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Old 11-30-2012, 05:06 AM
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Estimated Power

Was wondering if anyone could give an power estimate on the engine I built?
355cid stock deck
Stock vortec heads 062
4vr flattop pistons sealed power H345ACP
rv cam .422in .444ex dur 204in 214ex @.050 with 1.5ratio
1 5/8 long tubes with 2.5" tru dual pipes and glasspacks
Edelbrock performer intake with edelbrock 1406 carb
stock crank and rods
hei ignition set at 32* max with vac can
I'm running this with stock stall thm350 and 2.76 rear gear 85c10
maybe CR estimate? What octane gas should I use?

Was wondering how much I will gain by adding 1.6ratio roller tips. Also is there any way to look for detonation without pulling heads or pistons, with the glasspacks I can't hear anything, I'm worried about too much vac advance.
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Last edited by johnbob; 11-30-2012 at 05:16 AM.
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Old 11-30-2012, 06:31 AM
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Quote:
Originally Posted by johnbob View Post
Was wondering if anyone could give an power estimate on the engine I built?
355cid stock deck
Stock vortec heads 062
4vr flattop pistons sealed power H345ACP
rv cam .422in .444ex dur 204in 214ex @.050 with 1.5ratio
1 5/8 long tubes with 2.5" tru dual pipes and glasspacks
Edelbrock performer intake with edelbrock 1406 carb
stock crank and rods
hei ignition set at 32* max with vac can
I'm running this with stock stall thm350 and 2.76 rear gear 85c10
maybe CR estimate? What octane gas should I use?

Was wondering how much I will gain by adding 1.6ratio roller tips. Also is there any way to look for detonation without pulling heads or pistons, with the glasspacks I can't hear anything, I'm worried about too much vac advance.
Well start here with rv cam and flat tops you may run into some issues.
United Engine & Machine Co. Incorporated

Your stock hei will need to be retuned thereis lots of good info on this site may want to run a search for that. Usally you can buy a kit with the adjustable hei parts. Usally you run high initial timming and as little vacum advance as is needed and same for mech advance.

Glass packs will make your car slower alot slower. Like -40hp with a good breathing engine. Do not use them. Use flowmaster or other performance muffler.

Use full roller 1.6 but you can always add those in later if your staying close to stock best to get it in the car then when money is right add in the full roller rockers in 1.6 ratio. Use some normal 1.5 stamped unless you end up with a much larger cam. This help save a few bucks there is always a few extra things you need when installing.

but it looks good should be close to 300hp if its tuned right. Also make real good tq with the small cam.
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Old 11-30-2012, 06:31 AM
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Estimated Power

johnbob, What head gasket did you use when assembling your motor? I need to know the compressed gasket thickness to figure your compression ratio. Also need to know the bore diameter. If you want to know the octane of gas to use I need to know the intake valve closing point or just the cam's part number. As for the gain by using 1.6 rocker arms to me it is not enough to justify the cost of the rocker arms.
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Old 11-30-2012, 08:23 AM
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cam card

Engine 4.030 bore 2 bolt main 010 block
Heres my cam card. This engine has been in my truck for 3 months or so, I have a summit distributor with SUM-850001R with max adv in by around 3200 with 10* initial 22* mechanical and 20* on the vac can-which worries me a little. Also I used fel-pro gaskets-blue I think they are .040" installed. I already ordered the roller tips but they were under a $100 new.
And as far as the exhaust I was thinking of changing it to a quieter one anyway. hcompton are you saying if I change it I will yield 340hp maybe with the extra lift? I thought the dual pattern cam would work well with the vortec heads am I wrong? I went to the link on compresion ratio and got 10.8 Holy ******* that cant be right can it? I have done compression tested it and was 180psi with plugs in it.
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Old 11-30-2012, 10:06 AM
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I would say 290 -300 hp
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Old 11-30-2012, 12:15 PM
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Quote:
Originally Posted by johnbob View Post
Was wondering if anyone could give an power estimate on the engine I built?
355cid stock deck
Stock vortec heads 062
4vr flattop pistons sealed power H345ACP
rv cam .422in .444ex dur 204in 214ex @.050 with 1.5ratio
1 5/8 long tubes with 2.5" tru dual pipes and glasspacks
Edelbrock performer intake with edelbrock 1406 carb
stock crank and rods
hei ignition set at 32* max with vac can
I'm running this with stock stall thm350 and 2.76 rear gear 85c10
maybe CR estimate? What octane gas should I use?

Was wondering how much I will gain by adding 1.6ratio roller tips. Also is there any way to look for detonation without pulling heads or pistons, with the glasspacks I can't hear anything, I'm worried about too much vac advance.
I'm assuming a head gasket that is .039 inch crushed and a deck clearance of .025 inch which gives a static compression ratio of 9.7 which should be generally acceptable with an iron Vortec L31 head.

