LT1 350 370 Hp...vs ZZ4, and others..

[Stan's Customs]

Just happened on a good original 370 hp solid lifter LT1 350 ci engine. ..

Curious what changes most would make to this engine for todays fuel, regarding cam, heads, compression etc.

I believe milling the piston domes to about 10.0/10.5 compression ratio and installing hard valve seats would be the minimun...Maybe the cam would still be all right, I'm not sure at that compression. Not sure about how the heads stack up against todays heads either...

The engine is not cheap (but fairly reasonable)...so I'm thinking the money might be better spent on a later engine...like the crate ZZ4

...or would just about any good 350, with Dart heads or similar, a hydraulic cam, be about as good...or better?

It's been a long time since I had one of these engines and I really liked my big blocks better. So I can't say that I remember the LT1 performance well enough to compare them to todays combinations...any thoughts... what's best smallblock route between the two for a comparable engine.....

 

[tigernut]

You didn't say what the LT-1 engine is going to cost.

You have lots of options on new crate engines anywhere from about 3k to 5k in cost.

The added benefit of buying a crate engine is warranty, which you probably won't be getting with the LT-1.

I'd go for the most amount of torque you can afford since that is the most important factor for a street driven car, imo. Anywhere from 400 to 500 ft lbs is possible in the above price range.

I went with a 383 (built my own, about 500 ft lbs of torque) and couldn't be happier.

Doug

 

[Stan's Customs]

Thanks tiger..

I guess what I'm really trying to find out is how these old engines run compared to the strokers and GM performance type crate engines of today...I just don't remember.

I have stroker in my 1980 Silverado I built back in 1984...still runs good. It is a forged 350 crank with space saver main bearings in a 400 block (instead of the offset grind)..

I think that my old LT1's used to run harder than the stroker...but my memory isn't what it once was.

I'm sure some of these guys guys with '70 or so vettes have more current seat of the pants comparisons than I do...or at least that's what I was hoping.

The money is about the same when done I guess ...less than 5 grand.....including freshening up, new carburetion, exhaust etc.

I'm speculating on the 370 hp cam...but I expect it is much better suited to a 4 speed than an automatic. I have both transmissions...but I doubt I'd appreciate the 4 speed after a while....so that is another area I need information on.

...and I'd like to know what folks think of the iron 2.02 angle plug head now...back when I was doing this stuff it was top shelf. Now....??

~Stan...

 

[Seaside63]

I remember back in the days when we didn't know better (or didn't care) and I pulled the stock 290hp 350 from my '68 Camaro SS and put an LT-1 in there.

The stock motor in that car was a blast but the LT-1 was a whole different animal. That little motor loved to wind.

6500 was nothing. Even touched 7000 a time or two but I was always scared because of that movie "Redline 7000" and I figured it would blow. But it was a tough, tough engine.

Given the choice today I would pick the LT-1 just for the nostalgic sound and the feel.

 

[allcoupedup]

A nice stroker will outperform the LT1 350 and the 365 SHP 327 almost every time. A crate stroker will even cost less. THe motors will have completely different feels though. If you are not too concered with ET, go with what you like to drive.

GOBS of torque and a low redline
OR
Fair torque and a screaming high redline


I went with a correct appearing 327 with the LT1 Cam. It isn't crazy fast but it sure sounds nasty. A high compression solid-lifter v8 with sidepipes at 6500 RPM is a sound I'm willing to sacrifice some ft-lbs of torque for.

Brian

 

[Stan's Customs]

Hello Brian...

I thougt that the stroker was the ticket...till I got one. Then I began to doubt that....

I really was under the impression that the old LT1 was a little better. I outran a few 383 mopars with one of mine.. "but" I had a substantial gear advantage and a 4 speed. I've come to the conclusion ( perhaps erroneously) that the torquers arn't the total answer ...especially in these light weight cars. I know everyone and their duck has 2 of them, and the dyno stats are great....but I don't know anyone that has a real LT1 350 /370 hp now. That's kinda neat for bragging rights (different) plus, I'd like to hear first hand that they just don't cut it any more from someone who still has one.....Sometimes the matched package is the answer...after all the 370 hp LT1 was the most powerful smallblock GM ever produced for over 20 years....up until '92 ? or so.

Is your car a stick or auto...and have you had a LT1 with the solid cam etc. lately...or is the 327 what is you are basing your information on..specifically?

