need engine help

[mrcrsr]

i am currently running 2 454's that i just rebuilt using speed pro hper. pistons, moly rings, large oval port heads(w/ small valves, 2.06/1.65), edelbrock performer intakes, harland sharp roller rockers, comp cams xm 262 cams(218/224 duration @ .050), stainless marine exhaust using the stock pachanga exhaust system- dumps forward into a 5" collector, then goes back w/ 5" hose w/ a stainless marine internal flapper, and then out the back, thunderbolt 5 ignition, and the 330 hp qjet carbs- now the questions- i am running 32 degrees total timing- set at 3500 rpm- is that good? next, the carbs- i have 2 new holley 750 vac secondaries- would that give me any more power then the qjets? next, what is the power output of these engines?? i am guessing between 400-420 hp- is that right? what can i do to get more power, outside of a blower?? thanx for the help!!!! also, i am running sock type oil pumps, w/ the oil pans and coolers stock as well, is this sufficient or do i need to upgrade?? rpm is 5000, pls help!!!!!

[SmokinLowriderSS]

You're not gonna be happy ... but then again, maybe you will be.
I ran your specs in Desktop Dyno, and it is usually pretty darned good. I had to infer your lift specs (I used .525") and lobe centers from a similar cam at Comp as yours don't show up on the site. I THINK the q-jets are 600 CFM but may be 650's, only make about 3 HP dif anyhow. I gave you the benefit of doubt on compression at 9:1. I'm running 8.5:1.
DD gives me back 336 HP @ 4500, 424 LbFt @ 3500. 339/426 with 660 CFM carbs.
Your exhaust system will give you fits from restrictiveness. Changing from my Niccson logs to Lightning headers will be good for right at 400 HP with a setup a bit hotter than yours (.565" lift, 280* duration, same heads, Performer RPM Air Gap manifold, 700 CFM Holley 4150).
Your holleys, 342HP/428'Q.
Big Chevys usually (but not always) seem to like a lot of timing. 35 to 36 degrees is very comon in good runners. That could net you a few ponies too as long as you stay away from detonation.
A big boost would be head-work by a pro shop. Porting a good set of large oval port heads (like 781's or 049's) is good for 70 to 80 HP according to the shop doing mine NEXT winter (headers this winter). I have 353049 heads.
A good porting, even with larger valves may only push you to 382HP/435Q due to your exhaust cramping you.
http://www.cpperformance.com They deal Lightning Headers, made for the big chevy, for both jets and I/O drives. look them over. They are fully water jacketed and are RELATIVELY inexpensive at $2,000 compared to other marine performance jacketed manifolds. Mufflered, with 4" outlets they boost your figures to 482HP/478Tq. 489/488 unmuffled.

[mrcrsr]

thank you for your help, if you could check this for me , i have stainless marine hi torque aluminum manifolds and stainless marine riser pipes, what would the hp be w/ the qjet vs. the holley??? thanx for the help!!

[SmokinLowriderSS]

Well, I cannot actually run "marine" type manifolds on what I have, but I can infer a lot. I ran yours as "H.P. Manifolds and mufflers", the same thing I run to get right figures with the Niccson aluminum logs, snails, and 2 7/16" outlets on my jet boat. This correlates VERY closely to what another program of impeller charts is telling me it takes to spin my impeller at the WOT RPM I reach.
If I uprate the exhaust listing 1 step to "Small-tube headers with mufflers", the figures reach 406HP with a 660 CFM carb, 410 with a 750 carb (469 pound-feet torque).
No way to define difference between a q-jet and a holley, just airflow volume maximum. The biggest q-jets I believe are 660CFM for big blocks, 600CFM is the only other one I believe, for small-blocks. Those HP figures are peaking right at or a touch above 5,000RPM.
I notice an error I made in my earlier post. That 480+ HP figure was with the headers added to the porting job, not to stock heads. The figures above are for headers on stock heads, the way mine are going on this winter. I will get a porting job NEXT winter.

[mrcrsr]

thank you very much!! i would think these would be similar to small tube shorty headers, they have runners built in to the manifold, and i would think these would be a nite and day improvement over the stock mercruiser junk!!! they are almost double the size internally, thanx again, and ps, what did you find for timing specs??

[SmokinLowriderSS]

I haven't done any real looking for timing specs. My "hotrodding Big Block Chevy's" book is in my detatched garage and it is late here. Check with a lot of people or a lot of sources. Rat chevys (the mice are the same most of the time) usually run well with anywhere from 8 to 12 degrees of initial timing and reach to a maximum of 35 to 36 degrees. anywhere arround 2500 to 3,000 RPM is good to top out at.
When I broke my 454 in this past spring, I set it at 8* initial. I am currently running her 12* initial without any signs I can find of detonation. I will be pulling the plugs this winter layover to see if anything appears there.
From the sound of your exhausts, you may have something close enough to run on the "header" setup. My logs are highly restrictive, Headers will be a big help, as will a porting job the next winter. Should put me very close to 500 HP Norm Aspirated. (490 HP/498 ft-lb)

[SmokinLowriderSS]

You can see that there is little difference in HP just based on carb size. One thing, a self-operating seccondary like a vac secc or the "air valves" on a q-jet may or MAY NOT open fully at 5,000 RPM. They will give the engine whatever it wants, restricted by the spring in the holley (various strength replacements are available easily) and by the springs in the Roc. I would dock the HP figures perhaps 5% based on this (yes, that may be 20HP). For a more pure "performance" setup, which will yield more power but may bring forth a few other issues of detriment, would be to switch TYPES of carb to a mechanical seccondary such as the Holley 1450 type carb. I am running one (was orriginal), the seccondaries do not open untill the primaries are open about half-way (saves some fuel there) but then open on a fast linkage to be wide open when the pri's reach wide open. That way your engine is assured of having the entire carb's output available to it, whether it uses it or not. DD assumes the carbs are fully open at rated CFM ability (such as from a 4150 double pumper or 4500 center squirter type carb). If this is not the case, then DD will err by calculating numbers higher than it should.
I have no driveability problems at all with my 4150 setup, but I have a jet drive that lets the engine rev very quickly to full power, am running only a primary power valve, and am running the large accel pump on the seccondaries (small on the pri's).