This is a pretty decent build except for the cam and gear ratios. The cam is one of those RV cams which in many ways are the rampy designs of the 1950's and 60's. While these wear well especially with today’s low to no ZDDP oil additives and they have a really nice exhaust note, it's hard to make modern power from them because in addition to low lift that doesn't take advantage of excellent flowing ports in modern heads, it holds the valves off their seats for a long time on the ramp. You will note the all important closing point of the intake has a 42 degree difference between seated at 71 degrees After Bottom Dead Center (ABDC) and the .050 inch of lift 29 degrees ABDC. So it's using 42 degrees to close that last .050 inch of lift. A 1.6 rocker will only make this worse by holding the valve open another 7% of lift while it's bleeding off cylinder pressure.

The issue is the difference between the Static and Dynamic compression ratios. What the Dynamic Compression Ratio (DCR) measures is the bleed off of mixture as the rising piston pushes it back into the intake until the intake valve is seated. Granted with the valve only open .050 inch there isn't going to be as much compression loss as if it were open further but still the rising piston on compression is putting a lot of backward force on the mixture which will become a high pressure bleed back into the intake till the valve is fully seated. When I run my DCR model (I'm also assuming you used a 5.7 inch connecting rod) at the fully seated value of 71 degrees ABDC the DCR is only 7.38 to 1. Using the .050 value of 29 degrees if it were seated at this point which it isn't the DCR would be 9.33 to 1. If I average these under the assumption that by .025 inch off the seat can flow damn little reversion so the chamber is building compression I get 8.4 DCR. This is a pretty good number where the 9.33 would be high and the 7.38 is way too low. However most engine designers don't consider the valve closed till the crank degrees come up with the valve .006 inch off the seat. So my averaged DCR may be optimistic.

This says a few things:

1) You shouldn't be experiencing detonation with this set up if my dimension assumptions are correct, you could safely push 2 to 4 more degrees of timing advance.

2) 1.6 rockers would possibly worsen the DCR by holding the valve higher from the seat during the ramp process, although it’s dropping faster so this might wash out the effect of being more open while on the ramp.

3) With your gearing the engine turns too slowly to develop enough mixture velocity to overcome the reverse pumping in normal driving, this is costing you power it's not making and fuel it throws away without using.


I'd recommend a faster cam like Comps XE series or Lunati's Voodoo. A 1.6 rocker works well with these as they don't spend so much ramp time between .050 and .006 inch lift as does the cam you have. So the DCR comes up. But these are harder on wear issues so you've got to be really careful about following the break-in procedure and additives list.

The 2.76 gears with a TH350 are too high; this is a good gas mileage, low emissions ratio that is OK if all you do is drive freeways at 70 mph or better. But for coming out of the hole or cruising town this just isn't the best way to go. A 3.08 with a 700R4 would be a better combination for both in town/drag strip and freeway driving.

I'd say this combination because of the cam and the less than optimium Performer intake this would be about 330 horses on an engine dyno. The intake also needs to be the Performer RPM. Why Edlebrock continues to sell the Performer is beyond me.

Bogie

Last edited by oldbogie; 11-30-2012 at 12:20 PM.
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Old 11-30-2012, 01:01 PM
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Well thanks for all the info oldbogie, so exactly what cam would you recomend I'm unsure what I need for duration and lsa and keep in mind the stock heads will only take .460 to .480 lift before hitting seals or so I've read. I'm not sure what cam specs to look for. Also i will invest in a intake when I swap cam if I can afford to.
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Old 11-30-2012, 04:16 PM
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Originally Posted by johnbob View Post
Well thanks for all the info oldbogie, so exactly what cam would you recomend I'm unsure what I need for duration and lsa and keep in mind the stock heads will only take .460 to .480 lift before hitting seals or so I've read. I'm not sure what cam specs to look for. Also i will invest in a intake when I swap cam if I can afford to.
This depends on where you want to go. Without attacking the valve guides for more lift there isn't much to do. The Comp XE256 would fit it would give you the same peak power as you have but would smooth out the idle and fatten the torque in the lower through mid RPMs.

The Edlebrock RPM intake would want a 750 CFM carb plus a bigger cam like the Comp XE268. With a guide shortening to take more lift the XE268 a set of 1.6 rockers, the Edlebrock Performer RPM and big Holley would take what you have over 400 horses.

Taking what you've got, which I think is pretty nice, adding a multi-strike ignition box will usually clean up the idle and lower rev range by eliminating miss fires. I'd certainly look at a 700R4 replacement for the TH350 with a 3.08final gear. The 700R4 has a deeper low and an overdrive 4th as well as lockup converter. This will give you both a harder launch and provide a nice low cruise RPM. The lock-up converter gives back some gas mileage at cruise if that's a concern.

The cam you have isn't very intense, that being a definiton of lift per degree of rotation. In this age of low to no ZDDP in oil that can be a blessing as the reduced loading between the lifters and lobes greatly extends their life. Todays high intensity flat tappet cams have problems lasting, you can google this and find plenty of unhappy people out there over this subject.

So it really comes to where you want the power to go will set the stage for the next steps if any.

Bogie
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