Well, I've finally decided to get a big block for the Cutlass and I'm looking for some advice.

I bought a 455 that I am told is from a 1975 Toronado. I think it has J heads. It is running and sounds good. I was told the compression was in the 115-125 psi range which I think might be a little low. I am thinking of getting it rebuilt, and might as well (dangerous word!) do some upgrades now as well.

The current drivetrain in the car is a 350 with th350 and 8.5" open 2.73 rear. When I put the 455 in, I will be switching to a 200-4R at the same time. The transmission is a fresh rebuild, stronger than stock with a shift kit. I do not plan change to the diff this year but probably will at some point.

My requirements are:
1) I want it to run on pump gas, preferably 87 but as long as it can run on 91, I'm ok.
2) Performance wise, I'd like it to be capable of a 13-14 second 1/4 mile.

So far my thoughts for engine upgrades are an Edelbrock Performer intake with a Q-jet, Performer RPM heads and a cam.

Any suggestions for a good cam?

Any other suggestions or things I should consider? What should I watch out for?

Any other good threads I should look at?

Thanks for any help.

 

That is a smog motor you can make minor upgrades. I think if your going to rebuild, I would go higher compression pistons and look into the pro comp heads also ask cutlasefi on your cam need

 

You could easily run low 13s with that engine with some minor upgrades. If the engine is in good mechanical condition install some good heads (Edelbrock or pro comps) mill them and run thin head gaskets to help with the lousy compression ratio, install a good modern camshaft and a good exhaust system. Airflow is the key, get the engine to breath and you can probably get the car into the 12 with decent traction.

When your ready to work on the rear-end install 3.42 gears at the minimum, 3.73 would be ideal. Your going to have the best of both worlds with that trans, low 1st gear for the best get up and go, and a overdrive will really tame the lower rear-end gear. With 3.73s and the trans in overdrive and the converter locked it will cruise basically the same way it does now with the stock trans and gear.

Your biggest challenge will be keeping tires on it, but thats the fun part!

 

Some good info here.

To go along with that;

In the interest of a budget I'd certainly entertain the Procomp heads, a used Performer and a cam change for the engine.
I'd also recommend the rear end change, but for a big block I think a 3.42 is sufficient.

You'll have a different car after these changes, guaranteed.

 

Thanks for the answers. But they now lead to more questions

I just finished installing a new 2.5" dual exhaust system on the car. I have headers on the 350 and will be buying a set for the 455 as well.

I've heard about the Procomp heads before. Who sells them? Anyone in particular that would be recommended to buy them from? Are they generally sold complete? If not, what other parts would I need to look into?

With the Procomp heads, is there anything else that I will need to worry about? I thought I read somewhere either Procomp or Edelbrock heads required an electric fuel pump. Is this because of different shape than the factory heads?

Will factory style A/C brackets fit Procomp heads?

I'm guessing milling the heads and using thin gaskets would achieve the same results as higher compression pistons?

Is there a benefit to milling the heads over different pistons?

Any suggestions for pistons?

cutlassefi, I'm guessing the best time to ask about cam need would be once I have decided on the rest of the parts?

Some of these questions may sound basic, but I am new to engines, so I am looking for all the advice I can get.

Fell free to pm me for parts buying recommendations, if you don't want to post on the forum.

 

Lots of good questions. To answer them, you need to decide if your going to completely tear down the engine and rebuild, or just freshen the top end.

Due to the lousy lack of consideration, both Edelbrock and Procomp failed to leave enough clearance to run a big mechanical fuel pump. The Airtex 40736 will just BARELY fit, to run the RobbMC pump requires some cutting and welding. BTR Performance charged $200 for the work on my head for the pump. However, for your goal, the Airtex pump should be sufficient. My friends 66 Cutlass ran low 12s with that pump. For 40 bucks its hard to beat!

Changing pistons, decking the block, milling the heads, thinner head gaskets all will change the compression ratio. If your completely rebuilding the engine, then changing pistons would be the ideal way to bump compression. If your just rebuilding the top, then milling heads, and thin head gaskets should get you into the low 9ish to one compression. That should run fine on pump gas.

Pretty sure the A/C brackets fit the heads. The aftermarket heads require specific rocker arms, pushrods and head bolts. Call around, see who has the best package deal on the heads and needed parts for the install.

