[Bob Rutledge]

Here is what I am looking at with my 400 build. Please give me tips or suggestions, and also what you think this is going to run me. Stock 78 lo-po, 400 bottom end has never been apart before with 6X-8 heads that have never been rebuilt before. The camshaft has a couple of wiped lobes, along with some very badly pitted lifters. I may be able to get some pics up later of the lifters. Anyway, the engine is in my garage, with the heads off. I haven't disassembled the bottom end yet, or taken off the timing cover. Should I leave all of that on and let the mchine shop take apart? This is going to be a fairly mild build, but I would like to see 300-ish horses if that is possible. I will tell you what I have bought so far, and I need advise as to what to have the machine shop do as far as the build goes. I have bought a Comp XE 268 cam, lifters, and full roller timing set. I have also purchased a new oil pump, pickup, and drive rod. I have not bought any bearings yet as no machine work has been done, and I do not know if the machine shop will have to cut anything down. Since it is going to be a mild rebuild, I am looking at stock rods checked for size, with arp bolts. I am also thinking of a set of KB hyper pistons for the build, or if anybody thinks I should just use cast stock type pistons. I was also thinking of trying to get the most cubes I can by having it bored .060 over if the walls check out to be thick enough. I am also thinking about having the block decked, and the heads cut enough to reach at least 8.5 or 9-1 compression. What was already on the car before I took the motor out is a set of 1 and 3/4 four tube headers into a 3" collector. True 2.5" exhaust into T/A splitters. It has a 2400 RPM stall converter I got off of e-rape a few years ago, 8mm wires, and an accell coil on a distributor that I have dialed in to get me to full advace at about 2400 rpm. The turbo 350 also has a B&M shift kit I installed the same time as the torque converter. Rear gears are the stock 2.41 highway gears. So, what do you think of this as a mild type street build? And am I to optimisitic to think I can get 300 horses from this?

[red76TA]

im building also building a low comp 400 - i figure around 8.8 to 1 or so
im thinking the xe 268 might be a tad too big for an under 9 to 1 400, i was thinking either the summit 2801 or 2802 for my motor, but im sure somone with alot more experience will give us some tips

[Bob Rutledge]

Hey red, here is a link to another site with for the same question. Thought I would post the link here for you to see some answers there already.http://passion4pontiacs.com/forums/showthread.php?t=596

[red76TA]

cool deal, thanks bob
ive got a set of midly ported 6x8's that are 98cc and my pistons are a hair out of the hole, so im figuring with a thin head gasket i should have 8.7-8.8 to 1
since i may have to take some trips in this car im probably going with 3.23's with a max of 3.42, im not trying to make a strip burner (yet) but a good driving, strong running ta that has somewhere in the 300 to 350 horse range
i also would recomend forged slugs- better safe than sorry and trw's are fairly cheap top end will be a performer or rpm with a qjet - if i have the money for the wfo aircleaner it will be rpm intake, but you know these things always cost more than you think

[Bob Rutledge]

Yep, they do. I am looking at shifting at 5500 or below rpm, so I was thinking KB slugs would probably do ok. Even cast OE's 30 over should probably be ok. I am on a fairly tight budget, and I just want some added torque, and midrange power up to 5500 rpm. The XE 268 looks like it would provide what I am looking for. I am going to gasket match the ports as I believe anybody can can do that, but I won't be doing much in the way of the chamber, as I would really hate to screw anything up.

[red76TA]

i know what you mean about the budget, but i went ahead and spent some money on the bottom end so i have something i know will handle what i throw at it (maybe nitrous or forced induction a little later on) i originally wanted to do a 455 stroker but my budget wouldnt allow, and i figure changing heads or adding nitrous wouldnt be as big an issue as having to rebuild the motor to handle my modifications, glad to know the 268 will work, gives me another option

[Bruce1223]

Bob, I'm looking at doing a cam swap in an engine very similar to the one you describe, so I'm in the process of trying to learn a few things before I can get myself into too much trouble. Will that cam you describe work okay with stock valve train parts?

Thanks, Bruce

[hurryinhoosier62]

Bob,
IF you are going to reuse the stock rods, have both the rods AND the crank
Magnafluxed. Nodular cranks can develop small stress cracks in the radius
on the rod and main journals. Make sure you use a COMPETENT machinist
who is familiar with Pontiacs. The tricks used on small-block Chevys sometimes won't work on Pontiacs. Also,if your budget allows, remove the
parting line from the rod beams and polish. Have the rods shot-peened afterwards. I used CompCams HE260 cam in the 400 in my '72 GP. They(CompCams) still sell this grind. It's pretty civilized,but definitely gives a boost in low to mid-range torque and HP. Back to the rods, alot of guys here
will tell you to replace them. If you have the money, I would be sure to look
into PPR's I-beam rods. Thy're reasonably affordable($395 a set). The heads
I would use would be 6X-4s milled to 85cc. With a 0 deck clearance and .039
head gasket you should be about 9.3-9.5:1 on the CR.

