Help with 383 Build

[Scott Danforth]

Re: Help with 383 Build

your machine shop will have really good advise on the gaskets.

for oil pump, I use the Melling high volume pump, pickup, and intermediate shaft. same pump that most of the engine builders around here use.

 

[Tail_Gunner]

Re: Help with 383 Build

Update... The bottom end is almost finished. I need some advice on an Oil Pump and head Gaskets. The machine shop said that all cylinders may not work out to exactly zero deck height but would be very close. I'm also going to have them install the heads and measure the pushrod length before I order them from Summit. Those roller lifters are very expensive. This may turn into a winter project if they don't speed it up. Thanks

Ohh here i go again..Do not let them mill.... deck..... or any mod to those head's use factory gasket's and have fun. You do not want to change your compression ratio at all.

 

[pennyduke]

Re: Help with 383 Build

Ohh here i go again..Do not let them mill.... deck..... or any mod to those head's use factory gasket's and have fun. You do not want to change your compression ratio at all.

Bondo and everything I read says to zero deck the block with Vortec heads. Why are you telling me not to do that now? Just asking.

 

[joewithaboat]

Re: Help with 383 Build

Bondo and everything I read says to zero deck the block with Vortec heads. Why are you telling me not to do that now? Just asking.

Zero decking is always a good idea when doing a performance build. Gunner is bench racing and worried about you have to much compression ratio.

Your piston manufacturer will have info to figure the theoretical ratio from the parts you are using. The only way to really know is to measure everything.

If you plan to own the engine for a long time i would invest in the stainless core Felpro "perma torque" as they require no re-torquing. Last time i bought a set the were right at 100.00. Use good bolts and thread sealer. I like PST as it doesn't throw off the torque readings.

 

[greg82255]

Re: Help with 383 Build

For what its worth, I had the block zero decked and the heads shaved and used Fel-pro 1003 head gaskets (I think it's .041") with ARP bolts, along with ARP thread sealer and bolt lubricant. No need to re torque them.

 

[pennyduke]

Re: Help with 383 Build

Thanks guys, I will continue with the Zero decking. I will also check out both head gaskets.

 

[Tail_Gunner]

Re: Help with 383 Build

Zero decking is always a good idea when doing a performance build. Gunner is bench racing and worried about you have to much compression ratio.

Your piston manufacturer will have info to figure the theoretical ratio from the parts you are using. The only way to really know is to measure everything.

If you plan to own the engine for a long time i would invest in the stainless core Felpro "perma torque" as they require no re-torquing. Last time i bought a set the were right at 100.00. Use good bolts and thread sealer. I like PST as it doesn't throw off the torque readings.

Yes that is right bench racing and CR. He is using flat top's with relief's in a high stress engine...think long term duty cycle not short burst's..high piston temp cold block enriched AFR's.. boats....mild compression... high lift cam. Benching at it's finest.......Opps did i mention hours of having fun at high rpm....

 

[pennyduke]

Re: Help with 383 Build

Yes that is right bench racing and CR. He is using flat top's with relief's in a high stress engine...think long term duty cycle not short burst's..high piston temp cold block enriched AFR's.. boats....mild compression... high lift cam. Benching at it's finest.......Opps did i mention hours of having fun at high rpm....

Tail_Guner, I really don't know what you are saying. Can you explain this to make it more clear. I pretty much built the same engine as Greg and his seems to be doing great.

 

[joewithaboat]

Re: Help with 383 Build

Penny
Your going to be fine. A 375 hp, 9.5 or 10 to 1, balanced, roller cammed, vortec headed small block will run 5000 rpm for ever as long as it has the right amount of good fuel, good oil and is properly tuned.

Your oil pump needs... std., h/v, h/p or h/v h/p will depend mostly on your bearing clearances. Id use a bolt on pick up for safe measure and a good steel collar drive shaft.

With a big cruiser that runs hard for a long time id be putting an oil temp gauge on it for safe measure, so you will know if you need more volume or a cooler. I'm not sure what your stock capacity is but if it is only 5 qts. Id be putting a bigger pan on for sure.

 

[Tail_Gunner]

Re: Help with 383 Build

I'd say 325hp at the prop, is about right. The Merc black scorpion runs 9:1 compression, vortec heads, with a larger lift cam than the 270, and MPI, and that is only 350hp at prop.

Cam: The duration at .050" tappet lift (intake/exhaust) is 222/230; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 509/528. Valve lash is zero/zero and lobe centerline is 112 degrees.

Guys, this is boat is probably 6K lb or more loaded. Why push the powerband above 5K?

That's what im talking about Penny running a large cruiser bigger cam...Low compression rules the day..Notice John talking about the merc scorpion..9.1..Keep the comp low..your combo will have a lot of tourqe at 3500. shaving milling is all good but making the right gasket selection after the fact is critical once its been done. Greg's combo had some push rod variance..probalby due to milling shaving decking who know's. You should be fine as Jowie says oil temp gauge would be a good ideal It's detontation or be ing safe from detonation.

 

[joewithaboat]

Re: Help with 383 Build

Penny

What pistons and head did you end up with? Can we get part and casting numbers?

