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400 sbc horsepower stumped

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400 engine
21K views 56 replies 14 participants last post by  ericnova72 
#1 ·
I have just finished building a 406 sbc stock crank scat 5.7 7/16 cap screw rods speed pro flat top forged pistons 5 cc valve releifs RHS Pro Action aluminum heads 200 cc runners 72 cc chambers howards hydraulic roller cam,241 int-245ex duration @50 . 545 int 565 ex lift 110 lsa matching lifters crane roller rockers 1.5 ratio, rpm intake holley hp ultra 750 dp cfm carb msd streetfire hei.1 3/4 headman headers .
I had it dynoed on a dynatech roller dyno it showed 427 ft lbs of torque at4200 rpm and only 319 hp at 6000 rpm fuel ratio was perfect throughout the run timing was 34 degrees tried with and without vaccum cannister less torque withe the vaccum canister hooked up fuel pressure was steady at 6 psi i cant figure out why these rear wheel numbers were so low am I doing something wrong does she need more air,such as a team g intake maybe or more fuel or cfm any advice.After 1500 miles took her to the track ran a 12.98@ 105.72 mph in a 1980 Z28 with a 3:42 rear and a M21 4 speed and firestone radials was not to impressed but for a daily cruiser not bad i guess. It just seems there should be more power coming out of of her any advice would be helpfull I was thinking about porting the heads an go with a 2.08 intake valve and perhaps a beehive spring set up. Im stumped any help please would really be appreciated.
 
#2 · (Edited)
i'M STUMPED

Thanks for the reply F-BIRD
have comp cams 987-16 springs on the head which is what howards cam recommended for my cam in a double spring ,as well RHS ill try another dyno shop ang see if theinstalls the 987 in their 1244 200 cc head for hydraulic roller applications up to .600 lift,my fuel pump is 120 gph carter with 3/8 fuel lines from the tank to the carb,my exhaust is 1 3/4 headman hedders a 2/1/2 dual flowmaster exhaust with h-pipe and high flow walker catalytic converters,.I shifted @6000 rpm and 6200 rpm even tried 6500rpm went smooth all the up the rpm band,I never thought about the tire slippage but that makes a lot of sense. Thanks again man for the information.Oh yeah I have a LUK 11 Inch clutch in no slipage,my 60 ft is horrible 2.13 but if I launch higher than 2600 rpm i either spin crazy or wheel hop.
On the street though which is 99% of the time the car drives great and is alot of fun but its missing that surge of power around .I'll get back to you with the 1/8 ET and MPH. ps are you selling the street slicks,if not whats your opinion on BF GOODRIDGE STREETSLICKS OR M/T ET STREET SLICKS
 
#3 ·
Take a look at M&H Drag Radials. I switched to them this year after having horrible traction problems with my MT Sportsmans on my little gasser. First test run with the new M&H DR's I pulled the front wheels off the ground!
I drive this car a lot in all sorts of weather and the tires even hook up good in the rain. Not sure yet how the soft compound will hold up mileage wise, but they sure put the pwoer to the ground.
Drag Radials
 
#7 · (Edited)
A few thoughts:

I was thinking to switch to a weiand team g and 2.08 intake valve over my 2.02's i have now as well as porting my RHS pro action 200 cc heads.what are your thoughts
Try as much open spacer under the carb as you have room for. If it picks up you know what to do. Port matching the intake/head (not gasket matching) may show some improvement depending on the mismatch.

Forget about 2.08 valve, at least for now. If you do anything, clean the pockets up and get a decent valve job on it (or at least verify what you have is decent) and maybe backcut the valves if not done already.

Was the valve spring installed height verified?

Was the cam degreed in? If the cam is out of phase or there's some other problem w/the cam/timing set, there can be huge losses.

Were there any unexplained dips or abnormalities in the read out that would lead you to believe the valve train wasn't under control? The pushrods should be =/> 0.080" wall. The geometry spot on?

Having the vacuum advance hooked up should not matter at WOT unless there is a restriction in the induction system causing vacuum to be present. Have you verified that the throttles are wide open when matting the gas pedal from inside the car? What ignition system are you using w/the Streetfire, or is that it?

