406 SBC buildup - Please Comment!

[pparaska]

(I posted this at www.chevytalk.org, but I wanted to see if you guys had any comments as well. The version I put up over there has links to alot of the parts manufacturers sites. Reply here or there at: http://www.chevytalk.org/forums/Forum64/HTML/013538.html - Thanks!)

 

First, let me describe the application:

Hot Street car - weekend, hit the strip a few times a year, some road race track days, cruise-ins, banging gears . I don't care much about fuel economy. Not enough miles to worry about that.

 

Datsun 240Z, near 2700 lbs with driver

5spd trans (Tremec TR-3550)

3.7:1 limited slip differential

255/45-17 rear tires (26" diameter)

 

Induction:

Holley 4D 700cfm TBI, with MegasquirtEFI computer

Edelbrock Vic Jr single plane or Holley 300-36 dual plane (probably the Vic Jr)

 

Heads:

Canfield 195cc, Pro Top Line 200cc, or AFR 195cc 64cc chamber, straight plug, AL heads

(These seemed the largest ports in the 200cc range I could find that had good flow over the 0-.500 lift range and were available with straight plugs and used standard rockers (non-offset). The larger port heads from these companies all seemed to have non-standard issues.)

 

Block: 2 bolt 400 Chevy OE block, .030" over

Crank: Scat 9000 3.75" stroke internal balanced crank for 6" rods (PN 9-350-3750-6000)

Rods: Eagle SIR I beam floating pin rods, 6"

Pistons: Probe Industries SRS Forged Pistons, 1.125 C.H., 15cc dish, PN 1302-12341-030

King Bearings, Moly faced rings.

 

Cam: Always an issue, huh? I'm thinking about grumpyvette's favorite SBC street cam , the Crane 114681. I'm considering having them do a 280/280 adv duration version, to keep the overlap a bit lower.

 

1-5/8" block hugger headers, 2.5" duals, X-pipe, 2 dynomax Hemi Super Turbo mufflers.

 

The engine will have a near zero deck, and use a ~0.040" head gasket. This means about 10.5:1 compression. With the 114681, that works out to a 7.95:1 DCR, about 196psi cranking pressure at sealevel.

 

DD2000 gives me the following, with the Pro Top Line heads (the others were close):

 

RPM_____HP________TQ(lb-ft)

2000 148.618759 390.124237

2500 196.450073 412.545135

3000 246.684708 431.698242

3500 305.872131 458.808197

4000 364.925842 478.965149

4500 416.953796 486.446106

5000 458.374084 481.292816

5500 475.051758 453.458496

6000 471.334625 412.417816

6500 449.146271 362.772003

7000 410.008820 307.506622

 

I'm hoping for a nice powerband from about 1500-5500 rpm. I don't want stump pulling low end torque, but I'd like to have some jump from the 2200 rpm cruise in 5th on the highway. Traction will be a problem .

 

So what do you guys think? Any changes or advice?

[Guest Thurem]

Waauuw Pete, 475.051758 hp, is this an accurate assessment or could it be more like 475.051756 hp. You know it would be nice with some numbers you could really trust. I know you will likely have a hard time getting your figures validated down to one millionth of a horsepower.

Anyways i'm just kidding, your build sounds like a nice one and I'm envious, even though it looks like your torque figures are gonna strain your Tremec to the max.

Thure

[pparaska]

Heheh. Yeah. I let DD2000 export a text file made for a drag race game and it put all those sig figs in there - I was too lazy to cull them down.

 

I know what you mean about the Tremec. Wish I'd bought the TKO now! Oh well, if I don't put DRs or slicks on it, it ought to be o.k.!

[Guest Anonymous]

web page Pete I came across these "400" cubic inch blocks on Racers Auction One is in the auction #31251 with a $490. bid on it .. The other is in the classifieds for $2000.00 but is new and aluminum with machine work on it. (and something else buy it and throw caution to the wind)

[pparaska]

Thanks for that lead.

 

This is probably going to blow your socks off though.

 

The guy that's building the shortblock, minus cam, timing set, lifters, oil pump, pan, is charging me $1450 to build this shortblock. Using HIS std bore 400 2 bolt block, included in the price! The crank, rods, pistons, bearings, rings are all new! That price includes all machine work, except maybe a bit more to have it zero decked.

