I would like opinions on the engine I've built and the horsepower it is going to have (+-) and if any change in the rear suspension/drivetrain of my C3 is needed (currently standard with a M22 in front and 3.70 at the rear)

I have the following combo already put together :
- 400 sbc with 4.165 bores
- steel crank with 3.250" stroke
- oliver rods 6.250"
- forged JE pistons
- CR is 10 : 1
- heads : Dart aluminum PRO 1 220 with springs 220 pounds on the seat and 550 open
- Crane street roller : 228/236 @ .05" and .507/.525 lift
- revkit installed
- victor jr matched intake manifold
- Holley 650 dp on top
- header/dual exhaust , 2,5" to the back, conventional mufflers

I only ran the engine 2X 15 min to breakin. It does seem to easily rev.

Thanks

 

When you dropped the stroke that much and did not install a camshaft that can rev into the 7000-8000 RPM range you sacrificed a lot of hp for drivability. If the engine hits 6500 strong I would be looking to get 500+ or - 20 hp at the crank. HP is all about RPM and you have the heads for it; and the bottom end for it, just not the camshaft to really get it up there. Let me know how it does, I have a Rodek 350+ aluminum block in similar bore I have been thing about installing the same stroke in. As for durability you should be ok unless you dead hook it!

 

As far as torque is concerned, i don't really know, but the engine pulls some 15 inch of vacuum at idle (which is more than reasonable with the cam) and knowing that this tells something about the filling of the cylinder, i would say that it will produce good low end torque also.

As for the higher RPM. Crane states that it should run to 6500 with a valve float at 6800. The float however is dictated by the lesser spring they use, so I shouldn't get valve float for around 8000. I'm personally counting on a 7500 rpm limit with this combo. The heads, the longer rod and the intake should be able to get me there. The carb may be a problem, but I didn't want to go with a 750 since I know these give serious streetability problems in the lower rpm range

 

I'll be very surprised if you can get 7500 with hyd lifters, even with a rev kit. 6500 is more likely. A spring good for 8000 will probably collapse your lifters on the upper end.

I also think you are going to run out of carb before you hit your rpm limit. There are a lot of people running 750 Holleys w/o any problems. I think those heads will want to flow a lot more than that carb will support.

 

Everybody can have an opinion and mine is not approving of such a mismatched bunch of items to end up with 354 cubic inches.

right off the bat. Your compression is to low. Your cam is to small. Poor choice of intake manifolds. Dart 220 racing heads are really kind of plain Jane out of the box and are really made to be given to a master porter before use to customize for the intended use.

The whole idea of loosing power by restricting displacement goes against logic. I have two stroker small blocks which both have 7500 rpm red lines. You are just not going to compete against them with a 354 ci unless it is just a gas mileage competition.

 

Well I think you should go out and run it and see what happens. I actually really like that bore stroke combo for endurance engines that need to make a lot of power. I don't feel that the cam you have will get you where you want to be but you will have to see for yourself. My experience leads me to think that you will want more camshaft. From what I have seen of the Pro 1's they flowed pretty well out of the box so you have the heads for whatever you want to do. I just think that right now you have a very streetable engine that is oriented towards the low/mid range. This is fine except it's not where big hp numbers are made and frankly, we are running a big hp, high RPM engine in our 79 are are not that happy with it. So just take it out and see what you think and let me know how it behaves. Keep us posted and if you want to know the specifics of our engine and what we do and don't like about it feel free to ask.

 

Ok, noted.

Thing is I want it to be streetable and occassionally would like to run it in the higher rpm range, especially on the highway's.

BTW it is a mechanical roller cam and not a hydr roller. The mechanical lifters should allow it to go way over 7000 rpm.

I originally was taking a look at a larger cam (240-248 @ .05 and .561 lift), but that would have meant using a higher CR (between 11 and 12/1) in order not to loose to much low end power/torque. This could have been a problem with detonation on pump gas, plus I would have had to use an even higher dome on the piston which is not good for promoting the flamefront either and thus even more change on detonation.
Plus I can always mount 1.6 rockers on the intake side.
My reasoning was that the combo would allow enough airflow at the higher rpm (because of the heads, lower mean piston speed and intake/exhaust manifold) to side-effect the smaller cam and create a sort of ramming effect.
However carb selection is a pain in the ... certainly with a dp.