 

X2

On stock brackets I have been advised that you can't just bolt on the stock brackets that mods will be required but not sure if it's year pacific or not it was a 67 442

 

I have not had a chance to test it myself, but the seller of the engine told me the compression was in the 115-125 psi range. From what I've found, that sounds like it is a little low, so I will probably be getting a complete rebuild of the engine done.

 

If the compression is low on all cylinders, the timing chain could be stretched. That screws up the valve timing and makes the compression lower than normal. A leakdown test would be much more informative. Also, were all the plugs removed, and the throttle wide open during the test?

 

Matt, I did not know that a stretched timing chain could cause low compression.

Unfortunately, the engine is out, so I'm not sure what I can test at this point.

I might check to see if I can take the timing cover off and have a look at the chain.

What compression ratio should I be aiming for, for a good street motor, with the goals I mentioned before?

This car will be driving a lot, and on some long road trips, not just around town.

 

You can do a leakdown test with the engine on a stand. For that matter, you could install a starter to the engine with it on a stand and run a compression test again. Remove all the plugs, wire the throttle wide open and see what happens. If the compression is equally low but with in spec I would do a leakdown test.

 

If a stretched timing chain makes more than a 10-15psi difference then it jumped a tooth. Then you'll have other issues. On a stock cam a change of even 10 degrees won't make enough difference to skew your compression readings that much.
And even if it jumped they should all still be even. You're really just looking for anything that's not consistent.

And on a big block you can still use a mechanical fuel pump with aluminum heads. You just can't do that on a small block.

 

i just put BERNARD Mondello tuned pro comp heads on my stock 400 motor. I won't be putting many miles on it so I didn't bother doing a leak down or comp test....STOP & take the time & do it...My engine was running perfect with no signs of ruff idle, rich exhaust or smoke. While on the dyno # 2 cylinder was down on the leak down but within 10% on compression test. There's definitely some hp lost in the hole. No biggy as I will eventually switch to the 455 block when i get around to it. You can use a Chinese holley fuel pump with a minor notch in the head. You will definitely need to modify the A/C bracket. I ground out the inside of the bracket to fit. the manifold bolt will not line up so you must cut the bracket. Depending on which rockers you use will determine the valve covers & clearance. I strongly recommend contacting Bernard (find him on ebay) (not Mondello ent) When you speak to him he can give you a quick history lesson. Also Cutlassefi will be very forthright & helpful. you can send a pm & I can offer a few more tidbits.

 

Thanks for the added advice everyone.

I've been talking with a friend lately as well and I think I am narrowing things down more and more.

Here is what I think I'll end up with so far:
-Procomp heads from Bernard Mondello, the premium package
-1.6:1 full roller rockers
-Edelbrock Performer Intake
-Quadrajet carburator
-pistons to raise the compression ratio. I'm thinking 15cc, to have roughly 9.5:1
-re-use the original connecting rods
-cam to be determined
-oiling pushrods
-baffled oil pan

How does this plan sound? Anything I have not thought about?

This should run fine on pump gas? Ideally 91, since 93 and 94 octane are only available at certain chains up here.

I need to talk with a local engine builder to get an idea on what the cost will be for that engine plan, I think it might be pushing my budget, but should be doable.

I'm guessing a th350 of unknown condition (haven't really checked it out, other than the car drives fine now) wouldn't last too long behind that engine?

Any other comments?

 

My thoughts, find an engine builder that knows Olds engines, your short block build is everything, do a search here and on ROP for clearances, bearings, rods, etc.
Jim
Just my .02

 

I never saw a budget #. Seems like your leaving some stuff out. everyone has concerns with the oiling system on olds engines. look into oil pump, bigger oil pan and your engine builder smoothing out some ruff edges in the block casting. don't forget a new timing chain & gear.

 

I did not post a full parts list, but I will be getting a new oil pump as well as a double roller timing set and new lifters.

I had not heard about smoothing out rough spots in the block, but I'll look into it.

My initial budget plan was $5000, but looking at parts alone right now is pushing $4000.

 

Ide think about getting some aftermarket connecting rods. You can get a set of eagles for about $480. Factory Olds connecting rods are a def weak link.

 

Any of the 15cc pistons will give you right about 10.0:1, depending on the deck.
A good engine builder will know how to figure all that out. They should also have at least a torque plate in order to hone it correctly. Ask a lot of questions, it's your money.
As mentioned ditch the stock rods. They're not worth the trouble and cost to recondition them. Buy the Eagles.
If done right plan on having approx. $7000.00 in it if you go roller, $6000.00+ if you don't.


Jmo