OK well I am not sure how much detail I should put down right off the bat, but I guess I will start general and work my way to more detailed as any advice rolls in. But first here is my problem.

I want to make 400 RWHP and I am positive this motor can do it, but it isn't.

SPEC time.

-block is a 1974 Non roller block from a truck.
-Bored 60 over to make it a 385.5, so a 385.
-Forged crank, rods and pistons.
-Edelbrock RPM Air gap intake.
-Trickflow AL. heads.
-750 Holley DP.
-Cam card is in attached pic.

Now, I did not assemble the motor and the place that did went out of business so they are gone, I am kinda flying in the dark now. It leaks a little oil, but nothing crazy. Like less than a quart per year, just enough to keep my garage floor moist. It sounds OK, and I have put 4000 miles on it. Coolant is clean and oil is too. Cut filters open and they seem fine as well.

Oh I also have hooker long tubes and a 4" mufflex cat back.

I dynoed the car and it made 344 HP and 343 TQ. Seems like it should be a lot more since the "kit" that I choose says the motor should be putting out around 500 crank so that should at least be 400 wheel.

Where should I start looking?

I have some guesses.

1. Bad rings, maybe installed poorly... I checked a couple cylinders with a simple bleed down test. Results seemed fine.

2. Bad intake install. It had a Vic. Jr, and I swapped the AIR Gap, so if that is the case it is my fault. But car idles fine so I don't think that is it. I was SUPER carefull. Although it was my first intake swap.

3. Way out of tune carb. Although I have had many people look at it and they seem to think it is OK.

4. Cam, lifters, SOMETHING... outta wack.

If I have to I will pull the motor and have it taken to a shop that will rip it down and put it back togeather. Making sure it is all OK, then dyno it out of the car. But I am trying to avoid that since I am broke right now.

Thanks for any help.

 

I wouldn't think that's a 500 GFWHP combo. The cam/heads/intake more like 425-450.

425 GFWHP and 20% drivetrain loss is about 345 RWHP.

 

Interesting.

Only reason I say it is a, or should make 500 HP is cuz that is what Trickflow advertised it as. I know that they are using PERFECT contions for their test and all, but I guess I thought I should be closer to the 400 mark. I guess I will just keep tunning the setup I have on the dyno. And running diagostic checks on everything. Can't hurt.

I guess when I get back on the dyno we will see what I have after tunning and all.

Thanks for the advice

 

Do you know the compression ratio? How about your total timing? On paper it seems like a combo that should run strong.

When you had it dyno'd was it also hooked up to a A/F ratio meter?

 

Dennis, what forged crank are you using. I noticed in your spec's that you didn't reference the stroke. You referenced "bored .060" over to reach 385.5 CI. I would be more concerned with the rear wheel torque number than with the HP. A 3.75" stroke should yield more torque. Are you sure they sold you a stroker rotating assembly?

 

What fuel were you running?
What do all the sparkplugs look like?
Can you post pic of dyno graph?

 

AWSOME! So exited to see people willing to help.

I will address everyones requests for info.

Compretion ration was supposed to be 10:1 I think. But I never really knew hands down. It was my first motor and I was still learning what everything was back then.

Timing is what have been plying with for a while. I think now it is set to around 36 or 37. Not sure what it was when it got dynoed though. I think around that. And around 17 initial. They dyno tuned it and played with the timing to get the MAX #s that they got.

Yes it was hooked up to an A/F meter, it is on the bottom of the dyno sheet.

I am running an Eagle forged crank. Here is a pic the guy sent b4 it went in.

Here is the dyno graph



He put in a stroker setup to the best of my knowledge. I guess I can attempt to confirm somehow.

I think I at the time I was running 93, but for no good reason. Might have been 91. The car runs now totally fine on 87 which is what I use now.

Plugs have been changed and checked and changed. They look fine though. Carb has been finicky to tune, so I have ran super rich, then lean and everything in between. But as the car stands now they are a light orange tint with no oil or anything like that.

Thinks that everything. Thanks so for any help that can be given.