Best Regards...Stan

 

[allcoupedup]

Stan,
I had a 327/??? mystery motor that I upgraded to 327/365 config with a few exceptions.

- LT1 CAM instead of 30-30
- lightly ported heads (still double hump)
- aftermarket rods
- roller tip rockers

I have a 3.36:1 rear end and HAD a close ratio (2.2:1 1st gear) muncie. I say HAD because the LT1 camshaft and the close ratio with the 3.36:1 rear was just unacceptable. I had to slip the clutch or really launch it to get it moving.

I switched to a wide ratio muncie with the 2.56:1 1st gear and the car is now a delight to drive. All of my comments are on this current engine. A 350 LT1 will probably get you about 25 more HP than the 327 but the 365 and the 370 HP ratings were probably more marketing hype than meat.

Strokers are everywhere but I wanted some nastalgia so I built an old school motor. With this corvette I want to drive it more or less "as it was" back in the day. The resto-rod thing is very cool but isn't my thing right now.

Brian

 

[Stan's Customs]

OK ..I've got the picture..

I too have a wide ratio 4 speed I could use....It occured to me that of all the 4 speeds I have owned...most were big blocks and all ...even the small blocs were close ratio. I have no idea how the wide step between 1st and second feels compared to the close ratio. Sounds like it may be a good thing..from your experience.

I believe the 3:36 gear is a good choice for the way I drive now too...

I really think that there is probably as much difference in low end torque between the 327 and the 350 as there is between the 350 and the 383...or similar amount anyway.

So maybe that would work...I don't know. I just didn't consider smallblocks fast in the old days...they were for my daily drivers when I started slowing down , having a family and so on....and still retain my dignity...

But even then the LT1 was a very desirable engine....So I'm with you on the nostalgia part...the cam sound etc, may fit the era for my non original car. Especially with the Grant deuces or something ...

I'm really having having a hard time with this car...it has to be the best I've ever done, and I'd like to do it for less than my home cost...

It's all critical...for that perfect package. I've had 2 or 3 that were perfect and a dozen that wern't if you know what I mean. Lots of trial and error back then.

~Stan...

 

[Tom Bryant]

One other thing to consider is that with the ZZ4 crate you get the fast burn heart shaped combustion chamber. These are far superior to the old LT1 heads. They tollerate higher compression ratios on available pump gas and are much more efficient. The ports are also much better.

The old LT1 is a great performer for it's technology but is best left for someone needing it for a restoration. The ZZ4 being new tech all brand new parts and with a really good warranty would make a big difference to me, prices being comparable.

Tom

 

[Stan's Customs]

Thanks Tom for yor post...

The ZZ4 is a well balanced engine for the money it seems, and the torque numbers 405lbs @3500 RPM are pretty impressive. I know some builders that really like this engine for the money...Whether it has any cool factor ..I'm too far out of the loop to know.

I'm a little confused about exactly what the differences between the Fast Burn 385 and the ZZ4 are though. The Fast Burn 385 only has 385 lbs@ 4500 Rpm...which is considerable less torque at higher RPM. Valve size (1.94")contributes to that...but I don't think the chamber configuration is the same either...is it?

The GM Performance folks rave about the Fast Burn head even though the numbers are better on the low end for the other ZZ4 head....there is 25/30 hp difference in the high end unless you get the hot cam package.

I'm thinking that a LT1 might have very similar low end torque numbers like the Fast Burn 385...and if the 370 hp rating is about right on the high end, that's only a 15 HP difference there....on the Fast Burn 385. But it has more high end h.p. than the ZZ4.

If that were so... I might settle for that just to have the venerable old Flagship LT1 motor....which sorta epitomizes the old school street small blocks....without going back to the 283's etc.

I wish I could find some specs at comparable RPM's for the LT1...Seems like its kinda in between the ZZ4 and the Fast Burn 385.

 

[allcoupedup]

Remember that up until 1971, all horsepower ratings were gross and then went to NET in 1972. Comparing an old rating to a new rating is like comparing apples to oranges.

370*.8 = 296

Brian


read below
SAE Net Horspower In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349. Because SAE net is so common, this is the standard we will use to compare all others.
SAE Gross Horsepower This is the old process that American manufacturers used as a guide for rating their cars. It was in place until 1971. SAE gross also measures horsepower at the flywheel, but with no accessories to bog it down. This is the bare engine with nothing but the absolute essentials attached to it; little more than a carb, fuel pump, oil pump, and water pump. Because the test equipment on the engine is not the same as in SAE net, it is impossible to provide a mathematical calculation between SAE net and SAE gross. As a general rule, however, SAE net tends to be approximately 80% of the value of SAE gross. SAE J245 and J1995 define this measurement.


