Squeezing a little more power out of my 454
I realize that I have not posted in here for a while, but I have been having one problem after another with my Nova. We put a 454 in the car around Christmas time. After 200 easy miles on the motor, my transmission couldn't hold up and gave way. I stayed sidelined for about a month getting the tranny redone. After it was done, I put maybe another 300 miles on the car, and then the 8.2 inch 10 bolt rear-end gave way (which I was expecting, so I wasn't too mad). Well I found a 12 bolt out a 70 Nova SS for 100 bucks, then bought a set of 3.73 gears to go in it along with a powertrax locker. The car should be back up and running this weekend.
With all that being said, I wanted to list my motor build, and I'm hoping some of you guys can maybe give me a few tweaks I might be able to do to squeeze a little more power out of the motor.
Here is my setup:
The motor is a 2 bolt main 454 that was completely rebuilt and by a reputable machine shop (McMurtry's for any of you in the southern Mississippi area). The rods were reconditioned and fit for ARP studs. (I realize this has nothing to do with "making horsepower," I'm just saying this so you guys know that the motor is very well built).
The pistons in the motor are stock compression.
The heads are closed chamber rectangular port heads that have valve springs to support a .600 lift cam. The heads have 2.19/1.88 valves in them. (the heads are casting number 3964291 which is an origional head off the 454 in the LS-6 Chevelle).
I figure my compression to be around 8.75:1
The cam specs are this:
Operating Range: 2300-6500 RPM
Duration Advertised: 284° Intake / 296° Exhaust
Duration @ .050'' Lift: 240° Intake / 246° Exhaust
Valve Lift w/1.7 Rockers: .574'' Intake / .578'' Exhaust
Lobe Separation Angle: 110°
The motor has comp cams aluminum 1.7 ratio roller rockers, Edelbrock RPM Performer dual plane intake, MSD 6AL ignition, 9mm race wires, and a Holley 750 carb.
Would a small shot if nitrous be a safe, viable option for the motor that I would see some gains with? (maybe a 75 shot)
That's about all the info I can think of at the moment that has to do with the engine.
On a side note, what do you guys Guesstimate the car would run through the 1/4 mile? I hate "bench racing" just as much as the rest of you, but with all the problems I've had with the car, along with the 1/4 mile track being quite a hike, I haven't made it there yet and I'm not sure that I ever will.
I guess the car to weigh about 3500-3600 pounds with me in it. It has the 454 mentioned above, a 2800 stall converter with a turbo 350 thats very well built, a 12 bolt positive traction rear end with 373 gears, and I have a set of 26/10/15 mickey thompson drag slicks to go on the car.
I am very sory for the long post, but I have been away awhile and wanted to ask the experts all the questions I have had in my head.
Thanks to everyone for their time, (and for reading this long post if you chose too)
There is a picture of my car, and we managed to get the 454 under the stock hood.. kind of gives to the "sleeper" effect.
Also a little concerned about the pistons...? You mentioned stock compression but are they stock cast pistons...? Also the compression you list is kinda low to support the cam...? With rectangle heads and the cam/compression issue mixed with the stall speed and rear gear it may be kinda lax getting off the line...? Most cam`s of that size tend to require about 10.5 to 1 or higher also more stall speed around 3000...?
Not sure what it may run in the 1/4 mile but once it gets wound up it should pull good in the mid-range area but tend to fall off on the top...? I would say a possible 12.5-13.5...? at best...?
Just remember the track tells the tale on a fast street car... (it breaks your heart) :embarrass
Thanks very much for your reply. As to the cam, this is what it recommends (copied and pasted off the Jegs site)
Xtreme Energy XE284H Hydraulic Flat Tappet Camshaft Only
RPM Range: 2300-6500
*Note: In order to use these camshafts in 1965-66 396/427ci blocks, it is necessary to machine a 3/16'' wide x 7/64'' deep groove in the rear main journal of the cam to allow oil flow to the top of the engine.
Street/Strip, 2800+ stall, rough idle, 9.5:1 compression.
Yes the pistons are stock. When I had bought the cam, I had also planned on changing the pistons out as well to bump compression slightly. But when I bought the motor to the builder to be gone through, he told me that an overbore was not needed, and the stock pistons were pratically new. The motor was pulled from a wrecked 87? Suburban that literally had less than 40k miles on it when wrecked. He said changing the pistons was totally not necessary, and if I wanted to it would only be for performance purposes. I chose to just put the stock ones back in.
When I guess my compression at 8.75:1, it it pretty much a total guess. I had heard that closed chamber heads were good for bumping compression some, but I don't know for how much.
Thanks very much for your reply, and I will check back in tonight after I get some sleep (just got off a 12 hour graveyard shift).
I'll give my take on it, you might not want to here it tho...
The rectangle port heads are a killer to any heavy street driver car... They just have such a large cross section in the intake runners they make the car lazy..... Then you have way to much cam for you static compression, this to will make a heavy car lazy.....
I am not sure what your after performance wise????
The first thing i would do is a cranking cylinder PSI test... Let us know what you find..... You really need a mininum of 165 or so to get the performance your after....
I'll tell you that you are real close on your set up but the things that you are off on will really effect performance.
As far as i know all big blocks had forged pistons. So you will be ok with a 100/150 shot of the juice....Big blocks are stout pieces and with a good tune you could get away with a 250 shot if you had it dialed it correct.....
I just fixed a 454 for customers 68 nova. He bought a crate 454 from gm and the thing was a total stone. The car has 4:11's and at a 15 mph float you would crack it and the tires would not spinn..... I bumped the compression up to 9:8:1 removed the rectangle ports and add the performer rpm ovals and a tick bigger cam. Now the car just goes up in smoke at anything under 25 mph.......
When you say stock do you mean flat top pistons? With 109cc chambers and 5-6cc valve reliefs the compression is actually a little closer to 8-1. Some "stock" big block pistons actually have a small dome, around 10-14cc, if that's the case your compression is around 9.5-1.
The cam is a tad large for 8-1 and about right for 9.5-1 but it is a 454, that's enough cubes to swallow a slightly big cam, even with the lower compression.
I think you'll get 13s at the strip easy, low 13s if the compressions a bit higher than you think. I wish I had a 454 to play with.
Enjoy it man, it sounds like it would be a hoot to drive.
Thanks very much for all the great replies guys.
I am not sure what kind of stock pistons were used in the motor, but they are stock.. here is a picture I was able to dig up of the motor on a stand, its kind of blurry but maybe it can be of use
I would be happy with mid-low 13's and 12's when I possibly hook the nitrous up to it. This is a car I try to drive 3-4 days a week when its running right, so I think that would be a pretty fast "semi-daily" driven car.
Thanks very much for your reply.
Thanks very much for your reply as well. I probably wouldn't consider anything over 100 shot of nitrous, but it's good to know I can possibly go higher if I choose too. I can also totally relate to the lack of traction. I can't really get any traction trough most of first gear, stomping it from any roll in first. Im hoping th positive traction, a set of traction bars, and sticky tires will cure it.
Thanks a ton for the responses guys.
Here are a few more pictures:
Stock looking outside.
327 emblems on..heh.
and the 454 under the stock hood.
Please don't hate on the yellow Accel sticker.. LOL.. I just haven't gotten around to taking if off yet.
Thanks alot, again, guys.
look like 8.1 pistons to me.comp will be way to low for that cam
Otherwise it looks good and I think you're looking at easy 13's if you can get it to hook..... and that's WITHOUT nitrous.
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