#1  
Old 10-19-2021, 03:48 PM
T/A addict T/A addict is offline
Senior Member
 
Join Date: Sep 2014
Location: Missouri
Posts: 159
Default New motor build input needed.

I purchased 2 400 motors a while back (from different people) that were supposedly "good running recent rebuilds")..... Well I'm having nothing but more and more issues with them as time has gone on and getting very very frustrated so I'm thinking it may well be time to quit buying used and build my own "first - so expect some rookie questions" motor. So here I am to ask the experts some good build recipes.

The car - 69 Firebird - will be mainly just a strong street car with maybe an occasional race/strip pass. Has a 12 bolt/4.10 so an OD trans will surely be a must..4L80E maybe. Not wanting to spend a fortune just something moderate, I do have some items already for the build and ideas..... Stroker kit

I have a set of 6X-4s that have been ported/polished and has all pos valve seals with 211/177 SS valves, guides/springs, elongated push rod holes all casting materials cleaned up, spring pressure should be about 110 to 120 seat and about 160 open, 90cc chambers- estimate will have to measure to make sure.
I'm set on using this set of heads.

I have one of the 400s in the car and one on the stand.... I've also been considering buying a 455 block. Would it be better to go the 400 or 455?
If I strip the 400 and use it what do I need the machine shop to do? I think a .035 bore for the stroker kit would be expected at least?

I'm thinking a roller cam like this one - Hyd Roller 227/235@.050 .525/.530 109LSA 4/7 Swap Rattler
: https://pontiacspeedshop.com/hyd-rol...-swap-rattler/

I do also have all new Dual Sync distributor, Sniper Hyperspark ignition box, Hyperspark coil so thinking I will go with a Holley Sniper.

  #2  
Old 10-19-2021, 04:05 PM
mgarblik mgarblik is offline
Ultimate Warrior
 
Join Date: Mar 2005
Posts: 6,035
Default

Couple of things that will be helpful is to state your HP goals for the engine or your ET goals at the track. The level of driveability for general cruising would be helpful too. From what you have posted so far, the limiting factor is the cylinder heads which you state you want to keep and run. As you make the engine larger, (stroker kit), those heads become more and more of a liability. This all of course depends on your finished goals. Check your valve spring specs on those heads as 160 lbs. open is not likely the correct spec. The seat pressure sounds a little low but makes sense. I would choose to build a 400 vs a 455 with the parts currently available. Nothing wrong with a 455, but you have 2 400's now. Check the block castings to make sure you have the good 400 blocks. I wouldn't want to spend a bunch of $$ building a moderate to high HP combination with the dreaded "557" block casting. That would be 500+ HP. Good luck with the build.

  #3  
Old 10-19-2021, 04:20 PM
T/A addict T/A addict is offline
Senior Member
 
Join Date: Sep 2014
Location: Missouri
Posts: 159
Default

Quote:
Originally Posted by mgarblik View Post
Couple of things that will be helpful is to state your HP goals for the engine or your ET goals at the track. The level of driveability for general cruising would be helpful too. From what you have posted so far, the limiting factor is the cylinder heads which you state you want to keep and run. As you make the engine larger, (stroker kit), those heads become more and more of a liability. This all of course depends on your finished goals. Check your valve spring specs on those heads as 160 lbs. open is not likely the correct spec. The seat pressure sounds a little low but makes sense. I would choose to build a 400 vs a 455 with the parts currently available. Nothing wrong with a 455, but you have 2 400's now. Check the block castings to make sure you have the good 400 blocks. I wouldn't want to spend a bunch of $$ building a moderate to high HP combination with the dreaded "557" block casting. That would be 500+ HP. Good luck with the build.
Not too dead set on any HP goals but if I could get 400-500 I'd be plenty happy, more the merrier though. I want it quite driveable but with plenty of attitude.
Withought knowing specifics of the springs I'd likely just buy new ones then.
I also made sure that neither one was the 557 block when I bought them.
Hmmmmm the wife and daughters will likely drive it at times so I don't want it too radical.


Last edited by T/A addict; 10-19-2021 at 04:26 PM.
  #4  
Old 10-19-2021, 04:51 PM
Steve C. Steve C. is online now
Ultimate Warrior
 
Join Date: Dec 1999
Location: Liberty Hill, Tx. (Austin)
Posts: 10,385
Default

" if I could get 400-500 I'd be plenty happy"

Is that goal based on a 400 build or a build with a 4.125" stroke kit ?

__________________
'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 )
Old information here:
http://www.hotrod.com/articles/0712p...tiac-trans-am/

Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine)
5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension
https://www.youtube.com/watch?v=qDoJnIP3HgE
  #5  
Old 10-20-2021, 06:22 AM
T/A addict T/A addict is offline
Senior Member
 
Join Date: Sep 2014
Location: Missouri
Posts: 159
Default

Quote:
Originally Posted by Steve C. View Post
" if I could get 400-500 I'd be plenty happy"

Is that goal based on a 400 build or a build with a 4.125" stroke kit ?
Either/or... If I reached that goal with this build using stock crank etc and not go stroker kit I'd be pleased, I'd even be willing to run one of the carbs I already have also then and could save the stroker build for a later bigger build.

  #6  
Old 10-20-2021, 07:36 AM
67Fbird's Avatar
67Fbird 67Fbird is offline
Senior Chief
 
Join Date: Mar 2021
Location: GA
Posts: 465
Default

425 hp from a 400 with good heads is ....like rolling off a log easy. Roller cam is expensive for such simple combo. No stroker needed for that level of performance.
Given the costs (at least around here) for machine work You might be 2 steps ahead by purchasing a build kit. Crank rods pistons combo! Obviously FORGED pistons (based on your head cc's) get you into the 10:1 range of compression. 4L80E is another $$$$$ good YES but $$$$ a 200r4 or the 700 are good alternatives each with their own pro's n con's..
TIP...don't forget the set screw INSIDE the block at rear of passenger oil galley(after you drill a .032 dia hole in it), and the dip stick tube goes IN from the oil pan.... sucks to have to pull the pan off a beautiful engine because you forgot to put the bottom tube in.

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 07:29 AM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017