 

Your picture leaves no doubt. Your crank is a 3.75" stroker crank. The part number, 35037505700, indicates a crank made for a 350 block, 3.75" stroke, using 5.7" rods.
How is the cam installed, 4 degrees advanced, 4 degrees retarded, straight up, etc.?
IMHO, your HP is in the ballpark, but the torque curve seems a bit low/late for an Airgap/750cfm, even with the big cam. The extra inches should be keeping it a little higher/earlier. Even though you have tuned & tuned, I still think it's in the tuning. The mechanical possibilities you elude to above can be checked on the dyno, where the additional tuning should occur. Pulling the motor back out shouldn't be neccesary.
Were the heads installed out of the box? If not, I've seen good heads lose HP/TQ by inexperienced head porters mistakes (don't mean to scare you).

 

I think I saw a picture that shows you have the twisted wedge heads.
If that is so then who determined the correct pushrod lengths to use on your engine. The intakes and exhausts will almost always be different.

It is really odd that your engine picked up so much power while showing a richer AFR.
Do you remember what exactly was done during the dyno session to cause the power and AFR to increase?

Can you describe your distributor please?
Does it use a vacuum advance mechanism? and if so is it hooked to full vacuum or ported vacuum?

 

Thanks again for all the insight. Going to make sure I address all points made.

Here we go.

Cam install. I wish I knew how it was installed. From what I know it was straight up. I think I remember him saying that way beck when but I am not sure. This can be checked by taking the timing cover off right?

Heads were installed out of the box. The Trickflow heads that I got are the ones that have the combution chambers CNC'ed. Def no modding to them was done.

I am not possitive what the heads I have are called. But they sell them under the lable "Kenny Dewinter" heads. Well at least that is what is engraved on them.
Here is a link to them on the trickflow site.

http://www.trickflow.com/partdetail....C&autoview=sku

I do remember the builder telling me that he checked the pushrods and had to get different lengths and stuff, so I think they are OK.

I was not there during the tunning so I am not sure what was done. They said that they just played with jets and timing.

I have a probillet dizzy (MSD). It doesn't have any vacuum advance on it, Just mech. I run an MSD Digital 6+ box. Sorta the same as a 6 but it has built in timing retard for N20 use.

I have a feeling like we are getting somewhere with this. Thanks for any more insight.

 

Just scanning over the read here but it looks like ALOT of cam for 10.1....could be the torque problem. Flat tops and 64cc cambers would be 9.5 .1 but with that cam it`s bleeding off alot of cylinder pressure...what kind of PSI do you get on a compression check? Bumping the cam 6* advanced would help but won`t get you 60Hp. I`d would have at least .125 dome in there with that much cam, and yes you`d still be able to run off some sort of pump gas.

 

That would be an interesting piece of information.

Did a few calculations regarding your static and dynamic compression ratios.
GIVEN: 4.060" bore
3.75" stroke
64cc heads
ASSUMING! .039" x 4.10" head gasket
flat top piston with 5cc valve relief
stock deck height of .025" in the hole
That yields a static compression ratio of 10.6:1
If that cam is installed straight with a 112 degree intake centre line (with a 112 degree lobe speration angle), you end up with a dynamic compression ratio of only 6.95:1.
There's your lost power and torque.
Greezemonkey is right. Way too much cam for the compression or not enough compression for the cam.
If the assumtions made in the calculations are accurate then you could benefit from a thinner head gasket (.026" compressed thickness) and a few degrees of cam advance. That bumps your DCR up to 7.5:1 which is the bottom edge for a performance street engine. Your SCR gets up to 10.9:1 which is probably the top edge for aluminum heads and pump gas.
Keep in mind this is all theory and until you can actually measure all the values, we're all only guessing.

 

I was wrong about the heads, I just needed to look at your pics closer. You have inline heads.
You can rule out a distributor problem if you've checked over your timing with a dial-back style timing light. At what RPM are you getting total SA by? and what is the total? I do doubt that is the problem.

