1971 chevelle ss 402?...

[TURBOSCHILZ]

Hey there guys, this is my first posting on here, so please be patient... Alright, I've got a 1971 Chevelle SS that I've had since high school back in the 80's, original 350, 245hp 2bbl, auto, floor console shift, green on green minimal options, but it is a true SS... I'm in the process of restoring it to it's original glory, but am opting for a 402 bbc and putting the original on a stand for the future (just want the extra boom boom if you know what I mean)...lol... I am extremely detail oriented and will be putting every stock part on this car that it would've came with out of the factory, if it were a 402 car of course, so I need MULTIPLE original part numbers and maybe a little help with decoding some castings...

1. First and foremost, I've recently picked up the 1971 bbc, casting #3969854, head casting #3993820, it is stamped "HI PERF PASS" on the block, can anyone please give me any additional info on this motor, torque, hp ratings, cam size, etc.?...

2. I need to know what all is interchangable from the 350, the car is 100% original with all original parts on it, so I need to know which parts were used on both applications to save me the hassle of purchasing parts that I already have, plus save me some cash...

3. Last but not least, I would like to establish a list of ALL required part numbers for the stock pulleys, starter, distributor, carb, etc., etc... Basically I would like to know any and ALL original part numbers that would be associated with the 402 LS3, particularly the 300 horse model, which I believe there were two available 300 and 330, is this correct?...

Thank you in advance guys, you guys are the best...
Jeff

[shadowgray396]

First off welcome to the site.

As far as I know only the 300hp was offered in 71. What you need is the engine identification code which consists of the engine assembly plant, the engine assembly date, and 3 letter suffix indicating the cubic inch displacement, the horsepower rating, and generally, what type of transmission was to be installed with the engine. The suffix codes on the motor would be one of these - CLA, CLB, CLL, CLP, CLS, CAJ, CLK, 71 was the start of lowering the horsepower on the engines.

The big block and small brackets are specific to either BBC or SBC. Also keep in mind short water pump and long water pump accessory brackets are not interchangeable. I believe the same is true on some of the pulleys but not total sure on that. Since you are doing a different motor I would go with a different distributor that you could update but look stock.

Possibly be able to use the starter and flexplate off the small block and use it on the big block also if you are using the same transmission..

[Hank70SS]

The HI PERF PASS means nothing, all big blocks have that cast into them. The casting numbers are correct for a 71 402 but could be from a different year as well, they're not unique to 71. The casting dates will tell if it's a 71, if that is important. The head casting date is under the valve cover. Engine casting date on the back of the block, near the casting number. The suffix code Ray mentioned would tell you a lot. Problem is the engine is now 40 years old, what cam is in it now and what other changes may have been made is hard to say.

The distributor, starter, power steering pump, alternator can all be used but you'll need new brackets. The only pulleys you might need are fan and crank pulley. I believe the fan and pulley from the 350 will swap as well so that leaves the crank pulley if there isn't one on the engine.

[Berg]

Hank is correct on the water pump pulley and accessories fitting. The motor mounts are even the same but you'll want at least a 3 core radiator unless you run an all welded aluminum one. The throttle cable will need to be changed too and you'll need a bracket that holds the cable. The thermostat housing will work and you can swap your smallblock sending units over for the oil pressure and water temp. Battery cables and heater hoses are OK too but you'll need a new set of upper and lower radiator hoses. Remember when upgrading to a bigger radiator you may also need a new top plate. The only pulley you will need to purchase is a crankshaft pulley. If you are reusing your accessories and their original pulleys you'll want the non-special hi-performance pulley for a long water pump setup. The fan shroud will also need to be swapped out. There are alternator bracket and power steering bracket kits out there that come with everything needed to drop a big block in your ride. FYI try to find original GM stuff. The aftermarket ones line up like crap sometimes. Some suppliers actually have stuff right from GM and some dealers can still get most of them since they were used for many years on trucks with big blocks. You could always do the junkyard thing too.
Shadow Gray is right about the suffix code. It will tell you what it came in and even though it is stamped Pass Hi-perf it could still be an engine out of a pickup truck. It just means it isn't a tall-deck (in most cases).

[TURBOSCHILZ]

Sweet, thanks for all the info fellas, sounds like I've got enough info to get me started... As for the radiator, it is an original SS car with the larger radiator, I think 3 core, with the 4 bolt top cover, do I need something more than this?... I'll list the casting numbers and codes below if you guys would like to take a crack at them, otherwise I do know that the block itself is unmodified and the stock bore...

Block:
3969854 PASS HI PERF
T0510TKB
E4-71

Heads:
3993820
26-7T (or 1, not sure on that one)
201

P.S. One more quick question, did a 1971 Chevelle SS BBC w/o ac and w/o smog come with a long water pump or a short water pump?... I believe that my stock 245hp 350 has the long pump, it also has the 4 blade fan w/o clutch, I would imagine that the 402/454 would come with the clutch fan, is this correct?... If so, how many blades?...

Thanks a lot fellas, you guys ROCK...lol

[Berg]

If you already have a beefy 3 core with the 4 bolt top plate you should be good on the rad. You should have a long water pump. I believe that the only year that could have had both long and short water pump from GM on Chevelles was a 1969. 1970-up should be a LWP. As far as the fan goes, the aftermarket kits have 7 blade fans and from my memory it looks just like the fans on both the big block and small block cars. They list it aftermarket as the same fan and clutch but i'm almost positive the LS6 and L78 cars had a special clutch on them. I think AC clutches were different too. They also come in thermostat or non-thermostat versions. You SHOULD be able to reuse your original fan but being it is only a 4 blade and direct drive I'd spring for either a thermostat clutch fan or a flex fan and spacer. Really the only big expense you'll have will be the headers/manifolds and modifying the collectors or engine pipes to fit the BBC. Front springs could be swapped out if you don't like the way the car handles. It wouldn't be a bad idea since the added weight may make it handle different. I personally don't feel that big of a difference.

[TURBOSCHILZ]

Sweet, definitely some great information, that should most definitely help and get me on track... Yea, by the sounds of it, the headers (manifolds) and probably an original 7 blade fan will be the largest expenses for me, sweet, I'll begin the search today and see what I can come up with... Would you happen to know if the crank pulleys were the same as the sbc, or maybe a casting number for the two groove, long water pump crank pulley?...

[TURBOSCHILZ]

Also I need to know about cylinder head parts as well... What were the stock length of the pushrods, did it have long slot rocker arms, 1.7, guideplates, etc.?... And what engines from what years would be interchangable for parts if I were to purchase used?...

[Hank70SS]

Don't have numbers for the pulley's, search ebay for some and they may list the numbers. Any long water pump, 396, 402 or 454 pulley's from that era should work. For 7 blade fan, 772, check Ebay and craigslist. The 772 was used for a number of years. I have one with dates of 73, most people are looking for correct dates for 69 and 70 so I got mine cheap. The rockers are 1.7 with guide plates. Most parts from a early 454 or 396 from the 60's are the same. Push rod length? Check Summit for stock replacement push rods, the specs will show the lengths. Chevy built millions of 396's and 454's and most parts are interchangeable. There are a lot of minor differences over the years so would need to know what parts in particular.

I moved distributor, valve covers, fan and fan clutch, alt, power steering pump, headers, engine mounts and probably more from a 71 402 to a new GM Performance 454 crate engine a couple of years ago. Finding parts that will work should not be a problem.

[TURBOSCHILZ]

Sounds good, thanks a bunch for the fan numbers, that should help... Will do, I appreciate the input, I think I'm ready to get going...lol Thanks again...