Brad_B

Good afternoon. I have not posted in a while. I have a ’77 that I am planning on restoring with my two daughters this winter. I started by getting a new motor built. I read lots of posts and tried to do my homework with regards to the engine builder. I asked for mild build (medium build?) 383 with around 450 hp that would still have good vacuum and good idle. I am not sure I got what I paid for….. I knew going in that it was more of a “budget build” and would not have super high end components, but I did not want crap either.

The new motor does not run very well at all. It feels like it is no more powerful than the old L48. I am concerned that it has too high of compression and will not run well on pump gas. The installer had a hard time getting it to not pre-detonate and had to retard the timing and put some 100 octane in it to get it to run ok.
I was wondering what you all think about the build and if I am going to be able to get this thing to run well with the following specs.

Here are the specs:
Bored over .040 flat top pistons
Heads – 64cc combustion chamber, 200cc intake chamber, 2.02/1.60 valves
Head gasket – 0.039 in compressed thickness
Cam (Melling 22280) – Intake 220 @.5”, Exhaust 224 @.5”, Lift .495 intake .502 exhaust. Lobe separation 110 degrees.
1.5 rockers and 7.205 in rods.
One of the things that I don’t know is deck height. I assumed 0.025”
Performer intake.

Based on online calculations, it appears that I have about a 12:1 static compression and something like 9.7 dynamic compression. This seems way too high! Am I looking at something wrong?

I am frustrated about this build and trying to figure out how to get this to run strong; if possible.

By the way, it has a Qjet on it that was rebuilt (be it a little while back) by Lars, so I am confident that it is not the carb. Everything else is new.

Thanks in advance.
Brad

jkippin

something is amiss.
without actually knowing how far in the hole you are or the actual gasket thickness its kind of hard to figure out exactly what you have.
Quick glance intake may not be a good match didn't say about the exhaust heads runners may be too big making it sluggish down low

Just to give you an idea, I have a true 11.0:1 .040 350 stock stroke
Performer RPM ,750 cfm carb, shorty headers, Comp retro roller cam pretty close to your specs heads are aluminum 180 runners
No detonation issues on 93 runs strong 443 Ft/lbs of torque and 423 hp. I'm making over 400 ft lbs from 1800 to 5800 max hp comes on over 5800. Its a fun street motor.

Brad_B

thanks jkippin. Patriot mid length headers with true duels. I am going to call the builder tomorrow to see how far in the hole I am. What you have is exactly what I was wanting. I will post up when I know. Thanks again.

Brad

7T1vette

You will have a difficult time getting an engine with 12:1 compression to run on ANY available pump gas...even if it has aluminum heads. When you asked for a 'medium' build, 12:1 compression is NOT it.

10 to 10.5 compression with aluminum heads is pretty easy to get running well on pump gas. Higher compression than that may require retarding the ignition timing...or putting some AV gas in with the pump gas. Neither of those options is good.

I'm sure that, at this time, the deed is done. The engine builder probably won't come through with any alterations, as you probably approved what he suggested [which doesn't work well]. The least expensive 'corrective action' would be to install thick gaskets under the heads to bring down the compression some. But that's not a good solution, as far as engine performance is concerned. The better solution {but more expensive solution} is to go with different heads that lower compression into a better range for pump gas.

Sounds like you did good research on everything...except who to choose for your engine build.

Wish you the best as you work to get your new engine up to speed.

claysmoker

Since he's at 5000 feet,he can get away with more compression on pump gas, but 12 to 1 with the small cam he has is too much. I'm at the same elevation with an engine that's 11.2 to 1 and quite a bit more cam. It's fine here, but at sea level race gas is the only alternative.

He should go find another engine guy.

jkippin

when you figured out your compression ratio did you take into account your valve reliefs? or the gasket bore diameter?
doing quick figuring I come up with a static of 11.1.It will be lower with figuring your valve reliefs and gasket diameter

10.4 static 9.7 dynamic would be more realistic numbers

Brad_B

Yea, I wish I had done a little more homework on the builder. I thought I had.... hindsight.

