Go Back  CorvetteForum - Chevrolet Corvette Forum Discussion > C4 Corvettes, 1984 - 1996 > C4 Tech/Performance
Reload this Page >

Anyone "know a guy" who's GM Performance L31R engine swap,350 passed SMOG Sniff test?

C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Anyone "know a guy" who's GM Performance L31R engine swap,350 passed SMOG Sniff test?

 
Old 04-10-2019, 02:51 PM
  #1  
Mikeceli
CF Senior Member
Thread Starter
 
Member Since: Sep 2002
Location: Petaluma CA
Posts: 11,534
Likes: 0
Recieved 6 Likes on 6 Posts
Default Anyone "know a guy" who's GM Performance L31R engine swap,350 passed SMOG Sniff test?

Limited response in the thirdgen f body forum, so I'm visiting from CFOT! Hi Folks!

Regarding my 1989 Camaro IROC Z Vert (autotrans) , I'm thinking about swapping the 305 TPI to a 350 L31. It is a Chev Vortec long block, w/ 9.4to 1 iron head Comp, It's roller Cam is listed as .414 intake .428 exhaust lift @ .50" , Duration 191* intake 196* exhaust 111* lobe separation. I would keep ALL emissions equipment in place and functional. I am looking for actual Sniff test results, good or bad, .

.Anyone know of L31 R 350 swaps, that maintained all OE smog equipment, running clean enough to pass SMOG? I realize standards vary, from state to state, w/ cali (here) being the toughest. Thanks._____________

Last edited by Mikeceli; 04-10-2019 at 02:51 PM.
Mikeceli is offline  
Old 04-10-2019, 03:17 PM
  #2  
bjankuski
CF Senior Member
 
Member Since: Sep 2001
Location: Glenbeulah Wi
Posts: 3,253
Recieved 183 Likes on 166 Posts
Default

This should pass without any issues, I believe that is a stock 1995 to 1999 vortec truck cam. No issues at all on the sniff test.
bjankuski is offline  
Old 04-10-2019, 03:38 PM
  #3  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 14,135
Recieved 611 Likes on 544 Posts
Default

I helped a friend put and L31 Vortec long block in an '84 (with CFI) and it passed -even with out a cat.

You're aware of the mismatched intake to head flange, right? The 305 TPI lower won't mate with the Vortec heads unless you stack gaskets and drill holes. We actually drilled and tapped the vortec heads to accept the CFI intake, then cut the heads off the original Vortec intake bolts, slotted the ends so we could use a screw driver, then coated them with RTV and threaded them in, flush with the intake surface on the head, to plug the original Vortec specific intake bolt holes in the heads.

Thing ran strong when it was done though...even with the small cam.




.

Last edited by Tom400CFI; 04-10-2019 at 03:39 PM.
Tom400CFI is offline  
Old 04-10-2019, 04:16 PM
  #4  
Hot Rod Roy
CF Senior Member
 
Hot Rod Roy's Avatar
 
Member Since: Sep 2004
Location: Mission Viejo CA
Posts: 3,034
Recieved 295 Likes on 277 Posts
Default

Originally Posted by Tom400CFI View Post
I helped a friend put and L31 Vortec long block in an '84 (with CFI) and it passed -even with out a cat.
I doubt that you can delete your cat in California. They crawl under my '84 and verify the part number on my cat. Delightful!

Hot Rod Roy is offline  
Old 04-10-2019, 04:20 PM
  #5  
84 4+3
CF Senior Member
 
Member Since: Aug 2017
Location: New Jersey
Posts: 1,629
Recieved 203 Likes on 179 Posts
Default

You can make it work, there are also vortec lowers available.

Originally Posted by Tom400CFI View Post
I helped a friend put and L31 Vortec long block in an '84 (with CFI) and it passed -even with out a cat.

You're aware of the mismatched intake to head flange, right? The 305 TPI lower won't mate with the Vortec heads unless you stack gaskets and drill holes. We actually drilled and tapped the vortec heads to accept the CFI intake, then cut the heads off the original Vortec intake bolts, slotted the ends so we could use a screw driver, then coated them with RTV and threaded them in, flush with the intake surface on the head, to plug the original Vortec specific intake bolt holes in the heads.