If you don't spark-knock on 87 octane then that's what you should use. I've worked with a slow-burn combo before that made 380rwhp on 87 octane. It was set up for a large N2O shot and required a good bit of tuning work to get right for NA running. The car liked to run in the 13.5:1 AFR range at the lower & midrange RPM and right at 13.0:1 AFR at the higher RPM, and with a little more spark advance ( about 5* ) than what I expected it to want with 87 octane. You may have a similar combo there for several reasons. The low static and dynamic compression would be large factors to consider when trying to predict burn speed in the chambers. The engine temp would be another factor. If your engine runs cool ( 180* or lower ) that would also slow your burn speed a bit. It's not a bad thing, but you have to adjust your tune for it.

I'm trying to concentrate more around the tuning aspect. I assume you've checked over a lot of more obvious areas already - car was dyno'd in 4rth gear (1:1 ratio), your carburetor throttle blades are opening completely, you don't have any mismatches between your carb & intake manifold or port mismatches where things bolt together, you're not running any kind of extra fuel additive, not running incorrect reach sparkplugs, and you're not running through a catalytic converter. Those are unlikely possibilities given the shape of your dyno graph. I do think you should be dynoing a little higher running through a manual trans and running radial tires on the rear.

You can check your cam timing by pulling the timing cover, but I doubt that it's a problem.

Your dyno graph seems very normal and smooth so I wouldn't think you have any weird problems like a misfire or valvetrain problem. On the other hand, a very smooth curve generally means the tune is still very conservative and not close to the edge of maximum power. If you had some air flow restriction you'd still be showing more power down low. A conservative tune would show less power down low just like your graph looks. It originally stems from a lack of cylinder pressure, but you can make up for a lot of it with the tuning.

If you weren't running a manual trans with healthy rear gear then I'd also suggest a milder camshaft. The next time the engine is apart you may want to consider reducing your squish distance a little depending on what it measures out to. If you're really serious about tuning it then I'd say to get a good wideband and install in your header collector so you better see what is going on. The WBO2 used by dynos that just clamp into the tailpipe usually don't read precisely and often read leaner by about 1 point.

 

Ok, looks like we are getting down to the real problem here. The cam or maybe my CR, so pistons.

But I will try and address everything you guys ask....

greezemonkey: The numbers I was getting from the compretion check was like 260 PSI, I think. That might be completly worng as I did it last summer and had no idea what I was doing really. I know I need the car to be warmed up and then disconnect the coil and plug in the checker, and crank. I will DEFINETLY do this test again, once it is above freezing outside. number might have been 170, ugh.. I wish I remembered. There was def a 70 in there.

moving on, will address the compretion check in a couple days.

skinny z: Thanks for doing all those calcs for me! The parts of the calculations that you were not sure about is why I want to just have the motor totally ripped appart and built back up with everything being checked and documented. Do you think that all this info could be learned from just taking off the heads in the car, and measuring things like that? Then when I put it back togeather, I could use a thinner head gasket, or maybe even get the heads milled down to increase CR.

In the next year or so I want to try to play with forced induction, turbos to be exact. I know that the cam will have to be changed so probably the springs in the heads too. Hopefully I won't have to change pistons.

305sbc: I am not sure what RPM I am getting my total SA. I think around 5000 though. The total is something like 37*. As for the other factros, yeah those things were all looked into when dynoing. As for the wideband. I have an LM-1 in my tailpipe right after the muffler, and I am running no cats so the gasses are still the same as at the header collector. I called the Inovative and they said that if I am more than a foot away from the exit I should be fine. My readings were very close to the dyno shop readings. I may move the sensor this summer if I feel like it is just a bad spot.

I guess as a semi-conclution to all this. I guess I am stuck with too big a cam. The motor is a nitrous motor, made to take about a 250-300 shot. This is my first motor ever, and I want to play with all forms of power adders so I figured I would start with N20. Then move on to turbos.

I will keep tunning I guess and hope to work the bugs out, maybe the CR is just too low and thats why I am not making the power I want. Maybe when the N20 is shot it will make a lot of power as this will pack a much more dense charge in the cylinder.

