Camshaft selection

[Fast355]

If going OD please skip the 700R4. Save pennies and get a 4L80E. There's more to a transmission than just the clutches inside. The 400 / 4L80E is just a better design all around.

I agree you can buy hundreds of gallons of gas for the agony and pain a 700r4 will cause. The are TRASH along with the 4L60E. At 6,500 lbs there is not a prayer of keeping it togather long enough to pay for itself. I LOVE my 4L80e though.

[Xenon]

So I was looking at comp cams cam selector thing... leaning towards the Comp 252BH-11... Fairly stock grind, works well with computer, which in my mind means good drivability and economy.

The thing that jumped out at me was the performance gain the Factory TBI manifold gives you over a dual plane 4bbl manifold... My only problem is I have the old style heads on my rig, and the TBI manifold wont bolt up. What would be a good choice of manifold to use with the tbi? the Holley tbi manifold maybe? or???

The other thing that made big gains was exhaust... It raised the tq numbers by up to 60 lb/ft and lowered the peak by 500-1000 rpm... is there a good set of headers & etc that work well with the tbi?

thanks guys


As an aside, I updated my avatar too. Truck has come a loooong way since the old pic. This one was taken just a week ago.

[Fast355]

So I was looking at comp cams cam selector thing... leaning towards the Comp 252BH-11... Fairly stock grind, works well with computer, which in my mind means good drivability and economy.

The thing that jumped out at me was the performance gain the Factory TBI manifold gives you over a dual plane 4bbl manifold... My only problem is I have the old style heads on my rig, and the TBI manifold wont bolt up. What would be a good choice of manifold to use with the tbi? the Holley tbi manifold maybe? or???

The other thing that made big gains was exhaust... It raised the tq numbers by up to 60 lb/ft and lowered the peak by 500-1000 rpm... is there a good set of headers & etc that work well with the tbi?

thanks guys


As an aside, I updated my avatar too. Truck has come a loooong way since the old pic. This one was taken just a week ago.

The factory TBI manifold is JUNK. I ran a Performer RPM with a marine adapter and a 2" bore 350 marine TBI and saw torque gains from off-idle through redline. I was running TBI heads and the stock cam even.

[Xenon]

Ok, thanks.

[EagleMark]

The other thing that made big gains was exhaust... It raised the tq numbers by up to 60 lb/ft and lowered the peak by 500-1000 rpm... is there a good set of headers & etc that work well with the tbi?

Pretty much all headers will help. But do not cheap out here! Good headers are expensive and worth every penny.

Ceramic coating keeps the heat in exhaust instead of it leaking out more under hood because of more tubes. Also keeps heat on O2 sensor. Besides they don't rust and rot! They will also look great years later! Good headers will not have exhaust gaskets blowing out at head constantly. Spark plugs will fit and not burn the wires.

I installed a set of Headmen Elite Ceramic coated headers on a 1990 Blazer I had a few years ago. Perfect fit! No spark plug or gasket issues in the year that I had the truck. Also kept enough heat in it was very noticeable when opening hood with a hot engine in summer and the single wire O2 sensor never got cool and went OL. Well it did but it was closer to 5f and low RPM highway drive...

[Fast355]

Pretty much all headers will help. But do not cheap out here! Good headers are expensive and worth every penny.

Ceramic coating keeps the heat in exhaust instead of it leaking out more under hood because of more tubes. Also keeps heat on O2 sensor. Besides they don't rust and rot! They will also look great years later! Good headers will not have exhaust gaskets blowing out at head constantly. Spark plugs will fit and not burn the wires.

I installed a set of Headmen Elite Ceramic coated headers on a 1990 Blazer I had a few years ago. Perfect fit! No spark plug or gasket issues in the year that I had the truck. Also kept enough heat in it was very noticeable when opening hood with a hot engine in summer and the single wire O2 sensor never got cool and went OL. Well it did but it was closer to 5f and low RPM highway drive...

I just picked up a set of coated thorley headers for my Express and they are a work of art. Definately do not skimp and buy cheap headers. Definately not worth it when you have to replace them a short time down the road.

[delcowizzid]

i only buy quality unless there is none suitiable for the vehicle im working with. i use pacemaker headers where i can. pipe over cone high build quality quarenteed fit and lots of r&d and also they are just accross the pond from NZ in australia.we did just use some hedman headers on an elcamino as they were cheap and all we could get here and they were known to fit LHD but they were awefully short looking and a couple of bends were questionable but all in all ok

[EagleMark]

Headmen also makes cheap headers...

[mecanicman]

I tend to agree with everything that has been said. IF you do decide to go the 700r4(not saying do it, just IF) put it in first before you do the cam swap as it may not be as big of a deal afterwards. A th400 has a 2.48:1 first gear where a 700r4 has a 3.06:1 first gear. The extra gearing with your 3.73 rear end may give you the off the line you are looking for and get you into the cam sooner. Just food for thought......

[405cubes]

Assuming you have a dual plane intake, and heads aren't humongous, 268 ends up off-idle to 5500 ish on the 400.

In the 400 the rv cams will actually get you making enough torque you're going to see mpg numbers go up.
You can cam a 400 a little larger than the stated rpm power curves stated by cam makers.
If you have stock 400 heads a dual pattern is really needed.

Low rpm power is what the 400 is good at. 262-268 gets you strong upper mid and good low torque.
The comp 264/268 works good on stock-ish heads like 882's etc.
The weak link is in the factory 400 heads, If I had to use them, I would go bigger like a 264/268 extreme energy comp.That would band-aid the factory 400 heads and do good on low end.

[loadedi812]

Stage 8 locking header bolts help keep gaskets in good shape, just make sure to get six point heads instead of 12 point heads. That way you can get a wrench on them to tighten em up if tubing clearance becomes an issue. That is if you decide to run headers.

[lionelhutz]

Being a 400 it will require a bit more cam then you'd use in an equivalent 350. I'd think it would do well with around 215* @ 0.050" on the duration and as much lift as you can get in that duration, which will likely end up in the 0.425" to 0.450" range for a flat tappet hydraulic.

As for the cam size -check the existing push rods. You might find longer push rods that would indicate a smaller base circle cam. You could look at the lifters too to make sure there aren't longer lifters in it. Otherwise, you may need to pull the cam and see if it has a part number on it.

As for springs - You could keep the same springs if you know the old cam was more aggressive. Since it seems you don't know what the old cam was it would be a good idea to just use the recommended matching springs.

[Xenon]

As for the cam size -check the existing push rods. You might find longer push rods that would indicate a smaller base circle cam. You could look at the lifters too to make sure there aren't longer lifters in it. Otherwise, you may need to pull the cam and see if it has a part number on it.

As for springs - You could keep the same springs if you know the old cam was more aggressive. Since it seems you don't know what the old cam was it would be a good idea to just use the recommended matching springs.

thanks. That's what I needed to know