402 Experts... Tell me what you know

[idahovette]

I would never do this. The bore is not big enough to utilize a 2.190/1.880 combination. The 049 - 781 head has to big of a chamber for a 4.125 bore, you would need a big dome to make this work, then heavy metal to make it balance.
]The best combination IMO is to use the 292 head (402) with a 2.100/1.780 valve combination with mild port work. Way more than 400 steetable HP.

Obviously, you and I don't agree on much, but since you are the big block guru we'll agree to disagree? The combo I have seems to work for me so that's what I will stay with.

 

[BigDaddy72]

I’m not trying to start any fights but 049’s or 781’s with 2.19 valves aren’t to big for a 402-396.

That motor with hyd flat tappet cam and 9:5 cr with a set of oval ports or Merlin cast iron heads will make 465 hp and right around the same in torque.

That is a tried and true street combo done many many times.

 

[BigDaddy72]

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

Here is one I ran across.

Hyd Flat tappet cam 9.5 cr
Open chamber Merlin oval ports
750 carb

Peak tq was at 4600
Peak hp was below 5500

Pump gas street motor.

Makes over 400 ft lbs from 3300 through 5600.

This would be a screamer in a swb daily driver.

A set of prepped 781 or 049 heads would be very comparable to the heads in this article.

Sorry buddy have to disagree with ya on this one.

 

[Mark Jones]

Not trying to change anyones mind here, but if I built a 402 with a cam with 240 degrees @ .050 I guarantee it would be over 500 HP. I build 375 HP 396s for NHRA stock competition, 840 rectangle port heads with factory installed 2.190 intake valves. We never use factory spaced bores on a engine like this, we always move the bore away from the intake valve, why because it makes more power. This was my reasoning for using a 2.100/1.780 valve combination, the 292 402 head usually comes in at about 111 ccs done this way, opening the door for a smaller dome to get the desired compression. Cylinder head flow with porting is an easy 300 CFM @ .500 lift, supporting over 600 HP potential. A 427 with its bigger bore would be a good combination with the bigger valves 1.880/2.190 781/049 head. Just my opinion. One other thing, that 400 in the above article is a disgrace when it comes to making power, but then again so is the 402.

 

[Ricko1966]

An L34 396 makes 360hp on oval ports. A manifold, a cam , and headers it's knocking on that magazine motors doors, and more than what the O.P. was even looking for.

 

[potent rodent]

what r u going to do with this truck , cruise ,drag, what , if u are going to just cruise u dont need no big ass square port heads for the street , those heads dont start working till around 4000rpm, i dont thing u are going to be driving around at 4 grand all day, just build u a mild 396 402 and use the 3904390 heads they are 98 cc closed chamber head , use a flat top piston and u will have all the power u want good luck

 

[jeff406cid]

I 've built small block 400's in the past and absolutely love them! Plenty of low-end torque with mild Cam and compression. Was able to push a 1970 Impala to low 13 documented with Time Slips and possibly high 12 after I did the last tweak but never got to the track.
I'm building a 402 just because I came across it cheap but it is a very low compression engine(71-72) and it's very hard it seems to boost it without spending some dollars on pistons and or heads. Even the head gaskets for a 454 has a larger Fire Ring which drops the compression even that much more. The original ones for the 396 402 are very hard to find but I was able to find a set. But the 402 does have much larger Valves and much larger intake runners than the small block so I'm looking to go low compression small carb, long tube headers a small lunati Voodoo Cam and try to make a torque monster out of it, I'm tired of getting left in the dust going up the hills on the way home! LOL.
If you have a 454 and like, that's the way to go, stick with it. Parts are plentiful and cheaper than the 396/402. If I could have gotten a 454 for the same price I would have.

 

[Mark Jones]

SCE makes the smaller bore head gaskets.

 

[BigDaddy72]

Quite alright Mark, I have a ton of respect for you and your accomplishments as an engine builder. I hope you didn’t take offense to my point of view.

Just a difference of opinion from an off the shelf parts /average guy street engine build.

I own a 68 ss camaro that has a 4spd and a 572 I’m building and I have a very good friend that thinks I’m a fool for not putting an ls engine and a 6spd in it.

I have another friend who thinks I’m crazy for not putting a Cummins in my k3500 instead of the 496 I built for it.

They are not wrong and neither am I (in my opinion lol)

But the point is you can drive from coast to coast taking many different routes. But all lead the same direction.

