[darbikrash]

I’m thinking about adding a set of ported round port Edelbrock heads, headers, single plane intake, and the OF 2.0 roller cam to my factory original 1969 GTO w/base 400. Compression shows 145-150 psi in all cylinders, and it is a low mileage car, so I would like to see if I can get a decent performance upgrade without going into the bottom end.

Assuming that all is factory stock 400 base GTO engine, here are some questions:

- What is the stock chamber volume of these heads? Looks like a “#5” cast just above the GM letters.

- Can the stock pistons accept a roller cam lift, OF 2.0 is ~ 236/246 duration .585/.603 lift. with the larger Edelbrock valves?

- How much higher is the Northwind intake than the stock cast iron Qjet manifold

[RH68]

The head number will be on the center two exhaust ports, not on the end.

[ponyakr]

That cam, intake, & ported round port E-heads are way too much for a stock street 400 shortblock, IMO.

If you want alum heads, go with 72-74cc D-ports.

If you want a roller cam, go with a smaller, low lift cam, with no more than 224° @ .050 lift, on the intake, and just over .500 lift.

KRE & Butler sell such cams. Butler says that a 114° LSA will produce better street manners.

https://butlerperformance.com/i-2935...tegory:1272239

But, for about $1000 less, you can go with a decent HFT cam set-up, rather than a roller cam set-up.

The Summit 2801 or 2802 should be plenty of cam for a mild stock shortblock 400. Unless you plan to spend a lot of time over 5000 rpm, I'd say the 2801 should be all the cam you need.

https://www.summitracing.com/parts/sum-2801

The Lunati 10510312 should fall somewhere between the 2801 & 2802, but costs more than the Summit cams.

http://www.lunatipower.com/Product.aspx?id=1759&gid=278

But, there are always lots of guys here with different opinions on cam choice.

"...What is the stock chamber volume of these heads?..."

I assume that engine would have #62 heads on it. If so, they probably have '75-'78 cc chambers, unless they have been shaved at some point. Some charts list 'em at 72cc. But, some here have said that most chambers measure slightly larger than listed.

http://classicpontiac.org/FAQ.asp?myPage=V8HeadInfo

http://wallaceracing.com/head1.htm

[tom s]

PM sent!Tom

[tom s]

FYI,I have a Holley Street Dominator if you want a stock height single plane intake.Maybe see you Sunday?Tom

[steve25]

First off you should do not want to run the round port Exh heads with there 29% larger then stock 215 cc Intake port on what sounds like what will be more of a street motor then a strip motor , especially if you going to run a single plane Manifold!

Go with the Edelbrock D port heads since they have a smaller port and you will then keep most of your low speed drivablity and get the top end kick also!

This is assuming you have atleast the base line GTO 3.55 rear gears like a non A/C car would have had in 69.

[Half-Inch Stud]

elec fuel pump

good mufflers, maybe the walker turbo mufflers are still the best choice.

tune the Q-Jet on the iron.
tune an HEI

[HWYSTR455]

Yeah, more info is needed to be able to properly advise/recommend. But with the assumption that the bottom end is completely stock, which I kind of doubt, going with the 65cc D port E-heads would probably be the best approach.

If in fact the bottom end is untouched, and the SCR is up there, you can get away with using the 72cc round ports, with careful cam selection. And although the OF is a good cam, it probably wouldn't be an option in this case. (potentially due to lift and SCR)

Cast pistons and stock rods would be a concern if you do jump up in power too.

Is it a numbers matching block and heads? If so, bag it, and build another engine to step up your game. About only thing you would be using from the original, if you were to go through it, would be the block. So not that big of an investment to save your complete original engine.

.

[darbikrash]

Thanks for the replies, very helpful especially the factory cylinder head charts for volume and valve size.

So I see the chamber volume (72 cc) of the factory cast iron head is the same as the round port Edelbrock, and the valve sizes are the same as well. SCR should be the about same then.

Edelbrock D port heads are 204 cc (intake), Round ports are 215 cc (intake) - not much difference. Flow numbers are better for the round port. Given as velocity scales with flow and volume there are probably similar port velocities?

The car is matching numbers, and as far as I know the bottom end is completely stock. It is a factory A/C car with auto, but the rear end has been changed to a later model 8.5 with 3.55 posi. I plan to run a 4 speed overdrive trans.

The original plan was to do a stroker using an aftermarket block, but it's just too much money.

I always mock up these builds in EA Pro to see where I am with cam and heads, and once I got discouraged with the cost to do a big CID stroker, I started seeing what I could do using the stock bore 400.

I was very surprised to see what can be had using the stock Edelbrock round port heads. The yellow line is HP from a bone stock RA III GTO, one of the standard configurations inside EA Pro. The peak shows ~366 HP. The red line is the addition of the round port heads, OF 2.0 roller, and headers. The blue line is torque for the stock RA III- white for the upgrade. Pretty big gains here.




