Good luck Tony.
655/610

OK guys. Made a couple pulls tonight and its not even in the ballpark. timing was at 36 and jets were 78 w/pv and 86. Jetted up 2 sizes and lost power. Tried 34 degrees and lost power. Peak hp was at 5700 rpm - 560hp, peak tq at 4900rpm - 559lbft. Checked cranking compression and all cylinders were right at about 160. Loosened lash .005 on cyl 1 as a test and pressure went up to 175. Valve lash was checked and none were out of line. What do you think the problem could be? My engine builder thinks the cam is wrong and the intake is not great. How much could port matching the intake be worth (if it was off by a lot)? Why would it not pull past 5700??

Here are the cam specs:

262/268 @ .050
lobe lift .390/.400
lsa- 112 recommended installed at 108, and is installed at 109
.585/.600 lift

Engine guys, please help!

That motor should make about 615 or so and have wall to wall torque...I think the cam spec is dead-on where 'd want it. I'm guessing the MCH heads flow around 315 @ 600....IIRC an out of the box street dominator only goes about 270 that's why porting pays off in the days where we have good heads.

Looking at the cam and your port area I'd have figured the torque peak to come in lower than 4900 (like around 4400) and the HP peak around 5300 but if you're cr is dead on 10.5 it should not start falling off too fast until 6000 or so. The way big (2 1/4) header isn't helping the cause either because wih those installed it took your motor more RPM to hit the sweet spot and the motor lost some momentum on the dyno below 4500... that's at least part of why your RPM peaks were on the high side of the RPM scale. You said you jetted up and it slowed down so I'm thinking you're restricted up top. for comparison mine ran a 1000hp with 84 + a pv primary and 90's in back. My cam was in at 107.

One of the best FLOWING out of the box Intakes is the Team G and it has really short runners that work well up high, can you borrow one and re-test? They're marginal for torque off idle to 4k on a street 440 (unless it's got a lot of compression) but on a 500 incher the torque at 3000 is still pretty decent.

you're about 50hp down from what it should be making pretty easy, did you get an HG/intake vacuum read on the pull? I'll bet it was too high (like 1 1/2" or so) and induction restricted.

Thanks for the feedback, Bobby. Manifold vacuum at 5700 is 1.5. Do you think the cranking compression is way low? As for the intake, how much do you think it could be holding back? What do you think about the torque numbers? They seem excessively low as well. Yes, the heads flow 315 at .600 according the MCH flow sheet.

Thanks, Tony

I have never been a big fan of the SD manifold myself. But I know Dwayne and other have coaxed some good number sout of them, I just never have been able to. I would be looking there first and foremost. Assuming of course the cam is where it needs to be and is happy where it is.

add 4 inches of plenum spacer then try it

Well... I have been watching this thread and waiting to see what kind of numbers you got with your 512 combo as it is soooo close to mine. Here is the combo and numbers as it was on the Dynojet.

512 stroker,4.25 Source crank,H-Beam Rods,.030 over,17cc dish pistons,10.5 compression,OOTB Stealth heads,OOTB EDDY RPM intake,950 Proform carb,1 3/4 headers,Hughes Solid 579/587 Lift 256/260 Duration LSA 108,Crane Gold 1.5 Rockers,Hughes springs,retainers and locks.Smith brothers pushrods,Melling HV pump,7 qt.pan,stroker windage tray.

I used the 1 3/4 headers as they were all cheapy dinged up headers and I didnt want to ruin the ceramic coat on my Hooker 1 7/8 Super Comps

566HP / 5400RPM
640TQ / 3800RPM

Primary jets are 78 with secondary 86. We tried jetting it up but the numbers fell down. The best runs were at 36 and thats where we locked it in.

Fuel was a 50/50 mix of 87 pump and C14.

my old combo,493, standard port eddie heads, my tunnel ram w/ 6 pack and 590 cam would run 5 mph more than a single 4150 1000hp, it felt like i ran smack into a brick wall with the car at 5300.

Yikes! That engine's potential is definitely higher than 560hp. I would presume a carb spacer, and intake porting/swaping is in your future.

I know it is never a good idea to race dyno sheets, however...compare the data.

Here is a very good engine to look at. (Not my engine, built by Straitline, Owned by Caper here on moparts)Straightline 496 info
Simple, very stout, reasonable inexpensive 496" - similar to your combo.
It is in Caper's 3700lb 69 dart, currently running 10.40's

496 CID Wedge - pump gas street engine (10.7 to 1) Built by Scott Brown at Straightline Performance.

* 654 HP- 5600 -RPM ------------ - Hand Ported Edelbrock RPM heads (300 CFM) - Ported Victor Single Plane
* 653 TQ- 4400 -RPM ------------ - Flat tappet, 263/273 @ .050 112LSA - 4150 Carb ( Quick Fuel 1050-AN) - 1" tapered spacer

Somewhat lesser flowing heads, but definitely a better breathing intake setup.

Thanks for the feedback guys. I was figuring the intake may be a restriction, but I never guessed by this much. I will say this, I know this dyno is conservative. FWIW - The last engine I did on this dyno (493, indy-1's 13-1, solid roller, dominator) also had numbers on the low side compared to other combos here on Moparts.

Topbrent - I know about your combo and as a matter of fact, that is the combo that I had in my mind when I thought somthing was seriously wrong with my dyno numbers. I didn't expect to make 650/650, but I figured it would be at least 600/600. Maybe I should try a Victor for comparison?

The increase in cranking compression when you loosened the lash, combined with the facts of only 175 psi at best and 1.5 hg vacuum on the top end get my attention.
I would be real tempted to try the cam installed very early matched by a much better intake. Put it on the dyno with better headers and it should really come alive.

I would guess 600-625 hp, low to mid 600's for tq. for your combo.

Might be that intake. Just more food for thought,
I built a 506 very similar to yours, but slightly milder.
10.25:1 comp
E-heads with valve job touched up
Straightline hyd. flat tappet 240/250 .540/.530 lift, 112 lobe sep.
Edelbrock Performer RPM intake
Out of the box Demon 850 carb w/1" open spacer.
Also on a conservative dyno, this thing made 577 hp and 644 tq. Had approx. .038 quench, so it liked timing at 35.
This has to be one of the best bang for the buck street engines I did so far.
It did pick up 8 hp with the open spacer, messed around with 2", 4 hole, open, etc., it liked the 1"open the best.
So it just may be a matter of messing around with different intake combo's.

I don`t pay a lot of attention to cranking comp. #`s as a friend of mine runs bottom 8`s and his #`s were around 150 he said and my lowly heap cranks at about 170, runs great on 91 pump swill and lays down decent #`s at the track. Your 505 should be putting out WAY more than that and agree about the intake.........get an M-1 or a victor and I`ll be she comes alive.

Intake cam and headers probably 60 + tq and 50+ hp.
Mild cam and a very mild intake = 6200 shift point way big headers kill hp and TQ below 5000?

What are good cranking compression pressure numbers? i did my 496ci the other day and it they were all around 200 expect two were at 185 (but i know why that is)

Gonna try an M1 intake and my 2" TTI headers tonight. I'll let you guys know how it goes.

That header comparison will be good info. If it was me, I would do that first, then add a carb spacer, then change intakes...