Low compression pistons

[shortbox]

I am having my 440 rebuilt and am looking to achieve about aprox 400 hp for street use only. It is a low mile,low comp engine that is in very good condition. It will have a roller cam,m1 intake,770 Holley,new rings and bearings. I have two questions, one is how much hp am I missing by not putting in new pistons and do my truck manifolds flow any better than car ones?

[Cooter]

See engine thread about dynoing a low comp. 440.

[chargerbr549]

The truck manifolds are pretty bad in the flow department, on my pickup 74 D100 I installed some shorty hedman headers and they were a definate improvement over the factory manifolds. You do have to run the mini starter with these headers.



http://www.summitracing.com/parts/hed-78070-lso?seid=srese1&gclid=CNvN4MGc170CFQaTfgodniUA3A

[cudaken]

I am having my 440 rebuilt and am looking to achieve about aprox 400 hp for street use only. It is a low mile,low comp engine that is in very good condition. It will have a roller cam,m1 intake,770 Holley,new rings and bearings. I have two questions, one is how much hp am I missing by not putting in new pistons and do my truck manifolds flow any better than car ones?

Short Box, if the engine is in good shape, why are you sort or rebuilding it?  If you have not tore down the engine yet, run a compression test first and post the numbers. If they are good, just add the wanted parts. How many miles on the 440?

Other question is the cam specks. When I think roller, I think high lift and long duration cams. Duration is where you would need the extra compression pistons.

I have no clue on the truck manifolds, I have never owned a truck.    If you are going to spend the money on the other toys, buy headers as well.

Cuda Ken

[shortbox]

Cud a ken I don't know the exact mileage but it is aprox forty thousand miles. I took it in to get it freshen up, re ringed, bearings etc. it checked out good,no need to bore it out. The thing is I am not sure where to stop, I don't need a 600 hp engine but I guess if I'm spending the money on a cam intake and carb, I may as we'll put pistons in also to make sure I get at least 400 hp. Oh I forgot about the stealth heads and the headers! It just keeps adding up. Haha

[BSB67]

I'm not sure that I understand you correctly, but If you don't want to bore it, I would not change pistons.   

[Cooter]

Old guy proved, heads are where your power is.

[cudaken]

Old guy proved, heads are where your power is.

Short Box, Cooter is right!

Now, with you only wanting 400 HP I would keep the stock head castings, have them matched ported, 3 angel valve job and some bowl work done.  Then a mild flat tappet cam (Why did you want a roller cam anyway)  headers, good intake to match the cam, 750 CFM carb, and a solid ignition system (I have heard great things about the Fire Core distributor's) and you should have the 400 HP goal and them some! 

I hope you took the 440 to a good Mopar Machine Shop! Maw Mopar was terrible about block deck height! Deck height is how tall the cylinders walls are, where the heads bolt on. It is common for them to be .10 too .30 taller than they should be!  I use to think only in terms of compression so if I lost say it went from 10 to 1 to 9.5 to 1 no big deal!  Then Neal our pr Fire Fighter pointed if the block is .20 over blue print height you lost .20 of lift from the cam, you lose duration from the cam and intake and heads do not line up well! 

If the shop has not checked the deck height, make sure they do! Other wise what on paper that should be a 450 HP 440, might only make 360? 

 

Cuda Ken

[BSB67]

I hope you took the 440 to a good Mopar Machine Shop! Maw Mopar was terrible about block deck height! Deck height is how tall the cylinders walls are, where the heads bolt on. It is common for them to be .10 too .30 taller than they should be!  I use to think only in terms of compression so if I lost say it went from 10 to 1 to 9.5 to 1 no big deal!  Then Neal our pr Fire Fighter pointed if the block is .20 over blue print height you lost .20 of lift from the cam, you lose duration from the cam and intake and heads do not line up well! 

If the shop has not checked the deck height, make sure they do! Other wise what on paper that should be a 450 HP 440, might only make 360? 

 

Cuda Ken

Blocks are about 0.020" - 0.025" over "blueprint" spec.  It has no effect on cam or valve lift.

[cudaken]

Blocks are about 0.020" - 0.025" over "blueprint" spec.  It has no effect on cam or valve lift.

How do you figure that BSB67? 

I maybe I did not make my self clear, but I am talking about lift and duration at the valve.

Cuda Ken

[BSB67]

Blocks are about 0.020" - 0.025" over "blueprint" spec.  It has no effect on cam or valve lift.

How do you figure that BSB67? 

I maybe I did not make my self clear, but I am talking about lift and duration at the valve.

Cuda Ken

It won't change it.  I honestly don't know how to respond other that you need to explain where the lift gets lost.

Let's try this: If the cam lobe is in continuous contact with the lifter, the lifter is in continuous contact with the pushrod and the push rod is in continuous contact with the rocker, and the rocker is in continuous contact with the valve,  where does the 1/4" of lift get lost? (maybe you meant 0.010" to 0.030" , not .1" to .3" )  Do all cams in a 383 have 0.70" more lift than in a 440 as the deck is that much lower?

[cudaken]

First of all BSB67, I did have the decimal point in the wrong places.  What can I say.

Let see if I can explain this. I am going to use easy math.

Cam lift 1 inch Block Height is 10 inches Push Rod is 10 inch Rocker Arm 1.5 Ratio.

So the valve lift off the seat should be 1.5 inches.

Now, if the block height was 10.5 you would move the rocker arm only .5 inch which would net a valve lift of 0.75 inch.