[Z Code 400]

Gentlemen,

The XE262H would be a great choice in a 400 with 8.75:1 to 9.00:1 static compression. You would hate the K2802 in a low compression engine.

A .030" oversize 400 with 6.7cc valve reliefs (pistons at zero deck) with a 0.038" head gasket and 98cc combustion chambers would yield 8.35:1 compression.

My .060" oversize 400 with L2262F pistons .005" out-of-the-hole @ TDC and a 0.038" thick gasket and 92cc chambers is only 8.85:1 compression...Robert

[vertbird]

XE262 would be the largest I would consider especially with the 2.41. If while "street" driving this car it will rarely see over 3k rpm with the 2.41, you'll want to make sure you're producing good power by 2500rpm. I used a more traditional grind crower 60240 (210/221/112) in my low CR modification. It's a good cam and I considered the XE series but couldn't find anyone actually with track times/results with XE256 or XE262, while Cliff R had actual track results with an almost exactly same combo. With head milling, recurved dist, ram air exhaust manifolds and cam change I dropped over 1.3 secs from my 1/4 and picked up over 8mph and that was without playing with it any. I would love to know what the XE262 would have done, but I'm pretty satisfied. If you go with the XE please let the forum know any track results before and after if you have any. Oh I just reread your post, you already have the XE268, make sure you zero deck the block and I wouldn't bore it more than neccessary because you'll need all the CR you can get. If you're having a machine shop do the majority of the work and reassembly then I'd just let them remove the timing cover etc. Try to make sure you're machine shop has some experience with Ponchos. I mailed my heads to KRE just to be on the safe side. I think 300+hp will be very possible but those 2.41 aren't doing you any favors with everything else in the build. JMHO but you may want to look for 3.08, 3.23 or something close.

[red76TA]

Originally Posted by Z Code 400

Gentlemen,

The XE262H would be a great choice in a 400 with 8.75:1 to 9.00:1 static compression. You would hate the K2802 in a low compression engine.

A .030" oversize 400 with 6.7cc valve reliefs (pistons at zero deck) with a 0.038" head gasket and 98cc combustion chambers would yield 8.35:1 compression.

My .060" oversize 400 with L2262F pistons .005" out-of-the-hole @ TDC and a 0.038" thick gasket and 92cc chambers is only 8.85:1 compression...Robert

im guessing your refering to me, so a little math - 98cc combustion chambers, 6.7 valve reliefs, .040 over, .005 out of the hole and a .039 head gasket = 8.8 to 1, what im shooting for now

oh and bob, sorry to hijack your thread buddy

[Z Code 400]

Hmmmmm.......I have run your combination every way possible and it still comes up between 8.35:1 and 8.44:1 compression.

Check out this calculator: http://www.csgnetwork.com/compcalc.html

[Z Code 400]

Bob,

The 6X-8 heads have large combustion chambers, so getting decent compression (with a 400) will be difficult. If you study my combination, even a 0.060" oversize 400 that is zero-decked and has 92cc combustion chambers is only 8.85:1 compression.

Your heads are probably around 101cc's and at 0.060" over and zero deck, you would have only about 8.25:1 compression. Keep in mind that decking a block isn't cheap, neither is milling the heads.

You should have them cc'd to be absolutely sure before ordering any parts.

I know you already have the XE268H and I feel it is simply too much camshaft for less than 9.00:1 compression. A smaller camshaft (like the XE262H) would be a better choice.

I would do a simple overhaul and zero-deck the block using the L2262F pistons. They weigh the same as stock cast pistons, so no changes to the engine's balance is required.

You could mill 0.030" off the heads (assuming they are indeed 101cc's) and that would give you around 8.50:1 with zero deck...Robert

[mchell]

Bob Rutledge,

I think you are on track for 300 ponies.......mill the 6X heads to get 9 to 1 as you initially stated.......the XE268h cam is a good performing cam in lower compression motors.....I ran that cam, as well as an 068 and the XE made more power........nothing wrong with you disassembling the motor...you will save a couple bucks in the process...go ahead.....bag and tag all your parts........zip lock bags and a couple boxes will ensure you have all the parts for assembly......a few pics won't hurt either

[Z Code 400]

Mchell,

Considering Bob's 6X-8 heads, he would need 90cc's to reach 9.00:1 with a zero-decked block, 0.038" x 4.200" gasket and 6.7cc valve reliefs. If his 6X-8's are anywhere similar to the ones I have recently measured, he is looking at a 101cc combustion chamber and that will require 0.055" - 0.060" milled from the deck.