If you really have a M21 close ratio Muncie (haven't we covered this before?), you need a lot more rear gear. It will be lugging in first and there will be a razor thin line between lugging it off the line and torching the tires unless you have mondo traction.
 
#6 ·
Are you running a rev kit with your hydro roller lifters?? lifters could possibly lofting off the cam lobe with out the rev kit at higher rpms.. Also add a 1" spacer to your rpm manifold, that will raise the power band of the manifold. that will help over 5000 rpm
 
#10 ·
I doubt it's flowmasters. I'm running a 388 with ETec 200 heads, 10.6 SCR and a 234* x 238* @.050" roller cam with a 680 cfm QFT carb and Air Gap manifold that put down 380 hp and 396 lb/ft on a chassis dyno. All in by 5800 rpm. This motor is a bit milder and a few cubes smaller than the OP. I'm guessing cats and/or carb calibration.
 
#15 ·
That engine peaked early for the cam compression and heads. I wonder how much that carb knocked off peak, or if it was from exhaust backing up. Without any diagnostics its hard to say what's going on. Looks like it performed well where you drive most of the time though.
 
#16 ·
Techinspector1 ran a dyno sim on it a while back with a couple of different scenarios. With an 800 cfm carb and 1 3/4" primary headers he said I would gain about 14 ponies. Not cost effective in my book. I like the streetability of the 680 and couldn't afford the 800 bux for 1 3/4" tubed headers. I sent the carb out to be computer calibrated and they changed the jets and air bleeds. When I got it back and did a plug reading I found that it was a bit lean so after numerous runs and jetting I found that I needed 1 size larger on the proimaries and two sizes larger on the secondaries. Been running like a champ ever since.
Tha cam is a rather low rpm cam, also. It's the Edelbrock 2201 Hyd Roller .539/.548 lift and has an operating range of 1500 to 6500. I think I could free up a few more ponies with the 1 3/4" headers but not for the price. Also, I know the E-Tec 200 heads are not the best of the bunch.
If I figure the 20% loss thru an auto trans it should be close to 475 hp and 495 lb/ft. I don't think thats bad for as mild of a build as it is. Obviously, a more vicious cam and a set of CNC ported AFRs would be a radical change.
 
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#17 ·
Nope. Never had it down the strip. This is a 96 C1500 short box (see avatar) that I'm guessing weighs close to 4k with me in it. My nearest strip is Kaukauna (WIR) and thats about 150 miles from here. Some day, when I get the rear end stabilized (cal-trac bars) and throw some stickies on I'll haul it down there. I've got 4.56 gears in there with 30" tires at the moment.
 
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#19 ·
We run a 355ci in a 81 camaro! it has a dp intake-770cfm holley-world products 200cc heads-with comp cams 540-563 with a 110ls has 1-3/4 headers with 3in exhaust with xpipe! but we run a 700r4 with a 3k stall and 3.73 gears. it runs between 12.0 and 12.20 traps 111mph on motor. have no clue on rwhp # never been on a dyno. So i would think your car should run better than the # it did. I dont like dynos they will hurt some feelings! My bbc didnt put down but 349 an 467. but it ran 7.42 at 94 and 11.40 at 117mph. i hope you get it figured out.
 
#21 ·
i may have over looked it but what intake are you using? i like a victor jr or team g myself. they don't hurt big motors on bottom end. also a bigger carb wouldn't hurt. a better cam from a company like comp or isky wouldn't hurt either, or you could give jones cam designs a try. try it with open headers too, & your ignition or fuel delivery could be off.
 