 

Talk about cheap! And this guy is an experienced circle track engine builder that's been at this for decades.

[Guest JAMIE T]

Ahhh. The saga continues, huh... Pete. The lil' '27 wasn't enough for ya. Guys, I think our pal Pete has the need, the need for SPEED!!!

 

Pete, the only thing I see that would make a differance is the choice of throttlebody size. That motor with the cylinder head choices will likely want a larger TB. I think throttle response will improve with a larger TB. I'm unsure of the cam selection, but if 'da Grump suggested it, it can't too far off. Is that a roller cam? Also, you KNOW you are giving up some with the 1 5/8 headers. But, I know how much that exhuast system means to you. But If you ever want to replace it, I'll take good care of it, as it rumbles beneath my LT1(and you heard how nice it sounded through stock Z28 exhaust).

 

You've got a good starting point Pete. Guys, if you haven't seen his car yet, it's so clean. He put enough energy into to light up Laurel, MD.

[jt1]

Sounds great to me, Pete. If your machinest has built previous 400's he probably knows this, but with any 400 with aftermarket rods sometimes the rod to cam clearance is very tight. In some combos the rods have to be massaged a little to clear the cam, dependent of course on the particular rods & cam. IIRC #2 is usually the closest, and you look for about 0.050 clearance. If the rods have to be cut, this needs to be done before before balancing. Just a little something else to check.

 

John

[Kevin Shasteen]

Pete,

 

The few things that come to my mind are:

 

1) Piston Comp. Height

I just dont like PCH's that small-does anyone have any documentation on Longevity/Durability(?) when PCH's that are nearing an inch are used?

 

2) If you keep your 3.7 geaging would the Edelbrock Dual Plane Intake not benefit your long duration cam better? Dont settle on just one Intake Manifold-as cheap as intakes manifolds are get both-test & tune; find out which one runs best. When you know you will only be driving on the street-put the intake on that does best on the street. When you are going racing-swap intakes.

 

3) As mentioned earlier-w/the restricted exhuast and a 280 Duration Cam-your powerband will not kick in till around the 3000rpm range. So my next question would be-would you not benefit from steeper rear diff gears?

 

4) The near 8.0:1 DCR will work great w/your 10.5:1 SCR and Alluminum Heads. I still dont like that restricted exhaust (Doh!). The restricted exhaust will compromise the rest of the package...as in less hp/torque. But, hey-what can we V8Z owners do about it?

 

Good luck-dont have to tell you to keep us advised(?) do I?

 

Kevin,

(Yea,Still an Inliner)

[Guest zfan]

Pete, Sounds like an awsome build you have going there. Best of luck and keep us up to date!

 

Mike

[pparaska]

Thanks for the feedback, guys! And no, I got used to the 327 right away - it could use some tuning and might have another 40 hp left in it. But it's burning a quart every 300 miles (with 3500 miles on it) and not slowing down. So I want it out of there anyway. I can't see going through that engine when what I really want is MORE POWER (well torque too ). Had a bit of a windfall, so the shortblock and half the heads are kind of a gift.

 

I know the exhaust will hurt top end. I COULD change it, but I have the feeling I'd only feel a difference near the HP peak, so I'm not sure I'll mess with that. I'm guessing I'll give up 10-20 hp up top, but I'll probably be gaining torque at low and mid rpm.

 

The TBI is an issue. I'll start out with it, as I picked the entire 700cfm 4D Holley setup super cheap from David Spillman. If I need more, I'll do port injection, and it'll be tailored to this engine. Again, I don't think it's going to be an issue except at the very top end. If I only spin to 6000, that's all this motor may really need. This is a 400, so I'm not going to be reving above 6000 rpm.

 

I'll start out with the Vic Jr. and if the low end is not enough or throttle response is not good, I'll try a dual plane. Good point on the dual plane, but I'm hoping that the usual issues of needing a dual plane for a good vacuum signal to the carb won't be an issue with EFI, even a TBI setup.

