[MalibuMike]

A 1980 2dr Malibu with TH400 transmission & 8.5"posi rearend with a 3.73 gear

[vinniekq2]

Build a mild oval prt engine and sneak into the high 11s. Too much power will cost you diff and suspension upgrades

[MalibuMike]

2dr 1980 Gbody Malibu with a TH400 transmission & 8.5" posi with a 3.73 gear

[MalibuMike]

Can yu giv me more insight to what yu mean by a "mild oval port engine", about how much horsepower would I be looking to produce out of this such motor yu speak of?

[vinniekq2]

horse power 400 or less,torque over 500 pounds.
My car was 550 lift cam.performer intake,later updated to victor oval port.830 holley,hooker headers,stock forged replacement LS-5 pistons,balanced. heads punched out for 2.10/1.88 valves,roller rockers.careful assembly

[MalibuMike]

So would I still be able to go with a 0.060 bore?

[vinniekq2]

bore the engine w/e the machinist says

[cobalt327]

Originally Posted by MalibuMike

Okay cdminter59 since yu say those oval port heads are sum of the best if I was to go .60 bore what size cam would yu suggest I use to get the best output? I'm just trying to find a few different part combinations to go with for the best price.

Only bore the engine as little as possible. If you can get by w/a 0.030" overbore, do that instead of going out to 0.060". The power it'll make will be basically the same, but at 0.060" over, you may have no room to rebore it later if needed and if you were to sell it, it'll be worth more at 0.030" over than 0.060" over.

You need to start by seeing what pistons are in it now, and go from there. If they're sufficient for compression (and the engine is sound- good bearing and piston to wall clearances, etc.), then basically all you need is a cam and lifters, dual plane high rise intake like the RPM, 750 cfm carb, long tube headers/dual exhaust system and a recurved HEI distributor to have plenty of power for any street driven car.

I wouldn't worry too much about HP numbers- it's hard to NOT make 400 HP-plus! Build it using the correct cam for the compression ratio and as long as you choose and assemble the parts carefully, you could have ~500 HP in a streetable package. But the street manners wouldn't be as good as a torquier combo, IMHO. I depends on how you're going to use it as much as anything. A daily driver usually needs to be milder than a weekend toy.

Even using a cam as mild as the XE268H and those heads along w/using an 18cc domed piston (about 9.6:1 CR) will get you an easy 450-plus HP/550 ft/lb torque. BTW, if you have flat top pistons, the CR will be about 8.1:1 using the 118cc heads and a quench of 0.041".

I take it the rear end has been changed? Because it came w/a low performance 7.5" diff from the factory, and if that same rear end was in it now, it wouldn't last long behind a BBC if you ever got traction.

[cdminter59]

Why are you stuck on the .060 bore? When taking a block in to the machine shop usually you would bore the block to what it takes to clean up the cylinder walls. Sometimes boring to larger bores can cause problems such as overheating. I not saying it will happen on your 454 the walls are pretty thick. There is 7 cubic inch difference between a .030 block and a .060 block. Bore it as you like and use Probe forged piston P2465F-060. Take a look at post #12 the parts I listed are the almost same as Vinnie built his engine. The specs on the Comp cam Xe274H is .552/.555 lift 230/236 duration. You will need a good 3000 rpm stall like Hughes HUP-GM30. 400 hp and 510 lbs torque is considered a mild oval port engine. Have the block zero decked. Work on the heads by installing 2.19 intake valves and 1.88 exhaust valves. With this setup your static compression will be 9.687 and the DCR will be 8.269 excellent for pump gas.

[MalibuMike]

I wanted to go with the .060 bore because to my understanding the bigger the bore the more power & the faster the car or hav I been misled?

[BOBCRMAN@aol.com]

Yes, the horsepower diffrence is small. Just don't do like a customer of mine just did and bored a 454 good std. bore block +.125 on the first build. Wanted "cheap" cubic in. (Cuatomer is ALWAYS right?)

Actually with a .030 bore you have a lot of choices for further builds. +.040 .060 .070 .080 .100 .125 .130 are common sizes for these blocks..

As mentioned, for street use, build for torque and drivability.

[cobalt327]

Originally Posted by MalibuMike

I wanted to go with the .060 bore because to my understanding the bigger the bore the more power & the faster the car or hav I been misled?

In this case, it would be a mistake. Let the condition of the cylinders dictate the amount of overbore.

Looking at it from a power standpoint, the extra size is worth about 1 hp and 1 ft/lb torque per ci. So the difference between 0.030" and 0.060" is about 6.5 hp and the same amount of torque, all else being equal.

[techinspector1]

Originally Posted by vinniekq2

you need to decide what you want from your engine,and match the parts.Make a list quick before tech gets here.
Ill mess with his coming post
Its all about combination,combination,combination,combination

Spit coffee on my keyboard.

[MalibuMike]

Okay I'm getting a lil better understanding how it (bore sizes) work, but I was "TOLD" the largest a 454 could be bored is .060... Neways, how do I build the motor for torque? Keep in mind guys, like I stated in an earlier post "this is my first time dealing with a big block" so be patient with me. As of now my motor has 336781 heads, would I be better off using these or swapping them out for a set of rectangle port heads?

[cobalt327]

Originally Posted by MalibuMike

Okay I'm getting a lil better understanding how it (bore sizes) work, but I was "TOLD" the largest a 454 could be bored is .060... Neways, how do I build the motor for torque? Keep in mind guys, like I stated in an earlier post "this is my first time dealing with a big block" so be patient with me. As of now my motor has 336781 heads, would I be better off using these or swapping them out for a set of rectangle port heads?

Keep the 781 heads. The 781 head is one of the most popular (along w/the 041 head) to use on a torquey 454 BBC.

Rectangle port heads are for high rpm use. The crossover point where the rectangle ports pulls ahead of the oval port heads at a higher rpm and lift than you'll be needing, so the rectangles are not for you.

You might want to consider adding 2.19" x 1.88" valves if you have the budget- but for a torque engine this isn't mandatory. Be sure to pay attention to the valve spring installed height so there's enough spring pressure and clearance. If you do get bigger valves, you should look at using 0.100" longer valves to have plenty of room for setting the installed spring height.

781 heads are right about 122cc chamber size. That means you'll need a domed piston to have any sort of compression. Flat tops will have you at or below 8:1.

More: 781 vs. rectangle port BBC heads.