I already said air/fuel was 12.8:1 where it made its most power. The tune is fine. I don't care about uncorrected numbers, they mean nothing to me. I picked up 2 mph over my cam only setup when I was making 403 rwhp. So the numbers are right. I should have picked up 4 mph from the heads alone and another 2 or 3 from the extra cubes. So 2 mph total is pathetic. Dynos don't lie like the popular belief goes. It will tell you exactly how much power your car is putting to the tires and it will tell you whether your new mod has caused you to gain power or lose power. You just don't expect to add 37 cubes and lose 15 to 20 rwhp across the entire rpm range. Then again, with the way my year has gone, nothing is surprising to me anymore.

 

Comp XER287HR is my recomendation on a cam shaft change, and I would have got the 225 TFS heads for the bigger displacement, but I know you didn't want to hear that, but like even Tony is saying the volume of the runner is going to effect the out come quite abit good luck!

 

Derrick do you know the compression of the motor? You posted awhile back that you have dished pistons with the pistons .014 in the hole. Sounds to me like the motor has low compression. Unless you have heads with 50cc chambers.

 

I suggested the 225s but TEA recommended I go with the 215s so that is what I went with. I think there is good evidence that the small bore 225 heads don't do any better than the 215 heads.

Shawn,

Compression is 11.5:1.

Piston is .014 out of the hole
Gasket is .054 thick
Pistons are -8.8cc
combustion chambers are 58cc
gasket hole is 3.910
bore is 3.905
4" stroke

I did the math, Weber did the math and Wiseco did the math and we all came up with 11.5:1.

I keep hoping it is something simple like some punk kid stuck a bananna in one of my tail pipes or something.

 

Find that bananna in the tail pipe yet?

 

No but we did install a bigger cam and it brought power back up to the same curve as my 346. I ran 10.28 @ 129.13 with my exhaust on. We pulled the exhaust and ran 10.27 @ 130.03 but I suspect some of that gain was due to the 50 lbs we lost when we pulled the exhaust off. So it would appear my exhaust system is not robbing the 20 to 30 rwhp I am trying to find. I'm basically running the times I would have ran with my 346 heads/cam motor if I ever would have had a chance to race it. I'm happy with the gains I picked up from my new cam but I still wish I could figure out why I'm not making any more power than my 346 made.

Looks like I'll have to figure it out next Spring. I put my car away for the winter. I'm fried.

 

Specs on the new cam? What does your exhaust consist of? Have you measured back pressure?

 

This definaitly sounds like a breathing problem. I think the increase in displacement really didn't matter because there wasn't a huge breathing increase. The reason I say that is because the bigger cam helped. What are your MAP values during the dyno pulls? Are they about the same as the 346 or are they going lower. It doesn't matter how big of an engine you put underneath an intake tract, it will only sustain as much power as it can flow. The only gains you should see from larger cubes is more torque below peak. If you don't change the breathing efficencies or gear of the car along with the added cubes, you are going to go about the same speed. Did you try going to a taller gear? You may be surprised to find that you will pickup extra speed. What RPM are you going through the lights? I guess all things to consider.

Also, on the breathing aspect of it, the 4" stroke is great and all, but it did nothing for more air to get into the chamber efficiently. If you still have the same bore size, you still have the same shrouding effect. I would guess if you went with a 402 you would see vast improvements in power because of the larger bore.

I don't really know the answer, just throwing some stuff out there for you to consider.

 

Ouch big time.

Buy Tony Mamo's shortblock, man! Do a search for his name in the for sale thread. It's a ledgendary 383. 600 HP (solid roller). He's doing a rings-bearing job on it and inspecting it, then hand-building it. However, it's used, so you might be able to pick it up for a good prce.

You gotta know it's the damn short block. It's the only thing left! Isn't that the official guess? Heads made the car hot, fried the short block?

 

Man I was going to just let this thread die but now I'm going to have to type a long winded reply...

There is no back pressure when you run open headers. As I said that only picked me up 1 mph and half of that was probably due to the 50 lbs we lost when we removed the exhaust. So it is not an exhaust issue.