This is certainly possible, but will likely require the same 0.055" - 0.060" removed from the intake face and shorter pushrods too.

Although the XE268H (with 224° intake duration @ .050") would not be my personal choice for a street car with a 2.41:1 axle, putting the intake centerline at 106° would yield improved idle vacuum and throttle response.

My vote would be 3.23:1 gears in a daily driver and 3.42:1 in a 'weekend warrior' car that is driven on special occasions.

The rest of the combination looks good....I would suggest a rear axle ratio change as previously mentioned...Robert

[aitstra]

I used the std forged TRW .030 over pistons, milled 6x-8 heads .080 to get to 83cc. Decked the block and this is about 9.2:1 with a felpro std gasket.

Machine shop took some off the intake side of the heads too - sorry, not sure what the amount was, and the intake needed around .025 off ea side to fit. Not sure I would go this route again - when I get alum heads I need a new intake as well.

Taking .080 off the heads is beyond what most will recommend. Wallace racing's head milling chart goes to .055 http://www.wallaceracing.com/headmill.htm

I have no problems so far - 6 months running, I used a pontiac 068 blueprint cam and am very happy with the results - no dyno numbers though.

Search this forum on rods before you buy new with the power level you are wanting... I had a set already polished and shot peened so got Arp rod bolts, resized and used em. Good luck.

Rear end change will help a bunch too. I went to 3:55 - good compromise for a 400.

Randy

[Will]

The XE268 cam would work if we were talking about some mid to high 3-series rear gearing and a 4-speed or stall converter. I've run the old Comp 270 magnum (224 @ .050") in an 8.5:1 400 with a 4-speed and 3.73 rear gears with 26" tires and it works good but is not making a lot of power below 2500 RPM.

This cam, and the XE268 will suck with a 2.41 rearend. If you're going to be keeping those gears please don't go any larger than the XE256. Or, if you do go larger, please replace those rear gears with a 3.08 gearset if you still want great freeway cruising capabilities. You'll be absolutely astounded at the difference between 2.41 and 3.08.

As for the rest of your plan in your initial post, sounds good (and cost effective) to me. Except that I would not bother with the KB pistons. A good set of Silvolite cast replacement pistons (the ones with 4 valve reliefs, NOT the 8 relief ones) will be just fine for a 400 turning under 5500 RPM. Also, the conservative in me says only bore as much as necessary to clean up the cylinders. You will not gain any real world power by going to .060" as compared to .030", all you will be doing is potentially shortening the lifespan of yet another "they don't make 'em any more" Pontiac block.

[Bob Rutledge]

Great replies, and I appreciate it. I will be going with a 3.23 gear I believe. I want to get the motor done first, drive it a bit, and then change the gears out. I probably won't have the motor in until spring, but I am looking forward to a nice street combo, that won't embarass me at the track for the limited amount of time I will spend there. I don't have any numbers on what the car ran bofore I took out the motor, so I won't be able to compare the old and new Will, I I believe I will go the route that you are talking about, with the silvolites. Also, I thought that with the 2400 stall converter I have, the XE268 would be a great choice, as I'll be launching with power just coming on strong, and it would be a monster all the way to 5500RPM. With the fairly early closing of the intake, I would think that the cranking pressure would be way up and that would help me out down low? Wrong or right?

[Mr. P-Body]

Either XE262H or XE268H would be a better performing cam than most others under 9:1. Your biggest concern here is to get your cruising speed (engine RPM at say: 65 MPH) above your stall speed.

SBI sells .060" shorter pushrods for the milled heads.

Jim

[mchell]

As a reference, I have put over 15,000 street miles and 500+ 1/4 mile passes on a set of #96 heads milled .080, and have used/using these heads on two different motors.........absolutely NO issues with intake fitment or warping......I assume you will be running an adjustable valve train....if so, you could probably use your existing pushrods......assemble and check geometry....

Not sure where the "rule" came from that you cannot mill Pontiac heads beyond .060...........Obviously, if its a rare head, you may not want to do that, but in my mind there are only a couple of heads that I would put in the don't mill range...........all other heads are cannon fodder.....make em work for you and use em...........With the addition of the D port Kaufman heads, I think that the standard iron hipo Pontiac heads are even less valuable .....