I went to AP Engineering for a dyno tune last Wednesday. Mods are as follows: Stock 350ci bottom end. 195cc AFR LT4 heads (203 cc after porting) flowing 280cfm @ 0.580 lift. Comp Cam from Combination Motorsports, XER lobes, 233/239 at .5, 283/289 advertised .569/.577 110lsa. Hooker longtube headers (no cats), Corsa catback, Ford 9", 17 X 11 wheels w/ 315's out back.

Dyno'd 368rwhp at 6200 rpm and 325rwtq at 5300 rpm on AP's Mustang Dyno. I was pleased with the torque. It would have been nicer to have a little more, but it is flat as a board from about 2500rpm on up. As far as horsepower goes, I know - 368 souunds low. And according to the tuner it is low, by at least 12-15hp at the wheels. Based on the graph, engine noise, and some other things, he said I have pretty bad valve float. This really pisses me off - I bought the entire valvetrain from Combination Motorsports - and here's the kicker - it is THEIR cam: Comp only grinds this cam for them. So WTF? They send me springs for their own cam that are inadequate? This cam should be peaking somewhere around 6500-6700 rpm, and the hp/tq curves drop like a stone after 6200.

I figure I'll have to pick up some new springs (or be happy shifting at 6000 - not likely). Seems to me like I should be getting a FREE set from Combination Motorsports, but I'll believe that when I see it. Anyway, assuming I can hit 380-385rwhp after a spring swap, what do these number translate to on a Dynojet? When I put this package together, I was hoping to hit 400rwhp. Kinda disappointed. Anyone know what I could gain from an electric water pump? Pulleys?

 

That 9" is costing you a hefty bit too.

 

What kind of lifters are you running?

Care to post the graph BTW? XE grinds generally all drop off after 6200 rpms, so no real big suprise there. Except that it happened on a 110LSA. You should probably pull closer to 6600 ~ then it'd drop like a stone. I've been in the same boat as you, and could only make power to 6000 rpms. Replaced the stock lifters w/ some Comp R's.... Problem solved. Like you, I also thought the valvetrain was awry, so I put some hefty springs in it ~ a tad more seat pressure than 977's. And to my suprise and disbelief, I didn't pick up anything above 6000. Power still dropped off. Actually.. It literally quit revving. And I had an AFR rev kit too.


PS - Mustang dyno #'s are typically quite a bit lower than Dynojet's posted numbers.

 

i dont mean to side track this topic, but im running an xe230/236 and i have a similar drop in power, but at 5300, i turned off the knock sensor and it seemed to help, but im not so sure its completely gone (havnt been back to the dyno), could i be getting valve float as well? stock lifters, comp pushrods, comp pro mag 1.6 rr's, and crane 10308 springs (part number is thunders) ...machine shop said springs were sufficient...dunno though, i only pulled mine to 5300 and made 325tq. 303rwhp right at 5300...still on its way up, but this little drop in power scared me so i let off. could stock lifters be the culprit?

 

Check out my post on my low dyno numbers for my Xe230/236. I'm leaning toward valve float. I have comp 987 springs and stock lifters. I'm having the springs checked tom and some Comp R lifters on the way. Another guy is having the exact same problem with his 230/236 and he has 987's and stock lifters. We could all be having diff problems but we do all have stock lifters in our sigs too.

 

I dynoed w/ my 230/236 and got a jump on the dyno at 4800 rpms... it would literally cut out 50-100 rwhp and it bucked hard so they let off. It was either knock from the exhaust that was touching the bracket that goes under it, or the water pump and opti that both died 3 days later.

Either way, at 4800 rpms I had 318 rwhp and at 3300rpms or so I had 332 rwtq.. both numbers where extremely low, it has 340-350 of both in it. I am replacing the water pump w/ a electric one, and getting a new opti... hope I have numbers soon!

 

In the MOFBA web site a electric water pump dynoes 7rwhp. I know it hurts to spend that kind of money for those results.

 

will62085 I'm having the same problem as you, at 5300 rpm there is a 15 hp drop and I max out at 330 hp. I have the same cam , springs and just installed new comp R's with no improvment. I'm installing combination motorsports 612 springs , hopefully that will fix the problem.

 

I have Comp's stock replacement lifters.

7rwhp for an electric water pump. Cool. My water pump is dying anyway. How about the pulleys? Worth the $$$ or are they a joke? On an LS1, I can see how they would pick up some power - everything is belt driven. Any gains to be had on LT1's?

 

2 hp or so. 5-6 under the curve.

 

Well I just typed a nice long post that vanished. So you get the brief reply
because I am too lazy to type it again.

Get some Comp beehive springs!

Search my user name for lots of info.

 

i was dropping 90 rwhp between 5300 and 5400, i have since disabled my knock sensor...and it pulls like a bat out of hell till i hit rev limiter at 6800...still needs some tuning up there, but its making power now, i think my roller rockers are making too much noise, and one is rubbig on the stock valve cover, i need taller covers, but try disabling your knock sensor, see if that helps, it helped me...good luck,
Will

 

In addition to already having the LT4 knock module, we tried turning off the knock sensor all together. No luck.

As far as springs go, assuming I don't hear back from Combination Motorsports, I want to get some that would allow me to run 1.7 rockers at some point. I don't know that I would pick up a significant amount of hp/tq from that, but more lift never hurt hp/tq curves, I figure.

It sounds like pulleys are nearly a waste of time - a difference of 2hp could just as likely be caused by a 10 degree drop in temperature on a different day dynoing . . .

 

I'm in the middle on my rebuild and don't want those kind of problems of hitting a wall should I change those stock lifters then? I will program out the KM anyway.

 

From talking with some tuners and reading this board, it sure seems like a lot of vendors/tuners underestimate how agressive the XE lobes are...