EA says vacuum at idle is 13.5" with the OF 2.0. Still not sure is there is valve/piston clearance. Other than that.....

[ponyakr]

"...OF 2.0 roller..."

With all due respect, the OF cam is a ridiculous choice for a factory stock 400 bottom end, street driven engine. That's just a simple fact. It's not just my opinion. It's for a high poweer street/strip 455 or bigger engine, NOT a 400. "...street/strip cam for 455-474ci engines...Power range is 2500-6000rpm...". That means that it's power range in a 400 wouldn't start til probably above 3000 rpm. Probably MOST street driving is done BELOW 3000 rpm. So, to buy a 3000-up cam for a street driven vehicle just don't make any sense to me.

http://www.sdperformance.com/viewPro...productID=1816

And there's no way a stock 400 needs the extra flow of round port heads. Lots of guys have gotten very discouraged because of oversized cams & mismatched parts.

[HWYSTR455]

I dunno, lots of people run RA IV cams in street engines, the OF isn't but a touch larger.

Could say the same about RA IV heads too, in comparison to E round ports.

.

[ponyakr]

Originally Posted by HWYSTR455

I dunno, lots of people run RA IV cams in street engines, the OF isn't but a touch larger.

236/245 dur @ .050" lift .578"/.582" lift with 1.52 ratio rockers 112 lobe sep

A TOUCH larger ???

More dur & a LOT more lift, plus the much more aggressive roller lobes.

And, Cliff has posted numerous times that lots of guys have complained to him about how disappointed they were with the 041, in their 400 engine.

I'm guessing that the OF would have very little low end power, under 3000rpm, in a 400. Would also probably require longer valves. But, what do I know ?

Butler says this one is similar to the 041 @ .050, but makes a lot more power. It's quite a bit smaller than the OF.

https://butlerperformance.com/i-2936...tegory:1272239

I think Cliff has posted that you can make almost as much power as with a small HR, by using an 041 with Rhoads lifters & 1.65 rockers. But he was using that combo in 455 & larger engines, not 400's.

[shaker455]

Originally Posted by darbikrash

I’m thinking about adding a set of ported round port Edelbrock heads, headers, single plane intake, and the OF 2.0 roller cam to my factory original 1969 GTO w/base 400. Compression shows 145-150 psi in all cylinders, and it is a low mileage car, so I would like to see if I can get a decent performance upgrade without going into the bottom end.

Assuming that all is factory stock 400 base GTO engine, here are some questions:

- What is the stock chamber volume of these heads? Looks like a “#5” cast just above the GM letters.

- Can the stock pistons accept a roller cam lift, OF 2.0 is ~ 236/246 duration .585/.603 lift. with the larger Edelbrock valves?

- How much higher is the Northwind intake than the stock cast iron Qjet manifold

A set of 72 E-heads either round or D-port is fine, both were built for street use and you will be fine.
That's great cam choice too!
Go for it!
I have used those intakes many times and the height will be fine.
While you got heads off check piston to deck height.

[HWYSTR455]

[QUOTE=ponyakr;5948326]236/245 dur @ .050" lift .578"/.582" lift with 1.52 ratio rockers 112 lobe sep

A TOUCH larger ???

More dur & a LOT more lift, plus the much more aggressive roller lobes.

QUOTE]

Yeah. A touch. Lift isn't going to make a cam act 'bigger' per se, and is beneficial.

9794041 308 320 231 240 .470 .470 114

OF @288 294 236 245 .578 .582 112

I don't recall exact advertised number for the OF, or where advertised is measure in comparison, but the 041 lobes look pretty aggressive to me, and 6/5 degree duration isn't squat. I've run much larger cams in 400s in the past, and with round ports, either iron or e-variety, is a good performer. I've done it with D ports even.

If I have this wrong, explain, I'm all ears. I realize those 2 cams act differently in the car than they look on paper, but would think the OF would be a BETTER choice than the 041.

.

[ponyakr]

"...would think the OF would be a BETTER choice than the 041..."


Just curious. Do you really think EITHER of those cams are the best choice for a street driven factory original 400 shortblock ?

[HWYSTR455]

Aside of sweating a little about the rods and hypers, yeah, why not? What's wrong with the shortblock?

.

[ramairthreegto]

I think it will end up like a lot of 80s builds.

A higher revving, higher RPM HP engine that seemed like a great idea.
And is. For a road course or the strip.

But a pain in the ass daily driver with no low end fun/driveability.

[geeteeohguy]

Nobody has mentioned it, so I will. The 145-150 PSI you are getting is pretty low. You might want to perform a cylinder leakdown test on the engine to verify the condition of the piston rings and cylinders. My base YS 400 has 25-30 psi more than that, and that's with 87cc heads. No sense bolting on performance goodies if you have a weak lower end.....