drspencer

'71 Convertible, matching #'s 350/270HP w/133K miles. Car is a blast to drive, but the original 350/270HP is getting a little tired.

If I remove the original matching #'s engine, send it out for a stock rebuild and reinstall it myself, that will cost $8K for a reputable shop in my area. Same shop just doing the necessary machine work, with me reassembling the engine, is $4K.

I'm strongly considering just storing the original engine and going with this GM 350/357HP crate engine GM 350/357 for only $6K.

More than anything, I would like to car to have good street manners. Not interested in headers, loud exhaust, lumpy cam, etc. Can anyone give their opinion on idle quality/street manners on the stock 350/270 vs the crate GM 350/357?

Additionally, If I choose the crate engine, I would prefer to use it with the stock intake & Rams Head manifolds. However, I was told that because the 350/357 crate has Vortec heads, the stock intake can't be used without modifying/drilling the Vortec heads. What intake could be used on the 350/357 crate (with the stock Quadrajet) and still fit under the stock, base model hood?

Thanks

carriljc

drspencer
The only reason I've looked into this is because my RamJet 350 comes with Vortec heads and I pondered what I would do if I wanted to swap in a carburetor (for fun....).
Hadn't looked in a while but there are A LOT of choices for a Vortec Intake Manifold from the last time I looked..... sounds easy. No need to drill anything. Just pick the Quadrajet (I believe it was a Q-jet in 1971) Manifold that you want.

BTW....I am using 2.5" Ramhorns and full 2.5" exhaust on my 68.....

https://www.summitracing.com/parts/p...SABEgJSrPD_BwE

drspencer

I had originally posted that in order to use the stock '71 350/270HP intake manifold on a GM 350/357 crate engine, you would have to modify/drill the Vortec heads.

I had further asked if anyone could recommend an intake (other than the stock 350/270 intake) that would fit under the base model hood when using the GM 350/357 crate engine & a Quadrajet.

Do you know of any?

Thanks

drspencer

I just looked at this Ramjet 350 crate engine with fuel injection. Is this what you have? Ramjet 350

That's a great looking setup, I'm surprised I never saw this sooner. I really like the idea of fuel injection, as well. Do you know if this will fit under the stock, base model C3 hood?

Can you comment on the street manners/idle quality of your Ramjet 350 vs the GM 350/357HP?

Thanks, once more.

carriljc

drspencer
That summit link I posted shows you various Vortec intake manifolds available to use with Vortec heads.
The Speedmaster Low-Rise Vortec Intake Manifolds 1-147-004 is specifically mentioned as being "low rise".
Here is the link again with multiple vortec intake manifolds available from Summit...and it even tells you the height of the manifolds. You can pick one for quadrajets and low profile to suit your desires:

https://www.summitracing.com/parts/p...ional-products

I cannot comment on the comparo between the 2 engines you ask about. Looks about the same to me. The block assembly on the 350/357 that you're looking at seems better with a forged crank (misleading info...other sources say nodular iron crank-- and that makes more sense), but it does have 4 bolt mains..... overall it doesn't matter much since the max rpm is 5600 for both. The CR ratio is lower than the the Ramjet 350 (9:1 vs 9.4:1). Herre is a better price on that 350 / 357 hp.
https://www.gmperformancemotor.com/parts/19433032.html

I got my Ramjet-350 20+ years ago now... wow. I did not like the GM MEFI controller (must be better now since it is a newer model). I went so far as to rewire the harness and hook it up to a 730 ECM and burn my own chips.... that was fun for a while and I could adjust just about everything with the Moates programmer. I do not, and did not, know enough to take advantage of those capabilities. Nowadays I'm running it with a "self tuning" EZ-EFI 2.0 retrofit kit for GM TPI engines.
I like it. The Ramjet 350 would not fit under a stock hood. I have an L-88 hood that I modified to use the cowl induction to feed the intake...that was entertaining.

I would not do it nowadays with all the LS options available. ... lots more potential with an LS engine and lots of knowledge out there to adapt one..... and there are a ton of used ones available.

4-vettes

I'm afraid I have no helpful information for you.
But I'm trying to understand how it costs 4 grand to bore 8 cylinders! I'm really having trouble with that.

Roadster71

I don't know how this compares with today, but almost 20 yrs ago I faced the same decision with my 71. I chose the then GM Performance ZZ4 crate engine. The intake that came with it fit fine under the hood. Everything else came off the old engine and bolted right up to the new including the ramhorns and tack drive distributor. Never regretted it.

