400/406 Builds

[Captainfab]

I imagine there are quite a few guys here that like me, enjoy seeing what others have used and done with their engine builds. It can often come in helpful when planning a new engine build. So I thought I would start this thread as a place to post your 400/406 engine build specs and any performance info you might have.

I'll start off with an engine we built for my son several years ago.

We started off in one direction and ended up on a little tangent. What we started with was a completely stock rebuilt 400 shortblock, which was bored .020. We topped that with a new set of Vortec 062 castings that were machined for screwin studs and guide plates. They were also machined for Comp 981 springs and the retainer to seal clearance checked. We ran Crane Gold 1.5 roller rockers with a Comp X4262 cam which has a lift of .462 intake and .480 exhaust and a .050 duration of 218 and 226. This is the cam here:
http://www.summitracing.com/parts/cc...39-3/overview/
For an intake we went with a Edelbrock Performer RPM, topped with a Holley 3310/750cfm vac secondary. For the ignition a Pertronics HEI was used.

This engine was installed in a '79 GMC K15, backed with a SM465, NP203 12 bolt rear and Dana44 front. The only performance info from this installation is that it had enough torque to break the center section of the 12 bolt from the axle tubes and spin it almost 90 degrees. This truck was later totaled in an offroad incident and this engine found a new home in a '85 IROC. It was backed with a TCI TH350, 3000 stall, a detroit locked 9" and 3.73 gears. With a set of sticky 28 x 10 slicks it would knock down 12.4-12.5 quarters on the engine and 11.5 with a shot or N2O. IMO that was pretty dang good considering how mild this engine was built.


OK guys post up your 400/406 builds

[john@thepier]

I will be doing a build starting with a 74 2 bolt main 400 block in the next few weeks, I will up date as I proceed. It will be going in a 67 GMC short bed 4x4 that is now sitting on a 72 SWB 4x4 chassis and will be followed up by a 350 into a NP205. I have some splayed steel caps for this so I know I will be doing at least that, a new crank, heads, etc. Do not know how much boring will need done but expect at least a 30 over. Should be fun and I will be back.

[Captainfab]

Looking forward to seeing how you build your engine and how it runs.

[burnin oil]

That 465/203 setup is rare. I am really surprised that The tcase chain didn't let go first.

When I was in high school I had a 30 over 400 with flat tops and 76cc heads that were decent. The cam was a 300HP 350 repop. Idle quality was awesome and would idle at 400 RPM off roading. Motor made enough to peel the floor open around the shifter for the trans. Looked like you took a tooth paste tube key to it on both sides. I never knew hoe the Bell housing didn't let go. The 10.5" wide tires left 3" wide black marks and got 14MPG with 3.07 gears. Intake was a Performer and ran through stock dual factory log manifolds that would twist 6000 RPM.

[Campbel45]

I'm still in the process of building my 408

Specs are:

sbc 509 400 .040 over

Scat internally balanced rotating assembly
-Scat crank
-KB 18cc dished pistons
-Scat 6" rods (7/16 cap screw)
-Comp Cam XE274
-Dart pro 1 215s 64cc
-0.027 head gasket
-Decked .020
-comp cams gold roller rockers
-Eddy performer rpm intake
-holley 750 vacuum advance
-MSD HEI

SCR: 10:1
DCR: 7.93:1

Have yet to complete it so I cant say what its like or numbers but I'll be sure to let you guys know!

[Captainfab]

That does sound like a good torquey engine burnin oil

Originally Posted by burnin oil

That 465/203 setup is rare. I am really surprised that The tcase chain didn't let go first.

When I was in high school I had a 30 over 400 with flat tops and 76cc heads that were decent. The cam was a 300HP 350 repop. Idle quality was awesome and would idle at 400 RPM off roading. Motor made enough to peel the floor open around the shifter for the trans. Looked like you took a tooth paste tube key to it on both sides. I never knew hoe the Bell housing didn't let go. The 10.5" wide tires left 3" wide black marks and got 14MPG with 3.07 gears. Intake was a Performer and ran through stock dual factory log manifolds that would twist 6000 RPM.

