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  #16 (permalink)  
Old 08-07-2014, 02:22 PM
How fast is fast enough?
 
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Originally Posted by TJSBBC View Post
So what you are saying here is that you ported through the casting. Head is junk in my mind. Don't know what your process to repair this but I would not use it.
porting through the casting is VERY common. Not sure why you'd think its junk unless you never saw any of the older racing heads. Or superstock heads- they're still swiss cheesed and then filled back in.

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Old 08-07-2014, 02:26 PM
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Actually they do have different. flow/velocity characteristics which makes them perform as well as they do.IMO,they would be closer to an LT4 head than an LT1.They can be ported & be improved,but,the tecnique is different than with other SBC heads.Rather than doubting your ability,I'm saying you should learn porting techniques specifically for the Vortecs rather than just jumpin in as you would any other head.Get familiar with how & why they do what they do.If their flow/velocity characteristics were not different,they wouldn't really be different.
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Old 08-07-2014, 02:33 PM
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Quote:
Originally Posted by ap72 View Post
porting through the casting is VERY common. Not sure why you'd think its junk unless you never saw any of the older racing heads. Or superstock heads- they're still swiss cheesed and then filled back in.
This ain't no superstock or race head either. Plus those engines were torn down and checked/reparied more often than any street engine would ever be.
I went through 2 heads in my porting days. Scrapped them. Again I said I would not use them, however maybe you would,they would junk to me. Plus these heads are easily attainable cheap. Why bother fixing.
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Old 08-07-2014, 03:26 PM
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Originally Posted by jokerZ71 View Post
Actually they do have different. flow/velocity characteristics which makes them perform as well as they do.IMO,they would be closer to an LT4 head than an LT1.They can be ported & be improved,but,the tecnique is different than with other SBC heads.Rather than doubting your ability,I'm saying you should learn porting techniques specifically for the Vortecs rather than just jumpin in as you would any other head.Get familiar with how & why they do what they do.If their flow/velocity characteristics were not different,they wouldn't really be different.
I agree.
xxxxxxxxxxxxxxxxxx
Just some info

In order of increasing head flow, all 350 cubes, 3 are GEN 2 and 1 is a GEN 1-E.
LT1 alum> 275-285hp/325lb/ft-decent intake-decent exhaust)
LT1 iron>260hp/330lb/ft(decent intake-good exhaust-same cam as L31 iron)
L31>255hp/330lb/ft (poor intake/poor exhaust-same cam as LT1 iron)
LT4=330hp/340lb/ft (decent intake-good exhaust)

And just for a fun comparison of engine power of the mid 90's
L99-200hp/240lb/ft (same roller cam as L31/iron head LT1-decent stock power for a 265 cube engine.
L30-230hp/285lb/ft (Vortec 305 059/520 GEN 1E heads and same cam as LT1 iron/L99/L31 iron) Vortec 305's only came with single cats, L31 got dual cats.

The LT1 was needed for MY1992, the 1st iron LT1 was needed for MY1994 The 1st L31 was required for 1996, same for LT4. The 210cc FASTBURN heads came about around this time as well often compared to the 190cc LT4 head.

Instead of porting a set of L31 heads, I would get into a set of CPP smallport Bowties. But I do understand grinding on stock heads for ultimate low buck status, but factoring in your time, it doesnt pay, esp. for the small power increase, machining fo screw in studs, accounting for low lift of stock L31 setup

A case can easily be made to step up to a performance casting.

peace
Hog
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  #20 (permalink)  
Old 08-07-2014, 03:39 PM
How fast is fast enough?
 
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If their flow/velocity characteristics were not different,they wouldn't really be different.

They really aren't that different. your talking about the differences between two oem sbc heads here... Not the difference between an sbc head and a 4v dohc pent roof head.
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  #21 (permalink)  
Old 08-07-2014, 04:14 PM
How fast is fast enough?
 
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here are some old pics from I think the 3rd set of heads I did. The blue tint on the chamber and bowls is to show the airflow pathway, this is what Vortecs are known for and it greatly increases swirl as compared to the older smogger heads or camel humps. The method to do this was not very scientific- I hooked a shop vac to a 4" cylinder to the head surface, installed a valve at .500" turned it on and lightly misted machinists dye into the runner.

Oddly enough very little dye stuck to the runner and most of it stuck to that area of the bowl- indicating to me that is where the strongest flow pathway is and where it should be promoted. (I did one prior to porting too but lost that photo). I also found that the valve would find a natural balance around .550" lift where the flow would go down if it came out more or less., this distance increased slightly with porting but not as dramatically as I was expecting.

Also, as shown you want to port right up to the valve seat- this is actually the most important area. This doesn't show the chamber side done but it does need to be blended into the top cut as well- that part always made me the most nervous but it is very important.

Also, if you notice the shadow the valve guide made in the dye on the bowl- if you can direct that flow more towards the spark plug then less ignition advance will be needed and more power will result- very hard to make any big changes to it though.

Sorry for the crappy pics, This was done years ago (5 I think) and I lost all the finished photos. And I have not touched a Vortec head since- PRAISE JESUS for that one.
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Old 08-07-2014, 07:17 PM
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here are some old pics from I think the 3rd set of heads I did.
Looks good!