Dean81

I assume this would also include parts and head work

drspencer

Good to know. Was the ZZ4 cam any lumpier at idle than the stock '71? Did you notice difference in street manners?

Thanks

drspencer

Pretty sure it does, but I didn't bother to ask. I still had a lump in my throat when they told me $8K for a stock rebuild (with me removing & reinstalling the engine).

I seem to recall getting a quote for $6K for this same service about 10 years ago.

Thanks

carriljc

In the big scheme of things those choices of intake manifolds are not outrageous....considering you want somewhat stock performance.

67:72

I have an originality/restoration mindset, so would do the rebuild. I understand you'd have the original engine set aside, but those things tend to get separated when cars change hands. If your car is basically original that's the direction I'd go. I'd also surmise that a future buyer who is looking for originality won't pay extra to offset the crate engine's cost and would still have to fork out the cost of the rebuild. It adds inconvenience down the road.

Where are you located? Perhaps someone here has excellent experience with a different builder.

PS- my stock 454 rebuild 3-years ago cost ~$5500 which included new pistons, cam, valves & guides, etc., plus break-in and dyno. The only mod-ing I did was bumping compression with domed pistons. The builder does circle-track race engines with some restorations mixed in.

drspencer

I'm with you on the originality mindset. But remember, this is just a base model car.

How much power do you imagine the original 350/270HP engine could be rebuilt to, while still retaining its polite street manners? Can anyone recommend a reputable engine shop in the Boston area?

Not sure it's germane to this discussion, but the 4-speed will be replaced with a 5-speed, as well.

Thanks

Eliredandblack

Dr.
From my looking at C3 Corvette prices over the years, the cars with Matching Numbers seem to bring more money, and appeal to more prospective buyers. That being said, everyone has their own options. I will admit that I am biased, because my 1973 convertible is all matching numbers, with the OEM engine that is somewhat tired. I have other cars that I use for out of town travel, that are obviously way more reliable than a 50 year old Corvette.

4-vettes

How much power can you build it to and keep stock rams horn manifold, stock 2 inch exhaust, etc. And keep it very streetable. I'd throw about 325 HP out there as a pretty close guess.
I'm running about 400, extremely streetable. Nice manors around town, etc. But when I push on the loud pedal, yup, let's go!
But I'm running a bigger exhaust, etc, etc.
If your crank isn't trashed and just needs maybe a polish and bearings, if your rods are still fine. I just can't see 4 grand!
I'd look around a bit.

theandies

I put a ZZ4 in my '71 way back in 2001 and it's been a great engine. Everything bolted on from the old one (except I had to buy a flywheels as I have a 4 speed). I can't compare to the original 270hp engine as that was gone a long time ago out of this car. It had an old truck V8 in in when I bought it.

drspencer

This car is strictly for cruising, no burnouts, auto cross, etc. I imagine I'd be pretty satisfied going from 270HP to 325HP, as long as it retained its street manners. I'm probably the only guy on the Forum that prefers a quiet exhaust.

My stock '71 is net rated at 270HP. What would that figure be if it were gross rated, as they did in previous years?

Thanks

drspencer

I understand, but those are the figures I'm seeing when doing a quick search in my area.

I would certainly be open to other recommendations in the Boston area.

Thanks

Newbomb2469

Obviously not my money, but think you can have the best of both worlds. You can store the original engine for numbers matching, and have a new engine for the performance you want. Yes, Vortec engines require a different intake manifold but there are plenty of options. Not sure if it fits under a standard C3 hood, but that engine can be ordered with an intake manifold and a carb, along with an HEI distributor.
Good luck on your decision

4-vettes

guessing, around 320.
If all you want is a nice clean rebuild of a tired, but not broken small block. Most of your parts are probably fine. New bearings in the bottom end, maybe just a hone and rings, but likely a bore and pistons.
look on Summit what a set of 8 Hyper pistons cost.
SurprisIngly inexpensive. And more than good enough for a street engine.
these shops quote you to line bore the mains turn the crank, etc. etc. When in reality, an engine such as what you want this is overkill.
you just need to freshen up a tired engine that really isn't broken.
Look around, don't get put on the elevator.
I'm not in your area. Sorry, but I've been a mechanic for 50 years.
Just a nice freshen up should outlast you.
More than enough.