How much HP do I have?

[ERA427]

So… surely someone will have good guess. I just got ERA #434. I’m trying to determine (through its specs), how much HP and torque it has.

I've found all the casting numbers.

It has: 1966 428 FE block
- 1968 Cobra Jet heads
- 1966 aluminum police interceptor intake manifold
- New Holly 750 4bbl
- Stainless side pipes from ERA
- Mallory ignition
- Tremec TKO

I spoke to the guy who rebuilt the engine in 1995 when the car was built. He told me that it was a stock rebuild. In other words, it’s not a custom cam, bored, etc.

My calculations are as follows. With CJ heads, I think I should be getting all the power of a stock Cobra Jet 428, which most people seem to agree is 410hp by the old measurement standards (yes I know it was rated at 335hp by Ford). So 410 seems like the starting place.

Then it has the PI intake, which according to the old ratings, added 15hp over a stock 428FE for 1966 (a PI 428 was rated at 360hp, compared to 345 of a stock 428). So I’m adding 15hp for that, and that would bring me to 425hp. I’d assume that a new Holly 750 must get me something more than the original 735cfm 4bbl that came on a 428 cobra jet. Not sure my ignition buys me anything. Anyway, I’m tempted to go with about 440hp and 450torque.

Thoughts?

[saltshaker]

Originally Posted by ERA427

So… surely someone will have good guess. I just got ERA #434. I’m trying to determine (through its specs), how much HP and torque it has.

I've found all the casting numbers.

It has: 1966 428 FE block
- 1968 Cobra Jet heads
- 1966 aluminum police interceptor intake manifold
- New Holly 750 4bbl
- Stainless side pipes from ERA
- Mallory ignition
- Tremec TKO







I spoke to the guy who rebuilt the engine in 1995 when the car was built. He told me that it was a stock rebuild. In other words, it’s not a custom cam, bored, etc.









Q

My calculations are as follows. With CJ heads, I think I should be getting all the power of a stock Cobra Jet 428, which most people seem to agree is 410hp by the old measurement standards
(yes I know it was rated at 335hp by Ford). So 410 seems like the starting place.




Then it has the PI intake, which according to the old ratings, added 15hp over a stock 428FE for 1966 (a PI 428 was rated at 360hp, compared to 345 of a stock 428). So I’m adding 15hp for that, and that would bring me to 425hp. I’d assume that a new Holly 750 must get me something more than the original 735cfm 4bbl that came on a 428 cobra jet. Not sure my ignition buys me anything. Anyway, I’m tempted to go with about 440hp and 450torque.

Thoughts?

With a stock cam you really have a CJ motor...the 735 cfm carb is a great carb and switching to a 750 isn't going to add anything. The PI intake is the same as the CJ ...just aluminum so you save weight. Original Cobras that had PI 428 motors with a 427 cam were rated at 390 hp. Together to 440 hp you need ported heads and a cam like a comp 282s and then you would be close if your CR is at least 10/1
Jon






Jon

[RodKnock]

Since guessing HP is not my area of expertise, how about some pics of 434?

[blykins]

385-400 is my guess. Just don't ever put it on a rear wheel dyno. You'll be very disappointed....

[DanEC]

When I picked up my motor from Keith Craft he had a couple restored CJ 428 motors sitting outside the dyno room. I asked the operator what they made and from memory I believe it was a little over 400 HP, maybe 415. So it sounds like your guess is as good as any if the motor was assembled with some care. I agree that the aluminum PI intake doesn't make you any more HP than the factory cast iron CJ copy - it just weighs considerably less.

[Cobrakeith]

Originally Posted by blykins

385-400 is my guess. Just don't ever put it on a rear wheel dyno. You'll be very disappointed....

Blykins, I'm just curious, how much of a hp/tq reduction will he see if he does put his Cobra on a rear wheel dyno? Will it be on the order of 20% depending on the dyno?

Keith

[Tim Brewer]

You probably have around 300-335 to the wheel. Just as Blykins has said, most people are disapointed when they first put their car on the dyno. Also, all the ratings from the factories were from the crank and not the rear wheels. You'll pick up some good HP by changing out your heads and intake.

[RICK LAKE]

ERA427 Here's a short story, FORGET about HP. TORQUE is what moves the car. I had a 452 motor with great heads and an FI system. 4.25 bore and a 3.98 stroke. On a motor dyno it made 368 hp and 448ft of torque. Idle is smooth. TAKe 22% for drive train drain. The ERA side pipes are the best for a street car for noise control but leave some power on the table with too much back pressure at higher rpms. I odered a set of race pipes and picked up 26hp at 6,000 rpms. Torque did take a hit of 8 ft loss. How much time does a motor run a 6,000 rpms?? The motor rans low 12's in the 1/4 mile. 106-108mph.
It sound like you have a nice street car that is very mannered. Enjoy what you have and DON'T worry about what you do not have at this time. Down the road you may want to have more power, save this motor and build a nasty one. Over time if you do this you may find out that the bigger is better doesn't always work out. Rick L.

[blykins]

Originally Posted by Cobrakeith

Blykins, I'm just curious, how much of a hp/tq reduction will he see if he does put his Cobra on a rear wheel dyno? Will it be on the order of 20% depending on the dyno?

Keith

Probably so, maybe a tad more depending on what sidepipes were used.

Cobras will typically lose 80-100 hp going from an engine dyno to a rear wheel dyno.