400 Sneaky HP build?

[whiskeychick]

Alright so by sneaky I mean that I am getting collector plates for my 78TA so I cannot change anything on the outward appearance.  However, what they cannot see won't hurt them

 She currently has a 6.6TA with the 6x heads and the original Qjet.  Hasn't see the road since 1990 and only has 130,000kms on it.  I also have another pontiac 400 in it that i can use as well, don't think its a TA.

So i'll clean up the block bore/hone, and have it decked, get a good set of pistons to match, and good bolts etc.
The 6x heads, just clean them up, and they should be fine?
Obviously get a good cam matched to my setup

Now the intake i can't use the edelbrock performer intake obviously because the only option besides stock is an era correct part, so if my stock intake is a real bottle neck is there another option out there that I don't know of?  Something from the 70's era that would flow much better?

And the stock 850cfm Qjet is the cherry on top lol

So basically I need a stock looking engine but want a bit more performance for out of it, nothing crazy but I want it respectable by todays standards. 

Oh and I have a set of original H.O. tri-y headers and a transverse dual exhaust for her for better flow out.

[rad400]

use the stock intake flows pretty well, stroke your other 400 to 461 use the 6X heads you have and 041 or 60919 crower cam 041 copy.et good internals eagle rods or tomahawk rods rpm rods all good. SRP pistion I think they are called that.

[whiskeychick]

So don't have to worry about porting or anything thing on the intake or heads?

any guess to what I could reasonably expect to run hp wise with the stroker, cam and rods etc?

And thank you!!

[ericwy]

And the stock 850cfm Qjet is the cherry on top lol

stock 850?  do tell.  My 77 factory Qjet is 800 cfm.  I was not aware a higher flowing model existed.

[rad400]

wiskeychick it will only helpperformance to port your heads and intake but if it just a daily driver or weekend worrior than you do not need too. I like your screen name.

[72blackbird]

It all depends on which 6x heads you have- 6x-8's with 98-102ccs will go from 7.8:1 on a 400 to 9.2-9.3:1 on a 455 or 461 stroker. 6x-4's have a smaller 91-94cc chamber, and will yield 9.6-9.7:1, too much for 91 octane.

Most Pontiac parts vendors sell 400/461 stroker kits, which use a 4.25" stroke crank that has 2.20" rod journals and use 6.8" long BBC rods and custom pistons. Typically these kits also come with bearings and can be balanced already- be sure to ask as a balanced rotating assembly is essential to a smooth running engine that lives a long life.

Geno

[800qjet]

There are lots of ways to be sneaky There are headers under manifold heat shield (had to trim it), The intake manifold is a '74 ho but you can't see the numbers, the valve covers have thick gaskets under them to clear the roller rockers, the quadrajet and hei are rebuilt and modified but you can't see that. All the vac. hoses, emission hoses and charcoal canister are there though they don't work. If someone looked underneath they'd see the headers but if you use manifolds  you are good to go. It's another story when it's running - I usually tell people that it's the loud mufflers and it's idling too fast.

[whiskeychick]

And the stock 850cfm Qjet is the cherry on top lol

stock 850?  do tell.  My 77 factory Qjet is 800 cfm.  I was not aware a higher flowing model existed.

My bad, 800 was thinking 750, I have 3 750's and my stock one.

It all depends on which 6x heads you have- 6x-8's with 98-102ccs will go from 7.8:1 on a 400 to 9.2-9.3:1 on a 455 or 461 stroker. 6x-4's have a smaller 91-94cc chamber, and will yield 9.6-9.7:1, too much for 91 octane.

Most Pontiac parts vendors sell 400/461 stroker kits, which use a 4.25" stroke crank that has 2.20" rod journals and use 6.8" long BBC rods and custom pistons. Typically these kits also come with bearings and can be balanced already- be sure to ask as a balanced rotating assembly is essential to a smooth running engine that lives a long life.

Geno

I will check tomorrow to see what heads I have the 8 or the 4, thanks for that info.
Been looking at the stroker kits, like the one from Butler, or Eagle heard good things about them.

Thanks rad400 lol

800qjet, that does look nice and clean.  And I got era correct headers so I'm good on that front, and so far as I know I only need to send them pictures they don't have to hear it   Its only unless I get in an accident that I may have issues, and have them try to void my insurance, but I would really like to see an insurance agent that would be able to pick up anything even if they heard it running lol

[1blk1]

Now the intake i can't use the edelbrock performer intake obviously because the only option besides stock is an era correct part, so if my stock intake is a real bottle neck is there another option out there that I don't know of?

have heard some guys grind the e-brock name off and use, who do you have to fool? would they know?

[800qjet]

re:  have heard some guys grind the e-brock name off and use, who do you have to fool? would they know?

I guess only inspection stations etc. and a limited number of car guys. In some ways it's like the numbers matching guys - even most die-hard Chevy guys at a car show don't know what Y anything is or if its fast or slow by looking at it - just that it's nice. There was a time when it was more important i.e. early 60's days when guys put a 409 in a '55 and told everyone that it was a 348. Or the opposite - telling people you had a 427 when you had a 396 to scare them off. People did race on the street and when money was involved there weren't any rules. I don't mean to encourage street racing - just remembering a different time.

[whiskeychick]

Now the intake i can't use the edelbrock performer intake obviously because the only option besides stock is an era correct part, so if my stock intake is a real bottle neck is there another option out there that I don't know of?

have heard some guys grind the e-brock name off and use, who do you have to fool? would they know?

Insurance company, I have to send them pictures in order to qualify for collector status plates.  The only issue that I can see is if anything happens, accident wise and they go over the car if they find anything that is not compliant to their guidelines then they can and will void my insurance, and I will be stuck with all the bills. 

And yea, 800qjet, I don't expect any of the insurance guys to know enough specifics about the car to be able to pick out the little things, let alone most of the car people that I know.  I just don't want to do anything to conspicuous

And thanks all for the replies

[72blackbird]

whiskeychick,
The average L78 400 has 6x-8 heads (98-102cc chambers), 7.6-7.8:1 and 180 hp. The addition of a 400/455 or 400/461 stroker kit and a good cam would not only double the stock output, but exceed it by 50-100 hp. You would have to put a better exhaust on it (RARE manifolds or headers and 2 1/2" duals), but the stock carb could be rejetted and the stock HEI could be retuned to compensated for the hp increase. Other than the noticeably louder exhaust note from the increased hp, nothing else would be obvious externally and only a mechanic would be able to tell the difference- a true stealth modification.

So what is downside? If it turns out you have a W72 you're all set- the 'xx' block is a reissued 481988 and is perfect for a stroker build. If you have a 500557 400, you're right at the edge of your block's durability- theses blocks are lightweight and have undercut main saddles. In short, the added power may make them crack from the boost in power. This is why all of the well-known engine builders recommend you use a 481988 or earlier 979xxxx 400 block. Only a Pontiac expert could tell you substituted your original engine for this block, so I wouldn't even worry about it if you plan to build one.

Geno

[rad400]

Depending on which insurance co. you have some have insurance for a modifed cars and then u can mod the engine and won't get into trouble.