[PunchT37]

Originally Posted by zeebo

you guys are the luckiest go grow up in that era..that wont be seen again for 1000 years....im so jealous..i needed to have been born 15-20 yrs earlier....

1000 yrs.? Nah. Never happen again.

I remember at 10 to 12 yrs. old sitting at the stop sign in my neighborhood telling the cars to "smoke em down". The one I remember the most was a green `71 Duster 340. That dude smoked the piss out of that car. He lived a block down. So, we rode our bikes down there. He was inside, but we could still see smoke comming off that thing with strips of rubber hanging off the tires. So, he ruined his tires for us.

The hot thing back then was flipping the air cleaner lid to get more carb sound. How many Q-jet sounds did we hear [in the neighborhood] back then?

Junkyard hopping to look for good Pontiac heads? I loved junkyards. Even found a complete `66 Buick Riviera GS out there with the 425, dual quads, cast valve covers, air cleaners, fuel lines etc. Nah. No more of that.

[4mula73]

Would the 500557 block be able to handle much more?

[Skip Fix]

557 blocks have variable longevity when leaning on them TomS here has a dyno mule motor using one making over 500 hp. My RAIV 400 I raced for years made right at 400 hp. Other guys have broken them at 400 hp esp #2 main saddle.

[4mula73]

Originally Posted by Skip Fix

Other guys have broken them at 400 hp esp #2 main saddle.

Good to know. Thanks

[Skip Fix]

A 400 with lighter rods and pistons wouldprobably be the best insurance for the block to last, but for my RAIV heads they are going on another earlier casting block when I freshen that motor up. I'll look hard at the 557 block too to seeif I broke it.

[zeebo]

looking to get my heads cc'd soon..will update

[4mula73]

I've been thinking about maybe camming up a bit more from the 256. What would you guys recommend? I want to stick with a Comp cam. Same setup as before except 6X-4s instead of 96s. Dual Energy 275? XE262? What do you guys think? Thanks

[1971WARBIRD]

Originally Posted by 4mula73

I've been thinking about maybe camming up a bit more from the 256. What would you guys recommend? I want to stick with a Comp cam. Same setup as before except 6X-4s instead of 96s. Dual Energy 275? XE262? What do you guys think? Thanks

the set up in my 78 TA that we are finishing;
78 557 400 block, +.030TRW pistons, tomahawk forged rods, block zero decked, bottom end balanced, 6X 4 heads milled for 9.2 compression, performer intake, 78 Qjet, comp 268XE cam. idles with some rump, smokes the tires at will (275x60x15's) with 3.42 gears.

[Cliff R]

+2 on running out of power early.

Not nearly enough camshaft for a 400 engine, even at 8 to 1 compression.

The best cam I've found for those engines is the Crower 60240. 210/221/112 with 270/276 duration seat to seat.

I've tuned 8 to 1 compression 400 engines using the larger XE262 camshaft.....I can't say "TURD" loud enough......FWIW......Cliff

[steve25]

You did yourself a disservice if as you say polished the Intake ports and or runners.
The as cast surface barring any major dips and ridges is whats needed!
I would use a fine type cut burr for cast iron and put texture back onto any polished areas.
You can polish the exh ports to a mirror finish if you care to, but your motor will burn the fuel that gets into it the chamber much better with a ruffer Intake, a polished wall surface does not aid air flow in oppsition to what you may have heard and or seen written .

[4mula73]

Originally Posted by steve25

You did yourself a disservice if as you say polished the Intake ports and or runners.
The as cast surface barring any major dips and ridges is whats needed!
I would use a fine type cut burr for cast iron and put texture back onto any polished areas.
You can polish the exh ports to a mirror finish if you care to, but your motor will burn the fuel that gets into it the chamber much better with a ruffer Intake, a polished wall surface does not aid air flow in oppsition to what you may have heard and or seen written .

I'm picking up the 6X-4s today, and to my knowledge, they are virgin. I didn't mean polish, just remove the big burrs, while keeping a somewhat rough finish. Is that what I should do, or just gasket match them?

