[prostreet64]

My son's car with the current combo and 409 cubes makes about 475 hp to the rear wheels. With no other changes other than stroke to get it out to 465-470 cubes, what increase in hp could one expect? And this is assuming we keep the current c.r. at around 9.7 which has been very pump gas friendly. I realize there are other changes that might work better with the extra displacement but that will come later. Just curious how much of a difference cubic inches might make.

[AIR RAM]

I completely mis read the question... disregard my deleted post...

The new stroked version would require several upgrades to take advantage of the additional cubes... Improved heads, fuel delivery, cam and intake manifold... So the two would not even be comparable.

You could easily get 500+ pump gas friendly HP from the stroker versions your looking at.

http://www.wallaceracing.com/calc-hp-bore-stroke.php

SPEED SAFE, NICK

[Scott Roberts]

11.39 at 3800lbs is very respectable on 409ci's!! Just to clear that up... the extra ci's would certainly help getting that pig moving... you would pick up torque for sure with the increase in arm.
However, I think a cam change, converter change, and gear change will need to follow...

[PAUL K]

Not sure .....but it seems his 400 is running strong. Many years ago my brothers Firebird ran mid elevens with a 455, 3000 stall and 3.73 gears. We changed to a 4" stroke crank, milled the heads to keep the compression the same, loosened the stall a few hundred RPM's and the car ran exactly the same....fwiw

[footjoy]

Prostreet64

69 Bird w/1970 400 block(409 cubes), #64 heads, Dude spec'd hyd. roller, 800cfm Q-jet by Jeff E., full original interior, ps, pdb, th350, and 3.73 gears. Pump gas, d.o.t. tire, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118+ so far.

What Stall does your son run.

Thanks Greg

[steve25]

If you do nothing but stroke the motor then the main change besides increased Torque levels will be lower VE numbers and a smaller power band that car will now need to be set up to take advantage of.

This assumes that the smaller CID motor was not over Camed to begin with.

Your 60 ft times should improve nice if you can hook up the added Torque , but in most cases mph will not go up by much, so don't be looking for a big gain to show up there.

You will enjoy a much better idle quality once again assuming the same Cam is run.

If you have any budget left after the new build and are stuck with the same Cam and top end parts, then maybe you can atleast drop on higher ratio rockers and the needed longer push Rods to gain some added top end and not have the HP numbers nose over as fast!

[prostreet64]

I should have provided a few more details. The current cam is a custom hyd. roller, 248/254 with lift at .557/.561 using 1.65 rockers. We are planning on keeping the cam. The heads flow about 250 on the intake side, so obviously there will be much to gain at some point with better flowing heads. Also the RPM intake might give way to a single plane at some point. Current converter is at 3500 stall so again there may be a change needed. Thanks for the input.

[J GLASGO]

Originally Posted by PAUL K

Not sure .....but it seems his 400 is running strong. Many years ago my brothers Firebird ran mid elevens with a 455, 3000 stall and 3.73 gears. We changed to a 4" stroke crank, milled the heads to keep the compression the same, loosened the stall a few hundred RPM's and the car ran exactly the same....fwiw

Have had the same results. It would not be worth the money, considering how well it runs now.

[PAUL K]

Originally Posted by prostreet64

I should have provided a few more details. The current cam is a custom hyd. roller, 248/254 with lift at .557/.561 using 1.65 rockers. We are planning on keeping the cam. The heads flow about 250 on the intake side, so obviously there will be much to gain at some point with better flowing heads. Also the RPM intake might give way to a single plane at some point. Current converter is at 3500 stall so again there may be a change needed. Thanks for the input.

The 250 cfm is the key there. Your car runs well. I'd keep picking away at the combination/tune up. Better places to apply the money and effort.

[chiefbigb]

I would think gaining 50 inches would be a sizable torque gain. It would run faster but would probably have a lower operating range without the top end upgrade. I would probably build a second engine and leave that one in there till it was done. No down time like that.

[slowbird]

Average power below peak hp should go way up, resulting in good gains on the track if car is setup right.
I remember John Langer talking about his engine when he went from 480'ish (can't remember exactly what the ci was) to 525. He said peak hp didn't change much but average power went way up and track performance showed nice gains.

[prostreet64]

Part of my reason for starting this post was to address the situation we are in regarding Curtis' car. When the weather is good it will run under the 11.50 roll bar rule and Gainesville Raceway is an NHRA owned track so there is no bending of the rules. Hard to justify spending $35. or more, plus gas driving to and from the track just to get in one pass and be told you are done for the day. So we are once again considering putting in a roll bar that would allow us to run down to 10 flat. The actual goal will be mid 10s if it can be done within budget. The idea is to start with the stroker kit and see what that buys us and then consider other heads. This is not intended to be a max effort of any sort because this is a street car, but just to make the car quicker and 'justify' the addition of the roll bar. No point in putting the bar in if we are only looking for low 11s; might as well leave things as they are and forget the track. But we don't want to do that so here we are. Looking at some of the other combos on here that run in the mid 10s it seems we need about another 100hp to the real wheels to reach our goal. Our hope is to get there without breaking the bank. LOL

[mgarblik]

Based on your projection of needing an additional 100 HP, stroking the engine from 409 to 465 is a 56 Cu In. increase, all with stroke. Getting 1.8 HP per inch gain with the other parts you have listed isn't realistic IMO. You would need major changes to the heads, induction and camshaft to gain 100 HP from where you are now. I like the idea mentioned above of building another engine with the needed parts to reach or exceed your goals, including the larger displacement. Then you could sell the nice engine you have now intact. If it's within a budget, I would consider going that route.

[prostreet64]

I didn't mean to imply we could reach our goal simply by stroking the motor, which is why I mentioned better flowing heads and possibly induction as the next things to consider depending on how much we still need to reach out goal. To build a separate engine on the side and then do a swap would be ideal but would cost more money. We have a very good 1970 block that has had a lot of work done on it and I would hate to start on a 'new' one.

[AIR RAM]

Have you considered just adding boost? Just 10lbs of boost would net you approximately 175-200HP gain over what you make now... adjust boost down or up to achieve your desired output. 8-10lbs would certainly get you deep into the 10s... It would be pump gas friendly after tuned properly, best part it would all be done without ever needing to open the engine up!

Just a thought... boost is easier than ever to obtain and safely run now days.


SPEED SAFE, NICK

[joes455]

Check out some of taman cam specs he has a proven combo with some what smaller cam.He is hitting 123 mph trap speed with a old faithfull stick.

[tom s]

I think the OP wants his engine compartment to look stock?Correct me if im wrong.Tom

[pastry_chef]

Originally Posted by joes455

Check out some of taman cam specs he has a proven combo with some what smaller cam.He is hitting 123 mph trap speed with a old faithfull stick.

The cam duration has the OP here at 118 MPH at more weight, only 250 CFM factory d-ports and a much smaller engine.

I'd do more displacement and better induction.
https://headsandmanifolds.wordpress....-head-porting/
The new package will want more valve lift to sing - jonescams.com

[J.C.you]

I would change intakes, to a t 11, and add a shot of nitrous. That can be hidden under the air cleaner if you are wanting a stock type look.

[prostreet64]

tom s you are correct. My son, and me too for that matter, wants to get this done without a power adder, and maintain a stock look under the hood. We will loose some of the surprise element if we go aluminum heads but that can be hidden to a certain degree. Thanks for all the input so far.