Porting a stock LT5

[Eric870]

Need info on Porting. Lots of Info (Links).

So what is the best set-up for a Stock engine?

Is there any advantage to porting the Heads on a Stock engine?

How big should the porting be? 35MM/34MM

Tools, what are the best tools for this job? Die grinder bit sizes ect..?

[A1990]

36mm and yes port the heads.

[Eric870]

36mm and yes port the heads.


Dennis, You have a 368. How much air is enough for a stock 350?

[1989ZR1#74]

36mm and yes port the heads.

And paint them Atomic Orange right?

[LGAFF]

Porting heads is a tricky piece, I have seen a few heads sent to the gods of speed due to misalligned porting....and ZR-1 heads are not easy to find and not easy to fix. Watch out for water jackets.

[Eric870]

Porting heads is a tricky piece, I have seem a few heads sent to the gods of speed due to misalligned porting....and ZR-1 heads are not easy to find and not easy to fix. Watch out for water jackets.

I do not want to F..up the heads. Risk vs. reward. Is it worth it? I do not want to mess with the engine it seems to me to be a low mile motor. I'm thinking maximize with bolt on?s and top end porting. But I have no fear it is a spare motor

[LGAFF]

I am a big do it yourself person, but if you do not know the weak points of the head, you need to stay smaller on ports, going 35/36 is a recipe for disaster......you can damage the area under the lifter or go through a water jacket, there are some very thin spots, and even people with experience have trashed sets.

Pete is not cheap but I know he is an expert at it. I have done a lot of intakes but I would not wander down a head port without a guide to help.

Be careful.....

[Eric870]

I am a big do it yourself person, but if you do not know the weak points of the head, you need to stay smaller on ports, going 35/36 is a recipe for disaster......you can damage the area under the lifter or go through a water jacket, there are some very thin spots, and even people with experience have trashed sets.

Pete is not cheap but I know he is an expert at it. I have done a lot of intakes but I would not wonder down a head port without a guide to help.

Be careful.....

Lee, that very good advice and based on your advise I?m planning on staying away from the heads. One of the reasons I bought the engine is so I could "do it myself" and learn.

[LGAFF]

Port matching the head is ok, if you go 35-36 on the intake, port match the heads so that the transition is good, but then only go into the head with a taper about an 1" or 2" into the head, also, the port match will not be a circle pattern, it will be a cresent....if you have questions, more than happy to talk, or reach out to the pros.....Pete, Ryan, etc.

No need to port the 2ndry in the head on a port match.

[A1990]

And paint them Atomic Orange right?
Naw, that's my thing...Pete won't work on them if you paint them AO

[A1990]

Dennis, You have a 368. How much air is enough for a stock 350?
I actually have 396, but I had Marc do his 500 package on my car when it was a 350. 36mm porting and heads ported too. Take a look at what Marc does on his 500 package.

If you are going to do it yourself, I would error on being conservative too.

[LGAFF]

I have 391 rwhp on the 92, without touching the heads, wonder if port matched with 93-95 intake cams would get you low 400s for cheaper, which is close to a 500hp package for a lot less $.

I am doing a port match on the 90 and dropping a few hundred pounds from the car, hoping to match a 500hp car performance....no AC, etc

I almost traded the 90 on a Viper up in WI a month ago, but couldn't walk from the project at this time.

[Eric870]

Port matching the head is ok, if you go 35-36 on the intake, port match the heads so that the transition is good, but then only go into the head with a taper about an 1" or 2" into the head, also, the port match will not be a circle pattern, it will be a cresent....if you have questions, more than happy to talk, or reach out to the pros.....Pete, Ryan, etc.

No need to port the 2ndry in the head on a port match.


So I thinking i can always take more out later and its hard to put back. 35MM through intakes and taper and port match 1" into the heads. 35MM though the plenum? what kind of gains can I expect from this set-up?

[LGAFF]

If the cam timing is good, 390-400 rwhp....thats about as much as can be squeezed out of it.

[LGAFF]

Save some budget for good tires, grip gets harder to come by at that point.

[Eric870]

If the cam timing is good, 390-400 rwhp....thats about as much as can be squeezed out of it.


