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...
Stroker kits for a modular will not give you big HP numbers, they will give you more low end TQ, which is what the 4V is missing. For hp numbers, you needed to go with a Big Bore. That aside, by your admission, the numbers are nice and broad. Don't worry about peak numbers. How does it feel compared to the old engine.
yep...just read a great post the other day someone had a link to about how stroker engines lose hp but gain torque...your numbers look about right....
280rwhp / .85 = 329+/- engine hp 320rwhp / .85= 376+/- engine hp theoretical 47 engine hp increase with a measured 40 hp rear wheel increase. I'd say chances are you have way more than 376 engine HP or you've done something to relduce friction from your drivetrain. I say you gotta pretty good deal, but that's just my opinion...
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.
WTF is all this crap in this thread? You arent making the power you should be. On a standard bolt on 4v, you could make those numbers with a tune and probably just mild cams. With the 3.70 Bore & 3.75 Stroke, your engine would be a 5.2L(taken from SHM site), your torque should be in the 320s or 330s and your HP should be in the 330s+. Im making 310 at the wheels on my old stock short block on a 2v and my heads. Here is a link to Mr. Bob Cosby's 99 cobra with just bolt ons. You should be WELL over these numbers. Im just using these as an example to what a cobra can put down. Im well aware that the 98 4v and the 99 4v are a little different. But I could have sworn the 98s had the B heads( a better head design). Im not too up to date on my 4v knowledge though. http://members.cox.net/bobcosby/cobra/images/t45sae.jpg
First, I appreciate all the input and the numbers. irregardless of the numbers, the curves are good, and the car runs great. that is the upside. the downside is, like mogs01gt, i know a lot of people who have way more power with similar and sometimes fewer mods. a friend of mine has around 310 rwhp on a 97 cobra, with all the same bolt on mods with the addition of MSD coil packs. just bolt ons. so adding a stroker, ported heads, and cams to that, only got me 10-20 hp? i fully agree. something is just telling me that somethin is wrong. I am thinking too much port on the heads, or possibly a need for new injectors/fuel rails. what do y'all think?
Could be the port, but I would look at the tune also. Was this a reputable machinist that has performance mustang 4V experience? And/Or was it a good tuner
who did the Tune and build up of the engine? As always, start with the cheap stuff first . Retunes foir performance issues are usually free from the tuner. if the car is running good with out any bucking or missing, it may not be the tune. Are you positive SHM sent you the right parts? Maybe do a compression check first, that would alteast tell you if you are getting any blow by or any cylinders arent up to snuff. With the power you SHOULD make, yes maybe larger injectors and a bigger fuel pump would be wise. There is no reason to pay that much on parts, then to skimp on something as important to an engine as fuel.
HPP Racing did the tune. www.hppracing.com. I cant find a single negative thing about them on the boards. as for the guy that assembled the engine, it was a middle-aged guy who has a good name and has been in the business for years. the car runs fine, no misfiring or bucking or anything. runs smooth.
I haven't heard a bad word about HPP either, I doubt its in the tune. HPP would have recognized if your injectors were tapped and at 320 rwhp they almost assuredly aren't. I would think your car would easily be pushing north of 350rwhp and close to that in torque.
Just got off the phone with SHM tech support. this guy, (contrary to Chris in the sales dept.), told me to expect between 310-330rwhp with my setup. He said the odd thing in my case was the fact that the A/F mix was 11.4 (as they usually run 13:1 on their cars) and that my torque was lower than my HP (usually about even). he suggested getting a compression test and a 'leak down' test. i have never heard of a leakdown. can anyone inform me? This is all contrary to Chris (the sales guy), whose numbers were much larger when attempting to sell the product. go figure. meanwhile, random question: i currently have 2 chamber flowmasters, would i see a difference if i switched catbacks to Magnaflow or Magnapack? lemme know what you think, what your experience is, if ya want.
Yes, your A/F is too rich. Since you are N/A you need to lean that thing out, which will give you some more HP. Your TQ/HP numers are a slight difference. On a 4V you never see monster TQ numbers like a 2V, and they are generally lower. What is your CR? As far as the heads, the B heads are holding you back a bit as well, contrary to what Mogs is saying. Stage one is very mild port. What is your cam profile? There could be many reasons involved. Again, other than what a dyno is saying, how does the car feel to you when driving????
Standard bolt on 98's do not make that kind of power. When you start at 260rwhp like the 96-98's do, 320 is way too much for standard bolt-ons. And B heads are not the way to go for N/A.
yea, leaning out is what i would have expected as well. but every time they made it more rich, it got more power. it didnt want to be lean at all. (much to the shock of everyone in the shop). the CR as advertised by SHM should be between 10.25 and 10.5:1. however, oddly, the Manley website lists the CR for my pistons at 10.96:1. is there a way to determine the compression of an engine after its built? the intake and exhaust lift is 0.452. duration @ .050 intake and exhaust is 209. thanks everyone.