Jkippin, I think you are correct. I went with another calculator (Summit) and I was in that 11.2 to 10.6. The heads are aluminum. So now I am thinking something else is wrong... That should not be too much.

Claysmoker - Do you get 93 octane over there? We just have 91 here.

So is that cam not a good choice with those heads?

jkippin

the intake is killing you being a plain performer dead around 5500 small runners. How much timing do you have? how much tuning have you done Just because you may have some decent parts isn't going to make power alone

Brad_B

thanks so much for the help j. I was not able to put the light on it today, but will be able to tomorrow after work. It appears to be retarded a lot as the distributor is turned quite a bit. I know that does not necessarily mean that it is, but based on the tuners comments I think it is. I will check tomorrow and see.

I have not messed with the tuning yet because I was thinking the build is messed up and I did not want to give the builder any ammunition saying I messed up the timing and that caused detonation and messed the engine up.

Sorry if I came across any way but thankful for the comments. I am frustrated and it may have come out. My wife says it has!!

Thanks for the help. I will get back tomorrow with some timing and deck information.

toobroketoretire

Assuming you have a .025" deck height and pistons with 4 valve reliefs I'm coming up with around a 10.5 to 10.75 compression ratio which would be suitable with 93 octane gasoline. But to avoid pinging you may have to run a 4-6 degree initial advance. The advantage of a 383" is the increased torque it'll deliver at the lower rpm's. If you were hoping for tire smoking torque you'll have to put some lower rear end gears into it.

claysmoker

Just 91 here. Works fine. You have flat top pistons and 64 cc chambers so your compression should be under 11 on a 383. You won't get 450 flywheel HP with that cam anyway, more like under 400 and at 5000 ft. you lose 15% NA, so 60 0r 70 HP plus loss through the drive train you are looking at under 300 hp at the wheels.

REELAV8R

Two things I would change to get that engine in line.

First is if you are .025 below the deck change the head gaskets to a felpro .015 steel shim gasket. With .025 below the deck plus a .039 head gasket you have a squish of .064". which is horrible and detonation prone in a big way. .025 plus .015 and you get .040. Perfect for detonation resistance. Plus you get a sizable compression bump which you need at 5000 feet.

Second is that cam is a poor choice for your altitude. At 5000 feet 220@.050 may be ok, but 283 @.006 is not. That is a slow opening ramp and is going to provide poor low end performance. You need more like 270 @.006 and 220@.050 on at a min of 110 lsa, but I think a 108 would be even better, to get some performance. I couldn't find the intake closing on that cam even on mellings site.
http://www.melling.com/Portals/0/Cat...cs_223-227.pdf

I'm willing to bet it is close to 70*. At higher altitudes you need more compression and earlier intake closing to make power.
I would also take advantage of the very reason roller cams exist, higher lift of the valves with faster ramps. get above .50 on both intake and exhaust. I'm using .549 lift @ 4000 feet.

http://www.melling.com/Portals/0/Cat...cs_223-227.pdf

The heads with a 200cc intake....I'm not so sure that was a good move but it could be delt with with better cam and higher CR.

I get 10.3 CR with a 8.1 DCR with the numbers you provided assuming a 7cc flat top and .025 in the hole, and this calculator. Put in 5000 feet and you get a DCR of 7.1. The calculator says an intake closing of 76.5*

http://www.jeepstrokers.com/calculator/

Brad_B

Thanks very much guys. So what I am hearing is this:
Cam is small for elevation/hp claims. I bought an advertised 450 hp motor. I get the altitude difference, so if it was 400 or close here I would understand.
If not a zero deck height, then my quench is very high and the motor would be prone to detonation. A new head gasket could help this (and compression ratio).
Intake is too small.
Heads have a little too much intake, but may be able to salvage with a better CR and cam.