I cannot run the car for a while since it is a body-off and I'm currently building her up (paintwork), but needed to be sure I could use the engine with the base drivetrain. Taking that it would max out under 500 hp tells me it will be ok.

So far, with breaking in, I liked the fact that the engine was a lott more free running/spinning than with the other 350 combo's I used.

You may ask yourself why I didn't use I higher cubic inch with the 400 block, but I don't like these engines. The produce a lott of sideloading on the cylinder walls, thus loss in power and engine life. If you add higher rpm to that equation, things will not improve in this field.
I do not live with by axioma 'there is no substitute to cubic inches'

I will keep you posted asap on the engine.

Yves

 

I originally was taking a look at a larger cam (240-248 @ .05 and .561 lift), but that would have meant using a higher CR (between 11 and 12/1) in order not to loose to much low end power/torque. This could have been a problem with detonation on pump gas, plus I would have had to use an even higher dome on the piston which is not good for promoting the flamefront either and thus even more change on detonation.

I understand that flat tops and 354 ci really limits a motor to @ 10.5 with 64 cc heads. My 383 has 11.2 compression and my 434 has 11.8. Do to larger solid roller cams they run fine on our premium fuel.


Plus I can always mount 1.6 rockers on the intake side.
My reasoning was that the combo would allow enough airflow at the higher rpm (because of the heads, lower mean piston speed and intake/exhaust manifold) to side-effect the smaller cam and create a sort of ramming effect.

I have used some big heads and single planes on my 355 ci motors in my 79 Vette (230+ cc Dart ported heads off a circle track car). I have found that the total size of the individual cylinder intake tract has alot to do with how a motor acts for street driving. It takes time to get a big dead still air moving. The ram effect is caused by properly shaped intake tracks that have the ability to over fill the cylinder over a narrow operating range. The VJ without turtles in the base of the plenum and some flow bench time is not a good example of tuned ram port designs. The smaller plenum lower operational rpm range Weiand Team "G"s are more suited to street race higher rpm motors. I'm just saying that big intake and heads designed for 8000 rpm race motors don't magically run nice when you put a milder roller cam with them

However carb selection is a pain in the ... certainly with a dp.

I did not say anything about your 650 carb, I would call it a wise choice. I only run what flows about 820 cfm on my 434. Some people consider it small. I call it responsive. The loss of few hp at higher rpm doesn't bother me

I cannot run the car for a while since it is a body-off and I'm currently building her up (paintwork), but needed to be sure I could use the engine with the base drivetrain. Taking that it would max out under 500 hp tells me it will be ok.

I don't think that you have the cam timing to get to 500. I did a dd2000 run with simular head flow numbers and got a peak hp of 466 @6000 rpm peak Tq was 458@4500

So far, with breaking in, I liked the fact that the engine was a lott more free running/spinning than with the other 350 combo's I used.

Modern metals don't have the lower feet per minute limitations. People hardly ever worry about piston speed. It is the valve train that has the higher failure rates as rpm goes up.

You may ask yourself why I didn't use I higher cubic inch with the 400 block, but I don't like these engines. The produce a lott of sideloading on the cylinder walls, thus loss in power and engine life. If you add higher rpm to that equation, things will not improve in this field.
I do not live with by axioma 'there is no substitute to cubic inches'

I would have opted for 3.50 or 3.60 inch stroker motors even in higher rpm motors. It is a seat of the pant TQ difference with lower rpm drivability. My 4 inch stroker was able to drive 20 miles home with the shifter stuck in 4th gear. You could not do that in a 354

I will keep you posted asap on the engine.

Yves[/QUOTE]

 

Thx gkull, but is it possible to input it with the following cam :

- 244/252 @ .05" and lift .543 intake, .561 exhaust lobe seperation 112.
- CR would obviously stay the same.

I checked to CR on my engine with the 64 cc darts (that came out on 70 cc in reality and the real CR in fact is somewhere around 10.2 as i recall with a + 3CC dome.

Thanks

 

Compression and cam timing is a balancing act. Too much cam and too little compression is bad

DD2000 is the most accurate if you could please give me the .050 valve event numbers from the cam card.

I use a 236/242 112 in my 383. IMO unless you have a lite car and manual tranny I would not recommend going above this number in less than 383 ci. Big flowing heads don't require big cams.

 

Sorry, my bad. When you said rev kit I assumed a Hydra-Rev and I will take back the carb response. I missed the stroke & was assuming a larger engine with the big heads.

