Tony Cavotta
Member
Has anyone ever heard or relieved 4 banger like we would V8
Model A or B block relieved like V8
- Thread starter Tony Cavotta
- Start date
"Just a little deuce coupe with a flat head mill
But she'll walk a Thunderbird like it's standin' still
She's ported and relieved and she's stroked and bored.
She'll do a hundred and forty with the top end floored".
I question the 140 part but...If it was in the song ... it must be true Heh?
But she'll walk a Thunderbird like it's standin' still
She's ported and relieved and she's stroked and bored.
She'll do a hundred and forty with the top end floored".
I question the 140 part but...If it was in the song ... it must be true Heh?
Jim Brierley
Well-known member
What jetmek says is true. I have rounded the edge a little before but can't say it helped, and you can't go very deep or you will run into the rings area.
BRENT in 10-uh-C
Well-known member
Tony, expounding on what Mr. Clarke said in post #2, ...the top of the valve seat is flush with the deck surface of the cylinder case (block), so there is nothing to be gained by undercutting, however there are two or three things that I feel can help in performance though;
#1, The top edge of the bore can be radiused slightly on the edges where the fire ring is not touching. This will aide slightly in transitional air flow.
#2, while it may seem counterproductive because it slightly lowers the compression ratio, often times the volumetric efficiency can be increased if the valve is unshrouded on the backside by opening up the valve clearance area in the cylinder head.
#3, having a multi-angle seat machined (3-angle, 5-angle, infinite-angle) allows the gasses to better flow over the sharp edge of a 45° angle. Ultimately, look for ways to allow the incoming and egressing air/gas to happen more efficiently.
alexiskai
Well-known member
This diagram, from this article on flathead V8s, sort of illustrates what Brent is referring to. Area C corresponds to #1 in Brent's post, while area A corresponds to #2. Worth noting that the author of the article is ambivalent about #2, saying the exact shape of the removed material is critical. Again, the article is specifically about V8s.
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d.j. moordigian
Well-known member
What everyone else said..PLUS THIS,...there isn't enough deck thickness in a A,..and
it's worse in a B/C block..!
djm
it's worse in a B/C block..!
djm
BRENT in 10-uh-C
Well-known member
How far down the hole was the piston, -or more specifically, was the top ring lowered to get it out of the heat some??
rotorwrench
Well-known member
Relieving has been done but the builds for this likely use custom made everything for the build. Relieving for the V8 engines was originally done to lower compression ratios on truck engines. Crow foot cylinder heads were made that work with a relieved block on the V8s. Most folks have been going the blower type supercharger route to get flatheads to breath. It certainly works better than normal aspiration in most cases. On 4-bangers, going overhead valve is generally the first choice to make the 200 cid Ford get up and go.
Pete
BANNED
For sure, blowers are cheap hp but most vintage racing rules do not allow blowers. Exception, LSR.
And definitely, a racing engine has "custom made everything" in it as noted by the similar cost to a NASCAR or WoO engine.
hardtimes
Well-known member
Yeah , Ive heard of it ....and before I knew better, I’ve done it.
If mostly stock engine... little to gain if any, and lots to lose.
The A/B blks were thin when new and even thinner the older they are.
So intentionally removing metal from that area is not a good idea ...unless you don’t mind cracks and leaks.
When I eventually learned and saw A/B crack potential ... where relieving takes place... well your choice !
Jack Shaft
BANNED
It's not about increasing valve relieving..its about valve lift and timing, raising compression and adding fuel.that where the money is..flathead V8? Meh, lousy power to weight ratio, propensity to run hot and burn oil..a well-built and tuned model a will make a fool of it..