Here is a side by side of the intake port on the 062 heads. I filled the push rod side with a weld first so I wont break through this time its only a problem on 1,2,7,8

And after looking again there is no hardened seat on the 062 I have just looked that way my bad.
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Old 08-07-2014, 07:30 PM
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Here is the bowl side.
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  #24 (permalink)  
Old 08-07-2014, 08:45 PM
How fast is fast enough?
 
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Blend in the bowl cut and try to blend in the top cut to the chamber. I cheat and use a dremel for the top cut- takes longer but it's more precise.
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  #25 (permalink)  
Old 08-08-2014, 06:17 AM
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Quote:
Originally Posted by Hogg View Post
In order of increasing head flow, all 350 cubes, 3 are GEN 2 and 1 is a GEN 1-E.

LT1 alum> 275-285hp/325lb/ft-decent intake-decent exhaust)
LT1 iron>260hp/330lb/ft(decent intake-good exhaust-same cam as L31 iron)
L31>255hp/330lb/ft (poor intake/poor exhaust-same cam as LT1 iron)
LT4=330hp/340lb/ft (decent intake-good exhaust)
. Actually

alum LT1 300HP 205/207 cam Corvette

iron LT1 (better flow than alum version) F-body/ImpalaSS(260HP) 275-285HP 205/207 cam '92, 202/207 '93-'95, 200/207 '96-'97 ... Std. B-body 191/196 cam

iron L31 255HP (good intake/good exhaust) good HP for 191/196 cam

alum LT4 330HP '96 Vette... 203/210 cam (improved ports, short turn radiius) (limited '97 F-body use) (LT4 Hot Cam 218/228)

Last edited by BuzzLOL; 08-08-2014 at 06:43 AM.
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Old 08-08-2014, 06:54 AM
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Originally Posted by BuzzLOL View Post
. Actually

alum LT1 300HP 205/207 cam Corvette

iron LT1 F-body/ImpalaSS(260HP) 275-285HP 205/207 cam '92, 202/207 '93-'95, 200/207 '96-'97 ... Std. B-body 191/196

iron L31 255HP (good intake/good exhaust) good HP for 191/196 cam

LT4 330HP Vette... 203/210 cam (improved ports, short turn radiius)
You mean "In addition", not "actually".

OK, so you added the LT1 Vette,a nd some cam numbers great. I purposely left out the LT1 Vette because it has an air intake and exhaust that isnt comparable to the others. We could have also delved into the 1997 LT4 Firehawks and LT4 SS Camaros with teh balanced and blueprinted LT4 engines that used Extrudehoned stainless exhasut manifolds, high flow exhaust in order to actually make the LT4's 330hp rating while using the standard LT1 F-body calibration, thus avoiding recertifying for emissions.
LT4 has LS1 power in the GEN 2 package.
then there are the 305-335hp LT1 powered Firehawks/WS6 Pontiacs and SS Camaros, but who's counting?

But if you think the L31 had a good OEM intake and exhaust. You are "BUZZed".

L30-305/L31-350 CSFI intake-nothing good about it


on right(marine intake on left)


Stock 1/2 ton L31 exhaust of right, 1-7/8 and even smaller in the bends (not good)



peace
Pauly
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Old 08-08-2014, 08:03 AM
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Blend in the bowl cut and try to blend in the top cut to the chamber. I cheat and use a dremel for the top cut- takes longer but it's more precise.
Most definitely, I generally do all the heavy cutting on all the ports first. And come back with sanding rolls at the end.
I forgot how much longer it takes to do cast iron and the Carbide bits get dull fast. Even when using a good bit of cutting grease.
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Old 08-08-2014, 08:29 AM
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Originally Posted by TJSBBC View Post
This ain't no superstock or race head either. Plus those engines were torn down and checked/reparied more often than any street engine would ever be.
I went through 2 heads in my porting days. Scrapped them. Again I said I would not use them, however maybe you would,they would junk to me. Plus these heads are easily attainable cheap. Why bother fixing.
Because I can fix a holes in the push-rod side for free. I enjoy porting heads and honestly I take pride in doing a good job. I spend about 2.5 hrs on each intake port just on raw material removal.
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  #29 (permalink)  
Old 08-09-2014, 01:04 AM
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Originally Posted by Hogg View Post
You mean "In addition", not "actually".

OK, so you added the LT1 Vette,and some cam numbers great. I purposely left out the LT1 Vette because it has an air intake and exhaust that isnt comparable to the others.
. Actually, YOU included the alum. LT1 head which is basically only the Vette head... but then you paired it with the F-body HP numbers... just thought I'd insert the correct numbers in case somebody is tucking the info away for reference later... wasn't concerned about the limited edition tuner special models years later... those can have any kind of spec.s...
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Old 08-09-2014, 01:13 AM
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Originally Posted by ap72 View Post
porting through the casting is VERY common. Not sure why you'd think its junk unless you never saw any of the older racing heads. Or superstock heads- they're still swiss cheesed and then filled back in.
. X 2... I've struck water while porting... part of the learning process about a particular head... just heat the head up and spend 5 minutes welding up the hole, resume porting, put the heads on a hot daily driver... the antifreeze 50/50 mix protects the weld fine... not going to toss heads I just spent a week porting...
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