Brian

 

[Stan's Customs]

Yep you are right Brian..

....therein lies another part of the problem...and why seat of the pants comparisons is what I'm searching for.....

Wouldn't it be nice if Hot Rod would do an article comparing old GM crate motors to newer GM crate motors with a dyno test to show the stats...

It is really hard to guess at this stuff since GM in the old days used to underrate their motors sometimes (especially big Hp engines) to help new car sales...insurance was based on Hp by many insurance companies back then...in fact, maybe all insurance companies used that table.

In any case I'm pretty sure that an LT1 with 11:1 compression pistons and 2:02 heads, aluminum intake and a solid lifter cam... will have no problem beating 300 HP all to heck and back...SAE ratings or otherwise. Now then... the smog engines in the later years...would do good to meet their ratings.

Regards...Stan...

 

[Tom Bryant]

The iron Vortec and the fast burn 385 and ZZ4 all use the new chamber.

 

[Stan's Customs]

Thanks Tom...thats what I'm puzzled about.....

The ZZ4 uses an intake that is for 1986 and back. The fast burn and iron Vortec use the same late model vortec style intake.... So I thought that the chamber would be different too...especialy since the ZZ4 chamber is 58cc's and the fast burn chamber is 62 cc's.

I'm still not sure what the main differences are between the ZZ4 and Vortec style head. ...other than different intake.

The chambers are the same configuration, and the valves are larger in the fast burn. Perhaps the difference in the cc's is the valves are unshrouded a little better on the fast burn.

According to Eric at Barry Grant...there has been some issues with the 3 deuce set up on the fast burn heads (intake issues). I asked them what crate GM engine BG used in their advertised testing. He didn't know for sure and the person who did wasn't available till next Monday. So they are going to find out and let me know...next week.

I would like to know what the port volume is on the L98 (ZZ4) castings and have a little better picture of what these heads really are...I must be looking in the wrong places, I can't seem to find that little tidbit.

 

[Tom Bryant]

Here's the poop on the fast burn heads from the GM Performance parts site. I can't seem to find the specs on the ZZ4 heads right now either.