So with this in mind, would you start by putting in another head gasket and intake. This is relatively easy and cheap. See what improvements are made.
Next, would potentially be heads and cam.

With the motors propensity to detonate, changing the head gasket might be the key to getting it to run better. It seems this might be the first step. Yes, all the power potential would not be there, but it would run well.

I spoke with the builder today and he was a) concerned that the installer let it out of the shop running the way it does and b) has done this build before with zero issues with detonation. He is looking into the machining and will get back to the installer and I tomorrow. He seems keen to make it right. We will see......

Thanks again all.

Cheers
Brad

REELAV8R

To say a cam is small usually means of too short of duration. I would not say that cam is too small for the advertised HP.
The cam dictates the when and how the power is made.
The heads dictate how much HP can be achieved.

The issue with that cam as I see it is the @.050 duration is acceptable, the advertised or .006 duration is high.
At higher altitudes you need to accelerate the air and close the intake valve earlier to retain enough of the stroke to compress for good torque. The air is thinner. This means you need more volume to do the same job as less volume would achieve at lower altitudes.
I think your Performer intake is probably ok. With the thinner air it will compress and accelerate better with that intake than one with more CFM capability but slower air movement due to the loss of air density and larger runners.
Opening the valve higher allows for a larger gulp of air per valve event. Particularly the intake. More volume = higher cylinder pressure= more torque.
That engine proabably is a 450 HP engine at sea level. At your altitude you can figure approximately 3% loss per 1000 feet. That puts you at 382.5 HP.

Keep in mind this is DENSITY altitude. Meaning a sample of air at 44*F for 5000ft. You probably don't drive your car when it's 44*. So if you figure in temperature then the air is less dense than your altitude above sea level.
Your density altitude on a 70* day is around 6700 feet just accounting for temperature. This is where the engine thinks it at and this is how it will perform. So on a 70* day your 450 HP engine is only a 360HP engine.
http://www.asiresource.com/DensityAltitudeChart.PDF

It really depends on what you want to spend and achieve as to what you do. If the heads are off then it's a good time to change the cam as well. Give the guys at Straub tech a call and see what they recommend for a cam.
http://www.straubtechnologies.com/contact-us/
Be prepared to have all you engine specifics as well as power train specs so that a good decision can be made.

One thing that helped my 77 a lot was a high stall torque converter. I have a Th-350 with 3.08 rear gears still. So starting off the line would be doggy with the stock 1800ish stall converter. A higher stall allows the engine to get farther into the power band before the converter is stalled or "locked" essentially.
I currently use a 2600 stall converter, but could use more, or a lower rear gear, 3.36 or 3.55 would be better. The other side of the coin is those gears increase my cruising RPM's. So a balance has to be found if the transmission remains unchanged.

See what the builder has to offer and go from there is what I would do. But do your homework so you can recognize good vs bad advice.

If you have the time and inclination this is an excellent book with good info.

I just looked up the elevation at Arvada CO, you're higher than 5000 ft. 5332 oofta!

Full disclosure. I am not an engine builder. Just a hobbyist like most here.

Brad_B

Thanks for the reply REELAV8R. I really appreciate it. I wasn't able to get to the shop over the last two days (dang work gets in the way of all the fun!!), but I am planning on getting down there today. I will know then what the builder is willing to do and all of the specs of the engine.

Your discussion on altitude makes sense. In my head, the reason why was always air density, but I could not put it into why hp decreased like you did. My house is actually about 6,000 ft and my office is at 7,200 ft. Engines start to lose their breath up here!

Thanks again. I will update when I know more.

Cheers
Brad

REELAV8R

There a lot of challenges when running an engine at that altitude. Your jetting is going to be very lean to get the mixture right. You timing will need lots of advance at idle to get it to idle right. You'll need more timing at WOT and cruise as well.
Fuel burns much slower the lower the pressure gets. Your cylinder pressures are going to be very low. This requires lighting the fuel earlier, hence the advanced timing.
I would do a compression check just out of curiosity. I bet it's much lower than one would expect where you are. Not saying you need to, it just would be my curious mind wanting to know.

