454 gen IV crate question [Archive] - Chevelle Tech

: 454 gen IV crate question


oldgm
Mar 28th, 11, 3:59 PM
have a 454 gen.IV #10069286,1990 4 bolt crate,has solid lifters and rect.port gm iron heads #14096188 . does anyone know if this motor came with the solid lifters and big port heads. any info would be greatly appreciated. no numbers in front of block,decked. trying to research this motor in my 70 chevelle .thanks for the help, oldgm

68chvlss396
Mar 28th, 11, 4:11 PM
Here is some info from Mortec on your block and heads. Could be a late LS6 crate. It would have XAA stamped on the block.

10069286...454.......90-91...4-bolt, Mark IV, Short deck

14096188...70-71...rect...OPEN...454 service replacement, also used on later
Mark IV LS-6, LS-7 and 454 HO crate motors, 116cc chamber

oman
Mar 28th, 11, 5:29 PM
have a 454 gen.IV #10069286,1990 4 bolt crate,has solid lifters and rect.port gm iron heads #14096188 . does anyone know if this motor came with the solid lifters and big port heads. any info would be greatly appreciated. no numbers in front of block,decked. trying to research this motor in my 70 chevelle .thanks for the help, oldgm

I have one of those motors. It is a later Gen IV motor, I believe I bought mine in 1989. There are several posts on here that talk about the "guts" inside those motors. You could also research P/N 366250. That is the part number that the engine was sold under.

I participated in several of the posts mentioned above and I can't take the time to retype much of the info that is in my head. If indeed it is an XAA motor is is the best of everything with the exception of the crank. The LS-7 crate had a better grade of steel used in its crank. Other differences included CR, Cam and wrist pins but that is another story. The point is that if the engine is an XAA motor it was almost the top of the line. More likely THE top of the line for street use.

Do the search on XAA and you should find the posts. BTW the XAA is on the front of the block on a pad behind the water pump and just below the "China Wall" where the intake sits. Decking the block would not have removed the XAA stamping.

osdmike
Mar 28th, 11, 6:53 PM
I have the XAA code 454 in my Camaro.That would be the 425hp crate engine, very similar to the -71 Corvette 454.(see pic. below)
Block casting number: 10068286 block. 4-Bolt IV Short deck. 90-91
I believe the part list below is printed before 1990.

The part numbers are little different.

I have the#3967416 crank.
#14011077 alu heads.
Im not sure if the alu heads were ordered with the engine from the beginning.They are "GM replacement" heads.
But its a XAA code, bought from GM.
The "XAA" is placed in front of the thermostat housing.

Some info I found.
The suffix code for -70 Chevelle 454LS6/450hp:
CRR,CRS or CRV


454 LS7 suffix is XCH.

sz0k30
Mar 28th, 11, 7:03 PM
As far as I know there is no such thing as a Gen IV big block engine. You can have either a Mark IV, a Gen V, or a Gen VI - no Gen IV.

Fasglas
Mar 28th, 11, 7:37 PM
Most of the crate motors had one of these too. I bought both an LS-6 and LS-7 back then (still have them both). I don't know what I did with the paper that came with the LS-6, but I still have the one that came with the LS-7...

oman
Mar 28th, 11, 7:59 PM
Most of the crate motors had one of these too. I bought both an LS-6 and LS-7 back then (still have them both). I don't know what I did with the paper that came with the LS-6, but I still have the one that came with the LS-7...

We have a matched set of paperwork!!! Somewhere in this house I have the docs from the LS6

oman
Mar 28th, 11, 8:08 PM
I have the XAA code 454 in my Camaro.That would be the 425hp crate engine, very similar to the -71 Corvette 454.(see pic. below)
Block casting number: 10068286 block. 4-Bolt IV Short deck. 90-91
I believe the part list below is printed before 1990.

The part numbers are little different.