Thanks for the advice. Expect a few threads abot turbos or more N20 tunning soon from me.

 

Looking at the cam specs it does not look like a dedicated nitrous cam but does look like it would take a fair amount on No2.... did they gap the rings for a 250 shot? If so hit it with the sneeze( when the thaw comes :-), a little to start with and then move up to keep on top of the tune up. Might be a hidden strip hero under the hood?? Low cylinder pressure is not 260...170 is mediocore def good for pump fuel.

 

what spark plugs are you running? I tried running a AC r45ts plug in my first set of aluminum heads. No one told me I neede to run a longer shank plug. the tip was about 3/4 of an inch from the combustion chamber. It made a huge difference.

 

I am running the plugs the instructions said to run. I have tried a couple sets so far. I think the ones I have now are a heat range hotter. Made them a lot more expensive, but Maybe I will try a few different ones next time I dyno tune.

The cam is not a dedicated N20 cam. But the builder did say that he built it to be able to run N20 safely. So I assume he gapped the rings the right way.

I guess I will check compretion as carefully as I can when the thaw comes. Then tune a 100 shot, and a 250 shot. All I have ever ran is a 100 shot to make sure it was all hooked up right.

 

What brand & part number plugs? They don't make a huge difference in power by themselves but they do come into play as far as how you can tune the engine. An engine tuned closer to the edge of maximum power will make more combustion heat & cylinder pressure, so then would work better with a colder plug. An engine with a very lazy tune will like hotter plugs. The problem is that hotter plugs can destroy your engine when using the N2O. A melted ground strap from a plug can easily take out a piston. It will form a hotspot on the piston surface and the melting point of steel is much higher than the melting point of aluminum so the heat is already there to burn a hole in the piston.

A nitrous engine is built looser, usually with forged pistons with looser side clearances (0.003" or more) and with wider ring gaps - sometimes 0.030" or more. This will reduce power a bit when NA, but is necessary to prevent problems when using lots of N2O. Large amounts of N2O will also need colder plugs to survive the combustion temps under load.

It's common practice to tune a nitrous engine to run very close to the lean limit and with lots of spark advance while running N.A., then pull timing when on the nitrous. Using a dedicated second fuel system with race gas also gives great results with large N2O systems. It allows you to run on 87 octane when N.A. then increase the octane when using the N2O. The added fuel is usually only 20% - 30% of the total fuel being used so it's best to run very high octane like C16 in your dedicated fuel system (separate fuel cell).

It seems to me that this is what your engine is set up for. Since a lazy tune costs you power N.A. and also tends to foul cold sparkplugs, I'd say you need to put in some work fine tuning your N.A. running to stay near the lean limit on 87 octane.

 

I think you are exactly right. I was not origionaly going to run N20 until the guy building the engine recomeneded it. So He said he would gap the rings the right way and so one. He gave me all his paper work from the engine build so maybe I can look though it to see if I can learn more detailed info about the build. As for the plugs, I am not 100% sure right now. I will go check them out first hand on the car and get back to you. I wanna be 100% sure what I got in there. Been awhile since I have tried something new.

I will post back later today. Hopefully getting everything in the right balpark will make the tunning a bit easier.

As for the seperate fuel system, I strongly considered that. My system now runs of a 15 gallon fuel cell. If I was going to stick with N20 only, then yes I would totally do that, but as things stand now, it is just my car that I wanna drive to work and stuff, and go to shows. Then use the juice when I finally get time to take it to the track.

I may never go as high as 250, but I may. I have jets for 100 and 250. I think. The digital box I have retards the timing automoatically which is nice. Motor is all forged so I think with the right tune, timing and settings that they car will take the 250 shot OK. I will def have it tunned by a dyno shop when dialing it in.

Thanks for the heads up about the plugs I have pretty much set them and forgot about them for a year now. About time I take a look.

 

Many good points and suggestions above.
Something else: No matter if the compression ratio happens to be too low for that cam, your hp curve should be on a strong climb at 6000 rpm with that cam, not falling off like shown. If you're running no more valve spring than that cam card calls for (110 lbs on the seat), then that's a big problem. That cam will want to rev to high 6's. You'll need 130-140 lbs on the seat to let it do that.

