Looking to get 400 hp from 460 build. Suggestions?

Hello. I am looking to help my dad with some engine work on his 1975 Montego MX 460.

He built the car 10+ years ago and is now looking to get a little more pop out of his 460. The Montego is a show car/Sunday driver. So we are really just looking to 400 hp or a little above. It runs great as it is, but .........well you know..........more power is never a bad thing!

Here are the specs on the engine/trans/rear end.

1977 460 block bored .030

Keith Black Silvolite Flat Top Pistons (9.7:1 advertised compression if I remember correctly)

Stock D3VA2A Heads

Crane Powermax cam (#353902) Lift -  .487 in     .518 ex          Duration -  204 in     216 ex

Holley 4160 750 cfm Carb

Stock exhaust manifolds with 2 1/4 pipes. No catalytic converters. Dual flowmaster mufflers. H style crossover pipe

Edelbrock performer intake manifold

Stock Duraspark ignition

Dual roller timing set. Set on 4 degree advance setting

Ignition timing is as follows: 14 degrees initial 36 degree advance with full advance at 2800 rpm. (Lighter springs installed)

C6 Transmission with shift improvement kit and Saturday Night Special converter.

Limited Slip 9 inch rear with 3:70 gears


We really want to keep stock exhaust manifolds. I realize that headers would be a great improvement, but we want to retain the stock look. That being said, headers are not an option.

Also, I realize that the D3VA2A heads are probably limiting the power quite a bit. But, I think that with some work, we can make them flow well enough to hit our 400 HP street engine goal. I really would like to do some mild porting to them to help out the flow, mainly on the exhaust side.


Can anyone give me some suggestions to help me hit the 400 HP goal for this engine? Head porting techniques? Better cam? Different tuning? Or anything else that would make this engine build better. Any suggestions would be greatly appreciated. Thanks!

nearma12 wrote:Hello. I am looking to help my dad with some engine work on his 1975 Montego MX 460.

He built the car 10+ years ago and is now looking to get a little more pop out of his 460. The Montego is a show car/Sunday driver. So we are really just looking to 400 hp or a little above. It runs great as it is, but .........well you know..........more power is never a bad thing!

Here are the specs on the engine/trans/rear end.

1977 460 block bored .030

Keith Black Silvolite Flat Top Pistons (9.7:1 advertised compression if I remember correctly)

Stock D3VA2A Heads

Crane Powermax cam (#353902) Lift -  .487 in     .518 ex          Duration -  204 in     216 ex

Holley 4160 750 cfm Carb

Stock exhaust manifolds with 2 1/4 pipes. No catalytic converters. Dual flowmaster mufflers. H style crossover pipe

Edelbrock performer intake manifold

Stock Duraspark ignition

Dual roller timing set. Set on 4 degree advance setting

Ignition timing is as follows: 14 degrees initial 36 degree advance with full advance at 2800 rpm. (Lighter springs installed)

C6 Transmission with shift improvement kit and Saturday Night Special converter.

Limited Slip 9 inch rear with 3:70 gears


We really want to keep stock exhaust manifolds. I realize that headers would be a great improvement, but we want to retain the stock look. That being said, headers are not an option.

Also, I realize that the D3VA2A heads are probably limiting the power quite a bit. But, I think that with some work, we can make them flow well enough to hit our 400 HP street engine goal. I really would like to do some mild porting to them to help out the flow, mainly on the exhaust side.


Can anyone give me some suggestions to help me hit the 400 HP goal for this engine? Head porting techniques? Better cam? Different tuning? Or anything else that would make this engine build better. Any suggestions would be greatly appreciated. Thanks!

A good valve job including some "under the valve" bowl porting with some more camshaft and you're there.

Also may want to check into the differences in factory exhaust manifolds(excluding CJ), I believe there was some discussion on here a while back about certain ones having larger exits. I think they were for a truck? Providing they will fit your chassis should help somewhat.
Sheldon G

[/quote]A good valve job including some "under the valve" bowl porting with some more camshaft and you're there.[/quote]

Any suggestions on a proper cam for this build?

STR-LGL-70 wrote:Also may want to check into the differences in factory exhaust manifolds(excluding CJ), I believe there was some discussion on here a while back about certain ones having larger exits. I think they were for a truck? Providing they will fit your chassis should help somewhat.
Sheldon G

I'll check into some different exhaust manifolds. Possibly a better flowing truck set. Thanks

buy a set of headers, 72 torino fit

One thing you can do to gain a little HP is port match the exhaust manifold to the heads. Sometimes castings, especially the cast exhaust manifold can be all over the map.

If you want to take it to the extreme you can do what they use to do back in the day and that is Acid Porting. Some classes in Drag or Round track racing didn't allow porting of the intake, heads, or exhaust manifolds. Acid porting would eat away at the cast iron and leave no visible signs of porting. It's not a big gain, but back in those days a guy would do anything to gain a little advantage. Creative rule bending or cheating, whichever you want to call it.

Doug Rahn wrote:One thing you can do to gain a little HP is port match the exhaust manifold to the heads. Sometimes castings, especially the cast exhaust manifold can be all over the map.

