Hi all,
My life was just complicated earlier this evening when a kind gentleman offered to sell me a set of pink rods....with the pistons still attached! Here's the problem.

Our school project car is a "71 'vette, which we will turn into an LT1 clone. I had just scored a decent deal on a set of TRW 9.75:1 pistons. I was satsified building the motor with these flat tops, but the rods I am buying have a set of TRW 11:1 domers on them.
Our engine is a four bolt main 010 engine block, scat crank, pink rods, camel hump 202 heads, LT1 cam and all the other LT1 stuff that goes with it. We are hoping to bring a good return on our investment with this car and so far we are doing quite well with it.

I will take a poll here and now. Should we build with the flat tops and keep the domers for later or vice versa? Why or why not?

Thanks in advance.

 

11-1 with iron heads means race gas or ping ping bang. Even 9.75 is pushing it on pump gas. Plus, what about piston to head or valve clearance? Most dome pistons are meant for kidney bean or fast burn chambers, not old factory heads. Are they compatible?

 

Unless I am mistaken the 11:1 TRWs, 64cc 2.02 heads, etc., are what the 1970 LT1 came with. This combo would make ours more authentic, except that they lowered the CR in 1971, which also accounted for the loss in Hp from 370 in '70 to 330 in '71.

Your point about gas is valid, but judging from some earlier threads regarding LT1 clones, some apparently may feel that authenticity might outweigh driveability. If it were my car, which it isn't, I would want to gas and go, and not have to pour in additives. But hey, that;s why I am asking.

 

The cam was smaller for 71 also. Just make sure about the piston clearances, TRW makes alot of different 11:1 pistons. As for the heads, I can't find the exact specs for them, but I can tell you this...in 70 the casting numbers used were 3927186 and 3973414, and they did not use them in 71. The thing is the 186's were used on all available 350's that year. The 414's were only used on LT1's and they also used 3927187's on only L46 motors. I also know that pre 69 350's were 64cc chambers and after that 76cc, also those numbers don't show up till 69 (186 &187 used in 69 & 70) Long story short...as far as I know the LT1 did not get it's power from the heads, it got it from the big solid lifter cam and the comp ratio(made by the pistons, not the chambers) Besides, it was only 70HP more than base and 20 more than then the L46. Good luck

 

I guess firstly I would debate the fact that the LT-1 cam was changed for 1971 and on. Secondly, as mentioned already, get the part number on those pistons and check the actual dome volume. Do not assume they make 11:1 compression with 64cc heads. As stated earlier, you are fine with pump premium up to 10.5:1 maximum (10.25 preferred) with the LT-1 cam due to it's very late closing inlet valve as long as you watch your timing.

 

For a project like yours...which will not be a numbers matching vehicle...why bother adding cost for the pink rods? That goes for spending extra money to add engine performance, IMO. You will have a nice looking Corvette with a "good" performing engine. Also, can you be sure that these "pink" rods are the "real deal"...and that they are usable? Can you justify the extra expense with how much you will get for the car? If you are going to raffle the car, I doubt that you will draw much more money for it having the "pink" rods; most folks won't even know what they are.

 

Yes, they changed the cam...lift, 70, .485/.485 ,71 & 72, .459/.485, as for duration, it's not in the book (GM shop manual), I guess because the techs only need the lift (which in the book is lobe, I did the math) to determine which cam they're dealing with. I did see the whole specs for it once and although I don't remember specifics, I was surprised that they were not that radical, more mild then I expected considering how praised the LT1 was/is (no offence to it, I praise it myself).

 

>>>>>For a project like yours...which will not be a numbers matching vehicle...why bother adding cost for the pink rods?<<<<<<<

For the same reason that Chevy did. This motor will put out just as much torque and HP as the original when finished. It will be nice for the new owner to know they ae getting a solid performance engine, with the best of everything.

AS to the other specs, we are indeed using the 186 heads, and that the 70 cam is different from the 71 is news to me as well. Not saying it is not true, but that to this point I was under the impression from manufacturers that they were the same.

I think they are real pink rods because the seller says they are, and he is a member of this forum. I will trust a man until I am given a reason not to. Niave'? Maybe, but it works for me.

 

Checked the piston #s. They are #2304s, .100 dome and according to TRW they make 10.63:1 with .030 overbore and 64 cc head, which is what we have. According to the casting numbers on the heads they are 1969 date coded #3927186 heads.

Does this affect the prevailing opinions at all?


>>>>>Can you justify the extra expense with how much you will get for the car? If you are going to raffle the car, I doubt that you will draw much more money for it having the "pink" rods; most folks won't even know what they are.<<<<<<

The expense was not that much, since the forum member who sold them to us was very kind in pricing them. With our class project cars, we always offer them first to the forum that is host to our "restoration chronology". We then put them on eBay if nobody on the forum wants it. The first car (1972 GSX replica) was sold before it was finished by a customer who walked into the shop. The second car (1963 Lincoln suicide door convertible) was sold on eBay to a Lincoln forum member. He would have bought it from us directly but did not have the money until the eBay auction. I feel that poeple who buy $20g+ cars have some knowledge of what they are looking for and want the best their money can buy. At least I would hope so.

The point of these restorations is threefold, the kids have fun working on classics, we earn money for the school and the students learn to do things right, which is why we only do frame-off , nut and bolt restorations on our projects. BUt that is also why we try to attian donations of parts and $, since we must cover our costs as well. So far, we have done okay, but not great, financially on these and have not yet lost money.

 

Sounds like you are getting good support from Forum members...good for them! Putting the effort into making a nice engine is commendable and the knowledge for the kids is a real plus. If that extra effort and cost is "good for you", so much the better! Keep up the good work.