I have the#3967416 crank.
#14011077 alu heads.
Im not sure if the alu heads were ordered with the engine from the beginning.They are "GM replacement" heads.
But its a XAA code, bought from GM.
The "XAA" is placed in front of the thermostat housing.

Some info I found.
The suffix code for -70 Chevelle 454LS6/450hp:
CRR,CRS or CRV


454 LS7 suffix is XCH.

The XAA engine ...sold with the P/N 366250 came with iron, rectangle port, open chamber heads & 2.19 1.88 valves. The difference between the Vette motor and the crate version is the pistons. Vette engines (installed in factory built Corvettes) had small dome pistons yielding a nominal CR of 9.1 to 1. Crate engines P/N 366250 had the high dome 11.0 to 1 1970 LS6 pistons. Adding the open chamber ...71 and later heads... to the 366250 crate engine with the large dome pistons resulted in a 10.2 / 1 CR. The Vette motors ran the open chamber heads with the samll dome postons to meet GM's self imposed CR limit of 9.0 to 1 that was ineffect after 1970.

oman
Mar 28th, 11, 8:10 PM
As far as I know there is no such thing as a Gen IV big block engine. You can have either a Mark IV, a Gen V, or a Gen VI - no Gen IV.

Thank you I never knew that.

osdmike
Mar 28th, 11, 9:16 PM
The XAA engine ...sold with the P/N 366250 came with iron, rectangle port, open chamber heads & 2.19 1.88 valves. The difference between the Vette motor and the crate version is the pistons. Vette engines (installed in factory built Corvettes) had small dome pistons yielding a nominal CR of 9.1 to 1. Crate engines P/N 366250 had the high dome 11.0 to 1 1970 LS6 pistons. Adding the open chamber ...71 and later heads... to the 366250 crate engine with the large dome pistons resulted in a 10.2 / 1 CR. The Vette motors ran the open chamber heads with the samll dome postons to meet GM's self imposed CR limit of 9.0 to 1 that was ineffect after 1970.

Would My "077" open chamber heads (118cc) be approx. 10,2:1 CR ?

oman
Mar 28th, 11, 10:06 PM
Would My "077" open chamber heads (118cc) be approx. 10,2:1 CR ?

Yes. 118 cc was the size of the head offered on the GEN IV 366250 Crate motor.

Whoops! I should say "Yes 118 is the size of the head offered on the Mark IV 366250 Crate motor". I am a slow learner as outlined above with the observation offered about Gen versus Mark designations. Just kidding, no jab at you intended.

You should be as close to 10.2 @ 118 cc's on your 077 heads as GM was close to 10.2 with the 118 cc head they offered on the motors as they were delivered "out of the box". The only issue might be the chamber shape. I can't tell if the 077 is shaped the same as the heads offered on the 366250 motors as delivered from Gm. As long as you are running Ok with the 077 heads then I have to assume that clearance is OK as far as the dome to combustion chamber.

I can't say for sure what the true compression number is 10.2 / 10.00 / 10.3 / 9.9 but as long as you have the original pistons supplied in the 366250 engine you are right in the 10.2 range.

Not that this concerns you..just an FYI. I pulled the pistons out of my crate motor when I got it and went to the lower dome / lower compression 71 Vette LS6 pistons. Looking back I am glad I did. I have run up a fair amount of milage on the engine and never had an issue with "looking around" for an acceptable grade of gas. At 9.1 to 1 it runs on almost anything. I think the true compression with my setup is 9.0 at best but given the crap gas we have I think I made the right move.

osdmike
Jul 6th, 11, 11:10 PM
Yes. 118 cc was the size of the head offered on the GEN IV 366250 Crate motor.

Whoops! I should say "Yes 118 is the size of the head offered on the Mark IV 366250 Crate motor". I am a slow learner as outlined above with the observation offered about Gen versus Mark designations. Just kidding, no jab at you intended.