[4mula73]

Originally Posted by Cliff R

I've tuned 8 to 1 compression 400 engines using the larger XE262 camshaft.....I can't say "TURD" loud enough......FWIW......Cliff

Could you clarify what you mean- is it just a general lackluster performer, hard to tune, or what? Thanks

[steve25]

The motor does can not fully burn the fuel that makes its way into the chamber, as polished surface makes the fuel clump/ball up, a ruffer suface keeps the fuel in a far smaller particle form which burns better/more complete and also faster instead of just being passed out the Exhaust.
On the 6X heads you can port match the Inatke if they need it, but on the Exh side DO NOT DO A GASKET MATCH! leave it at the stcok size.The place on these heads where the Exh needs work is in the valve bowl on the short turn side where there is a big machining lip left.
This is what needs to be ground off and belnded in with a polish job.
If you have a metal grinding burr that can do it (small 1/4" ball cutter), bullet nosing/boat tailing off the valve guide in each bowl will pick you up flow also.
You do not need to fully grind off the air injection boss at the base of the guide on the roof, but making it into just a tall triangle shape will help the flow also when you have bullet nosed the valve guides.
I would also get your Exh valves back with a 30 degree angle so that the main 45 degree seat angle is .060" to .080" wide.
NOTE..... that if your seats have already been recut and you will go in and do any grinding in the valve bowls, be sure to line the valve seat area with two thin strips/layers of duct tape so that if you slip grinding you do not nick a valve seat!

[mechanic17]

Baron and Cliff,

I actually have both a 744 cam and a xe268 new in the boxes. Never can get desktop dyno or PT engine analyzer to show good power from the 744 in any CID. Scared to use it frankly, as personal testimony is scarce around here. The damn lobes look almost like a roller cam. Does it "need" high compression and Rhoads? And how much would be too much SCR for the XE268?

BTW, I currently run the 041 in my 400 at 10.2 SCR and like it alot. But I'm always building another motor, currently a 350 w/17 heads.

[4mula73]

Originally Posted by steve25

The motor does can not fully burn the fuel that makes its way into the chamber, as polished surface makes the fuel clump/ball up, a ruffer suface keeps the fuel in a far smaller particle form which burns better/more complete and also faster instead of just being passed out the Exhaust.
On the 6X heads you can port match the Inatke if they need it, but on the Exh side DO NOT DO A GASKET MATCH! leave it at the stcok size.The place on these heads where the Exh needs work is in the valve bowl on the short turn side where there is a big machining lip left.
This is what needs to be ground off and belnded in with a polish job.
If you have a metal grinding burr that can do it (small 1/4" ball cutter), bullet nosing/boat tailing off the valve guide in each bowl will pick you up flow also.
You do not need to fully grind off the air injection boss at the base of the guide on the roof, but making it into just a tall triangle shape will help the flow also when you have bullet nosed the valve guides.
I would also get your Exh valves back with a 30 degree angle so that the main 45 degree seat angle is .060" to .080" wide.
NOTE..... that if your seats have already been recut and you will go in and do any grinding in the valve bowls, be sure to line the valve seat area with two thin strips/layers of duct tape so that if you slip grinding you do not nick a valve seat!

Thanks for the advice!

[tom s]

We made 585 HP with that block!603 TQ.Tom

[Skip Fix]

When I freshened my 78's original motor I used a custom XE262/270 on a 112. Actually degreed as a 270/278. Power was OK, idle a little lump. When I rebuilt a 400 with 6x-4s on a 400 for the 81 to replace the 78 motor in it I used a Summit 2801 and it seemed like a better cam for the low compression 400 than the XE. Just as good an idle, slight rump and decent power.

Not to mention the first XE they sent the outer cam journal was too big to fit in the block! and I ended up eating shipping for Comp to replace it!

[Cliff R]

"Could you clarify what you mean- is it just a general lackluster performer, hard to tune, or what? Thanks"

I've worked on enough 400's with that cam in them to know to stay away from them. They will idle with a bit of "attitude", throw a little power at you early in the rpm range, and be seriously lacking in upper mid-range and top end power.

If you just want a "rumpity-rumpity" sounds and enough power to do a decent burn-out in a hard right hand turn leaving Dairy Queen, you have the right camshaft.

If you want about the same idle quality and a much broader/flatter torque curve, with stronger upper mid-range and top end power, cut the Crower 60240 or Summit 2801.

If you bump the compression to around 9.5 to 1, get the Crower 60916 or Summit 2802.....Cliff

[4mula73]

Thanks for all the input guys. Another question: do the 1.66 valves in the 6X-4s really cause a significant loss over the 1.77 valves in the 96s?

[1971WARBIRD]

street motor, no. they did a test years ago that did 1.66 vs 1.77 in a 455 which are even more exhaust challenged. the engine made more torque with the 1.66 until they got into higher performance cams which were more designed for strip not street. it was in High Performance Pontiac, called "Indian Head" i believe back around 1990-1991.