SBC HP Estamation

[1BAD70CHV406]

Alright buys im new here but im not new to cars. Heres my build and let me know what power u think its putting down to the ground? And what time ill run in the 1/4 mile.

406 sbc (stock crank, rods and stroke)
edle AVS thunder serise 800cfm carb
edle RMP Air Gap (ported also)
xe284h comp cam (the cam kit so whole new valve trian)
1.6 not 1.5 full RR (brings the lift up to .540 int. .543 exh)
flat top 10.8:1 pistons
ported and polished factory heads with new valve job (im a collage student so new heads are going to have to wait)
long tube cerimic headers
3000 stall
Turbo 400 trans with shift kit
Z-Gate sfloor shift
Full Mallory ignition (dist., control box, coil)

all going into a 70 c10 LWB

Thanks for your thoughts

[meansting04]

should make plenty, with good mid and top end power to pull you through the lights, 3 speed is gonna be hell on the revs though. What kind of revs can your valve train handle, thats a decent sized cam so hopefully everything eles can handle the extra stress.

[Wild83C10]

Depends on the heads. Can you give more specifics on heads?

I would have to say 450hp, high 12s depending on the truck weight, tires.
Either way it should be fun to drive.

[Marv D]

Originally Posted by Wild83C10

Depends on the heads..

couldn't have said it any better

These days making 1HP per cube with a SBC is pretty easy. but it's all dependant on the heads.

[1BAD70CHV406]

the heads are 882's i know not the best to start with but i am not a begginer at porting and i have made some amazing improvments on these heads ill try to post some pics when im done.

[mongoose]

cam might be a little big... 882's are 76cc no? depending on the deck hight and head gasket... you won't be any where near the 10.8.. be closer to 9 to 9.5..

but.. 375ish?

[1BAD70CHV406]

So y do you think i wont make 10.8 comp...considering that the piston manufacture stats clearly that based on 76cc heads it will make 10.9:1. they are a -7cc flat top with 2 valve relifs. the deck hight was trued up and the heads have been decked also... there is no way ill be putting down only 375 hp!

How is the cam to big... i have spoken to comp cam techs and they have said that cam would be perfect with my set up the cam runs between 2500 and 6800 rpm and i have matched all my parts to go with that set up

[mongoose]

are you sure they said 76? thats a lot of compression for a flat top and a big chamber

[Rodms]

882's are good heads and you can build them to certain specs and it will suprise you t?hey flow good but can't get the comp up,I'm guessing about a 12 in the 1/4 and don;t know what you did for weight

[Marv D]

I think this falls under the heading of don't ask the question if you arent going to like the answer.

You want exact compression? you are going to have to give us the nominal compressed thickness of the head gasket (typically 0.039 - 0.040" for FelPro gaskets 1010, 1020 or 1003,,,,,, 0.040" to 0.045" for cheap builders gaskets), AND the exact deck clearance. Just "trued up" isn't a measurement and having the heads "decked' will make some changes, but,,,, 0.008" flat milling for every cc of chamber reduction. How much was milled and WHAT do you have???????

A 4.155 bore, 3.75" storoke, -7cc for valve reliefs in flat top pistons, a 0.000" deck clearance, 4.20" x 0.039" Felpro head gasket bore, and 76cc chambers (remember some of the emmissions era heads were as high as 80cc on the 400 heads,, if you didn't cc the heads AFTER milling your still guessing)

the above will yield 10.11:1 compression. Unless you reduce the valve reliefs or DRAMATICALLY reduce the chamber, your NOT going to have 10.9:1, NOT going to happen. NEVER believe the advertised BS compression ratios and least of all never believe the phone jocky at the mail order warehouse. If he was an engine builder he sure as hell wouldn't be spending his nights on the phones for $8 an hour.

Increase the deck clearance to 0.024ish of a standard production sbc and you have 9.57:1 compression,, use a thick 0.045" gasket and it drops to 9.45:1. Very SMALL measurement make very BIG drops in compression ratios.

Use some of those KB pistons that place the piston 0.060" in the hole, a 0.040" head gasket and a standard 0.024" deck clearance and your at 8.3:1 compression.


The 284ex is a lot of cam, even for a 406. It's is going to need some very decent heads and more than 10.1 compression to make better than 370-380HP in a 406.

I would like to know what cfm your getting out of the 882 heads after you port them. A good friend has kept record of every set of heads that went across his Superflow flow bench. A set of cleaned up, mildly pocket ported 882's typically go 206/142 with 1.94 intakes,, at .600" lift. What are you getting (measured) at the .507/.510 lift of the xe284 cam?

[nxtruck]

I agree with everything that Marv has stated above. I don't think anyone here is trying to rain on your parade. Just trying to give you a realistic idea of what to expect from your combo.
One thing I might add to this: take a close look at the exhaust-heat crossover passages on the 882s. You should notice that they have two passages that branch off from the intake surface of the head. Every other smog casting head ( 441, 993, etc. ) has only one passage leading down from the intake surface. The 882 casting is more prone to cracking than the other smog castings because of this. I had an '86 Suburban with a mild 383 and 882-casting heads that I drove for about 4 years. In that amount of time, I replaced 3 heads because of cracks stemming from the twin exhaust- heat passages. After the third time, I decided to replace both heads and had some 993 castings worked over for it. I drove it for the remainder of the time that I owned the truck and had no more cracked heads. I'm throwing this in here because I don't know how much time or money you've spent on these castings. If you haven't done much with them, you may be wise to try to find some different castings to use. Some vortec castings would really wake your combo up, compared to the smog castings.
Hope some of this helps you. Good luck with it!

