Want to build a 409 SBC

D

donniejr81

Member
I have a 1984 Corvette that I was wanting to put a true 409 W-engine in, but was met with much resistance from several people. So, I was thinking of maybe building a 409 SBC, via a 400 SBC with a .040 overbore. I've seen that kind of bore on a 400 run on the street with no cooling probs. I was told it just has to be an early 70's block due to their slightly thicker cylinder walls. I'm looking for streetability, reliability, good driveability, and the tire shredding power of a 409 W. I basically want all the pro's of a big block in a smaller package. Are my goals unreasonable?? Any input would be greatly appreciated.

Donnie
Radcliff, KY
 
walkerheaders

walkerheaders

Well Known Member
Supporting Member 6
a 400 small block is the wise choice. I built a .040 over for a customer with an aftermarket forged crank, Hbeam rods and aluminum heads topped with a blower and 2 afb's AWESOME POWER.
 
J

jr.W

Well Known Member
donniejr81 I agree a early 70's block but I would still have it sonic checked.
A engine builder locally just finished dynoing a basic 400 for a 4x4 ,stock bottom
end(5.7 rods) junk 882 heads with good valve job intake and a little 600 carb
it made 425hp and 500lbs trq at less than 6000 rpm.

jr.W
 
bubbletop1961

bubbletop1961

Well Known Member
I agree. A good choice. Ive been using 400's for about 10 years. The one I have had no problems getting my 3900lb sled into the low 12's. And thats on pump gas. Youll like it.
 
D

donniejr81

Member
Thanks for all the input, its appreciated. After thinking it over, I think I am going to go the 409 SBC route. I think the stock rods in a 400 are 5.565" or something like that, and I've heard of several ppl using 5.7" and 6.0" rods with different sized pistons to maintain the stock stroke. Why is that? Should I go that route? Will that require a different crank as well? The engine will probably never see a drag strip and be primarily a weekend car, so I wont be running RPM's like a die grinder. I'm hoping for a reliable 350HP and 375-400lb TQ, on pump gas.

My plans are .040 overbore, Brodix aluminum heads w/ 2.02 intake and 1.6 exhaust valves and 70cc chambers, flattop pistons w/ valve reliefs, 260 in/268 exh and .444" lift on the cam with 114 CL and 1.6 roller tip rockers. THe car already has true dual 2 1/2 exhaust with X-pipe no cat and chambered pipes instead of mufflers. Then I'm possibly considering a 2x4 induction possibly running a low rise Edelbrock intake and a pair of mild Carter 500 AFB's. Am I going in the right direction?? Any ideas??
 
bubbletop1961

bubbletop1961

Well Known Member
I've been using stock 350 5.7 rods on a stock 400 cast crank for along time. shift between 6000-6500. The most ever with a big roller was around 6800-7000. Never any botom end problems. I have been using 2 bolt main blocks also.
I think that cam is pretty small. maybee somthing around 500-525 lift depending on what converter and gears your running.
 
D

donniejr81

Member
My Vette weighs about 3250 with me in it. It has the stock Dana 36 3:07 posi rear, 700-R4 tranny with stock Corvette convertor (which is in the neighborhood of about 1800RPM or so whereas the regular 700-R4 convertor is like 1600 I think). The car will rarely see above 4500RPM, the cops around here already know me. So you think I need a little more cam?? Lift...duration...or both?? My compression should be around 10:1 with my aluminum heads if I did my math right. Thanks too, for your input.
 
J

jr.W

Well Known Member
Donnie the 114 lca is to wide for a 400. If I were you I would get a copy of
David Vizards book how to build max performance sbc on a budget. There is
a large wealth of knowledge in it for sbc's. If you are going to alum. heads
I would look at AFR's they are about the best out there for sbc.

http://www.gofastnews.com/board/engine-technology/

p.s. check out this site David is the moderator.
 
bubbletop1961

bubbletop1961

Well Known Member
donniejr81 said:
My Vette weighs about 3250 with me in it. It has the stock Dana 36 3:07 posi rear, 700-R4 tranny with stock Corvette convertor (which is in the neighborhood of about 1800RPM or so whereas the regular 700-R4 convertor is like 1600 I think). The car will rarely see above 4500RPM, the cops around here already know me. So you think I need a little more cam?? Lift...duration...or both?? My compression should be around 10:1 with my aluminum heads if I did my math right. Thanks too, for your input.
Click to expand...

