhere in between like ceramic coated steel?

I can see what's available.

Also, what is your trans, converter (if auto), and gearing/tire size?

View attachment 514601
Click to expand...
Damn it’s nice having a tech guy insight!
 
Aegis43 said:
@tarussell @BoondocK5

Remember, I built that engine for my '70 Camaro SS. After running it for a year I just had to put a big block in that car. Rather than the small block just collecting dust in my garage, I swapped it into the Blazer (original 5.7 tired). I know it's the wrong cam for a 4,600 lbs 4-wheel drive. What can I say? But those AFR heads want bigger headers, I'm sure of it.

As a "free" member I can't post a picture of the cam card :frown1:
Click to expand...
If I’m not mistaken after several posts you will be able to post pictures - once that happens please post up the cam card.

That’s a ton of lift for lower end performance duration numbers.
 
Yeah more than 5 posts and you can link pics from a hosting site. With a paid membership you get unlimited pic storage here and can post them anywhere.
 
Some Lunati profiles were pretty high lift, I don't see that exact profile in the old catalog, but it's possible. Howards has a [email protected] small chevy hyd roller lobe that's .560 lift with a 1.5 rocker, which would be .597" at 1.6 rocker ratio, so it's certainly possible, a cam card would confirm. I based the my peak RPM guess on the cam duration, CID, and the head size.
 
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folkenheath said:
Do you have any pictures of the mismatched header vs exhaust ports? Are they shorties or long tubes? What size is the collector?

The gains depend on your current header. If its a 1 5/8 long tube with a 3" collector, you may be just want to upgrade the exhaust. If its a shorty header with a 2.5" collector, then I would get new headers too.

If I put your engine in my app I come up with 1 3/4" primary tubes and 3" collectors as optimal for around a ~6K peak with your camshaft being 225@050.

What would your budget for headers be? You thinking mild steel painted or stainless or somewhere in between like ceramic coated steel?

I can see what's available.

Also, what is your trans, converter (if auto), and gearing/tire size?

View attachment 514601
Click to expand...
I can't post pics in this forum with my level of membership. You can tell by the number of times I've posted vs how long I've been on this forum that I'm very not hard core.

That being said, I'm definitely not interested in mild steel painted. The ones on it now are Hedman Elite pn 69830 long tube ceramic coated, 3" collector. The port shape is very much round. The exhaust port shape on my heads is sometimes called rectangular, but they're more square-ish. They're sweet headers.

For new headers, I'd prefer ceramic coated or stainless. I guess my budget would be around $600 to replace them with right ones.

It has a 700R4, 1800 stall (stock?), 33" KO2s and 3.42 gear. It's my daily driver. Half hwy miles. Off road is forest service roads. Zero rock crawling. I'd like to switch to 3.73 gears someday, but priorities, and $1000+, you know ...

email is [email protected] if you'd like me to produce file pictures of the heads and headers. Certainly mismatch can't be seen installed, as the flanges cover everything. Although I'd take a pic anyway if you want.

When the engine was in the Camaro, like I said, it had Hooker Racing Heart stainless 1.75" headers, 3" collector and 2.5" exhaust.
 
Schoenfeld has options for port size, shape, height, and plug angle

www.schoenfeldheaders.com

Schoenfeld Headers Home

Schoenfeld Headers is the world’s largest manufacturer of circle-track headers, but we specialize in a variety of high-quality exhaust parts, including turn-downs, extensions, tubing bends and elbows, race mufflers, insert mufflers, mandrel bends.
www.schoenfeldheaders.com
 
@nvrenuf @folkenheath Well, I've got 10 posts now and when I click on "insert image," it still presents as I need to paste a link. But trust me, I was looking right at the cam card when I typed the specs. And it does have 1.6 Lunati roller rockers. I bought the cam in July 2020. That was before the private equity firm now known as Edelbrock Group bought Lunati. I don't think Lunati manufactures any cams anymore. I think they're private labeled Comp Cams now. I've talked to them. They're coy about it.
 
Aegis43 said:
@nvrenuf @folkenheath Well, I've got 10 posts now and when I click on "insert image," it still presents as I need to paste a link. But trust me, I was looking right at the cam card when I typed the specs. And it does have 1.6 Lunati roller rockers. I bought the cam in July 2020. That was before the private equity firm now known as Edelbrock Group bought Lunati. I don't think Lunati manufactures any cams anymore. I think they're private labeled Comp Cams now. I've talked to them. They're coy about it.
Click to expand...
Yeah the 5 post thing is so you can link.
The uploading of pictures is only for paid membership which is $25 /year IIRC.
I will also concur you need a better torque converter to wake it up.
 
Ok, I get it. Gear ratio change before anything else first. Maybe I'll think it's just fine after that and exhaust mismatch won't really matter. Thank you guys for your comments.
 
Personally I'd change the cam to something more truck like.
Way easier than a gear change, and makes more sense in the end.
 
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