If you want to take it to the extreme you can do what they use to do back in the day and that is Acid Porting. Some classes in Drag or Round track racing didn't allow porting of the intake, heads, or exhaust manifolds. Acid porting would eat away at the cast iron and leave no visible signs of porting. It's not a big gain, but back in those days a guy would do anything to gain a little advantage. Creative rule bending or cheating, whichever you want to call it.

With most "acid ported" stuff, it was ported with a hand grinder, left rough and then given the surface treatment with acid. Worked well for that purpose of disguising the work.

A correct camshaft grind will depend upon a whole lot of the rest of the vehicle combination and how it will get used 80% of the time.

Update: After some though, we have considered getting a set of shorty style headers.

So.....With headers and a bigger cam, can we get the power #'s we are aiming for? (400hp)

If so, can anyone recommend a cam profile? Specs for the car are in the first post. It is a street driven car with power brakes.

Also, is there a thinner head gasket that can be used? I believe the ones that are in the engine are thicker, so the compression ratio is lower than advertised by the manufacturer of the Pistons. Would like to bump up the comp ratio without machining the heads if possible.

If necessary, we can still do some porting to the heads. Not sure if it will be necessary or not? Opinions?

Thanks for all the advice so far!

nearma12 wrote:Update: After some though, we have considered getting a set of shorty style headers.

So.....With headers and a bigger cam, can we get the power #'s we are aiming for? (400hp)

If so, can anyone recommend a cam profile? Specs for the car are in the first post. It is a street driven car with power brakes.

Also, is there a thinner head gasket that can be used? I believe the ones that are in the engine are thicker, so the compression ratio is lower than advertised by the manufacturer of the Pistons. Would like to bump up the comp ratio without machining the heads if possible.

If necessary, we can still do some porting to the heads. Not sure if it will be necessary or not? Opinions?

Thanks for all the advice so far!

The Keith Black pistons I have used ended up @ -.020 deck on a 10.320 block. I guess you could order .020 thick Cometics if you needed to do that, but be careful on your compression. Drop the head .020 and your compression will get out of hand for pump gas and smallish cam.
.020 off the gasket thickness could be as much as .40 change in compression.

I calculated it to be closer to 10:1 with 0 deck and 9.6:1 with .020 deck to piston.

IDT-572 wrote:

nearma12 wrote:Update: After some though, we have considered getting a set of shorty style headers.

So.....With headers and a bigger cam, can we get the power #'s we are aiming for? (400hp)

If so, can anyone recommend a cam profile? Specs for the car are in the first post. It is a street driven car with power brakes.

Also, is there a thinner head gasket that can be used? I believe the ones that are in the engine are thicker, so the compression ratio is lower than advertised by the manufacturer of the Pistons. Would like to bump up the comp ratio without machining the heads if possible.

If necessary, we can still do some porting to the heads. Not sure if it will be necessary or not? Opinions?

Thanks for all the advice so far!

The Keith Black pistons I have used ended up @ -.020 deck on a 10.320 block. I guess you could order .020 thick Cometics if you needed to do that, but be careful on your compression. Drop the head .020 and your compression will get out of hand for pump gas and smallish cam.
.020 off the gasket thickness could be as much as .40 change in compression.

I calculated it to be closer to 10:1 with 0 deck and 9.6:1  with .020 deck to piston.  

Ok, for some reason I was thinking that the true compression ratio of the engine was closer to 9.0 or so. Guess we don't need to bump the ratio up then.

So, it looks like we will be doing some mild port work, cam and headers.

Has anyone used the info from http://www.reincarnation-automotive.com/bbf_technical_index ?

Thanks!

nearma12 wrote:

IDT-572 wrote:

nearma12 wrote:Update: After some though, we have considered getting a set of shorty style headers.

So.....With headers and a bigger cam, can we get the power #'s we are aiming for? (400hp)

If so, can anyone recommend a cam profile? Specs for the car are in the first post. It is a street driven car with power brakes.

Also, is there a thinner head gasket that can be used? I believe the ones that are in the engine are thicker, so the compression ratio is lower than advertised by the manufacturer of the Pistons. Would like to bump up the comp ratio without machining the heads if possible.

If necessary, we can still do some porting to the heads. Not sure if it will be necessary or not? Opinions?

Thanks for all the advice so far!

The Keith Black pistons I have used ended up @ -.020 deck on a 10.320 block. I guess you could order .020 thick Cometics if you needed to do that, but be careful on your compression. Drop the head .020 and your compression will get out of hand for pump gas and smallish cam.
.020 off the gasket thickness could be as much as .40 change in compression.

I calculated it to be closer to 10:1 with 0 deck and 9.6:1  with .020 deck to piston.  

Ok, for some reason I was thinking that the true compression ratio of the engine was closer to 9.0 or so. Guess we don't need to bump the ratio up then.

So, it looks like we will be doing some mild port work, cam and headers.

Has anyone used the info from http://www.reincarnation-automotive.com/bbf_technical_index ?

Thanks!

Yes. I tested his work on a local flow bench, and it flowed BETTER than what he claimed.