I will check the timing when i receive my new tool:-D

[LGAFF]

Should get it out tomorrow :thumbsup:

[Eric870]

Save some budget for good tires, grip gets harder to come by at that point.


I thinking Headers, DM flywheel and a chip. Thats probably a good start...

[Polo-1]

Go Big or Go Home...... wimps 35-36mm ports:p

http://i7.photobucket.com/albums/y292/kpie/KP2.jpg

[Locobob]

Why don't you just come over to my place sometime Eric. I have ported heads and intake laying around plus working on another intake right now. I'll give you the grand tour of porting stuff. :thumbsup:

[Pete]

Naw, that's my thing...Pete won't work on them if you paint them AO



:p



I would take LocoBob up on his offer,he has done a few port jobs he does good work.:thumbsup:

Pete

[Paul Workman]

I'm a DIY'er as well. I learn more by doing than watching, but I can tell ya from first hand experience too that education costs money, especially when it comes to heads! Honestly, unless you stay under 35mm, as Marc H told me; "85% of the risk comes from 15% of the gain!

Leaving heads on:
One of our Canadian engine builder friends ;) told me that a 4% taper is "a good thing". I did some reading on the subject, and dayam if he wasn't right - or at least agreed with 2 other sources I found. Bottom line: tapering from 36mm to 33ish at the valve guide or a cm above it is mathematically poifecto (according to some sages). Unfortunately, I can't quantify the results, cuz I never got the chance to dyno it against the 390/400 rwhp benchmark for a top end porting. But, I can tell you it was a friggin amazing leap in performance!

Heads off (full porting):
1) For a proven way to go, send your heads to Pete for a CNC and be done. In the end, the cost is 'bout the same as DIY...or so it was for me.
2) See #1 or make sure you have a professional head repair outfit lined up, just in case.:rolleyes: Don't worry 'bout pin-holes in the weld (there is a cheap way to fix those). Do worry about pin holes where welds did not take place - as a thin spot will eventually crack and you'll have coolant or oil (depending) gushing in.

Gotta run just now. But from one DIY to another, if ya just hafta, then PM me and I'll show you in painful detail where the quicksand is :jawdrop: and how to avoid at least some of it!

P.

[ZZZZZR1]

Go Big or Go Home...... wimps 35-36mm ports:p

http://i7.photobucket.com/albums/y292/kpie/KP2.jpg

Wow... I have penis envy! :worship:

[Eric870]

Why don't you just come over to my place sometime Eric. I have ported heads and intake laying around plus working on another intake right now. I'll give you the grand tour of porting stuff. :thumbsup:

Robert, I will defiantly take you up on that offer.

[A1990]

Why don't you just come over to my place sometime Eric. I have ported heads and intake laying around plus working on another intake right now. I'll give you the grand tour of porting stuff. :thumbsup:

You'll be in great hands with Robert. :thumbsup:

I remembered you were both in Oregon, didn't put it together you are in the same place...

[Polo-1]

Wow... I have penis envy! :worship:

NJ is the LT5 Porn King

http://i7.photobucket.com/albums/y292/kpie/39mmc.jpg

That's NJ cutting more after GVD has worked them over:jawdrop:

I never heard how that 427 ran:icon_scra

[Locobob]

NJ is the LT5 Porn King

http://i7.photobucket.com/albums/y292/kpie/39mmc.jpg

That's NJ cutting more after GVD has worked them over:jawdrop:

I never heard how that 427 ran:icon_scra

Yeah, would have liked to have seen some numbers on this build

[Eric870]

I'm about done with my rookie intake porting job. Here are some before and after Pics.

Look how big the injector port is on a 1990.
BEFORE

[Eric870]

AFTER

[LGAFF]

Looks good, what are the specs??

[Eric870]

Looks good, what are the specs??



Primary: 35.5MM at the Plenum tapered to 34.5 at the head.

I Port matched at the head and I used a break Cylinder Hone to taper the top of the head. Only about 1.5 inch. (see picture I will Add.)

I've been taking it very slow. I can always take more out later but I can't put it back.

[Eric870]

Yes, That is a Cork..a large one just cut it at the right size and it fits perfictly.