That combo sounds like a screamer Campbel45. If you haven't bought the heads, I would suggest a little smaller intake port. Maybe around 190-195cc? Please do keep us informed when you get'r runnin.

Originally Posted by Campbel45

I'm still in the process of building my 408

Specs are:

sbc 509 400 .040 over

Scat internally balanced rotating assembly
-Scat crank
-KB 18cc dished pistons
-Scat 6" rods (7/16 cap screw)
-Comp Cam XE274
-Dart pro 1 215s 64cc
-0.027 head gasket
-Decked .020
-comp cams gold roller rockers
-Eddy performer rpm intake
-holley 750 vacuum advance
-MSD HEI

SCR: 10:1
DCR: 7.93:1

Have yet to complete it so I cant say what its like or numbers but I'll be sure to let you guys know!

[Captainfab]

Anyone else care to contribute to this thread?

I know there has to be many more 400/406's out there.

[cadillac_al]

I just freshened up a stock 400 two years ago. It was the first Chevy engine I ever took apart with the original plastic still intact on the timing gears. I just did the cheapie rebuild with new bearings, oil pump, timing chain and gears and new cam and lifters. It runs fine but runs out of steam at an early rpm. I plan to buy a tach for it this year. I am convinced that this Edelbrock performer cam is just too small for a 400. It should be better than the stock cam you would think. When I measured the stock cam, the lobes were almost exactly the same height as my new cam. I was very surprised not to find any bad lobes on that stock cam too. Moral of the story: don't get too conservative on camshaft selection in a 400 sbc.

I may be just too used to winding out 350's that I notice the 400 shutting down early. That's why I am getting a tach, so I will know for sure what is going on.

[Captainfab]

Yep, that Performer cam is a bit small for a 400. A stock mid 70's 400 will have low compression, poor flowing heads and a small cam, so they aren't going to rev very high. Now you can take your basic short block and add some smaller chamber heads to bump the compression and a bigger cam, and that 400 will be a totally different animal. Something similar to the one I posted above.

Originally Posted by cadillac_al

I just freshened up a stock 400 two years ago. It was the first Chevy engine I ever took apart with the original plastic still intact on the timing gears. I just did the cheapie rebuild with new bearings, oil pump, timing chain and gears and new cam and lifters. It runs fine but runs out of steam at an early rpm. I plan to buy a tach for it this year. I am convinced that this Edelbrock performer cam is just too small for a 400. It should be better than the stock cam you would think. When I measured the stock cam, the lobes were almost exactly the same height as my new cam. I was very surprised not to find any bad lobes on that stock cam too. Moral of the story: don't get too conservative on camshaft selection in a 400 sbc.

I may be just too used to winding out 350's that I notice the 400 shutting down early. That's why I am getting a tach, so I will know for sure what is going on.

[burnin oil]

Edelbrock had a different part number for thr 400sb performer cam but I have no idea what the difference is. Checking the lobe lift doesnt tell the whole story as you need to compare the base circle. The lobe can only be so big and fit in the cam tunnel so the cams base circle gets made smaller. If you are still running the stock rods on your motor you dont want to run it that high in RPMs as they are the weak link. I have knocked several stock rods. This is the reason alot of guys go to the 5.7" rods. That extra 1/4" of stroke does alot to max out piston speeds so 5500 is probably all you want to spin. With after market rods and everything forged I have spun almost 7k RPM on a stock bock but it is probably not the smartest idea. I am also a huge fan of HV oil pumps for some reason.

[nicks diner]

I'm in the middle of a 406 build and I've come to a crossroad.4bolt ,gm crank, flat tops 10.5 1, mild flat tappet, roller everything, Vic Jr coming out for air gap, ported camel humps. I have a choice to install AFR227 with a matching cam. Kinda new at this and looking for around 500hp for the street mostly. Don't have the specs on the cam yet but I got 3.73 gears posi. Any input would be great and I apologize ahead of time for any dumb questions.

BTW going in a 68 C10 SWB
Flat tappet is going to be replaced with the new hydraulic roller.