You should be as close to 10.2 @ 118 cc's on your 077 heads as GM was close to 10.2 with the 118 cc head they offered on the motors as they were delivered "out of the box". The only issue might be the chamber shape. I can't tell if the 077 is shaped the same as the heads offered on the 366250 motors as delivered from Gm. As long as you are running Ok with the 077 heads then I have to assume that clearance is OK as far as the dome to combustion chamber.

I can't say for sure what the true compression number is 10.2 / 10.00 / 10.3 / 9.9 but as long as you have the original pistons supplied in the 366250 engine you are right in the 10.2 range.

Not that this concerns you..just an FYI. I pulled the pistons out of my crate motor when I got it and went to the lower dome / lower compression 71 Vette LS6 pistons. Looking back I am glad I did. I have run up a fair amount of milage on the engine and never had an issue with "looking around" for an acceptable grade of gas. At 9.1 to 1 it runs on almost anything. I think the true compression with my setup is 9.0 at best but given the crap gas we have I think I made the right move.

Since we have 98 octane here in Sweden I have set the timing at 38* total.
But is it possible to run 95 octane with 10.2 :1 CR?....if so, what should the timing be set at?

Are there any advantages or disadvantages to run a lower octane?

Are there any other things I should consider?

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Schurkey
Jul 7th, 11, 12:08 AM
Since we have 98 octane here in Sweden I have set the timing at 38* total.
But is it possible to run 95 octane with 10.2 :1 CR?....if so, what should the timing be set at?

Are there any advantages or disadvantages to run a lower octane?

Are there any other things I should consider?

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You should consider that Sweden and the USA probably use different methods for describing octane rating.

I think your 98 octane is about the same as 92--93 in the USA.

http://en.wikipedia.org/wiki/Octane_rating

oman
Jul 7th, 11, 9:08 AM
Since we have 98 octane here in Sweden I have set the timing at 38* total.
But is it possible to run 95 octane with 10.2 :1 CR?....if so, what should the timing be set at?

Are there any advantages or disadvantages to run a lower octane?

Are there any other things I should consider?



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I think the issue is as follows. Yes you can run 10.2 with lower octane but there might be a price for that decision. Sure you can run lower octane but as pointed out above are you sure the rating systems are the same? I can't tell if the octane rating in the US is calculated the same way as it is in Sweden. Let me say this however. At some point you are going to have to back down on the timing to run lower octane gas. How far back on the timing? Can't say. As sure as death and taxes at high timing numbers, with low octane, the thing is going to ping. Pinging is destructive that is also a sure thing ....without a doubt.

I have gotten to where every little bit of perf. just doesn't matter to me anymore. I don't want to be searching for high octane gas in a mid to low octane gas world. I would rather be a little lower than I might otherwise want to be on compression and free to stop at any station to fill up.

In the end this really boils down to what you want. If you just must have that extra few HP then leave the compression but be ready to reach a day when you have to turn back the timing. You might not like turning back the timing any more than you like cutting the compression.

"You can't have it all" or at least "You can't have it all and count on things being the way they are now". Gas can only get more expensive, government is gonna keep screwing around with formulation of gas (look at the CRAP E-10 / E-15 we have in in the US). If you stay at a higher compression and higher timing settings you are gonna be caught in this squeeze sooner rather than later.

If I were you I would consider this equation of gas / compression and performance. This is just another go round of the issue with lead removal in the US back in the 1970's. The gov removed lead and all ya heard was weeping about "Compression, timing, power loss" Essentially people just had to get used to the fact that w/o lead ya can't run higher compression ratios and or higher timing on the street. Also at some point if you crank the timing back far enough you run into heating issues...low timing settings will add to cooling issues. I think you are contemplating essentially the same problem we faced here years ago. The only difference being that today the issue is octane rating not lead content.

osdmike
Jul 7th, 11, 9:38 AM
Thanks for the answers!
Most engine builders in Sweden aims to be able to run on 95 octane these days.
I'll check the octane rating the US. vs. Sweden, and see what I can come up with.

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