BTW you did mean 5.7 inch connecting rods in your specs didn't you?

If you drive your car to work on a 70* day, your car thinks it's at 9,500 feet. That means your engine is down to about 322 HP, if it's tuned properly to that altitude, otherwise you are probably sub 300HP. Take out 30% for power train losses and you're down to 210 HP or less to the wheels.
So yes, it's going to be a dog. Although, better than stock.

Add to that a cam that doesn't come on until 2000 rpm (at you altitude probably 3000rpm) and you got a recipe for poor low end performance.

Brad_B

So I got the installer and the builder on the phone today and we came up with a plan. The builder thinks it's the carb and the installer thinks it's internal/compression issue. The builder is sending a carb down that they know works well. If that works, I will get a new carb. If not, they will take the motor back and replace. I betting the carb doesn't fix the problem, but I actually hope it does.

I will say that I am happy that both parties are trying to remedy the problem.

If they have to replace the motor, I may have some room to change a couple of things, cam in particular, if I want to. Let's see how this plays out.

Brad

REELAV8R

If you're running a Q-jet now do not exchange it for your new carb. The q-jet is an excellent carb, you want to keep it either way you end up going.
Glad to hear that they are willing to work with you. Hope they do a good job for you.
What you really need is someone that knows how to tune for altitude. It may end up being you. Few understand how or why altitude makes a difference.

Brad_B

So the saga continues..... Took to the installer and they received the carb from the builder. Q-jet none the less! They will be putting it on tomorrow and see what happens.

I had a conversation with the installer and ran it around the block with him. He says he thinks it runs ok and it is that the torque is coming on later (so higher hp little less early torque type motor) so with some gears it would be great. I have a couple of questions for you all about that. Does that make sense based on the heads and cam above? Seems to me it does not. Gears will make a big difference I know, but I wasn't planning them yet.
He is also claiming that needing to retard the timing to prevent detonation could also be because of the tall gears (3.08). I know these cars are a system of parts that need to work together, but I have not heard detonation tied to gears. Could it be?
I personally think that they are grasping at straws, but maybe not.
To give an idea of performance, my LR4 suv (mfg says 0-60 in 7.5 sec) smoked the Vette and we could not get it to break the back end loose even when power breaking. Seems off to me....
Brad

REELAV8R

Yes, based on the cam it makes sense. That cam is for sea level performance not 6000+ feet.
Also the heads have 200 cc runners on the intake. This slows the velocity of the intake charge, thereby not filling the cylinder very well until the velocity increases as RPMs increase. Problem is by the time the velocity and RPMs get high enough you are probably running into not filling the cylinder completely due to the lower duration of the cam @ .050.

He is telling the truth. Timing can absolutely be tied to the gearing. Then the necessary retarding of the timing further reduces the engines performance.
Seems like this engine was built for a car with 3.55 or 3.73 gears. Yours has a 3.08. In addition it's probably a 3.08 with a TH350 or TH400 transmission.
This is it's like trying to start out on a 10 speed bike in 5th gear. It will take lots of low end torque to do get moving quickly.
That engine is not going to make lots of low end torque.

The builder provided you with a "one size fits all" engine.

Unfortunately it doesn't work that way.
You, being the novice, did not know that.
He, being the builder, should know that.
Not all builders, or maybe "assemblers" know the difference and the effects of gearing and altitude on an engine performance and how that should be applied to the specific car and it's use.

Is the torque converter still stock?

Changing the gearing to suit the engine is less than ideal and more expense, but it is an option. It will also raise your cruise RPMs, which may or may not bother you.
At your altitude you would probably need something like a 4.11 rear end to get decent performance from that engine.

Check out this page to see how rear end ratio will effect your RPM at various speeds. Assuming 27" tire diameter and you final drive in the transmission is always 1:1.

http://wallaceracing.com/gear-speed.php