 

I am running what springs came in the heads. The setup was a "kit" that Trickflow put togeather that summit sells. So I figured what they gave me is what I am going to use. I would never rev up to 6 grand anyways. I guess further solidifiying the point that I have too much cam.

 

If you would take a look at your order. Summit should say on their page what springs come with them, and/or if you can specify different springs which is common.
TFS says 1.460" diameter dual springs, in which case they shouldn't be a problem, but you may have different ones.

 

yeah, those are the ones that I have.

 

Good points...bigger cam should be pushing the power band into the higher RPMs...and it does look like it`s falling off early for the small cubic inch...weak valve springs will limit rpm and cause slight miss fires that you won`t hear or feel

 

Is that the case? If the comp ratio and cam are mismatched ( as they appear to be) then at what point will the engine stop making power? Is it at the high end of the RPM range oor generally depressed overall. If compression and compression pressures are low then torque production will be reduced. Consequently HP is down as well seeing that HP is a product and torque and RPM. This is not to say that something is amiss with the valve train. However if torque production was on a level with what is to be expected then the HP should follow. If it didn't then I'd say it's safe to say that there's another problem.

 

I am running Autolite AR3924 racing plugs.

Gonna have to look them up to see what heat range they are. I think I switched to these about a year ago.

 

1

 

Not a bad plug but it looks oily.
You might want to switch to AR51 plugs when you're going to spray the N2O.

 

My plugs might be a bit oily cuz the looser ring gaps due to it being a N20 motor. Not sure, but just an idea.

 

Well, that plug shows some problems, oil on the threads can be leaky valve seals. The heat mark on the strap is at a good point for N02 use but for motor..no good. Looks like it def wants a hotter plug but on top of that the timming is at least 3-4 degrees retarted (you want to get that heat into the bottom of the strap or even the first thread. As far as the heat range that electrode is oil fouled it looks like so that`s one reason, second the porcelin looks fuel washed. A word of caution......with plugs looking like this dont even think about spraying this thing...oil is not what you want in the combustion chamber..loose gaps won`t cause this either, poor oil control (bore size and shape, hone finish, scraper rings, windage, poor intake sealing) and bad valve seals. Your plugs should look a lot cleaner if the motor was tight and the tune was on.

 

Thanks for the heads up about the plugs. I will try and advance the timing a bit and get a new set of hotter plugs, then tweek the carb a bit and go from there.

The plug could be looking fuel washed cuz it takes a lot to get this motor to turn on when it is like 20* out. I fire it up a couple times a month just to keep it all lubed. But out here it is so damn cold. Takes a lot of gas to get it to finally fire up.

I also don't drive it around I just fire it up for a few minutes until she has a little heat in her and turn her off.

But like I said, I will get some hotter plugs, advance the timing a bit and drive it around for a while and pull the plugs and take pics and post them back. Might be a couple weeks till I can report back pics.

As for poor oil control, that would be strange unless trickflow sent the heads a but messed up. As for the intake, I installed it, but I am a very very cautiose person. And put silicone down on the heads, the intake and used gasket prep on the gaskets. Installed it very carefully. If there is a problem with the intake I would be very suprized.

But anyways, I guess I will see if I can afford to get a set of colder plugs on summit right now.

Any suggestions?

 

OK so I looked around online and got a bit confused.

I am running AR3924s, looke like they have a heat range of 5.
I found my old set of plugs. Barely used at all. These are AC Delco FR1LS, these seems to have a heat range of 6. Making them even colder. Not what I want.

So then I started to look on summit for some heat range 4 plugs. So I looked some up and found FRM 104 plugs. But after doing a google search about them, I found out that people refer to these as one step colder than stock!!? Now I am confused. I found the info on a GTP forumn. I just wanna make sure I am getting a hotter plug before I buy, so I won't get a thing till I get some info from you guys. Thanks.