 

The cam is a solid flat tappet, BTW. At this level of duration, a solid is almost as good as a roller. Of course a roller would allow more lift, and that'd help torque just about everywhere. But the difference in performance isn't worth the extra $500-$600 I'd need in cam/lifter/valvetrain parts, not to me anyway.

 

This is a semi-budget build. So that's driving alot of these issues. Even still, it'll be a bunch more torquey throughout the 1500-6000 rpm range than my 327. Cubes and heads alone are what I'm working on now.

 

And yes, the builder is well aware of the 400 and the cam/rod clearance issue. He's made it clear he wants the cam I'll use so he can do the clearancing work. That's why I'm sending probably the biggest cam I'd use (the 114681 or something similar) so that it'll be clearanced for that. I might end up using my 12-677-4 or even my 12-222-4 Comp solid flat cams, if the 114681 is too radical for me - but I have a feeling that won't be the case .

 

I also discussed the compression ht issue and the need for oil rail supports and their longevity. Grumpyvette likes the total seal rings because they have a 3rd rail that works a bit better than the rail supports. However, this builder says he's done a bunch of 6" rod 383 and 400s with rail supports and has never had a problem or a come-back.

[ZROSSA]

Assuming that the dd2000 is reasonably close, What a torque monster. 390 ft @ 2000 rpm. 412 ft beween 2500 to 6000. Thats a very nice power band and should be very easy to drive, If you get traction. I noticed that the cam was still making power past your red line. You might be able to find one that works a little better in the range you are driving in. You dont want to be tempted into pushing it into the break parts zone.

 

Cheers

 

Douglas

[zthis]

why 1 5/8 Block Huggers ? i had them on my Z upgraded to 1 3/4 Hedman

weldups full lenght what a difference. The gains in mid and top end were

great. Bottom end was not an issue.

[Kevin Shasteen]

Pete,

 

I) Cam related question:

 

How bout looking at a camshaft w/spec's similar to what you were interested in, except using an Intake Duration slightly less-this way the Exhaust Restriction (however significant it may be) will be offset by a later exhaust valve closing? Kind've like the Ford 5.0 cam's; since the 5.0's have severe exhaust shortcomings-their cam's exhaust lobes are usually longer in duration than their intakes?

 

Just an idea.

 

Kevin,

(Yea,Still an Inliner)

[DavyZ]

Pete it sounds like you have done your research and have come up with a good plan regarding the 400 SBC. I would not change exhaust right away since what you have a pretty nice to begine with. In other words, "why throw away money when you can use what you have for the time being with the 400 SBC?" My stinginess is kicking in so I say go with your current exhaust system and try it with the bigger motor, because you have very little to lose IMO. However, if you have to change headers anyway because of an oxygen sensor or something, then you might want to look at the bigger headers. Just my opinion.

 

Good luck on this new motor! I wish you the BEST!

 

Davy

[pparaska]

Douglas - good point. I know what you mean about having a hard time taking your foot out of it when it's still pulling. The 327 is like that - wants to keep pulling at 6500 rpm!

 

My main reason for going to that cam is I feel it's as big as I'd ever want to go on duration and lift and it's being used to give the builder maximum interference problem for the rod/cam interface. If it's too much, I'll probably just slide the XS274S-10 (PN 12-677-4) Comp Cam in that the 327 has in it.

[quicker240]

I went from 327 to 406 a couple of years ago.Monster torque upgrade.I had 15 to 1 compression so it would only run on 110 octane gas.roller cam required constant valve adjustments and valve train was VERY noisy.It would spin tires at 70mph with no downshift.It was not very practical.Soooooo,I pulled it back apart,cut the domes off the pistons,swapped the 52cc heads for 7occ chamber heads,took the roller out and put a hyd flat tap in.also added the fuel inj. system.I know i gave up some power but it should be way more practical.If it dont rev though,the roller is goin' back in.You are gonna love that new motor man!good luck.hoping to see smoke from mine this week for the first time in two long years.I will be in Georgia!!

