I went to the parts store to get new lifters for my 85 2.5 . they sold me roller lifters. I came home , tore into it & NO roller lifters. do I have a weird engine here ? it's coded H 24 4 . August 24 1984. WHEN did they go to Roller cams ? If this is a 1984 motor, DO I NEED TO WORRY ABOUT THE RODS ? I'm rebuilding it, rings/bearings/ head, timing. is this an early 1985, left over 1984 ? I guess it's best to know what it REALLY is so I can get the correct parts. Thanks

Cam part # is 10029787. You can look it up on the GM site but I don't think the Duke came with full roller rockers.

The rocker part # is 10121095. The pic I have is not very good but it looks like a standard rocker

Arn

LIFTERS not Rockers. I've been told by a number of places that all the dukes/ tech 4s had roller LIFER Cams.

They switched to roller lifters in 87, they will not work with that cam profile. I am not sure if you can add a roller cam to the 84 block, maybe someone here can verify if it is possible.

Rockers and lifters are different, I think the roller lifters were in the '87/'88s, along w/the balance shafts and DIS.
Feel free to correct if I'm wrong.

86, 87, 88 Dukes had roller lifters.
Depending on when GM made the switch over on the factory assembly line, some 85 dukes had roller lifters as well.

I think that the head casting number will help identify the motor, it is located just under the valve cover. That number is used engine rebuilders to insure that you are getting the correct replacement motor like at rockauto.com, maybe you can cross reference it there.

[This message has been edited by jetman (edited 08-12-2008).]

The switch to roller lifters was sometime in 1985. My parts car was factory roller lifters, and was 1985. My 1986 coupe also has a roller cam and lifters

OK, How do I decipher the HEAD CODES ? Thanks

quote Originally posted by Arns85GT: Cam part # is 10029787. You can look it up on the GM site but I don't think the Duke came with full roller rockers. The rocker part # is 10121095. The pic I have is not very good but it looks like a standard rocker Arn

Well I'm embarrassed. Can't read

Lifter for the the 84-86 Duke is #5233745 roller. It is a roller lifter.

Arn

I thought the Duke & the tech 4 were both the 2.5 & the same engine .?? whatever these are in the 2 '85s I have, Have NO Roller Lifters. what other differences are there in a tech 4 & a "Duke" ?? & did they change from year to year ? What PARTS ARE interchangeable ?? Thanks

quote Originally posted by Lou6t4gto: I thought the Duke & the tech 4 were both the 2.5 & the same engine

They are the same engine, some people call it a duke, the label on air cleaner says tech 4. While not impossible, I cannot imagine any 85 fiero having an 84 engine for as much trouble as GM had with that engine. Matter of fact, some of the 85 Fiero's actually got the 86 roller lifter engine but that was only a few as they were switching over production from the manufacturing years. If you have 2 of the 1985 duke engines, both with the flat lifters then you can mix and match any parts, you should be good to go.

For more information, go to theogres cave, look under powertrain/ engine/ 4-cylinder. Theogre has more information on how you can tell the differences between the production years on the duke engines.

So, now that we've determined that I have 1984 engines in my 1985 cars, I've heard all sorts of bad things about the 1984 RODS ! WHAT is the casting number for these "Known Bad Rods "? Were they ALL bad ? can I (should I) change them to 1986 rods ??? anyone got a set ? I really don't want to spend all this cash on a rebuild, only to have rod failure. Thanks

quote Originally posted by Lou6t4gto: So, now that we've determined that I have 1984 engines in my 1985 cars, I've heard all sorts of bad things about the 1984 RODS ! WHAT is the casting number for these "Known Bad Rods "? Were they ALL bad ? can I (should I) change them to 1986 rods ??? anyone got a set ? I really don't want to spend all this cash on a rebuild, only to have rod failure. Thanks

How did you determine that?

casting # on the block H 23 4 - Aug 23 1984. no rollers.

It wasn't until the latter part of '85 when GM switched over to the roller cam in the Duke. As long as you don't have a bad lobe or cracking on the face of the flat tappet lifters they can be just cleaned up and re-used .....AS LONG AS....you remembered to keep each lifter marked for position. You will have to use oil for a diesel engine or put in some EP addatives to go with a flat tappet cam these days. The amount of ZDDP has been reduced in recent years and it's the stuff that keeps flat tappet cams from wiping out the lobes.

You could use the roller lifters IF you buy a roller cam and the shorter pushrods. Don't have to worry about oil choice in that case. Fit's in the '84 block with no problemo--- Get a new timing set regardless. The fibre sets last a very long time and are cheap to buy.

Can't tell you about the rods. They've lasted 25 years so they're probably fine to re-use. If you want some insurance...you could do some polishing on the beams and then have them bead blasted to reduce any stress risers that might lead to a crack. If you're not racing it and shoving the RPM's up to 7K then it is unlikely you will have a problem.

Hope that helps

David

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His Fiero: 1984 2M4 Coupe

Her Fiero: 1984 2M4 Convertible

will I be able to use Mobil One ,WITH an additive that has Zinc ?

I've been told by some pretty knowledgable people that the oil designed for diesel still has all the additives of the old oil in it. I can't rhyme them off but there is more than zinc.

Good to have DPWood around. He is one guy who really knows Dukes. The parts listing I have does not address the switchover to roller in 85, it just gives a roller part number.

Lots of pitfalls eh?

Arn

[This message has been edited by Arns85GT (edited 08-14-2008).]

quote Originally posted by Lou6t4gto: casting # on the block H 23 4 - Aug 23 1984. no rollers.

Forgive me staying on this topic but I want to make sure that you understand that you probably have 85 Duke engines. The casting # on the block states when it was manufactured, not what model year it was installed. They used to manufacture engines several months before they put them into cars on the line. Two other differences are the oil capasity and the ECM used was different. Hate to see you buying parts only to discover later that they don't fit.

Perhaps some more forum members can chime in here with more information for you on this subject.

quote Originally posted by Lou6t4gto: So, now that we've determined that I have 1984 engines in my 1985 cars, I've heard all sorts of bad things about the 1984 RODS ! WHAT is the casting number for these "Known Bad Rods "? Were they ALL bad ? can I (should I) change them to 1986 rods ??? anyone got a set ? I really don't want to spend all this cash on a rebuild, only to have rod failure. Thanks

Only if you constantly pull the engine past 4500 RPM, these things were economy car engines and must be treated as such. Bottom line is if you drive like grandma going for groceries you will be fine and get great MPG, hotrod to car and will be reading your tread on an engine swap.

In past research to convert the 2.8 V6 to a roller cam I recall pushrod guides and a thrust bearing being required as the roller cam doesn't
provide the longitudinal thrust that the flat tappet cam does. This may not pertain to the L4 though.
Norm

no "biggie", going to be my wifes car. probably will never see past 4000 rpm. it is a 4 cyl Automatic, not expecting a race car, & she will drive it like "Granny".