12464298 Cylinder Head "Aluminum Fast Burn"
The all new 23° Fast Burn small block cylinder head has the highest performance potential of any 23° small block head developed by GM. The Fast Burn head combines new technologies with the best of GM motorsports and production cylinder head technologies. The design creates tremendous power on engines from 350 to over 400ci. The name "Fast Burn" refers to the head's ability to quickly and completely burn the air fuel mixture, resulting in higher cylinder pressures and more power. The shape of the combustion chamber is designed to accomplish this "Fast Burn" with flat top pistons, so flat top pistons are recommended with this cylinder head. It is not recommended that the combustion chamber be modified or reshaped, as this could decrease the efficiency of the chamber. This head is designed with a .400" deck. This new technology removes material from other portions of the head, allowing for considerably larger ports and water jacketing. The deck also provides unsurpassed clamping force for cylinder head gasket retention. The super rigid .400" deck thickness can be machined down to .340" safely for all-out performance applications and higher compression. Other ways to adjust compression ratio with the Fast Burn head include top of piston design and piston installed height. Unlike the GM Performance Parts Bow Tie heads and most aftermarket performance heads, this head requires no additional porting for maximum performance. In the past, the industry has added material to heads to allow substantial porting, which can result in poor "out-of-box" performance and additional cost. The Fast Burn head utilizes GM Performance Parts' Cast-Ported technology, which means that improvements in flow, combustion and cylinder fill were incorporated into the machining tooling, achieving maximum performance "out-of-box". While additional porting is not recommended, light sanding to remove minor casting imperfections and polishing of combustion chambers and exhaust ports is acceptable. All Fast Burn heads are CNC machined to exacting tolerances, thus eliminating the need for "blue-printing" of machined tolerances, resulting in a cost savings and unsurpassed "out-of-box" performance. This head has taller than typical rocker cover rails, providing exceptional clearance for rocker arms and valve train supports typically used in all out performance applications. The rocker rails are CNC machined for superior rocker cover gasket sealing. Front head faces are drilled and tapped for typical accessory drive bracketry. The Fast Burn head accepts both center bolt and early style four bolt flange mount valve covers. Signature etched with GM Performance Parts logo. Intake manifold mating surfaces are drilled and tapped for both Vortec and conventional raised port style manifolds. "D" shaped 78cc exhaust port and runners provide adequate flow for applications well in excess of 500 hp. Raised runner (.240" higher than conventional 23? head) intake ports with 210cc ports and runners provide adequate flow for applications well in excess of 500 hp. Raising the top of the intake valves provides a better "line-of-sight" through the port and onto the back side of the intake valves. The 62cc fast burn combustion chambers - the most efficient ever to be incorporated on a GM Performance Parts cylinder head - produce higher cylinder pressures by burning more of the available fuel before the piston starts its power stroke downward. By more completely using available fuel, the engine produces more power per quantity of fuel. The 2.00" hollow stem lightweight intake valves are utilized to reduce loads on valve train systems at high rpm's. The 1.55" sodium filled lightweight exhaust valves have all the same benefits of the hollow stem intake valves, and additionally they are able to perform under extremely high-temperature performance applications. This head has specially designed "deep" valve seats which can accommodate up to 2.02" intake valves / 1.600" exhaust valves. Lightweight valve spring retainers combine with the lightweight valves to help ensure long-term high rpm durability. Screw-in 3/8" rocker studs are used, and accept most available roller rocker arms. Uses all conventional "low cost" readily available 23° rocker arms and valve train supports and hardware. This head is a bolt-on 30 hp increase when used on our ZZ4 crate engine. When tested on a 383 ci small block engine with 9.5 to 1 compression ratio and .540" lift roller cam, single plane intake manifold and 750 cfm Holley carburetor, the Fast Burn heads produced 497 hp at an incredibly low 5800 rpm. Total ignition timing to be used on a Fast Burn head will vary based on a number of factors, but most configurations made the most power with 34 to 36° of total timing.

Technical Notes: Use intake manifold P/N 12496820, P/N 12366573, 12496822, or 10051103 with the Fast Burn cylinder head. Use intake manifold gasket P/N 12529094 and eight attaching bolts P/N 12550027. Use Fel-Pro exhaust gasket P/N 1470 for these Fast Burn heads (some trimming may be required for your application. This head includes intake valves P/N 12555331, exhaust valves P/N 12551313, valve spring cap P/N 10212808, and valve springs P/N 12551483.


Notice that the fast burn heads are worth 30 hp over the ZZ4. If I'm remembering right the ZZ4 and L31 iron Vortec heads are the same except for material. The iron Vortec is the best as cast iron head GM has ever offered. The fast Burn 385 with the GM H.O.T. cam installed is supposed to make 425 HP. I rode in a '68 with this combo at Sharkfest a few years ago. It was very fast but the owner complained that it didn't sound hot. The idle was quite smooth. A product of modern hyd. roller cam designs.

I think that the Fast Burn 385 has even more potential and I'd like to try one with an aftermarket cam from Crane or Comp that would have noticable lope but not loose it's low rpm responce.

Tom

 

[Stan's Customs]

Thanks for that info Tom...Where did it originate. It is a little different than the information in the GM Performance Parts catalogues.

GM's 2004 catalogue about the same thing..and on the 2005 again not word for word but close..."except" they say in fast burn head description by itself...."Heads provide a 25-horsepower increase when used on the ZZ4 crate engine." ....that's the 2005 catalogue head section.

Seems like they never give common comparisons...marketing I guess. The 383 flowing more air would be a difference...but they say the Fast Burn is the same as the ZZ4 except for the upgrade to the Fast Burn heads....That's 30hp difference in that comparison too...

They conveniently don't tell you a lot about the 12556463 heads...they may be as you suggest like the iron 194 heads..but they don't act like it.

Any way...my fried pies are burning as my Mama would say. I'm still looking.

 

[Stan's Customs]

Oh yea...the cam lope is another thing ...I bet the same cam in the 350 would have more lope. The stroke and cubes of the 383 would tame the idle some...I think.

Old school at least......today's cam profiles who knows.


Woah...that's not the stroker...never mind, that's the 385 HP...

Smaller heads with less flow volume contribute to a lumpier idle too.....maybe the fast burn heads are just too darn good, heh!