Another way to think of it, you can not reach the top shelf standing flat footed. If you stand on your toes, you can. I if the shelf was raised 4 inch, you now can not reach the top shelf.

I followed the same logic as you are now till I was talking on the phone with Neal. (Do you remember Neil? Chryco Psycho) But he made me understand. He all so stated that is the reason Mopar Performances makes adjustable push rods.

With adjustable push rods and rocker arms, you can compensate for the higher deck height. You can also think of it backwards. When we have are heads milled 0.010 we have to add a 0.010 shim under the rocker arm.

Cuda Ken     

[BSB67]

Now, if the block height was 10.5 you would move the rocker arm only .5 inch which would net a valve lift of 0.75 inch.

   

No.  The push rod would fall out. 

The only way you would loose lift is if the push rod is too short, and of course, you would know this as it would rattle like marbles in a tin can.  As long as there is 0.0" preload or more on the hydraulic lifter,  you will have all of your lift and duration. 

[c00nhunterjoe]

Lift is lift. Its the same if its in a B or a RB engine with the same cam. Deck height doesnt affect the end result. You have to change your pushrods if you start milling blocks or heads so that you keep the correct preload on hydraulic lifters and valvetrain geometry.In theory, if you milled too much off the heads and block and didnt change pushrod length to accomodate, you would end up with a valve that is held off its seat. Granted thats a bit far fetched, but thats the basic logic.
The amount of travel the valve will make is the same no matter what your pushrod length or deck height is. The only thing you can do to change lift is change cams or rocker ratios.

[Cooter]

Ole Ken will figure it out sooner or later.

[cudaken]

You have to change your pushrods if you start milling blocks or heads so that you keep the correct preload on hydraulic lifters and valvetrain geometry.In theory, if you milled too much off the heads and block and didnt change pushrod length to accomodate, you would end up with a valve that is held off its seat. 

If you folks would think backwards of the above quote you would see my point! If the block is taller than factory speck but the push rod is factory speck that will effect the pre load correct? If the pre load is off you have slop in the valve train right So that slack has to be taken out first by the travel of the cam lope before it starts to lift the valve off the valve seat!

Cooter  I do have it figured out I believe.

Cuda Ken

   

[BSB67]

You have to change your pushrods if you start milling blocks or heads so that you keep the correct preload on hydraulic lifters and valvetrain geometry.In theory, if you milled too much off the heads and block and didnt change pushrod length to accomodate, you would end up with a valve that is held off its seat.  

If you folks would think backwards of the above quote you would see my point! If the block is taller than factory speck but the push rod is factory speck that will effect the pre load correct? If the pre load is off you have slop in the valve train right So that slack has to be taken out first by the travel of the cam lope before it starts to lift the valve off the valve seat!

Cooter   I do have it figured out I believe.

Cuda Ken

 

If your point is; if you completely mess up on machining/parts selection, yes you could have push rods banging around.

Do you believe that all of the factory blocks, say 0.025" taller than blueprint spec, are "missing" 0.038" lift?

Nobody machines block decks to get their valve lift.

[cudaken]

If your point is; if you completely mess up on machining/parts selection, yes you could have push rods banging around.

Do you believe that all of the factory blocks, say 0.025" taller than blueprint spec, are "missing" 0.038" lift?

Nobody machines block decks to get their valve lift.

No BSB67, I am not saying all! I had a 440 that the right bank was over 0.040 and the left bank was 0.015 over. I all so had one where one deck was 0.10 under blue printed specks?  I all so had a Maltese 440 block that had ridge rim that needed to be bored 0.10 to get the stock bore? 

If the deck height is checked, then you can order the correct push rods or and rocker arms. If not check, who knows what you have. As many here have warned new comers, not all machine shops know Mopar.

Cuda Ken

[BSB67]

Old guy proved, heads are where your power is.

......if the block is .20 over blue print height you lost .20 of lift from the cam, you lose duration from the cam....
  [/color]

I honestly don't know what point you are trying to make at this point. 

Your statement from above is still incorrect.

[c00nhunterjoe]

So then if i mill my block .025, mill my heads .020, and use a .015 head gasket instead of a factory .45; by your theory, my .510 lift cam is now at .600 lift...... your theory is invalid and doesnt make sense.

[cudaken]

I had a few PM's with Ron. It seems I either misinterpreted what Neil told me or I was having a senior moment.    The factor I guess I still do not understand complete is the per load of the lifter.

So BSB67 and Joe, you where right and I was wrong. Guess I was having a Cooter Moment.

Cuda Ken, wrong again.

[Challenger340]

if the block is .20 over blue print height you lost .20 of lift from the cam, you lose duration from the cam and intake and heads do not line up well!

Say what ??
Block deck height has absolutely NO EFFECT whatsoever on Camshaft Duration or Lift.

[c00nhunterjoe]

I had a few PM's with Ron. It seems I either misinterpreted what Neil told me or I was having a senior moment.    The factor I guess I still do not understand complete is the per load of the lifter.

So BSB67 and Joe, you where right and I was wrong. Guess I was having a Cooter Moment.

Cuda Ken, wrong again.

Dont beat yourself up. Its why we are all here.  

Think of hydraulic lifter preload as adjusting the lash on a solid lifter.

[cudaken]

I still think the principal is sound, but I still need a little help with preload.

From what Ron as told me the preload range is 0.020 to 0.040, now is that all lifters made more or less? How do you test preload? 

If you have to little preload what happens? I am guess a lot of valve train racket and if so the valve would be on the seat longer?  I am pretty sure if there is to much preload you start bending push rods. 

Wondering again, Cuda Ken