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OPEL-LESS!!!
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Discussion Starter · #1 ·
what size chevy valves do you guys use when punching the heads out? 1.94's i'm assuming? and how much does it normally cost for the hardened seats and getting the chevy valves put it? one of my dads friends has a machine shop and he can do all the porting and polishing i want but i read that porting does no good unless you get bigger valves.
 

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Big valves, porting, etc is a question of the correct combination of everything... cam, carb, manifold, compression, etc. If you just throw big valves at it, hog out the ports and don't make everyghing else in the system match, then the engine will run worse than if you just left it alone. Every part in the engine needs to "play" together nicely

Hummm.... I seem to be repeating this theme a lot.
 

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OPEL-LESS!!!
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Discussion Starter · #3 ·
ya i hear ya about repeating the theme alot. i was gonna try to do the internal work i wanted first, so as money permitted i could just do the bolt on items or things that didnt take so much work to do while the motor is still int he car. carb, cam, ignition, ect.
 

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Bob is right, ya know. The internals of the engine realy do need to be selected as a system: Compresson Ratio, Intake/Exhaust valve sizes, Head Porting, Camshaft, Carb, Manifold Porting, Exhaust Maniflod/Header, Exhaust system and etc. They don't HAVE to be, but if you don't make the modifications as a package, you will be very unhappy with the results and much of the money spent on step one will have to be spent again when you get to steps 2 and/or 3 etc. For example all the gaskets will wasted each time you dig into the engine and that's $100 that could be put to better use.

I know, because I've been going through the same thing. What I can/am willing to do now may not be what I want/can afford two years from now. HOWEVER, I DO HAVE A PLAN. And I've been trying to follow it. Pistons, piston ring type, compresson ratio, valve sizes, cam shaft selection, exhaust and etc.

My advice to you is...

Build two engines.

1) Build the first one as a less expensive/reliable engine that you can always have around as a back up. Don't put tooo much money into it. Put what is necessary rings, bearings, lifters gaskets, water pump, and the like to make it a good/reliable engine. Cut corners where you can by reusing the good parts you have, rocker arms, camshaft, rods, pistons if the bore size will let you... If you have more that one set of engine parts, pick and choose... just make sure the pistons are all of the same type... all flat tops or all dish.... I know you won't do this... but others have.

2)At the same time start gathering parts for your 'OTHER" engine. This is engine where you lighten and prep the rods, purchase forged 2.0 liter pistons, mill the head .050", have a custom cam ground to match the FLOW BENCH NUMBERS from the head in which you just installed big valves, and ported only the amount necessary... Sorry just dreaming.....

Its hard, but you must try to make the decision of how much HP you want out of the performance engine. There seems to be several increments/levels of improvments. The first step seems to be in the 115 to 125 HP range. This can be achieved by spending a MODEST amount of money in all of the above areas.

Make a comprehensive search of BOTH lists (this and Yahoo Groups) and build your self a couple of three ring binders of the posts describing what others have done and what their results were.

Presently, I have 5 of such binders... and they grow daily.

Keep asking questions and keep using the search function

Good Luck
Paul
 

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OPEL-LESS!!!
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Discussion Starter · #5 ·
thanks alot paul, i see where your coming from. being 15 and only working in the summer with a boss who gets behind in his pay roll to say the least, its hard to do what i'd like. anything wrong with rebuilding a motor out of 4 motors i have? have 3 good blocks, cranks, sets of rods/pistons, and ect. using a 68 or 72 head with forged crank/rods out of a 70 with flat tops. just got the money today to get my main/rod bearings with some new rings, we have ridge reamers and hones and hopefully the cylinders in one block is within specs. we have a valve grinder to do a valve job on too. if this POS goes like it has been, its time for that chevy 151 HO 4 banger with 145 horse and time for a chevette 5 speed with shifter mods. i wanted to do that anyway to be reliable, and cheap chevy parts are great plus it has to be great performance with nearly 50 HP increase in ponys and a extra gear. by the way i have 2 sets of everything for sale in the way of motors.
actually have 3 but i need one set for myself. can email or go through this thread. have many other parts too (dang it i keep gettin too chatty all the time....somebody smack me)
 

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greensmurf20,

I took the opposite approach and have been very pleased with the results.