[Captainfab]

With flat top pistons and a small chamber head such as the 'camel humps' I believe you are going to be closer to 11-1. This is too high to run pump gas especially with a mild cam and the less efficient combustion chamber of those heads. With those pistons you will need a head with a combustion chamber of around 72-76cc. You will also want to choose a cam with a intake valve closing point that will help create a streetable dynamic compression.

Sorry to say but those AFR 227 heads are way too big for street use. The low and mid range power is going to suffer. I would recommend a head with a intake size of 190-195cc. Depending on what you want a 180cc head would likely be just fine.

Changing the Vic Jr for a Performer RPM air gap as well as upgrading to a roller cam is a good decision.

[nicks diner]

Thanks Captain. My mechanic is building this 406 he assures me on the compression and that it will be on pump gas. I'm thinking of sticking with the camel humps which have the larger valves and are well ported. What are you thinking on the est power with my setup? Ignition is MSD 6al and like I stated full rollerr everything with a much more aggressive cam and full length headers and a 750 double pumper with a one inch spacer. Thank you.

[westie 666]

Last year I got a 406 that was built a few years ago and dropped it in my 77, it has Holley intake with Holley 750 dumping gas into it, I don't know what went into this motor but was told it was all good gear.
Now I have a big problem with it running on and pre ignition, was told it is also running backwards, to combat this I shut down with truck in gear, put it on the dyno to try and fix it but no joy.

Any ideas??

Cheers
westie

[Captainfab]

I have to disagree with your mechanic if he is indeed installing flat top pistons and the 'camel hump' heads. Not knowing the specifics on your parts I took an educated guess and entered some numbers in this online compression calculator and came up with 10.99-1.

http://www.summitracing.com/popup/ca...ion-calculator

That is definitely not going to be pump gas friendly especially with iron heads. Even if you install a wild cam, the dynamic compression is going to be way too high. I would suggest reading through this thread and see what Mike went thru with his engine, and he has pistons with a 12.5cc dish.

http://www.67-72chevytrucks.com/vboa...d.php?t=573986

I think there are a few other members here with more engine building experience than I, that will agree with me.

Originally Posted by nicks diner

Thanks Captain. My mechanic is building this 406 he assures me on the compression and that it will be on pump gas. I'm thinking of sticking with the camel humps which have the larger valves and are well ported. What are you thinking on the est power with my setup? Ignition is MSD 6al and like I stated full rollerr everything with a much more aggressive cam and full length headers and a 750 double pumper with a one inch spacer. Thank you.

The first thimg I would do is see where your timing is at. Not just the initial, but the total and also the amount the vacuum advance is adding. How is the engine built? what is the compression? What cam is in it? Is the carb in good condition and tuned properly? Depending on how the engine is built, it would likely run better with a smaller carb.

Originally Posted by westie 666

Last year I got a 406 that was built a few years ago and dropped it in my 77, it has Holley intake with Holley 750 dumping gas into it, I don't know what went into this motor but was told it was all good gear.
Now I have a big problem with it running on and pre ignition, was told it is also running backwards, to combat this I shut down with truck in gear, put it on the dyno to try and fix it but no joy.

Any ideas??

Cheers
westie

[nicks diner]

As I mentioned the hump heads where completely ported extensively. Does this make any difference to the compression ratio.?

[nicks diner]

As I mentioned the hump heads where completely ported extensively. Does this make any difference to the compression ratio.?[/QUOTE]

Update Dart aluminium 210 brand new not ported. How do you feel bout those over the humps?
.

[Captainfab]

Typically head porting focuses on mainly the intake and exhaust ports with just a light clean up in the combustion chambers. If larger valves were installed, the porter may have unshrouded the valves, which could enlarge the combustion chamber. However I don't think there is enough meat in the casting to open the chambers up from 64cc to the necessary 76cc's.

Your mechanic is probably thinking he can build this 400 with the same thoughts as most use when building a 350. It is very common to build a 350 with flat top pistons and small chamber heads such as the 'camel humps'. That same thought can not be used with a 400 and have it run on pump gas. The 400 has a larger bore and a longer stroke, which pushes the compression way up as compared to a 350.