I also do not believe it is a fuel issue. Injectors are SVO 30# and they are running about 92% duty cycle under WOT. Air/Fuel is right around 12.8:1 where it made the most power.

It could be the intake. The intake was port matched for the ETP 225 heads and now it is being used on the TFS 215 heads. Mike at TEA said the TFS 215 heads have nearly the same size intake runners so he thought it wouldn't be an issue. Maybe it is though? It's hard to tell without throwing on an intake that isn't ported or one that is ported for the TFS 215 heads. The rest of my intake tract goes like this, 90mm NW TB, SLP bubble shaped bellow, 85mm GM MAF, Direct Flo Lid, FRA. So I don't see a problem with any of those as far as flow is concerned. Besides, everything is the same as was on my 346 except for the 85mm MAF.

It could be the drivetrain but it is very doubtful. I had my converter inspected, refreshed and tightened while my engine was being built. So it is essentially as good as new. I also had my TH350 inspected by Rossler and he gave it his blessings. So both of those should be fine. My 4.10 12-bolt rear is almost 3 years old and has maybe 60 passes and 3,000 miles but there is no indication that anything is wrong there. I was cutting 1.34 sixty foot times last weekend and pulling 129 to 130 mph trap speeds at approx 6900 rpm. The pumpkin is leaking a tiny bit of fluid but not a lot. The pinion angle is -2 so that wouldn't be robbing any power either.

It could be the shortblock. Obviously 22% leakdown is not desirable for a brand new motor. Maybe when I overheated my motor was hurt. Maybe not. Doesn't seem likely in my opinion since it only got up to 235 while running and only for a short time but it is possible. Regardless, would 22% leak down really be causing a 20 rwhp loss across the entire curve? I don't think so but that's just my opinion. Either way, there is no way in hell I am removing this motor and having it rebuilt. I've been through way too much this year to go through all of that again. I think $10,000 and 10 months of BS headaches is enough for one season. I'm going to run this motor until it pops. I plan on spraying a 200 shot next year so maybe the looseness will help.

Funny thing is I have heard comments like "dude you're running 10.2s and almost dragging the rear bumper, what are you complaining about?" Don't get me wrong here. That is great and all but I know what my car should be running and how much power it should be making and its just not getting it done. What right do I have to go tell a guy who built a 7 second car that he shouldn't be complaining about running mid 8's? He knows better than anyone else what his car should be doing. Plus, in my case I have plenty of evidence that shows my 383 isn't making any more power than my 346 even with the addition of a much bigger cam. Both the dyno curves and the track numbers support that arguement.

I figure I'm about 20 rwhp short and about 2 tenths and 2 mph off of where I should be. I have some 1-7/8 ARH headers I am going to install over the winter. Those should help a little bit. Maybe I'll try an unported FAST too just for the hell of it.

 

You took 225 heads off, maybe you should have put 225 heads (TFS) back on the 383, just a thought.

 

I agree, strokers like to breath!!

 

That right there is the most telling comment in this whole thread. It has to be an air in air out issue. Those injectors should be running out at about 450 RWHP. At that level they should be real close to 100%.
Closing in on 500 rwhp, they should be in excess of 100%.
It shouldnt take bigger intake ports. I've done 383s with 205cc heads that made well over 500 rwhp. Seems like you have bottleneck issues.

 

I'm surprised you say that because I told Mike I wanted 225s and he talked me into the 215s. He said the small bore 225s don't perform any better than the 215s. Do you even realize I bought these heads from your company? Maybe you and your employees should try to get on the same page. You coming in here and telling me I should have bought bigger heads after your employee talked me into the smaller heads isn't very reassuring. I don't think that is my problem though.

As for MAP, MAP at WOT on my 383 is identical to the MAP readings I was getting on my 346 at WOT. I don't know what, if anything, that indicates. MAF readings were sort of all over the place on my 346, fluctuating from 350 to 400 at WOT. On my 383 they are much more stable at approx 355.

 

Sounds about on par now

 

I agree your looking at something that might not be a problem with the converter unlocked.


I recently finished a 408" L92/L76 that made 501 rwhp with a 237/241 camshaft and pulled to 6500. I dont exactly think the camshaft is lacking or causing the falling off top end results.