upgrade path for NA 231?

[nicad]

Hi all. I have a 1987(?) Buick "Regal" 231 in a Porsche 914. It is a street car only- not used for race or drag. Since it is a "classic" car and the area I live in, emissions are not a concern, and everything for that has been stripped off.

The rods are aftermarket billet I believe (info from previous owner). The heads have been gasket-match ported and have been modified to accept stud-mounted roller-rockers with slightly higher ratio than stock rockers. It has a "medium" lopey street cam in it (no idea of the specs?), and a 4brl Weiand single-plane manifold. The entire rotating assembly has been blue-printed and balanced. The exhaust is "Thrush"(?) long tube headers to 2.5" collectors going directly into 24" long turbo mufflers. A bit noisy!!

It had been running a Holley 390cfm 4brl carb and GM HEI distributor, BUT I am currently in the process of replacing the distributor and Holley carb with a 500cfm TBI + EDIS ignition system under Megasquirt-II control

With the carb it ran out of steam around 6000rpm-- due to either the 390cfm or possibly stock/weak valve springs. The valve springs will be addressed at some point.

From what I understand this setup (either Carb or TBI) should be around 200-220hp at the crank??

So... without going turbo or nitrous... What all else can I do to get more oomph?

I know the CR needs to be addressed. What are my best options for increasing the stock 8:1 CR? How far can be done safely on Premium pump gas? What kind of typical power gains can be had by increasing the CR? I should be able to pretty easily add a knock sensor with the Megasquirt system if necessary.

Thanks in advance!

 

[jdpolzin]

I think you answered your own question. Swap into a good set of valve springs. Good flowing headers, heads, etc. Anything to try to get it to breath. Why are you against turbo charging it? It's easy power! Hell, between a few of us, we had a hot air SFI turbo conversion kit for cheap!

Problem is, your not going to change your cubic inches, your not going to change compression, your not going to use nitrous, your not going to turbocharge it, motor is already built, you already have an intake manifold, you have a decent carb........there's just not a whole lot left you can do.

Maybe play with timing?

 

[WarWagon]

It's a street car so since the engine is built already and you don't want to have to re-rebuild it. How much more revving do you want? 6K is great for this engine in NA form on the Street. I'm not sure on how the engine space is on your vehicle since it's been swapped, Perhaps that's why you don't want to use a power adder since it's a street car. However for the limited engine space you may have, The best, most reliable and safest way to get more "oomph" as you said is: Nitrous. A Zex kit to be exact. It's small. It takes up almost no room when installed on the engine. You don't have to have all the rest of the "stuff" that goes with having a Turbo Or Supercharger of any kind. One of the best parts is you can dial in how much more power "oomph" you want too add. Keep it small but if you ever felt like you Perhaps wanted to race your vehicle you can kick it up too an extra 200hp instantly.

 

[charlief1]

If you're willing to tear into the engine you can do a lot to it. Bumping the CR is as easy as getting some of the 83-85 3.0 liter pistons. They're flat tops but have a lower pin height so you end up a little over 9:1 on your compression. You can also buy some custom pistons made to fit in what ever ratio you want. But the pistons will cost around $800 not including shipping.

As far as the carb, switch over to a spread bore and it will react better and have more top end. If you're hitting 6K and running out of steam it could be a number of issues. The cam may be smaller than you think. The springs may not have enough tension to allow it to rev over 6K. The heads may not have been ported so they can't suck enough through them.

If you like everything but the max RPM you're getting, remember that the engine wasn't designed to go much over 6K to begine with so you're going to need to reinvent the wheel, in a mannor of speaking.

 

[mat231v6]

you can do a turbo set up i know you don't want to but why not i had about the same thing you have in your engine before i switched over to a turbo. you can still use the tbi setup and the stuff is cheap to switch. here is a example.

 

[dr_frankenstein]

If you're willing to tear into the engine you can do a lot to it. Bumping the CR is as easy as getting some of the 83-85 3.0 liter pistons. They're flat tops but have a lower pin height so you end up a little over 9:1 on your compression. You can also buy some custom pistons made to fit in what ever ratio you want. But the pistons will cost around $800 not including shipping.

As far as the carb, switch over to a spread bore and it will react better and have more top end. If you're hitting 6K and running out of steam it could be a number of issues. The cam may be smaller than you think. The springs may not have enough tension to allow it to rev over 6K. The heads may not have been ported so they can't suck enough through them.

If you like everything but the max RPM you're getting, remember that the engine wasn't designed to go much over 6K to begine with so you're going to need to reinvent the wheel, in a mannor of speaking.