 

[Jack]

I thougt that the stroker was the ticket...till I got one. Then I began to doubt that....

I have stroker in my 1980 Silverado I built back in 1984...still runs good. It is a forged 350 crank with space saver main bearings in a 400 block (instead of the offset grind)..Best Regards...Stan

Stan: But the 400 block w/ a 350 crank ain't a stroker ... it's DE-stroked ... does not have the grunt of a stroker. 350 block w/ 400 stroke is a stroker ... and has the grunt.

Tom: Sorry 'bout your chow dog pal. The ZZ4 has aluminum L98 vette heads w/ "conventional" 58cc chambers ... they are NOT "fastburn" chambers like the Iron 64cc L31 Vortec and the Aluminum 62cc "fastburn" 12464298. If I recall correctly, intake port volume is 170cc for ZZ4 58cc L98.

here's the ZZ4 L98 head http://www.sallee-chevrolet.com/Cylinder_Heads/images/12556463.jpg you can see the chamber is conventional.

here's a Brodix head with the vortec/fastburn chamber http://brodix.com/IK Series.html

Nowadays, virtually all non-GM sbc aftermarket heads have the Vortec "heartshaped" / "fastburn" chamber but most use the old Gen 1 style 12-bolt intake manifold flange. Dart, Edelbrock, Brodix, AFR do ... ProTopline and their clones did.

 

[Jack]

Sallee Chevy has their own sbc crate motor P/N SC450BLB for just under $5700. It's all brand new ... based on HT383 short block but w/ more cam & 12464298 fastburn heads. Makes about 450 hp/460 tq on pump gas.

Sallee also has GMPP’s P/N 12498772 … about the same as above motor but w/ slightly different cam making about 425 hp/450 tq on pump gas. Cheaper at just under $4800.

Both of these are true strokers & should run circles around a good LT1 up to about 6000 rpm. You’d probably need a different flexplate or flywheel because both of these have newer one-piece seal cranks having smaller 3.00” bolt circle on crank flange.
JACK:gap

 

[Stan's Customs]

Hello Jack thanks for help....you are exactly right on the stroker... I really had to try and remember what we did there..

After I get to thinking about it. That motor was one that I built for a boat the first time in '78 or '79. Wrong combination for a boat so I pulled it and did something else. Later in '84 I decided to perk up my '80 SWB Silverado. Since I still had that short block, so decided to freshen it, get some 1:94 valve heads and put it in my pickup. Now back to '78/'79...

I know that the reason for the boat build was to stroke the engine.....and I had a perfect a steel crank that I wanted to use since the 400 doesn't come with a steel crank, cast only....I do remember that pistons were expensive for the combination that we used, Venola (I think) was the only company that had them for the wrist pin placement that I needed. Now this is where it gets real fuzzy...I don't remember what rods we used. I really thought that we used GM stock rods. If that is right then we used the forged 350 steel crank with space saver main bearings (I am sure of that part) then offset ground the rod journals for the small journal 327 rod and that's how we must have stroked the engine.... seems like I vaguely remember remember the cubes being a little less than if we had used a cast 400 crank for some reason....??

Any way...I'm sure its stroked ...I just can't remember exactly what we did to do it....strokers were still a pretty new approach back then. Lots of us still wouldn't build any engine with a cast crank. We were spoiled, with there being so many used forged cranks to be had...we didn't have to run cast stuff.

Thanks very much for the pics of the head chamber...I suspected as much since Chevrolet was so uninformative in the new catalogue and didn't show a chamber picture like they do on other heads. They're kinda sneaky some times...

One thing you can say about those heads ...if GM's torque figures are right on the ZZ4.... 405 lbs. at 3500 rpm is pretty darn good. I'm not sure that they don't work better than a fast burn head...at least with an automatic, 3.20's/30's gears, in a 3,000 lb. C1 cruiser.

I know bigger numbers can be had than the ZZ4 or LT1 for instance.....but these new high flowing heads flow lots of fuel too...No really big thing, but on a 1,000 mile cruise mileage is a good thing , especially if you can have it "and" a lot of low end torque.

Have you used any of the aftermarket heads you mentioned Jack? There are so many to choose from...it's difficult to weed out the best ones. From old days , seems to me what looks good on paper isn't always what feels the best when the pedal's to the metal....personal choice preferences/experience information would be appreciated.

From you any one else that cares to chime in...

Thanks for the help....

~Stan