 

I mentioned the .050 numbers above for another cam. This one would put my dynamic CR well below 8:1, something that my current cam doesn't do.

 

Valve event numbers are:

Intake valve open - Before top dead Center or BTDC
Intake valve close - After bottom dead center or ABDC
Exhaust valve open - Before bottom dead center or BBDC
Exhaust valve close - After top dead center or ATDC

So a 244/252 LC 112 might look like this on a cam card, but advancing or retarding the event numbers can really change the cam characteristics. So I'm just guessing without the cam card as to how it might really be ground. With the following valve event numbers and your combo you get 504 hp at 6500 rpm and 462 TQ @5000 rpm. It has been my street experience that 350 ci motors really start to have streetabily issues once you exceed mid 400 hp. Like the 350 ZO-6 @ 405 hp. They have to really be modded to get over 450 hp and they become a not so user friendly motor.

IVO = 12 IVC = 52 degrees
EVO = 60 EVC 12 degrees

 

Ok, on the cam in there right now (at .050") :
intake : BTDC 7.0° ABDC 41°
exhaust : 55 ° BBDC 1 ° ATDC
Lobe cla intake 107°
Lobe cla exhaust 117
total 112

for the other cam :
intake btdc 15 ° ATDC 49°
exhaust B BBDC 63° ATDC 9°
LCA intake 107 °
LCA exhaust 117°

Frankly I think 466 hp with 458 tq is not so bad, although I expected it to come up with around 500 hp and the max tq to come in at around 5500 to 6000.

As for the larger cranks on the high inch motors. I have a 3.250" stroke vs the 'normal' 400 size that is 3.750". In torque arm length this means a difference of (3.75/2)-(3.25/2) = 0.25 I would not think that would make such a large difference in tq. However the bigger ci produces much more tq and hp low down. If you want to make an engine like that run at 7000-8000 you would have to have some real good head to keep up with the air demand of the engine.

 

DD2000 and your 3 degree retarded valve event numbers compared to my guess. Comes out 496 hp @6500 463 TQ@5000.

Torque has a direct link to CI. You can use a multiplication factor of @ 1.3 for hotter roller cammed motors. So 3.25 = 354 ci 3.75 = 408 ci difference of 54 ci X 1.3 = 70.2 foot pounds of TQ. It is also across the entire rpm range.

I could feel the difference going from a 355 ci to just a 383. Then 383 - 427. I reinstalled my 383 and drove around. Really fun car with a 5 speed and 4.11 rear gears. Now I went back to a very hot rodded 434 and the car would be dangerous for a novice driver.

 

Gkull,

I could use the second cam, but I need to get my CR up I would think. Can you use a steel shim gasket with aluminum heads ? These are a lott thinner than the fel-pro's i'm using.

Thx for the dynoresults.

 

Very minimal compression is gained by thinner head gaskets. Correct attention to quench height determines the gasket thickness required.

My 383 uses a silicone coated .021 copper head gasket to get its .041 quench. A smarter person would have milled the block and used a .038 compressed gasket.

 

I talked to a Crane reprentative today.

He recommends a cam that is only marginally better somewhere in the 234/244 @ .05 region. He advised against a camshaft that would allow it to run to or over 7000 rpm. He said the vacuum would suffer to severly.

Gkull, did you use the larger cams on engines (like 250-260) at .05 and at what compression ? How was vacuum ?

Thanks

 

I'm a firm believer in big cfm flowing heads with lots of lift with a smaller duration cam.

You can look at duration as time. Time that the valve is open. At 7200 rpm your intake valve is opening 3600 times per minute. Divide by 60 seconds and you are talking 60 times per second. So you have very little "time" to fill the cylinder.

Big duration hurts overall performance worse than big cfm and lift.

My present 248/250 solid roller motor has 11.8 compression. The biggest cam that i ever ran in a small block of 358 ci was something like 268/276 @ .050 106 lc with 15:1 compression and 9000 rpm every time down the track.

 

Two additional questions. A cam in the 240-250 range would require compression to be 11/1. How much CR can be tolerated on premium gas with aluminum heads ?

Also: if i'm going to mill the head for compression I might as well take a good look at valve deshrouding. Because of the bigger bore I could substantially deshroud the valves. Any idea how many cc's I would lose in this way ?

Thanks