 

I`m not sure how auto light does thier heat range, I use NGK and the heat range goes down when the numbers go up....I use a R5671A-7 on motor, -8 on a small hit, -10 on the new combo which should be 300+HP worth of dope. Looks like the same plug would work in your heads.

 

OK, so I guess I will order a set of those and make sure that I go hotter then what I got.

SO i looked up some NGK plugs. I don't know how other companies do heat ranges wither, but I am assuming similar to NGK. I will look it up though.
At first glance I found these:

http://store.summitracing.com/partde...5&autoview=sku

But then I looked up the ones you posted and they have no resistor, what does this mean? Also it says that they are heat range 7. I am assuming that is way to cold for me right? Getting a bit confused about all this... again...

 

Did a bit more research and found that a resistor plug helps with radio noise and also prolongs plug life.

Can anyone recomend a good "street" hotter plug by NKG?

Or is the one that I posted above OK?

Thanks.

 

here, take a look at this.......I`d say a -6 which is hotter would be perfect but this style doesn`t go that hot. I was unaware that it did not have a resistor.

 

Still confused.

The ones in my car seem to be 5 now. And I used to have 6 so I got 5 to get them a bit hotter. But you are saying they look too cold. So was under the impression that I need 4s.

What is goooooing onnnn???

Ugh... Very lost about something I thought I knew at least a little about.

On the LS1 boards, I found a thread that talked about all the plugs I have and have had. They all say that this part NKG is the best thing to run off N20, and that one step colder is the best for on the juice.

http://store.summitracing.com/partde...5&autoview=sku

ANy thoughts.

 

You are right , my bad I don`t know the autolite #`s...3924 is as hot as it gets.

 

That's what I was saying but looking at it from the different angle of improving the tune to build more heat instead of picking a plug that will stay clean with a bad tune.

Those plugs have been in there for a long time and seen numerous cold starts so I wouldn't assume too much from just that.

 

From just to cold start?

These plugs have been in for about 3000 miles I would say. But the last 7 or so times the car has been fired up is has just been for a minute to let it lube up a bit. Tomorrow it is supposed to be nice out. Maybe I will take her out for a spin and then pull the same plug out and post a pic. Maybe my timing is off. I will try to advance it a bit, see what that does too.

 

If you do have forged pistons and wider ring gaps then you have a lot more blowby and oiling during cold-start. You also said you don't have vacuum advance. You can increase your initial SA and decrease your mechanical SA which could very well help, but your SA for cruise and coast will always be a little less than optimum. What you're seeing on your plugs is mostly from your idle and street driving.

I don't think this is a terrible situation. I just think you should tune closer to the edge for NA driving and you'll still probably have to check & clean your plugs at closer intervals no matter which plug you run. Hotter plugs are self-cleaning to an extent but oil doesn't always burn off completely.
I prefer to run a cooler plug and just keep an eye on them.

 

I am sorry, what is SA again?

 

Spark Advance

 

I just came across this thread and noticed on your dyno graph that your AFR's are slightly above the red dash line between 3500rpms and 5500 rpms. You want your AFR's to be just below that line to make good power.

 

I know that, but I don't see that gaining me the power that I think I am loosing. Thanks for the heads up though. I will be going back to a different dyno over the spring and keep my eyes out.

thanks. later.

 

One side note on the oily plugs. On the Dutwiler heads the intake rocker studs are open to the runner. If these wern't sealed up, oil will get into the intake runner. I am running almost the same setup, only a 230/245 cam with 11.2:1 compression, and put down the same numbers, losing 45 hp through the stock intake plumbing. Also, out of the box those heads flow less than 250 cfm, so 500 fwhp is possible with a high VE.

 

Im courious ifanything was ever figured out here? Kinda looking at the dyno numbers and the way the engine was setup I doubt the cam was install straight up. Im thinking if the timing cover was pulled it will be retared a bit.

 

I have decided that I am going to save up some $ and drop the car off at an engine shop. Have it broken down and built back up so that I know how it is all put together. That way I can stop playing these guessing games and get this figured out.

 

Sorry to hear that. You have tons of time and money in this project. Let us know how it plays out.