I may disagree with someone else but it doesn’t mean they are wrong and I am right or the other way around. We all have to stick to what we think will make us or our project succeed.

 

[jeff406cid]

SCE makes the smaller bore head gaskets.

Huh! Well son of a biscuit. I looked everywhere and through every listing and couldn't find them for anything. Everything was for "396"-454 but had the 4.370" bore or was out of production. Great to learn new things, thank you very much Mark!

 

[Mark Jones]

Quite alright Mark, I have a ton of respect for you and your accomplishments as an engine builder. I hope you didn’t take offense to my point of view.

Just a difference of opinion from an off the shelf parts /average guy street engine build.

I own a 68 ss camaro that has a 4spd and a 572 I’m building and I have a very good friend that thinks I’m a fool for not putting an ls engine and a 6spd in it.

I have another friend who thinks I’m crazy for not putting a Cummins in my k3500 instead of the 496 I built for it.

They are not wrong and neither am I (in my opinion lol)

But the point is you can drive from coast to coast taking many different routes. But all lead the same direction.

I may disagree with someone else but it doesn’t mean they are wrong and I am right or the other way around. We all have to stick to what we think will make us or our project succeed.

No offense taken, I don't expect everyone to fall in line with my thinking, theres reasons why I do things a certain way, which might not make sense to everyone.

 

[Mark Jones]

what r u going to do with this truck , cruise ,drag, what , if u are going to just cruise u dont need no big ass square port heads for the street , those heads dont start working till around 4000rpm, i dont thing u are going to be driving around at 4 grand all day, just build u a mild 396 402 and use the 3904390 heads they are 98 cc closed chamber head , use a flat top piston and u will have all the power u want good luck

If a person must use a closed chamber head IMO the 390 casting and the 702 are the best one to start with. Example of a 390 head with a 1.880/2.190 installed with the chambers unshrounded.

You must be registered for see images attach

 

[Grit dog]

Appreciate all the input guys.
I’m not a Chevy engine guru. I know my way around a wrench but am learning a lot from this thread.
For the price of admission, I might just find a reason to use the engine stand that I bought at a garage sale 25 years ago and haven’t had the “need” to use once since I bought it.

Use for the truck? Not drag racing a 3/4ton 4x4 brick on 35s. Not towing more than maybe the boat to the lake in the summer, have a diesel for real towing. Really just a cruising truck, kid drive it to school if he can afford the gas, tires will be too spend by for smoke show burnouts but it does those pretty well already.
Keep the discussion going if ya want. Love the knowledge gained here.

 

[hirschdalechevy]

I will throw in my 2 cents,

This is all 454 not 402 but my engine guy, (that built engine's for the outlaw circuit back in the day) was a big block guru, (30 years ago). Anyway I fixed up a 1979 1/2 ton stepside, 4x4 from the ground up.

New paint and interior
4 inch lift with 35 inch tire's
Swapped in 8 lug axle's with 4.11 gears, with locker
454, 0 deck, flat tops
3904390 heads, unshrounded and ported with hardened valve seats
mild 268h comp cam.
dual plane intake.
3310 holley carb.
turbo 400 trans. with turbo 350 first and second gear ratio
2,000 rpm converter

We went to heads up drag day in redding c.a. and turned a 14.6 in the quarter mile on 35 inch rubber with a small cam and little closed chamber heads. Not bad for a 4x4 truck. It was my daily back then and it towed **** down the highway all the time, (92 pump gas), with tons of bottom end torque.

My 1977 crew cab 4x4 I just sold has 12 inches of lift, 44 inch tires, 4.88 gear's and basically the same 454 short block as the step side with 3964290 closed chamber heads and more port work with a 270 comp hyd. roller cam is a beast as well. Used to haul a 25 foot travel trailer all over the place with my 77 and could do 80mph up 8 percent grade's if I wanted to.

Anyway I think on the cheap you could make a 402 big block with closed chamber heads an animal for a truck with the right combo. Sure a 454 or bigger would be the way to go but I think the 402 could be a fun engine.

You must be registered for see images attach

 

[Grit dog]

^Appreciate y’all’s experience. (Can you use 2 apostrophes in the same word? Lol)

This ain’t happening tomorrow or maybe ever but I’m convinced enough that this would be a good truck motor that I may take it off my buddys hands and save it for, something.

And bad ass looking crew cab there!