#22 ·
id go with a super victor intake, and 220cc runner heads along with a super sucker 2" carb spacer

The RHS heads are great but you really need a 220 runner head on that 400 people say bla bla bla but I ran the 220 CC RHS heads on a .030 327 with only 10.5:1 in a 74 nova that ran 7.30's 1/8 mile and yes I shifted it @ 7000 Track times is far more important than any "advice" never forget that
 
#23 ·
horsepower stumped

Hey F-Bird I checked the throttle andf when the pedal is to the floor the carb is wide open full travel, air fuel ratio at WOT was 12.1 and in cruise mode any where from 13.0 t0 14.3 the secondarys are 76 size jets I havent checked the primary.
my 60ft time is 2.079 my reaction time is.077,launched at 2500 rpm any higher with the firestone firehawks and it would smoke them,my 330 ft mark time is 5.625 my 1/8th time is 8.655 @ 81.34mph my 1000ft mark time is 11.246 does not show mph for that my 1/4 mile time is 12.98@104.47.
Yes we did go over the tranny issue it is a m21 with a low 2.20 fist gear,and the rear is a 3:42.
heres one more for you with a 26 inch tall tire and 1.1 final drive with a 3:42 rear end how can I be revving 3000 rpm @ 100 KMH or 60 MPH Ive tried 3 different tachs all set to 8 cylinder auto meter,auto guage and sun pro,as well my GPS was reading 100 KMH @ 3000rpm and I had a police officer friend clock me 4 times with my speedometer reading 100 kmh and his lazer gun read 100 kmh double stumped now but I'll stick with the first issue for now should I hollow out my converters. i really dont know where to start,

Thanks for taking the time everyone to help me out.
 
#24 ·
high 12s at 105

Ive been there and know how you feel.
There are quite a few comments I want to make,hope fully they are beneficial.If you like bigger numbers on the dyno then use a mustang dyno instead of Dyno Jet,thats not important other than for bragging rights.Check fuel delivery like already mentioned.A dyno pull is in high gear only where a race is for all the gears.If your fuel pump has nough pressure but your lines are the original diameter,you "might" be running out of fuel on the top end.That will make your MPH lower.

Like the other poster said,if you are not shifting very fast that will hurt your E.T.Please,no insult intended,,,muncies are expensive and break regularly so slow shifting may be because of the wallet.

Generally speaking,if your torque is a lot higher than your horse power then the camshaft might be too small.Hydraulic rollers are heavy and on occasion have mild valve float,so a rev kit or slightly stiffer spring may be required to get that extra 500 "clean" rpm.

2.1, 60 foot times is not very good for a mouse Camaro so traction and tire/suspension issues exist.Exhaust is always a factor.
All in all if you pick up a tenth or two in each department your car will be in the low 12s soon. Your car just needs a lot of tweeking,you are on the right track.Engine has been tuned,the rest will come quickly.
good luck
 
#26 ·
It is never going to 60' good if you have a 2.20 low gear close ratio M21 Muncie and a 3.42 rear gear unless you have some massively sticky tires. And on the street, even tires won't help enough- you'll need a prepped launch pad at the drag strip to have any chance of a good 60'.

It's going to either lug, spin or you will slip the clutch too long. You might get lucky one out of ten times and get a decent 60', the rest of the time it is going to be bad. There is just a razor's edge between lugging and spinning.
 
#28 ·
Horsepower stumped

I,ve tried MSD 8.5 mm wires but had arching problems as well the plug boots kept melting where as the Gaylord have plug boots that for me have greater longevity on the plug as well have greater clearance with the 1-3/4 headman headers that I have.
As for thetranny and rear end I plan on either going with a 4.10 ratio and trmec 5speed, or a ricmond 5speed with a1-1 5gear and a 2.92 or 3.08 rear, 1st gear ratio with either tranny is3.27 the tremec has a.68 5gear and the Richmond has a 1.1 5gear which will dictate my choice of gear ratios.
As for the mufflers the dynomax ultraslow welded mufflers are going on they flow 1700 cfm each which satisfies the motors 2.2cfm per hp minimum.
In the end the car is driven almost daily and sees the track twice month so street ability and reliability are at the top of my list which until now has been great.I drove it to Montral and back with no issues and averaged 13mpg.
Any thoughts on this would be greatly appreciated as they have been up until now.

Thank You Again to all who have taken their time to help me out with my car.
 