I started with an early(higher compression) engine. Added a 2" exhaust with free flowing muffler, 2-1/2" over axle pipe and a '75 manifold. Added 38 DGAS on a hot-street/torquer intake. Compared to stock this did a good job of waking the motor up.

I then built another motor. It's likely in the ~150 hp range even with the same exhaust, carburetor(although it's been modified) and intake. Eventually I'll open the exhaust up a bit 2-1/4", add a custom built header, custom fuel injection and so on. The point being however, that I don't NEED to do those upgrades. The motor is quite amazing as it is...

-Travis
 

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OPEL-LESS!!!
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Discussion Starter · #7 ·
ya i had a 72 motor in my car but i got the origional with it (70) which did have the forged bottom end and flat tops. spun a rod bearing though, even though it did have a broken ring in every cylinder it was better than the motor that was in it when i got it. didnt think it needed bottom end work once i read up on it.
 

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greensmurf20 said:
didnt think it needed bottom end work once i read up on it.
Depends what you're doing. I'm running custom forged pistons and 5.5" crower rods....It should really be bullet proof now:)

-Travis
 

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OPEL-LESS!!!
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Discussion Starter · #9 ·
if it aint bullet proff it outta be!!!lol, just doin a bone stock 1.9 now since i found out how much opel performance is. have a weber carb comin from the PO but i'm not sure what it is.
 

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Jared/Greensmurf20

Travis's approach in not unlike what I was describing. It appears he started with a "stock" high compresson engine and imroved it with "bolt ons", because that is where the best bang for the buck is to be found. Smart move on his part. He then built a second engine when he wanted to change/improve the internals. That is the same approach I've taken, except I didn't have an extra engine to build. After 50,000 miles on the "stock" high compresson rebuild, I decided to go the next step.

You asked a question in one of your above posts and I meant to give you an answer. You asked what size of valves are people using. I will give you an "unqualifed" answer. Actually there are several valve sizes depending upon performance level. So here goes.......

Intakes first, starting at the stock size and going up...

Stock 1.9 liter - 40mm/1.57": stock Opel 2.0 liter 42mm/1.65"; Chevy 1.72", Stock Opel 2.2 & 2.4 Liter 45mm/1.77"; Chevy 1.84"; Chevy 1.88" and Chevy 1.94"

Exhaust..

Stock 1.9Liter - 34mm/1.34"; Opel 2.0 liter 36mm/1.42"; Opel 2.2&2.4 37mm/1.46"; Chevy 1.5"; Chevy 1.62"

Now I didn't say why, when or in what combination to use them. Please ignore any round off errors or mistakes made when I copied information from someone else's post. I'm just using it to prove a point and to get you started thinking.

I only listed these to let you know that there are many combinations and to reinforce Bob's (& Bob's) past comments about using a system approach to engine building.

BTW the comments I remember about the Largest Intake valves, 1.88 and 1.94 in the 1.9 liter/93mm bore; they will be shrouded by the cylinder wall and will flow worse than the 1.84s. Only use these with a 95 mm bore.

Most of the big (modest big anyway) valve discussion lately has been about the Chevy 1.72" Intake and 1.5 Ext. However, there have been discussions that said the exhaust port is efficient enough to handle a SMALLER valve than this and may be more efficient.

There are volumes informantion out there and at such a young age you have lots of time the explore, digest and understand the the finer points.

GL
Paul
 

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OPEL-LESS!!!
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Discussion Starter · #11 ·
yep time and time and more time i have. i'm just not going to start experimenting with something so obsolete and expensive as opels. this motor will be up for grabs at the start of winter. paul finally got it to sink into this thick mind of mine. goin chevy 4 banger style next year!!! and some chevette or vega 5 speed should be a nice addition. got a brand new clutch kit with less than 50 miles on it! tune up with less than 50 on it! redone the brakes with less than 75 on em. might as well make use of the opel stuff i have already gotten drivetrain wise instead of throwing a couple hundred bucks away for nothin. thanks a bunch everybody!!!!
 
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