Gunner

That dead air space between a flat top piston and the bottom of the head surface is where you run into trouble. Most engine builders shoot for .040. with steel rods and that is good to 6,500rpm. Getting this space to a minimum promotes good air movement, proper cylinder cooling, good flame travel.

If two flat to piston engines were built and the only difference was one was zero decked and had .040 clearance from gaskets and was 10 to 1 c/r. (10 to 1 is generally the max with iron heads and pump gas.)

The other had the same piston .015 in the hole and a little less c/r, same heads and gaskets.

The dead air space in the lower c/r engine will likely cause it to be MORE detonation prone.

If this cruiser needs less c/r, which it might, I dont know for sure. An open chamber head or a dished piston might be needed. Leaving dead air in the quench area to lower c/r now wont help you.

 

[pennyduke]

Re: Help with 383 Build

Penny

What pistons and head did you end up with? Can we get part and casting numbers?

Gunner

That dead air space between a flat top piston and the bottom of the head surface is where you run into trouble. Most engine builders shoot for .040. with steel rods and that is good to 6,500rpm. Getting this space to a minimum promotes good air movement, proper cylinder cooling, good flame travel.

If two flat to piston engines were built and the only difference was one was zero decked and had .040 clearance from gaskets and was 10 to 1 c/r. (10 to 1 is generally the max with iron heads and pump gas.)

The other had the same piston .015 in the hole and a little less c/r, same heads and gaskets.

The dead air space in the lower c/r engine will likely cause it to be MORE detonation prone.

If this cruiser needs less c/r, which it might, I dont know for sure. An open chamber head or a dished piston might be needed. Leaving dead air in the quench area to lower c/r now wont help you.

Below is the Scat bottom kit I went with. I used stock 1996 vortec heads with a new valve job, screw in studs and new springs, retainers and keepers. The Block is a 1988 2 bolt main 350 bored .030 over.

http://www.summitracing.com/parts/SCA-1-91100BIE/

 

[joewithaboat]

Re: Help with 383 Build

Below is the Scat bottom kit I went with. I used stock 1996 vortec heads with a new valve job, screw in studs and new springs, retainers and keepers. The Block is a 1988 2 bolt main 350 bored .030 over.

http://www.summitracing.com/parts/SCA-1-91100BIE/

Depending on whose pistons those actually are, Scat uses several makers ( prob KB), ...zero deck, .040 gasket, 64cc chamber is putting you 9.7 to 9.8 c/r. I think Vortec heads usually check in pretty close to 64cc if untouched. If you kept stock valves and had the seats ground the chamber may check a little bigger, with the valves sunk a bit.

Most of the major piston companies, are going to assume zero deck in there advertized c/r numbers. I think most use the .040 gasket thickness as well.

You will end up in the High 9's looks like.... Id do the zero deck thing for sure!

 

[pennyduke]

Re: Help with 383 Build

Yes they are KB pistons. I get like 9.7:1. I will use high octane gas just to be safe.

 

[Tail_Gunner]

Re: Help with 383 Build

You may want to increase your ring gap .002-.003 this will prevent ring butt during high rpm.John nightl jump in here he will tell you merc does the same. Again you have cold walls and hot pistons

 

[John_S]

Re: Help with 383 Build

Yes they are KB pistons. I get like 9.7:1. I will use high octane gas just to be safe.

If you had a boat like Greg's or an even faster/lighter hull, then that compression might be OK. Stay with a low 9's for that heavy cruiser.

http://www.kb-silvolite.com/article.php?action=read&A_id=36


Yours is more like the motor home, dragging anchors...

 

[pennyduke]

Re: Help with 383 Build

If you had a boat like Greg's or an even faster/lighter hull, then that compression might be OK. Stay with a low 9's for that heavy cruiser.

http://www.kb-silvolite.com/article.php?action=read&A_id=36


Yours is more like the motor home, dragging anchors...

I think it's too late now. I'm stuck at 9.7:1.

 

[Scott Danforth]

Re: Help with 383 Build

my stock AQ271C had 9.4:1 CR with 76cc open chamber heads and flat tops. ran well with 87 octane. with the change to vortec heads while retaining the stock flat tops, I am closer to 10.3 and running 91 octane

9.7 and vortec heads you should be able to still run 87 octane. at least 89.

 

[Tail_Gunner]

Re: Help with 383 Build

I think it's too late now. I'm stuck at 9.7:1.

It's fine i should have elaborated more on the subject its a preventive measure Penny..risk reward kind of thing and since you were building it would be a long term good ideal ...saftey sam kind of thing. While i dont like to recomend oil company's Chevron Techron is a very good brand. My little 4.3 is running over 10.1 iam not getting any knock count's even using regular...Use preium however

 

[joewithaboat]

Re: Help with 383 Build

You may want to increase your ring gap .002-.003 this will prevent ring butt during high rpm.John nightl jump in here he will tell you merc does the same. Again you have cold walls and hot pistons

Unless you are using "file fit" rings the "as is" gap on run of the mill rings are usually double what the minimum would be.