Charlie can you tell me more about these pistons?

A.j.

 

[charlief1]

The pin height is lower and there's no dish in it. The PCH drops to 1.81 if I remember right and since there's no dish it bumps the compression up.

 

[dr_frankenstein]

The pin height is lower and there's no dish in it. The PCH drops to 1.81 if I remember right and since there's no dish it bumps the compression up.

very nice indeed.... have you tried running them yet?

A.j.

 

[charlief1]

Haven't had the chance yet Aj. I can't find a forged piston for them so I don't want to chance it on the new engine.

 

[dr_frankenstein]

Haven't had the chance yet Aj. I can't find a forged piston for them so I don't want to chance it on the new engine.

I think these will be the ticket for my cousins NA build. anything to get that compression up is a major help.

A.j.

 

[charlief1]

If you want another option, get the early 3.0 rods along with a set of of pistons from the 93-95 series II engine. This drops the PCH to 1.4 and bumps the compression.

 

[VKREGAL]

I remember seeing 10:1 pistons for the 350 buick from TA performance, that could be an option if they're still available.

 

[Freddie's Buick]

...Why are you against turbo charging it?

A Porche 914 with an N/A 3.8 doesnt need turbocharging. Heck as described it may even give an SFI a run for the money!

Jeez how much more 'oomph' do you want, that thing must be wicked fast.:biggrin:

That's a very light frame. Light mods on that baby will go a long way. I'd go electric fuel pump, electric water pump and custom made shorty headers and aluminum heads. I would c.c. the entire combustion chamber along with the highest CR pistons you can get for a 3.8 to get the max compression, (maybe even some decking)?

The only weight issue I see is the engine itself so that's why I'd look into lightning up that engine as much as possible. I'm with the other fellas as to the RPM drop-off. I don't think it's related to the carb it has to be somewhere in the valve train assembly and cam mis-match. The aluminum heads stage I or II may be the ticket.

 

[nicad]

At first I came here looking to turbo it. But I am limited by the strength of the 914 trans-axle (they say it can handle up to 300hp, ??? tq), and I think a tubro would be overkill and have to be seriously tuned back to stay under that... which seems like a lot of work just to have to restrict it down.
So, now I am looking to simply add some power to the NA setup and call it done.
The last major thing I know of that is left to do is the CR. I understand that 8:1 is great when boosting, but horrible for NA. I would like to know more about the 3.0 pistons. Is 9:1 enough or how far can we safely go? When does valve clearance on a 'medium' street cam become an issue?
Do I need to run forged pistons in a NA engine turning 6000 to 6500rpm?

I personally ported out the heads so I know they have been done. Done right tho-- who knows??!

The 914 w/231 V6 transplant does move pretty good, but it just seems like it should have more "oompth!".

Thanks!!

 

[charlief1]

If you're anything like me you'll have ported the heads like I did.:biggrin:

 

[mat231v6]

If you're anything like me you'll have ported the heads like I did

The heads have been gasket-match ported and have been modified to accept stud-mounted roller-rockers with slightly higher ratio than stock rockers. It has a "medium" lopey street cam in it (no idea of the specs?), and a 4brl Weiand single-plane

i think he did. btw nice work on those heads.

 

[nicad]

What would be a good brand/type of valve springs to use?

I hope to get it fired up this weekend running on the new TBI+EDIS setup!

 

[charlief1]

You can use the springs of an LT1 chevy V8 and it will work nicely, or you can do some searching like I did and go beehive. The LT1's are sold by Kirbans so you should be able to get them fairly cheap.

 

[Finallall]

If you're willing to tear into the engine you can do a lot to it. Bumping the CR is as easy as getting some of the 83-85 3.0 liter pistons. They're flat tops but have a lower pin height so you end up a little over 9:1 on your compression.

3.0 will bump your compression up but you have to machine reliefs for the valves in the pistons. Also I read in the Buick Performance Stage book the increase in CR is more like 12:1.

The best way to get the CR up is to get the Speedpro Hyper pistons. They will give you 9.5:1 CR which is optimum for the street on pump gas.

Summit sells them. Here's the link: Speed Pro ZWH522CP - Speed-Pro Hypereutectic Pistons - Overview - SummitRacing.com

I only wish they still had these in 20 over cause that's what my engine is bored out to.

Edit: One more thing I forgot to mention is anytime you mix and match engine parts like pistons and rods (ex; 3.0 pistons/rods) you will have to rebalance the whole rotating assembly. Another thing to consider.