#29 ·
I am currently using the tremec 5 spd with .82 over drive and a 3.5 rear ratio.If you go tremec make sure its new or has the updates to make the 2-3 shift faster.It just wont shift fast. Compared to the muncie its like shifting a truck transmission.Other than that it seems tough enough for my application.I dont drag race though.I have tried a few times to launch my car without good results,anything over 1700 rpm and the tires fry,under 1400 rpm and it is very slow.

Are you sure you dont have 3.73 gears?Tremec also offers a .68 overdrive if you decide you need 4.56 rear gears.
 
#30 ·
Horsepower stumped

I have had the rear end apart and the ring gear is stamped Richmond,3:42 my tire is 28 inches tall measured fully top to bottom with a straight edge and from the axle centerline X2 it's a firestone fire hawk 255/60/15 ,still can't understand why I rev 2900 @ 60 mph?. The teeth on the ring gear are 41 and the pinion teeth have 12 which comes out to 3:41666=3:42 .Going through the traps I'm pushing 3rd gear @ 6600rpm I can't figure it out .in the end I figure the dyne could either have not been calibrated or there was some funny business going on.in 1st gear @2200 rpm when I floor it the rear tires light up like Christmas tree no clutch dropping just pedal to the metal I'm going to try a mustang dyne with and without the exhaust hooked up to see if my flow masters are holding anything back,if they are then a higher cfm rated muffler will be put on.
PS has anyone ever had any problems with the MSD STREETFIRE HEI Unit.
 
#31 ·
I have had the rear end apart and the ring gear is stamped Richmond,3:42 my tire is 28 inches tall measured fully top to bottom with a straight edge and from the axle centerline X2 it's a firestone fire hawk 255/60/15 ,still can't understand why I rev 2900 @ 60 mph?. The teeth on the ring gear are 41 and the pinion teeth have 12 which comes out to 3:41666=3:42 .Going through the traps I'm pushing 3rd gear @ 6600rpm I can't figure it out .in the end I figure the dyne could either have not been calibrated or there was some funny business going on.in 1st gear @2200 rpm when I floor it the rear tires light up like Christmas tree no clutch dropping just pedal to the metal I'm going to try a mustang dyne with and without the exhaust hooked up to see if my flow masters are holding anything back,if they are then a higher cfm rated muffler will be put on.
PS has anyone ever had any problems with the MSD STREETFIRE HEI Unit.
The thing that makes the most sense is a tach that's out of calibration. You could have clutch slip, but if you did I'd expect you to smell it and notice the degraded hook up and/or chatter that happens when the clutch plate and flywheel/PP glazes from slippage.

There are thousands of MSD Streetfire distributors running just fine. But that doesn't mean you couldn't have a bad one. Easiest thing IMO is to swap it out for a known good unit- even a stocker, as long as the advance curve is correct.
 
#33 ·
Horsepower stumped

I have tried 3 different tachometers 4 if I include the factory one ,they were an auto gauge,auto meter z series, and a sun pro all set at the 8 cylinder setting where applicable,as well with a timing gun with a digital readout on it and all of these pieces showed the same rpm across the board in neutral and under load as well as the dynojet dyne I've been on unless my tranny's 4th gear is not a 1.1 final drive but I'm not prepared to open her up unless she's broken,
As far as the 220cc AFR full cnc race port heads are concerned does anyone think they will make enough of a difference over the RHS 200cc's I have now aside from the bigger runners the afr's have 2.10 intake valves versus 2.02 I now have exhaust remains the same at 1.60, and the afr's flow45cfm more than the rhs's, as well from the hydraulic roller set up I will go solid cam flat or solid roller I've not decided yet ,my hydraulic roller set up is
241int@50 245ex@ 50. 541int lift 565ex with 1.5 rockers, all howards products.
 
#34 ·
your heads are more than adequate.Flow test them and see what the porter says?Once you have flow tested your heads you can determine if your current cam is the correct choice or if you need more. Local guy here has similar heads on a 10.8s 350 powered 68 Camaro.He too is using a smaller cam similar to yours except solid.vic junior manifold,flowed HP holley,etc.not a street car anymore but still streetable.
 
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