The Dart heads are good heads. However heads with an intake port of 210cc's are a little too large for a street engine. You want to be in the 180-195cc range, depending on what rpm range you want your power to occur in. If you stay with the flat top pistons you will also want a head with 72-76cc combustion chambers. Most any domestic made aftermarket head will be much better than those 'camel humps' Of course you have not mentioned what the flow numbers are on those heads since they were ported.

[nicks diner]

Well since he is backing this motor with a 100% 1 year warranty and no question about it it will run on pump gas perfectly I'm going to stick with the camel hump heads for now. getting the roller cam new springs new push rods installed next week and I guess we can go from there. Thank you for your patience and insight. BtwI think he mentioned a 190+ cfm flow.

[Captainfab]

If those 'camel humps' flow 190cfm, that is an improvement over what they would have been in stock form, but still don't flow as much as a stock Vortec head.

I hope your mechanic is correct and you don't have to take advantage of his warranty.

You haven't given enough info on this engine build for anyone to give you any sort of guess on hp or tq output. We at least need the specs on the cam.

Originally Posted by nicks diner

Well since he is backing this motor with a 100% 1 year warranty and no question about it it will run on pump gas perfectly I'm going to stick with the camel hump heads for now. getting the roller cam new springs new push rods installed next week and I guess we can go from there. Thank you for your patience and insight. BtwI think he mentioned a 190+ cfm flow.

[Marv D]

Have you 'seen' the flat tops,, with a 11cc D-Dish the camelhumps are a lot more pump gas friendly and in line with what the mechanic stated. Also as a FYI, the AFR227's require a $1100 shaft rocker system. The 180-210 'can use' the standard stud rocker, but even then you have geometry issues. AFR is a GREAT head, but the 220's and 227's are a bit misrepresented on the car rags stsing "accepts standard SBC rocker components" Accepts and "right' is two totally seperate things there

That said

One of my favorite 406's we built with a MAJOR budget. Stock 511 block, good machine work to get it straight, square and true bores
Used a Stock GM 400 crank
5.7" rods and some cheep KB Hyperetectic flat tops
Comp XE284 hydraulic flat tappet cam (this was back when oil was oil and not crap)
Set of used Edelbrock 170cc E-tec vortec heads
Vortec RPM airGap
Prosystems 780cfm carb
1-5/8" Supercomps and Dynomax mufflers

He ran a Hughes street TH350 and B&M 3500 converter
4.10 gears and (at the track) a set of 26.5x 9" slicks

He 'almost' hit 10's in 3000' air (11.15 @ 120ish) Was in a light chassis but damn impressive for less than $3000 he had in it... well until it detonated and one of those hyper-u-cracked-it pistons turned to sand and or the stock block went BOOM!

But until then,, it was quite impressive
http://www.small-block-chevy.com/dana1.JPG

[nicks diner]

What is your guess on the power # on my motor with the humps? Btw love the Apache

[Marv D]

My estimates are never very popular so I'll refrain.

[nicks diner]

I failed to mention that this mechanic is a well respected mechanic in the Orlando area and a personal friend of mine. With that said he told me that the flow is actually 200 / 150.he is going to custom grind the cam which will be for mid range with 3.73 gears posi. when I get the specs for the cam I will post and I will keep you keep you updated. Thank you

[jjzepplin]

I built mine quite a while ago but here goes-.30 over silicon skirted forged flat-tops-file fit rings- ARP everywhere I could put them-Rods resized-line honed block- Stock heads redone with 2.02/1.60 stainless valves and bowls blended-unshrouded-screw-in studs-1.6 roller rockers hardened pushrods stock crank turned and polished .10 .10 clevite bearings and steel marine head gaskets high volume oil pump and 4x4 pick-up and baffled pan for hard-steep angles-Comp 4x4 extreme(mild lope) cam hydraulic lifters Carter electric fuel pump with oil pressure cut off switch and 670 cfm Holley 4x4 carb on air gap intake with rear plumbed to the front thermostat housing for full rear engine coolant flow.
Missed a few things but she still has gobs of compression and runs on pump gas just fine with the curved Hei dizzy. Built everything myself so I am sure all of it is in there.
Might one day stuff a bigger cam in but it runs so good why screw with it?