[mongoose]

Originally Posted by Marv D

I think this falls under the heading of don't ask the question if you arent going to like the answer.

You want exact compression? you are going to have to give us the nominal compressed thickness of the head gasket (typically 0.039 - 0.040" for FelPro gaskets 1010, 1020 or 1003,,,,,, 0.040" to 0.045" for cheap builders gaskets), AND the exact deck clearance. Just "trued up" isn't a measurement and having the heads "decked' will make some changes, but,,,, 0.008" flat milling for every cc of chamber reduction. How much was milled and WHAT do you have???????

A 4.155 bore, 3.75" storoke, -7cc for valve reliefs in flat top pistons, a 0.000" deck clearance, 4.20" x 0.039" Felpro head gasket bore, and 76cc chambers (remember some of the emmissions era heads were as high as 80cc on the 400 heads,, if you didn't cc the heads AFTER milling your still guessing)

the above will yield 10.11:1 compression. Unless you reduce the valve reliefs or DRAMATICALLY reduce the chamber, your NOT going to have 10.9:1, NOT going to happen. NEVER believe the advertised BS compression ratios and least of all never believe the phone jocky at the mail order warehouse. If he was an engine builder he sure as hell wouldn't be spending his nights on the phones for $8 an hour.

Increase the deck clearance to 0.024ish of a standard production sbc and you have 9.57:1 compression,, use a thick 0.045" gasket and it drops to 9.45:1. Very SMALL measurement make very BIG drops in compression ratios.

Use some of those KB pistons that place the piston 0.060" in the hole, a 0.040" head gasket and a standard 0.024" deck clearance and your at 8.3:1 compression.


The 284ex is a lot of cam, even for a 406. It's is going to need some very decent heads and more than 10.1 compression to make better than 370-380HP in a 406.

I would like to know what cfm your getting out of the 882 heads after you port them. A good friend has kept record of every set of heads that went across his Superflow flow bench. A set of cleaned up, mildly pocket ported 882's typically go 206/142 with 1.94 intakes,, at .600" lift. What are you getting (measured) at the .507/.510 lift of the xe284 cam?

Thanks, I have a hard time explaining things in detail... hopefully he will understand better.

[Wild83C10]

I'm not a big fan of comp cams and the people they put on the phone to select cams for you. I'm a fan of cammotion, they give you more realistic cam specs. Comp Cams throws some numbers at you that you would like to hear.

Marv threw out some great info, he knows his stuff. But like we are all saying, heads are key to any motor.

[Rodms]

If I was going to use a comp cam ,heck I would do a 305 with the 525 lift and for sure revalve the heads!

[1BAD70CHV406]

so can you just drill steam holes in double hump heads bc if so then ill just go out and get thoughs now...even though i have already completly ported the 882 heads...lol

[mongoose]

look to the cheaper aftermarket to get anything out of the combo listed...

some ik200's.. for example.

[1BAD70CHV406]

Originally Posted by mongoose

look to the cheaper aftermarket to get anything out of the combo listed...

some ik200's.. for example.

Ya i was just tooking into thoughs and i think that is exacly what i am going to get

[Wild83C10]

What's your budget for a set of heads?

[1BAD70CHV406]

Originally Posted by Wild83C10

What's your budget for a set of heads?

Under or around a thousand i have found a set for 895 assembled for the pair. Why are you asking

[Wild83C10]

For less then a grand there are plenty of aluminum options. Trick flow, patriot, edlbrock, ect. Just shot for something with at least a 200cc runner.
I'm sure you could still recoup some money from 882 you have.

[shawn57nomad]

If you are looking for great BUYS on heads check out competitionproducts.com for DART and others or try Speedway Motors they are running a special on DART right now for fraction of the price of anyone else...AND they all know what they are talking about.

[1BAD70CHV406]

ok i know this post is ole but i have taken your guys advice and went out and got a set of brodix track 1 heads cleaned the bowls a little and gasket matched and also a nitrouse kit gunna runa 150 shot...

SO what are you new guesses about HP and 1/4 mile times

[mongoose]

dd says 440... but take that with a grain of salt.

[oneday]

Lets start a pool.I say max.375 hp @ wheels. I'm with slurry! It takes alot of beer to figure this out!

[Marv D]

From the hip,,, going back to your original combination and substitute a set of Track ones,, 450-475 plus the N2o. BUT... and you knew that had to be coming right
Now the 284h cam is closer in line with the package,, but I really like to see the cam changed to the XR284 hydrulic roller. I think you'll be surprised how much that $600 (cam, lifters and pushrods) adds in reliability and added power in a USABLE range here. IMO you would be easily over 500HP, and add the hose for enough to shread the tires of most any combination.