I change my tune on that. Thats a pretty conservative set up. I still say a little on the small side, but pay close attention to the manufactures rpm range. You dont want to over cam yourself into a dead spot off idle.
 
D

donniejr81

Member
I'm needing a little more 409SBC input. I'm hoping to be in the 9.5-10:1 CR range with aluminum heads. Given the 3:07 gearing, 700-R4 tranny, and dual 500 Carter AFB's...any cam recommendations?? I already have a set of 1.6 roller tip rockers that will be on it too. I was thinking a factory L82 Corvette camshaft. The specs on it are: 291int/287exh duration with .450int/.460exh lift on a 114 lobe C/L. Chevy put that cam in some of those heavy (3650lb) C3 Corvettes with all smogged up 8.5:1 350's. Think that would work in my setup? I know my 1.6 rockers will add about .030" or so lift.
 
bubbletop1961

bubbletop1961

Well Known Member
This might be going out on a limb here. But if your looking for all torque and not alot of rpm. I remember seeing some cams that were listed as off road 4x4 cams that were being advertised as just that. Alot of torque down low were you need it. Might have to look into that. Any one on here have experience with cams like that?
 
D

donniejr81

Member
I'm in the parts round up phase right now. I have a '73 ( I think) stock bore 400 block with crank and rods ( pretty sure they are 5.565 ). I got a decent deal on a set of dished (20cc I think) .040" pistons for almost free, and a pair of Carter 500AFB's and a lowrise dual quad intake. After a sonic check of the block, I was going to punch it .040 over and have the rods shot peened with a re-man crank. I would prefer it to run on 87-89 octane but if not, no biggie. I'd like an idle just a tad above stock...say a little lope below 800RPM. The two major things I'm needing advice on is cam and head selection. I dont have to be a penny pincher as far as budget is concerned, but have to keep it within reason to keep my female counterpart happy!! Looking for a dependable but torquey setup.
 
J

jr.W

Well Known Member
If the pistons are for a stock 400 they will need the short 5.565 rods.
If you can the longer 5.7 rod would be a good idea or 6.0 even better.
The side load is less. If you are going to regrind a stock crank I would look
at a new scat replacement crank, they are fairly cheep(around 200$) and
much stronger,and a grind will probably cost over half of that. Same goes
for the rods, recon on your rods with bolts is probably about $150.00 new
scat 4340 rods about $200.00 or less. As for heads I would buy the AFR's if you do
the research they have the best flow in a street type head and the cost is in the
ball park with the rest of them. I will do some figuring on the cam this weekend.

jr.W
 
D

donniejr81

Member
OK, thanks that'll be great. I appreciate your input. I've built a few 350 SBC's and some Olds and Mopars, but no 400 SBC's. I've heard even though they are still a SBC, the stuff that makes a 350 scoot may not be as well on a 400. I'm checking into the AFR heads too. I've heard nothing but good about them. And, I'm most definitely going with the Scat crank and rods. Hopefully 5.7's or 6.0's, I just have to sell my pistons for the 5.565's before she'll "allow" me to buy new ones with my own $$$...Go figure!!
 
J

jr.W

Well Known Member
Donnie I did some searching and found some cam specs. that will work.

http://www.iskycams.com/timingchart.php?product_number=201271&timing_chart_id=96

This cam will work well if you have it ground on a 106 lobe center, not
the 108. I did assume you are using headers, if not I would change to a duel
patter profile.
A side note if it were me I would pay the extra $ and get GM lifters they have
a hardened foot on them so they are less likely to fail during the break in period.
When you get to that point do some research there has been many problems
with cam break in in the last few years.

jr.W

p.s. with 10.0-1 comp. you may possibly be able to run 89 oct. fuel with the alum. heads.
I would go no less than 9.5-1 with this cam.
 
You must log in or register to reply here.
Top