Thing ran strong when it was done though...even with the small cam.




.
The port velocity of vortec heads plus the velocity of the crossfire intake is probably a well matched combo. The stock intake wasn't great, I've heard switching from that to the marine intake is roughly the equivalent of porting a crossfire so it was probably an honest 300 or close to it, the marine ones were rated around there at that time.
84 4+3 is offline  
Old 04-10-2019, 06:11 PM
  #6  
Tom400CFI
CF Senior Member
 
Tom400CFI's Avatar
 
Member Since: Aug 2004
Location: Park City Utah
Posts: 14,135
Recieved 611 Likes on 544 Posts
Default

Originally Posted by Hot Rod Roy View Post
I doubt that you can delete your cat in California. They crawl under my '84 and verify the part number on my cat. Delightful!

Wow. That is....thorough.
Tom400CFI is offline  
Old 04-10-2019, 06:56 PM
  #7  
ex-x-fire
CF Senior Member
 
ex-x-fire's Avatar
 
Member Since: Dec 2009
Posts: 1,580
Recieved 65 Likes on 58 Posts
Default

Vortec heads have no internal egr ports, you must run a tube from the manifolds to feed an egr.
ex-x-fire is offline  
Old 04-10-2019, 08:40 PM
  #8  
Mikeceli
CF Senior Member
Thread Starter
 
Member Since: Sep 2002
Location: Petaluma CA
Posts: 11,534
Likes: 0
Recieved 6 Likes on 6 Posts
Default

Yes, I am aware if the Vortec style intake manifold requirement and was planning for it.

Originally Posted by ex-x-fire View Post
Vortec heads have no internal egr ports, you must run a tube from the manifolds to feed an egr.
EGR situation makes the swap not worth the trouble, since I'm in cali. LORD, this state hates old cars!

Thank you all!
Mikeceli is offline  
Old 04-11-2019, 01:22 AM
  #9  
Hot Rod Roy
CF Senior Member
 
Hot Rod Roy's Avatar
 
Member Since: Sep 2004
Location: Mission Viejo CA
Posts: 3,034
Recieved 295 Likes on 277 Posts
Default

Correction:

Originally Posted by Mikeceli View Post
LORD, this state hates old cars!
But they sure do like my tax money!

Hot Rod Roy is offline  
Old 04-11-2019, 05:42 AM
  #10  
bjankuski
CF Senior Member
 
Member Since: Sep 2001
Location: Glenbeulah Wi
Posts: 3,253
Recieved 183 Likes on 166 Posts
Default

Originally Posted by Mikeceli View Post
Yes, I am aware if the Vortec style intake manifold requirement and was planning for it.



EGR situation makes the swap not worth the trouble, since I'm in cali. LORD, this state hates old cars!

Thank you all!
They will nt know by looking that the egr ports are not there, but I am not sure if the elimination of the egr ports will actally pass the nox test.
bjankuski is offline  
Old 04-11-2019, 04:03 PM
  #11  
cuisinartvette
CF Senior Member
 
Member Since: Oct 2004
Location: Valencia Ca.
Posts: 68,395
Recieved 1,170 Likes on 1,071 Posts
St. Jude Donor '05
Default

I know of someone who owns a test only place & can answer your questions, is there still a requirement where its smogged no more than 30 mi from your mailing address?

Last edited by cuisinartvette; 04-11-2019 at 04:05 PM.
cuisinartvette is offline  
Old 04-12-2019, 01:36 PM
  #12  
Mikeceli
CF Senior Member
Thread Starter
 
Member Since: Sep 2002
Location: Petaluma CA
Posts: 11,534
Likes: 0
Recieved 6 Likes on 6 Posts
Default

Originally Posted by cuisinartvette View Post
I know of someone who owns a test only place & can answer your questions, is there still a requirement where its smogged no more than 30 mi from your mailing address?
Thanks, but I was only gonna do a 350 swap, if it was simple and passable. I suppose I could use a non-Vortec setup, but I doubt it's worth the trouble.
Mikeceli is offline  
 


Thread Tools
Search this Thread
Sponsored Ads
Vendor Directory

Contact Us - About Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: