1976 455 Riviera Engine with 1970 heads 1231786 CR?

Brushwolf

New Member
About a decade ago I picked up a very nice running rusty 76 Riviera with 455 and slipping 400th. Was going to do a quicky install of the motor in a 65 A body, but later I got a pretty good offer on that car and sold it. 455 is all cleaned up and pretty, but not fully assembled and has been a garage window decoration ever since. All dressed up and no place to go..

It has been turned once in a while to keep it loose. I had also picked up an aftermarket 455 billet flywheel, clutch, NOS Lakewood BOP bell, and pulled a Super T10 out of another car I parted (3 groove input shaft). All that stuff was going on the 455 on a low budget build.

Being too busy at the time to work on the motor myself, I had paid a young reasonably competent mechanic neighbor to pull the motor and install a TA moderate upgrade cam and lifters, replace the timing chain and intake. Forgot what grind cam I bought, but it was beyond stock - though nothing extreme being a low CR was still anticipated.

While the motor was being worked on though, I bought a set of reconditioned 1231786 heads from a guy who went to aluminum heads. They are the standard valves, not the stage 1. But they have the smaller chambers than the 76 heads. Also picked up a good used Offy 360 intake to lighten it a bit. So, the motor then came further apart than originally anticipated.

Long story, but the mechanics life fell apart and he never finished it, so I got it back partially together. The 1970? heads and aluminum Offy 360 intake are just sitting on it with a couple bolts. I have a few boxes of parts here to reinstall, and to add to the confusion I have a 2nd bunch of parts from a 73-74 455 that I bought disassembled and someone then bought that extra short block and heads. Those 73-74 parts are now co-mingled with the 76 parts.

So, not sure if there is any difference between timing covers, rockers, shafts, pushrods, etc.. But I have two later years (73-74? and 76) versions of all of them in boxes and not sure what belongs to which motor any more. Still have the new set of lifters for the new cam and a double roller timing chain amongst the parts.

The now long ago moved out of state mechanic neighbor said my timing cover was OK and he had done Buick motors previously and knew about the wear factor on timing cover that affects oil pressure, so maybe I am worrying about that needlessly. But, I never really knew what to look for regarding the timing cover and oiling issues.

But, now I want to finish assembly of the 455 and swap it into a 50's car that has a stuck SBC in it currently. The motor weight should be similar given the aluminum intake and swapping the heavy cast manifolds for headers. I have done multiple engine rebuilds on Chev, Ford and Mopar engines, but never a Buick.

Probably have done enough engine swaps that the mounts won't be an issue and I have a modestly used set of Ken Belle 455 headers I can modify if needed for exhaust. Don't think the Buick pan will interfere with the steering. Going to still try to keep this on the cheap though and not get carried away going through the whole engine as I tend to do every time.

But, I have some questions:

What CR is the likely result of 76 pistons and 70 head? About 12cc chamber difference I read in some places; 6-7cc difference I read other places...

Using a composition head gasket, but didn't 76 use a composition gasket anyway?

Any way to estimate hp and torque from this combo of block and heads with moderately upgraded cam?

The oil passages complication when swapping to older heads..... Applies to 1970 heads? Some places I read you should plug block oiling holes, other places I read you should plug head oiling holes... Which applies to this combo?

What to look for on infamous potential oiling issues?

Do I need to do anything with whichever timing cover I use?

I will probably keep the 76 HEI distributor. Do I need to change weight springs or anything?

Did Buick go through the same changes as Ford during that era, where depending on what year timing gears you use, that they retarded the cam on the newer engines of the era?

Would think using the aftermarket roller timing sets would prevent that happening, but idk. I got a Lunati degree wheel recently, but have not used it yet.

Thanks for any input and suggestions you can offer from your experiences with these motors.
 

tom telesco

Active Member
Brushwolf,

This is an excellent forum for MANY things basically relating to older Buick's.
The site/forum you should into joining ALSO is v8buick.com it's free just as this site is but v8 deals mostly with the 455's & is such a wealth of info you would be shorting yourself by not joining.
Just my thoughts.

Tom T.
 

Brushwolf

New Member
Thanks Tom.

Will do..
Brushwolf,

This is an excellent forum for MANY things basically relating to older Buick's.
The site/forum you should into joining ALSO is v8buick.com it's free just as this site is but v8 deals mostly with the 455's & is such a wealth of info you would be shorting yourself by not joining.
Just my thoughts.

Tom T.

** Update... have been dragging out all the parts and moved the motor to working area. Found out I am missing some head bolts and one rocker arm shaft bolt. Plus half a dozen of whatever those are that apparently hold the rockers in alignment on the shafts. Hopefully there are some mixed up with the Pontiac bolts and accessories that I put in my pole building
 
Just to start you off,

The '70 heads should be about 69cc, and if the '76 are about 76cc: CLICK HERE
The heads could make a 1/2 point difference in your compression ratio, going from a composite to a steel head gasket could do the same. I would suggest a '76 motor may want new pistons. Even if you are going for an economical replacement piston, find the shallow dish ones similar to what would have been used in the '70 ( I think they are only about 0.030" deep).

I always suggest getting the $50.00 desktop dyno to play with engine combinations to assess their value. It may not be the best, but it is better than depending on your imagination! Desktop Dyno, Click Here

The '76 would have used a composite, but that doesn't mean you have to.

The desktop dyno will help estimate torque with various combinations and set ups. You can advance and retard the cam, increase to stage one valves and see how much effect it will have for the money spent.

Your '76 block will have push rod oiling, no problem with the '70 heads, use the stamped steel rocker assembly and just bolt 'em on.

With a '76 block, you can get away with no oil modifications for mild street use, but if you disassemble you should do the recommended ones which on that block will probably on be to drill out the crankshaft holes. You should also at least do the front camshaft bearing groove around the back or buy grooved cam bearings. It already has the 5/8" pick up tube and some larger crankshaft oiling holes.

The only issues when choosing a timing cover is the older ones have a smaller oil hole and you will want the larger one.

All original distributors should be curved, you can do it with a weight and spring kit and an advance timing light. There are lots of good articles on the web, here is one ON SITE.

I don't know either, but I expect they did mess with cam timing. Your aftermarket cam and timing set will eliminate any oddities that may have been designed into the original equipment. I always use a timing set that has advance and retard key ways,

If you look on the cam, you might find a number etched into the end identifying it (punch them into the computer and you may identify the cam). If there are no numbers, you have a reason to play with your new advance wheel to estimate what it is, and they if you know it is a T/A, you should be able to match it on their site.

As a disclaimer, I only have limited experience and only build to a practical street performance level, I like A/C and want some mileage out of my builds so that I am happy to climb in the car and drive it 500 miles.
 
You are stuck with the composite gaskets. Whenever you are using a Buick big block or heads with oblong cooling ports (late 72s and later), a composite gasket is necessary. The steel shim gasket can only be used when both the heads and block have round cooling ports (67 - early 72). In case someone is wondering about the other possible combination, It is possible to mate the later oblong coolant port head to an early round coolant port block if you plug the coolant hole in the head that is exposed by lack of the second "scallop" at the top center of the deck of the block. If not, there will be a sizable coolant leak into the lifter valley.

The 75-76 pistons have slightly more dish cc then the 70 pistons, but there is less compression height in those pistons. This is the distance from the center of the pin to the top of the piston. This leaves the piston top further down in the bore reducing compression. I would wager, without using Destop Dyno, that your heads and the 76 short block will not yield more then 8.5:1 static compression. I am with Bob as to springing for at least a set of 70 replacement pistons. Maybe your bores would check out and you could get away with a hone and new pistons.

If you have a TA cam, there will be markings on the back that identify it. It may not be clear to you, but they will know if you can't figure it out. Then maybe select pistons based on what the cam might like for compression.

The Offy manifolds can be more restrictive then stock and are not well balanced for flow. I would have to find the old testing on these, but I would not use it on any performance motor. The B4B or Performer would save weight and have better flow characteristics out of the box. You might also want to consider the SP1 depending on your cam since you are going manual. You can slip it right up to the sweet spot in the RPMs with a manual. There are plenty of these manifolds used at a reasonable price.

You don't need to block any head or block oil passages as yours are already set to oil the rockers through the pushrods. The earlier heads (pre 70) oiled the rockers through the head. Here are some oiling mods from the Buick Performance Group. There are some in a sticky on V8buick as well. There are some good oil tips and overall tips in Steve Doves book "Guide to Buick Performance Engines" if you can find a copy. He wrote it in conjunction with some well known Buick builders at the time. You will have to figure out how far you want to go with oiling mods.

Make sure your double roller timing chain does not interfere with the fuel pump arm. You may have to bend it a little to stay out of the way.

You can't go wrong with 18*-20* mechanical advance at the crank all in by 2500 with 12*-14* initial.

Desktop Dyno2003 had been available as a free download in the past. You may be able to find it. That is what I use. Internal engine calculations have not changed much since 2003. Otherwise, carry on as you and Bob describe.
 
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LARRY70GS

Active Member
The 1975-6 pistons actually have a shallower dish, but they sit further down in the hole at TDC, could be as much as .065". 69cc is optimistic, my original 70 Stage 1 heads measured 72cc. But even with 69cc heads, this is probably the best you could hope for.

1976Block70Heads..JPG
 
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OK, lets try it with an aftermarket 70 455 stage one replacement piston that has a 23 CC dish instead of the stock 70 OEM piston that has cced at 25. It also has about .010" more compression height then the 70 OEM piston. Then we are going to give it a hopeful .040" piston to deck clearance because the compression height is greater in the 70 pistons then the 76 pistons. .045" is probably more realistic, but at least it is not .075" or .080" like stock 76 pistons would be. Then we are going to use an Orange Crush gasket that compresses to .038". Now we are getting somewhere a small aftermarket cam may find useful. I think your head CC is going to be greater then 69 because of the small valves taking up less volume in the chamber, but we are being hopeful!
 

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LARRY70GS

Active Member

IMO, custom pistons with a .038" overbore are the way to go. Yes more expensive, but you can custom specify both compression height and dish/valve notch cc's. That way, you get a zero deck short block that you can use as a stepping zone to higher power in the future. Do it once, do it right.


 
TA Performance has a cast 1607 piston with a 1.990" compression height and 23 CC dish. Speed Pro has a hypereutectic coated skirt H392NCP piston with a 1.985" compression height and a 23 CC dish. The TA piston to deck clearance should be about .035" in a normal untouched engine and the Speed Pro should have a .040" clearance in the same engine. This is .010"-.015" better then the stock 70 piston with a 1.975" compression height. I found a set of the Speed Pro pistons here for $266 shipped, but those were .040" oversized. They did say they had other oversizes available. The ad also has some useful information about them. The 1607 TA Performance pistons were $349 before shipping.

Be careful of the budget 455 pistons out there for the 455. Most have a dish of over 27 CCs and a compression height of 1.955". These are going to have a piston to deck clearance somewhere around .070". Your current 76 pistons would almost provide the same compression as these.
 
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