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Originally Posted by johnny98 i have a 98 cobra with an SHM 5.0 stroker kit and SHM stage 1 cams.
The stock motor threw a rod and broke several other things after approx. 166,000 miles. Damn good motor. puttin around 280hp to the ground to the day it died. so, time for rebuild comes...
I went with SHM because of the name it carried, and they had a hell of a deal on a stroker kit. on sale for 2100 bucks, manley rods and flat top pistons and a forged steel crank. Chris, the salesman informed me that the kit was balanced. (HA! my happy fat *ss it was balanced) anyhow, i also bought a set of SHM stage 1 cams, as i was informed these cams would be perfect for the setup i was going for (streetable n/a). meanwhile, a local shop did some stage 1 head porting to my stock cobra heads. said he 'opened them up a lot'.
as the machine shop got the parts from SHM, i was told it would take a lot of heavy metal added in order to balance the kit. a lot of heavy material was transferred from my wallet in order to do so. the kit was balanced, installed, and everything was fine. i just got the car dyno tuned today, and it put down 320 rwhp and 311 ft-lb of torque. the curves are broad.
while these numbers are nice compared to the 280 of before, consider this... that previous number did not include the long tube headers that i have added since then.
so is it really possible that long tube headers, stage one head porting and cams, and a stroker kit are only good for 40 rwhp after a tune? or is something drastically wrong?
lemme know what you think, suggestions to fix the power problem, maybe there isnt a problem at all, SHM bashing (i will never buy from SHM again) or whatever... |
reckon that woud be about right, at the end of the day you have only increased the cc by .4 litre, which really isn't much. A really highly tuned engine should be able to produce 100bhp/litre
4.6 x 100 = 460bhp
so with 5 litres, 5 x 100 = 500bhp, only 40bhp more.
Your 4.6 made 280rwhp and it is often excepted that a Mustang will loose 30-40hp thru the drivetrain regardless of output (except for extreme and exceptional examples) which means you had about 320bhp.
320 / 4.6 = 69.6bhp/litre
New engine 320rwhp + 40hp drivetrain loss = 360bhp
360 / 5 = 72bhp/litre
If you prefer to work on the 15-20% drivetrain loss theory then your engine is producing more than 360bhp but must also be loosing ALOT more thru the drivetrain - which is unlikly as it has remained the same over both engines.
The gains you should have got from a stroked engine is where the torque comes in and how much it produces over the entire rev range, if you have dyno graphs for both engines compare them, the 5.0 should have much broader curves than the 4.6, so although it doesn't produce massive peak numbers for bragging rights it should produce a considerable amount more power all of the time, making it a much faster road car.
PS MG Rover user a variant of the quad cam 5.0 'cammer' engine in the SV-R and they rate it at 385bhp.