[Mike C]

Cylinder heads in the 220cc range with 2.08/1.65 valves. With such a "large" engine and light car with a manual trans, the bigger heads will be worth more power and will be unnoticeable at lower speeds IMO. As far as camshafts, you have to go roller. If you just can't stomach the $ (hey it's only money, right? only ~ $500 more for LOTS more top end power and a broader powerband as well), then mechanical flat tappet. Otherwise it's hard to justify lightweight forged pistons and HD 6" rods for a cam that will only pull 5600 rpm in a motor of 400+ ci. With the massive amounts of gear multiplication you have, a cam in the 290 degree range advertised and 245 @ .050. This should give you a 3000-6500 rpm powerband, and if you really work on the ignition curve and carb, it will pull cleanly in 4th from 1000 rpm. This appears to be a max effort pump gas motor even if you want to call it mild... Even if you do decide a smaller cam, I would still consider mechanical valvetrain for an "occasional" driver. The Comp 282S is unbelieveably mild and will make big power. Comp told me switching from my "little" mechanical roller (280/280 236 @ .050 .540 net lift) to a compareable duration hydraulic ROLLER still would cost me 50 hp. Wow. 15 I could stomach, but 50 not gonna happen...

[pparaska]

Mike, I'm a true believer in mechanical flat tappet cams vs hyd flat for mild to warm engines. Past "warm", I'd be all over a roller (solid). The two cams I've had in my 327 are solid flat cams, as is that 114681 Crane cam. You won't hear about me putting a hyd. flat cam in, although it might not make much difference in this app, since I won't be revving beyond 6000rpm. I just like the positive action of a solid cam.

 

I've read and heard from several knowledgeable sources that in the 280adv or less range that

a mechanical flat is very close to being as good as a roller, except for maybe a slight advantage on the lift. Even the people at Comp Cams agreed that a roller just wouldn't give me much benefit when I had them help me select that 274/280 (PN 12-677-4) solid flat tappet cam. The extra lift of the roller could be handled with a set of 1.6 rockers on the lower lift flat tappet cam, of course. I see that method as a bit of a band-aid though.

 

Doing this shortblock with AL heads is stretching the budget, so I'm going to have to forget about a roller cam for the time being. The heads are much more important, and it's one or the other.

 

I'll have to revisit the issue of 220cc port heads. It seemed that I had to give up straight plugs and/or non-offset rockers to go beyond 195 or 200cc heads for the companies I was looking at. My biggest dilemna now on the heads is whether to spend extra money on the known-great AFR heads or save $300 on the Canfield or ProTopLine heads.

 

I'm not sure I'd want to go much beyond 6000rpm with a 3.75" stroke. 4000fpm average piston speed that many see as the max acceptable for reliability comes at 6200rpm for that stroke, etc.

 

The 220 heads don't seem to make much difference until 4500 rpm, and even at that point, it's maybe only about 10 hp. That's according to DD2000.

 

Thanks for all the comments guys! I'm listening, although I seem pretty convinced of this build .

[Mike C]

I think the iron heads with the roller cam is a better choice. Although I agree that keeping the straight plugs really makes exhaust a LOT easier... You lose the ability to repair after an explosion, but on an overbuilt, underrevved street motor, you shouldn't have to worry about that. The iron Eagle 215 look good and so do the Pro1 in addition to the ProTopline. Admittedly the AL is a little more forgiving with compression, but IMO, the roller is the way to go. My 355 was in a 79 Z/28 that was lightened and setup for the strip, it also had a super T10 and 4.10 gears. With a Comp 292H it ran 13.7's at 102 with a 1.9 short time. I scored this in a ridiculous trade and changed the intake from the LT-1 to a Victor Jr. (which probably didn't make much difference)added 1.5 AL rockers instead of the Comp Magnum 1.5 rockers and went to the smaller 280SR. Picked up 1 second and 8 mph with the same ported GM heads shifting at the same point... and my car had big sway bars, Guldstrand road race springs, and HD shocks and pathetic 2.0 short times. I'm sold on roller tappets now even if it means iron heads instead of aluminum. I will concede that you may well be right that the flat tappet cam will approach the power of the roller in less than 280 degrees if you can get close to the same lift.

[Guest Anonymous]

Has anyone have experiece or whatever concerning using the forged 6.209 rods from a 300 cube in line Ford 6 with short pistons in a 400 SBC > I understand with these long rods the compression can be 11 to 1 without detonation on pump gas.