 

Thanks '71 'Vette. I hope ours turns out as nice as your did.

Now, back to the question. Should we run the 10.63:1's or 9.6:1 flat tops?

 

If you are running the LT-1 cam you'll need the compression. If you go with the L-82 cam, then run the flat tops. Back to the pistons, .100 dome but what is the quoted volume from Federal Mogul, I'm guessing about 5CCs. You'll also need to see how far down in the hole they sit. Next you need to cc the heads, if they do not have the 2.02 valves unshrouded and polished chambers, that grinding will add a cc or 2 to the chambers. Then you can calculate your SCR with various head gaskets. By the time you are finished with your calc's I bet you will be around 10.5:1, however if you are a tad bit high, flycut the domes down.

One thing bugs me, you have a SCAT cast crank for an engine capable of 7K+

 

Yeah I also wish we had a forged crank. If anyone has an extra they would make us a good deal on, then please do not hesitate to get ahold of me in a P.M.. But that said, I understand that the scat, according to some anyway, is perfectly fine for the 350-400 HP engine.

TRW lists the volume at 2.4 cc.

WDYT, Scott?

 

Assuming the pistons are in the hole .025", 2.5cc piston volume, 64cc heads and a Fel Pro .039" gasket you are only at 10:1. If you drop to the Victor Reinz .026" gasket you are around 10.4:1 which is the gasket I would run with an LT-1 cam ASSUMING the above specs are valid.

 

I am having a hard time understanding how your car is going to qualify as an LT1 clone. Could you please explain it to me?

 

Corv3tt3,

Clones are kind of subjective, A purist would say that it does not qualify unless it has 4 spd Muncie, solid lifters, 11:1 compression, Holley 780 Vac sec, or even that all the parts must date code to between 1970 and 1971.

However, others would say an LT1 clone would have the Big block hood, a hi-perf 350 with the Holley 780 Vacsec, the correct air cleaner, ignition shields, the same lift and duration cam in a hydraulic, ram horn exhaust manifolds, camel hump heads, correct ralley wheels and tires, decals etc. That is how we are building ours.

I saw a "clone" of a 1969 GTO Judge that had chrome bumpers, bench seat, 350 Poncho and 350 TH. Basically a 69 Lemans with a Judge paint job and stickers. This car brought over $10,000 on eBay.

Now, our GSX clone we built last year was identical in almost every way to a Buick GSX, except it had a Comp Cam with the same lift and duration as the factory Stage 1 cam. But we could not justify spending $400 for a repro cam, when a Comp ran $120 for the same basic part. It also had early high comp heads that were machined to Stage 1 specs and it had SS valves.

I suppose the stainless steel valves would have disqualified it from being a clone in some people's books, eh?

 

I guess I happen to be somewhat of a purist. Be careful of using ebay as an example. People will say everything on ebay. Such as this 73 LT1 http://cgi.ebay.com/ebaymotors/ws/eB...m=270106042680

 

While I can appreciate what you say you're trying to accomplish here (having fun restoring an old Vette, teaching a few kids how to PROPERLY restore a vintage/classic car, and hopefully make a few bux in the process) I'm having a little difficulty understanding all the effort being expended here defining what is or isn't a 'clone'. A clone is a fake is a fake is a clone. PERIOD. The only REAL LT1's were those cars that bear the correct VIN. If you want to build a duplicate of such a car, fine- there is nothing ignoble about that in and of itself IMHO but quibbling about a few tenths of a point of CR is not going to make the car any more or less authentic since it's NOT an authentic LT1 to begin with. If you REALLY want it to perform there are a number of things you can do to a smallblock Chevy that will make it easily outperform an original LT1 while still looking externally identical and pump-gas friendly as well. I'm sure there are those out there who will 'correct me if I'm wrong', but isn't that really what you're after? While chrome-bumpered C3's are some of the sexiest-looking cars ever made, they're even more fun when you can be seen sitting inside them while they're actually being DRIVEN. Granted you certainly have better-quality gas in OK than the crap swill that I have to put up with here in SoCal, but (especially with a Chinese cast crank) I would still consider it imprudent to risk detonation and consequent catastrophic engine failure by running compression in excess of 10:1- before I de-compressed my 300HP '70 from 10.25:1 down to 9:1 it clattered like crazy unless I spiked 93 octane gas with race gas. If this car WAS an original numbers-matching LT1 then I could certainly see the sense in keeping every part and piece original-it would be a very valuable, nearly undriveable museum piece. Since it isn't, methinks it better to aim at creating a relatively valuable, DRIVEABLE car. Have fun!

 

Well said, Birdsmith. I agree with everything you just said. What I can do is use the flat tops with the 64 cc heads and save the domers for my 76 cc heads, making two pretty good combos. Sound reasonable?

 

The kind words are greatly appreciated. Again, if your intention is to make this car internally faithful to the original, then put the popups in there. However, it sounds like you're going to sell the car upon completion-since it's not a real LT1 but rather a (hopefully quite well-done) copy/clone/f**e (I know, the F-word's a little harsh) it seems to me that keeping the CR at or slightly below 10:1 would maximize the car's driveability and hence its value. And since you are in the business of restoring cars anyway, keeping the big squishies in a box along with the big-chamber heads may well prove useful in the future. As a point of comparison, along with my Vette I also have a '67 Mustang coupe Trans-Am CLONE (it's a good one-Rick Titus attempted to buy it from me several years ago) that I raced for several years with a 12.5:1 302. It absolutely SCREAMED-on 112-octane race gas. I can't afford that anymore, so I finally broke down and sprung for a 10:1 331 stroker kit. Now I'll hopefully actually be able to drive it once in awhile....