Opinions on 11:1 compression on 93 octane

[TexasRoadRunner68]

This is an old video when it still was carbed

Nice!

 

[TexasRoadRunner68]

Nice!

How are the street manners? Power still decent down lower? I have a 4 speed dana 3.54 I was hoping to keep stock.

 

[cdr]

How are the street manners? Power still decent down lower? I have a 4 speed dana 3.54 I was hoping to keep stock.

very good, I had a 3.54 gear & it drove very nice on the street, took a lot of carb tuning & timing curve to get it smooth @ 1800 rpm. very streetable cam in a 512ci,still had great low end TQ even with max wedge ports & single plane intake

 

[TexasRoadRunner68]

very good, I had a 3.54 gear & it drove very nice on the street, took a lot of carb tuning & timing curve to get it smooth @ 1800 rpm. very streetable cam in a 512ci,still had great low end TQ even with max wedge ports & single plane intake

What rockers did you choose? Also, if you built the bottom end, how much clearancing was needed on your casting to clear the rod bolts? I’m assuming you went with a girdle?

My car is a factory track pack, so no AC. I’m assuming you have the vintage air setup? Chris Birdsong put it in his, and it was blowing like 40 degrees. I had intended to keep the car original except the motor, which wasn’t original anyway…but the more I see the vintage air setups the more I want one. I’m sure I’ll have many hot summers until I have the funds for that…I’m just trying to get it back on the road at least

 

[cdr]

What rockers did you choose? Also, if you built the bottom end, how much clearancing was needed on your casting to clear the rod bolts? I’m assuming you went with a girdle?

My car is a factory track pack, so no AC. I’m assuming you have the vintage air setup? Chris Birdsong put it in his, and it was blowing like 40 degrees. I had intended to keep the car original except the motor, which wasn’t original anyway…but the more I see the vintage air setups the more I want one. I’m sure I’ll have many hot summers until I have the funds for that…I’m just trying to get it back on the road at least

I have T&D offset rockers, I had to grind the bottom of a few cylinders & on the side where the oil screen screws into, not very much, I have the factory AC set up with a Sanden compressor, it will freeze you out even when its 108 deg outside. no girdle, I dont think they do much good, an aftermarket block is the way I should have gone, but so far all is good .

 

[cdr]

 

[cdr]

This is one bottom cyl I had to grind on

 

[cdr]

Also DO NOT build a street engine over 10.25 to 1,, even with alum heads just my two cents

 

[Cranky]

I have T&D offset rockers, I had to grind the bottom of a few cylinders & on the side where the oil screen screws into, not very much, I have the factory AC set up with a Sanden compressor, it will freeze you out even when its 108 deg outside. no girdle, I dont think they do much good, an aftermarket block is the way I should have gone, but so far all is good .

How many miles/passes do you have on it now? Is the block still the same one you got from me awhile back? iirc, you did get one from me, right? lol Old Times starting in on me....

 

[cdr]

How many miles/passes do you have on it now? Is the block still the same one you got from me awhile back? iirc, you did get one from me, right? lol Old Times starting in on me....

same block I got from you, has about 12k miles & about 20 not so good passes LOL.

 

[Cranky]

same block I got from you, has about 12k miles & about 20 not so good passes LOL.

Not so good passes? lol To me a perfect pass is the round you won no matter if it was all over the lane

 

[mgoblue9798]

I have spoken with Hughes, who designed the cam I am considering using. They recommended it for a 500+ CI motor with 11:1+ compression and mechanical secondaries on the carb.

My 400 block just got checked and is good for the bore needed for the stroker kits. (4.375 I believe)

I do plan on using aluminum heads, which I hear can basically “take off a point”.

Hughes sells a 400-511 kit that would put me at 11:1 without zero decking the block. 440 source offers a 400-512 kit that could be 10.5:1.

I will post a photo of the cam card. Hughes seemed to think with the low altitude here and the abundance (as of now) of 93 octane gas, that 11:1 on pump gas would be doable.

The car won’t be a daily, but will probably see more street than track. Would you say 11:1 could work safely with the cam, or is it better to try 9.5-10.5?

I have heard some people say 11:1 makes the tuning window very narrow, however there are plenty of cars from the era that cam with 10.5:1 and iron heads back then. I’m assuming it should be fine, but I just want to verify.

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With the cam you have listed I don't think you would have any problem. If you are at all concerned deck the block if needed to get .040 or so quench.

 

[autoxcuda]

Something to think about, you can get 93 now but look at how many places in the country that you can only get 90-91 octane. That could coming to a station near you?. I would build for 9.5-10.5 to one for a car if it does street duty.

Extremely good point!

And the tale of “aluminum heads are like dropping one point!” is a bullshit tale that can’t be backed up. 11:1 aluminum is not 10:1. Especially on the street.

Also DO NOT build a street engine over 10.25 to 1,, even with alum heads just my two cents

There you go. Someone in your same area, same gas availability, same cam, that really drives it on the street.

Not running a dyno, not plugging numbers into some calculation, not building the motor then shipping it to a customer, not based on what others say on the Internet…